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Skywalking-13: skywalking module loading mechanism

2021-10-14 05:38:50 Switch

Module loading mechanism

Basic overview

Module yes Skywalking stay OAP Provides a mechanism for managing functional features . adopt Module Mechanism , Modules can be easily defined , And can provide a variety of implementations , Select any implementation in the configuration file .

For module related configuration files, please refer to :Backend setupConfiguration Vocabulary

Class diagram

Skywalking Module management related functions in org.apache.skywalking.oap.server.library.module It's a bag .

Through the class diagram, we can understand Skywalking The module mechanism is roughly divided into the following modules :

  • The module configuration : ApplicationConfigurationModuleConfigurationProviderConfiguration

    • PS: Just corresponding application.yml  Three tier structure : modular -> Module implementation -> The configuration implemented by a module .
  • Module definition class : ModuleDefine
  • Module provides classes : ModuleProvider
  • service : Service
  • Management category : ModuleManager
  • Some auxiliary classes

    • ModuleDefineHolder : Interface to be implemented by module management class , Provides functions related to finding modules
    • ModuleProviderHolder : The module defines the interface that the class needs to implement , Provide the service class function of the module
    • ModuleServiceHolder : The module provides the interface that the class needs to implement , Provide registration service to realize 、 Get the function of the service object
    • ModuleConfig : Module configuration class , The module definition class will ProviderConfiguration It maps to ModuleConfig
    • ApplicationConfigLoaderApplicationConfiguration Auxiliary class , take application.yml Load the configuration file into memory , Set up selector Corresponding Provider Configuration information

file

Class diagram source file :Skywalking-Module.uml

The source code parsing

ModuleDefine

package org.apache.skywalking.oap.server.library.module;

import java.lang.reflect.Field;
import java.util.Enumeration;
import java.util.Properties;
import java.util.ServiceLoader;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

//  Module definition 
public abstract class ModuleDefine implements ModuleProviderHolder {
    private static final Logger LOGGER = LoggerFactory.getLogger(ModuleDefine.class);
    //  Module actual 
    private ModuleProvider loadedProvider = null;

    private final String name;

    public ModuleDefine(String name) {
        this.name = name;
    }

    //  Module name 
    public final String name() {
        return name;
    }

    //  The implementation class can define the service class provided by the module 
    public abstract Class[] services();

    /**
     * Run the prepare stage for the module, including finding all potential providers, and asking them to prepare.
     *
     * @param moduleManager of this module
     * @param configuration of this module
     * @throws ProviderNotFoundException when even don't find a single one providers.
     */
    //  Preparation stage , find configuration Configuration class corresponding to ModuleProvider object , Perform initialization operation 
    void prepare(
        //  Module management object 
        ModuleManager moduleManager, 
        //  Module configuration class 
        ApplicationConfiguration.ModuleConfiguration configuration,
        //  The module provides the service loader of the class 
        ServiceLoader<ModuleProvider> moduleProviderLoader
    ) throws ProviderNotFoundException, ServiceNotProvidedException, ModuleConfigException, ModuleStartException {
        //  find configuration Configuration class corresponding to ModuleProvider object 
        for (ModuleProvider provider : moduleProviderLoader) {
            if (!configuration.has(provider.name())) {
                continue;
            }
            if (provider.module().equals(getClass())) {
                if (loadedProvider == null) {
                    loadedProvider = provider;
                    loadedProvider.setManager(moduleManager);
                    loadedProvider.setModuleDefine(this);
                } else {
                    throw new DuplicateProviderException(this.name() + " module has one " + loadedProvider.name() + "[" + loadedProvider.getClass().getName() + "] provider already, " + provider.name() + "[" + provider.getClass().getName() + "] is defined as 2nd provider.");
                }
            }
        }
        if (loadedProvider == null) {
            throw new ProviderNotFoundException(this.name() + " module no provider found.");
        }

        //  Copy the configuration file of the provided class to ModuleConfig object 
        LOGGER.info("Prepare the {} provider in {} module.", loadedProvider.name(), this.name());
        try {
            copyProperties(
                loadedProvider.createConfigBeanIfAbsent(), 
                configuration.getProviderConfiguration(loadedProvider.name()), 
                this.name(), 
                loadedProvider.name()
            );
        } catch (IllegalAccessException e) {
            throw new ModuleConfigException(this.name() + " module config transport to config bean failure.", e);
        }
        //  The module provides the object to enter the preparation stage 
        loadedProvider.prepare();
    }

    //  Use reflection to copy attributes 
    private void copyProperties(ModuleConfig dest, Properties src, String moduleName, String providerName) throws IllegalAccessException {
        if (dest == null) {
            return;
        }
        Enumeration<?> propertyNames = src.propertyNames();
        while (propertyNames.hasMoreElements()) {
            String propertyName = (String) propertyNames.nextElement();
            Class<? extends ModuleConfig> destClass = dest.getClass();
            try {
                Field field = getDeclaredField(destClass, propertyName);
                field.setAccessible(true);
                field.set(dest, src.get(propertyName));
            } catch (NoSuchFieldException e) {
                LOGGER.warn(propertyName + " setting is not supported in " + providerName + " provider of " + moduleName + " module");
            }
        }
    }

    private Field getDeclaredField(Class<?> destClass, String fieldName) throws NoSuchFieldException {
        if (destClass != null) {
            Field[] fields = destClass.getDeclaredFields();
            for (Field field : fields) {
                if (field.getName().equals(fieldName)) {
                    return field;
                }
            }
            return getDeclaredField(destClass.getSuperclass(), fieldName);
        }
        throw new NoSuchFieldException();
    }

    //  Get the corresponding module definition Provider object 
    @Override
    public final ModuleProvider provider() throws DuplicateProviderException, ProviderNotFoundException {
        if (loadedProvider == null) {
            throw new ProviderNotFoundException("There is no module provider in " + this.name() + " module!");
        }
        return loadedProvider;
    }
}

ModuleProviderHolder

package org.apache.skywalking.oap.server.library.module;

//  The module provides a holding interface , Through this interface , You can get modules Provider The object corresponds to Service Holding interface , To get the module Provider Object corresponds to the service object 
public interface ModuleProviderHolder {
    //  Get the object provided by the module 
    ModuleServiceHolder provider() throws DuplicateProviderException, ProviderNotFoundException;
}

ModuleProvider

package org.apache.skywalking.oap.server.library.module;

import java.util.HashMap;
import java.util.Map;
import lombok.Setter;

//  Modules provide abstract classes , All module providing classes need to inherit the abstract class 
//  A module definition can configure multiple modules to provide classes , By means of application.yml Switch 
public abstract class ModuleProvider implements ModuleServiceHolder {
    //  Module manager 
    @Setter
    private ModuleManager manager;
    //  Module definition object 
    @Setter
    private ModuleDefine moduleDefine;
    //  The module provides the corresponding service object map
    private final Map<Class<? extends Service>, Service> services = new HashMap<>();

    public ModuleProvider() {
    }

    protected final ModuleManager getManager() {
        return manager;
    }

    //  Get the implementation class of the service provider name, You need a subclass implementation 
    public abstract String name();

    //  Define the module definition class implemented by the module provider 
    public abstract Class<? extends ModuleDefine> module();

    //  Create a module definition configuration object 
    public abstract ModuleConfig createConfigBeanIfAbsent();

    //  Preparation stage ( Initialize things that have nothing to do with other modules )
    public abstract void prepare() throws ServiceNotProvidedException, ModuleStartException;

    //  Start-up phase ( At this stage, modules can operate with each other )
    public abstract void start() throws ServiceNotProvidedException, ModuleStartException;

    //  Notification stage after completion ( Execute after all modules are successfully started )
    public abstract void notifyAfterCompleted() throws ServiceNotProvidedException, ModuleStartException;

    //  The module needs to rely on other module names 
    public abstract String[] requiredModules();

    //  Register the service implementation class 
    @Override
    public final void registerServiceImplementation(Class<? extends Service> serviceType, Service service) throws ServiceNotProvidedException {
        if (serviceType.isInstance(service)) {
            this.services.put(serviceType, service);
        } else {
            throw new ServiceNotProvidedException(serviceType + " is not implemented by " + service);
        }
    }

    //  Ensure that all services are implemented 
    void requiredCheck(Class<? extends Service>[] requiredServices) throws ServiceNotProvidedException {
        if (requiredServices == null)
            return;
        for (Class<? extends Service> service : requiredServices) {
            if (!services.containsKey(service)) {
                throw new ServiceNotProvidedException("Service:" + service.getName() + " not provided");
            }
        }
        if (requiredServices.length != services.size()) {
            throw new ServiceNotProvidedException("The " + this.name() + " provider in " + moduleDefine.name() + " moduleDefine provide more service implementations than ModuleDefine requirements.");
        }
    }

    //  Get the service implementation object 
    @Override
    public @SuppressWarnings("unchecked")
    <T extends Service> T getService(Class<T> serviceType) throws ServiceNotProvidedException {
        Service serviceImpl = services.get(serviceType);
        if (serviceImpl != null) {
            return (T) serviceImpl;
        }
        throw new ServiceNotProvidedException("Service " + serviceType.getName() + " should not be provided, based on moduleDefine define.");
    }

    ModuleDefine getModule() {
        return moduleDefine;
    }

    String getModuleName() {
        return moduleDefine.name();
    }
}

ModuleConfig

package org.apache.skywalking.oap.server.library.module;

//  Module configuration class 
public abstract class ModuleConfig {
}

ModuleServiceHolder

package org.apache.skywalking.oap.server.library.module;

//  Module services hold interfaces 
public interface ModuleServiceHolder {
    //  Register the service implementation object 
    void registerServiceImplementation(Class<? extends Service> serviceType, Service service) throws ServiceNotProvidedException;
    
    //  Get the service implementation object 
    <T extends Service> T getService(Class<T> serviceType) throws ServiceNotProvidedException;
}

Service

package org.apache.skywalking.oap.server.library.module;

//  Service interface 
public interface Service {
}

ModuleDefineHolder

package org.apache.skywalking.oap.server.library.module;

//  The module definition holds the interface 
public interface ModuleDefineHolder {
    //  Determine whether there is this module 
    boolean has(String moduleName);
    
    //  Get the module definition object through the module name 
    ModuleProviderHolder find(String moduleName) throws ModuleNotFoundRuntimeException;
}

ModuleManager

package org.apache.skywalking.oap.server.library.module;

import java.util.Arrays;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.Map;
import java.util.ServiceLoader;

//  Module management , Managing the life cycle of a module 
public class ModuleManager implements ModuleDefineHolder {
    //  Whether all modules have passed the preparation stage 
    private boolean isInPrepareStage = true;
    
    //  All loaded module definition objects map
    private final Map<String, ModuleDefine> loadedModules = new HashMap<>();

    //  Initialize all configured modules 
    public void init(ApplicationConfiguration applicationConfiguration) throws ModuleNotFoundException, ProviderNotFoundException, ServiceNotProvidedException, CycleDependencyException, ModuleConfigException, ModuleStartException {
        //  Get the module name in the configuration class 
        String[] moduleNames = applicationConfiguration.moduleList();
        // SPI Load all module definition objects 
        ServiceLoader<ModuleDefine> moduleServiceLoader = ServiceLoader.load(ModuleDefine.class);
        // SPI Load all module provided objects 
        ServiceLoader<ModuleProvider> moduleProviderLoader = ServiceLoader.load(ModuleProvider.class);
        //  Modules defined in all configuration classes , Go through the preparation phase 
        LinkedList<String> moduleList = new LinkedList<>(Arrays.asList(moduleNames));
        for (ModuleDefine module : moduleServiceLoader) {
            for (String moduleName : moduleNames) {
                if (moduleName.equals(module.name())) {
                    module.prepare(this, applicationConfiguration.getModuleConfiguration(moduleName), moduleProviderLoader);
                    loadedModules.put(moduleName, module);
                    moduleList.remove(moduleName);
                }
            }
        }
        //  The preparation phase is over 
        isInPrepareStage = false;

        if (moduleList.size() > 0) {
            throw new ModuleNotFoundException(moduleList.toString() + " missing.");
        }

        //  Provide... In the object according to the module requiredModules Method , Determine the initialization order of the module ( The dependent modules are loaded first )
        BootstrapFlow bootstrapFlow = new BootstrapFlow(loadedModules);
        //  All modules enter the startup phase 
        bootstrapFlow.start(this);
        //  All modules enter the post completion notification stage 
        bootstrapFlow.notifyAfterCompleted();
    }

    //  Determine whether there is this module 
    @Override
    public boolean has(String moduleName) {
        return loadedModules.get(moduleName) != null;
    }

    //  Get the module definition object through the module name 
    @Override
    public ModuleProviderHolder find(String moduleName) throws ModuleNotFoundRuntimeException {
        assertPreparedStage();
        ModuleDefine module = loadedModules.get(moduleName);
        if (module != null)
            return module;
        throw new ModuleNotFoundRuntimeException(moduleName + " missing.");
    }

    //  Whether the assertion is still in the preparation stage , If it's still in the preparation stage , Throw an exception 
    private void assertPreparedStage() {
        if (isInPrepareStage) {
            throw new AssertionError("Still in preparing stage.");
        }
    }
}

BootstrapFlow

package org.apache.skywalking.oap.server.library.module;

import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import org.apache.skywalking.oap.server.library.util.CollectionUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

//  Provide... In the object according to the module requiredModules Method , Determine the initialization order of the module ( The dependent modules are loaded first )
class BootstrapFlow {
    private static final Logger LOGGER = LoggerFactory.getLogger(BootstrapFlow.class);

    private Map<String, ModuleDefine> loadedModules;
    //  Modules sorted in dependency order provide a list of objects 
    private List<ModuleProvider> startupSequence;

    BootstrapFlow(Map<String, ModuleDefine> loadedModules) throws CycleDependencyException, ModuleNotFoundException {
        this.loadedModules = loadedModules;
        startupSequence = new LinkedList<>();

        //  The dependent modules are loaded first 
        makeSequence();
    }

    @SuppressWarnings("unchecked")
    void start(
        ModuleManager moduleManager) throws ModuleNotFoundException, ServiceNotProvidedException, ModuleStartException {
        for (ModuleProvider provider : startupSequence) {
            LOGGER.info("start the provider {} in {} module.", provider.name(), provider.getModuleName());
            provider.requiredCheck(provider.getModule().services());

            provider.start();
        }
    }

    void notifyAfterCompleted() throws ServiceNotProvidedException, ModuleStartException {
        for (ModuleProvider provider : startupSequence) {
            provider.notifyAfterCompleted();
        }
    }

    private void makeSequence() throws CycleDependencyException, ModuleNotFoundException {
        List<ModuleProvider> allProviders = new ArrayList<>();
        //  Determine whether all dependent modules exist 
        for (final ModuleDefine module : loadedModules.values()) {
            String[] requiredModules = module.provider().requiredModules();
            if (requiredModules != null) {
                for (String requiredModule : requiredModules) {
                    if (!loadedModules.containsKey(requiredModule)) {
                        throw new ModuleNotFoundException(requiredModule + " module is required by " + module.provider().getModuleName() + "." + module.provider().name() + ", but not found.");
                    }
                }
            }

            allProviders.add(module.provider());
        }

        do {
            int numOfToBeSequenced = allProviders.size();
            for (int i = 0; i < allProviders.size(); i++) {
                ModuleProvider provider = allProviders.get(i);
                String[] requiredModules = provider.requiredModules();
                if (CollectionUtils.isNotEmpty(requiredModules)) {
                    //  Whether all dependent modules are in startupSequence in 
                    boolean isAllRequiredModuleStarted = true;
                    for (String module : requiredModules) {
                        boolean exist = false;
                        for (ModuleProvider moduleProvider : startupSequence) {
                            if (moduleProvider.getModuleName().equals(module)) {
                                exist = true;
                                break;
                            }
                        }
                        if (!exist) {
                            isAllRequiredModuleStarted = false;
                            break;
                        }
                    }
                    //  All dependent modules are in startupSequence, Then add the object provided by the module to startupSequence
                    if (isAllRequiredModuleStarted) {
                        startupSequence.add(provider);
                        allProviders.remove(i);
                        i--;
                    }
                } else {
                    //  If the module provides an object that does not depend on any other module , Join in startupSequence
                    startupSequence.add(provider);
                    allProviders.remove(i);
                    i--;
                }
            }

            //  If after one cycle , No object is added to startupSequence, Then it proves that there is cyclic dependence 
            if (numOfToBeSequenced == allProviders.size()) {
                StringBuilder unSequencedProviders = new StringBuilder();
                allProviders.forEach(provider -> unSequencedProviders.append(provider.getModuleName()).append("[provider=").append(provider.getClass().getName()).append("]\n"));
                throw new CycleDependencyException("Exist cycle module dependencies in \n" + unSequencedProviders.substring(0, unSequencedProviders.length() - 1));
            }
        } while (allProviders.size() != 0); //  When the supplied object list is not empty , Then it will be executed in a loop 
    }
}

ApplicationConfiguration

package org.apache.skywalking.oap.server.library.module;

import java.util.HashMap;
import java.util.Properties;

// OAP Application configuration class 
public class ApplicationConfiguration {
    //  Module definition configuration map
    private HashMap<String, ModuleConfiguration> modules = new HashMap<>();

    //  List of module configuration names 
    public String[] moduleList() {
        return modules.keySet().toArray(new String[0]);
    }

    //  Add module definition configuration 
    public ModuleConfiguration addModule(String moduleName) {
        ModuleConfiguration newModule = new ModuleConfiguration();
        modules.put(moduleName, newModule);
        return newModule;
    }

    //  Judge whether the module definition configuration exists for the specified module name map in 
    public boolean has(String moduleName) {
        return modules.containsKey(moduleName);
    }

    //  Get module definition configuration 
    public ModuleConfiguration getModuleConfiguration(String name) {
        return modules.get(name);
    }

    //  Module definition configuration class 
    public static class ModuleConfiguration {
        //  Modules provide objects map
        private HashMap<String, ProviderConfiguration> providers = new HashMap<>();

        private ModuleConfiguration() {
        }

        //  Get the configuration provided by the module 
        public Properties getProviderConfiguration(String name) {
            return providers.get(name).getProperties();
        }

        //  Whether there is a module to provide configuration 
        public boolean has(String name) {
            return providers.containsKey(name);
        }

        //  Add modules to provide configuration 
        public ModuleConfiguration addProviderConfiguration(String name, Properties properties) {
            ProviderConfiguration newProvider = new ProviderConfiguration(properties);
            providers.put(name, newProvider);
            return this;
        }
    }

    //  Module provides configuration classes 
    public static class ProviderConfiguration {
        //  Module provides properties 
        private Properties properties;

        ProviderConfiguration(Properties properties) {
            this.properties = properties;
        }

        private Properties getProperties() {
            return properties;
        }
    }
}

ApplicationConfigLoader

package org.apache.skywalking.oap.server.starter.config;

import java.io.FileNotFoundException;
import java.io.Reader;
import java.util.HashSet;
import java.util.Map;
import java.util.Properties;
import java.util.Set;
import lombok.extern.slf4j.Slf4j;
import org.apache.skywalking.apm.util.PropertyPlaceholderHelper;
import org.apache.skywalking.oap.server.library.module.ApplicationConfiguration;
import org.apache.skywalking.oap.server.library.module.ProviderNotFoundException;
import org.apache.skywalking.oap.server.library.util.CollectionUtils;
import org.apache.skywalking.oap.server.library.util.ResourceUtils;
import org.yaml.snakeyaml.Yaml;

// application.yml Load class ,  Three tier structure : Module definition name . Provide module name . attribute key
@Slf4j
public class ApplicationConfigLoader implements ConfigLoader<ApplicationConfiguration> {
    //  When the module provider is not configured , Use "-"
    private static final String DISABLE_SELECTOR = "-";
    //  This field selects the module provider 
    private static final String SELECTOR = "selector";

    private final Yaml yaml = new Yaml();

    @Override
    public ApplicationConfiguration load() throws ConfigFileNotFoundException {
        ApplicationConfiguration configuration = new ApplicationConfiguration();
        this.loadConfig(configuration);
        this.overrideConfigBySystemEnv(configuration);
        return configuration;
    }

    @SuppressWarnings("unchecked")
    private void loadConfig(ApplicationConfiguration configuration) throws ConfigFileNotFoundException {
        try {
            Reader applicationReader = ResourceUtils.read("application.yml");
            Map<String, Map<String, Object>> moduleConfig = yaml.loadAs(applicationReader, Map.class);
            if (CollectionUtils.isNotEmpty(moduleConfig)) {
                selectConfig(moduleConfig);
                moduleConfig.forEach((moduleName, providerConfig) -> {
                    if (providerConfig.size() > 0) {
                        log.info("Get a module define from application.yml, module name: {}", moduleName);
                        ApplicationConfiguration.ModuleConfiguration moduleConfiguration = configuration.addModule(moduleName);
                        providerConfig.forEach((providerName, config) -> {
                            log.info("Get a provider define belong to {} module, provider name: {}", moduleName, providerName);
                            final Map<String, ?> propertiesConfig = (Map<String, ?>) config;
                            final Properties properties = new Properties();
                            if (propertiesConfig != null) {
                                propertiesConfig.forEach((propertyName, propertyValue) -> {
                                    if (propertyValue instanceof Map) {
                                        Properties subProperties = new Properties();
                                        ((Map) propertyValue).forEach((key, value) -> {
                                            subProperties.put(key, value);
                                            replacePropertyAndLog(key, value, subProperties, providerName);
                                        });
                                        properties.put(propertyName, subProperties);
                                    } else {
                                        properties.put(propertyName, propertyValue);
                                        replacePropertyAndLog(propertyName, propertyValue, properties, providerName);
                                    }
                                });
                            }
                            moduleConfiguration.addProviderConfiguration(providerName, properties);
                        });
                    } else {
                        log.warn("Get a module define from application.yml, but no provider define, use default, module name: {}", moduleName);
                    }
                });
            }
        } catch (FileNotFoundException e) {
            throw new ConfigFileNotFoundException(e.getMessage(), e);
        }
    }

    private void replacePropertyAndLog(final Object propertyName, final Object propertyValue, final Properties target, final Object providerName) {
        final String valueString = PropertyPlaceholderHelper.INSTANCE.replacePlaceholders(propertyValue + "", target);
        if (valueString != null) {
            if (valueString.trim().length() == 0) {
                target.replace(propertyName, valueString);
                log.info("Provider={} config={} has been set as an empty string", providerName, propertyName);
            } else {
                // Use YAML to do data type conversion.
                final Object replaceValue = yaml.load(valueString);
                if (replaceValue != null) {
                    target.replace(propertyName, replaceValue);
                    log.info("Provider={} config={} has been set as {}", providerName, propertyName, replaceValue.toString());
                }
            }
        }
    }

    private void overrideConfigBySystemEnv(ApplicationConfiguration configuration) {
        for (Map.Entry<Object, Object> prop : System.getProperties().entrySet()) {
            overrideModuleSettings(configuration, prop.getKey().toString(), prop.getValue().toString());
        }
    }

    private void selectConfig(final Map<String, Map<String, Object>> moduleConfiguration) {
        final Set<String> modulesWithoutProvider = new HashSet<>();
        for (final Map.Entry<String, Map<String, Object>> entry : moduleConfiguration.entrySet()) {
            final String moduleName = entry.getKey();
            final Map<String, Object> providerConfig = entry.getValue();
            if (!providerConfig.containsKey(SELECTOR)) {
                continue;
            }
            final String selector = (String) providerConfig.get(SELECTOR);
            final String resolvedSelector = PropertyPlaceholderHelper.INSTANCE.replacePlaceholders(
                selector, System.getProperties()
            );
            providerConfig.entrySet().removeIf(e -> !resolvedSelector.equals(e.getKey()));

            if (!providerConfig.isEmpty()) {
                continue;
            }

            if (!DISABLE_SELECTOR.equals(resolvedSelector)) {
                throw new ProviderNotFoundException("no provider found for module " + moduleName + ", " + "if you're sure it's not required module and want to remove it, " + "set the selector to -");
            }

            // now the module can be safely removed
            modulesWithoutProvider.add(moduleName);
        }

        moduleConfiguration.entrySet().removeIf(e -> {
            final String module = e.getKey();
            final boolean shouldBeRemoved = modulesWithoutProvider.contains(module);
            if (shouldBeRemoved) {
                log.info("Remove module {} without any provider", module);
            }
            return shouldBeRemoved;
        });
    }

    private void overrideModuleSettings(ApplicationConfiguration configuration, String key, String value) {
        int moduleAndConfigSeparator = key.indexOf('.');
        if (moduleAndConfigSeparator <= 0) {
            return;
        }
        String moduleName = key.substring(0, moduleAndConfigSeparator);
        String providerSettingSubKey = key.substring(moduleAndConfigSeparator + 1);
        ApplicationConfiguration.ModuleConfiguration moduleConfiguration = configuration.getModuleConfiguration(moduleName);
        if (moduleConfiguration == null) {
            return;
        }
        int providerAndConfigSeparator = providerSettingSubKey.indexOf('.');
        if (providerAndConfigSeparator <= 0) {
            return;
        }
        String providerName = providerSettingSubKey.substring(0, providerAndConfigSeparator);
        String settingKey = providerSettingSubKey.substring(providerAndConfigSeparator + 1);
        if (!moduleConfiguration.has(providerName)) {
            return;
        }
        Properties providerSettings = moduleConfiguration.getProviderConfiguration(providerName);
        if (!providerSettings.containsKey(settingKey)) {
            return;
        }
        Object originValue = providerSettings.get(settingKey);
        Class<?> type = originValue.getClass();
        if (type.equals(int.class) || type.equals(Integer.class))
            providerSettings.put(settingKey, Integer.valueOf(value));
        else if (type.equals(String.class))
            providerSettings.put(settingKey, value);
        else if (type.equals(long.class) || type.equals(Long.class))
            providerSettings.put(settingKey, Long.valueOf(value));
        else if (type.equals(boolean.class) || type.equals(Boolean.class)) {
            providerSettings.put(settingKey, Boolean.valueOf(value));
        } else {
            return;
        }
        log.info("The setting has been override by key: {}, value: {}, in {} provider of {} module through {}", settingKey, value, providerName, moduleName, "System.properties");
    }
}

ConfigLoader

package org.apache.skywalking.oap.server.starter.config;

//  Configure the loading interface 
public interface ConfigLoader<T> {
    T load() throws ConfigFileNotFoundException;
}

OAPServerBootstrap

package org.apache.skywalking.oap.server.starter;

import lombok.extern.slf4j.Slf4j;
import org.apache.skywalking.oap.server.core.RunningMode;
import org.apache.skywalking.oap.server.library.module.ApplicationConfiguration;
import org.apache.skywalking.oap.server.library.module.ModuleManager;
import org.apache.skywalking.oap.server.starter.config.ApplicationConfigLoader;
import org.apache.skywalking.oap.server.starter.config.ConfigLoader;
import org.apache.skywalking.oap.server.telemetry.TelemetryModule;
import org.apache.skywalking.oap.server.telemetry.api.MetricsCreator;
import org.apache.skywalking.oap.server.telemetry.api.MetricsTag;

// OAP Start class , Load profile , Initialization module 
@Slf4j
public class OAPServerBootstrap {
    public static void start() {
        String mode = System.getProperty("mode");
        //  Boot mode 
        RunningMode.setMode(mode);

        ApplicationConfigLoader configLoader = new ApplicationConfigLoader();
        ModuleManager manager = new ModuleManager();
        try {
            //  Load configuration from configuration file 
            ApplicationConfiguration applicationConfiguration = configLoader.load();
            //  Initialization module 
            manager.init(applicationConfiguration);

            //  Send the start time to Telemetry
            manager.find(TelemetryModule.NAME)
                   .provider()
                   .getService(MetricsCreator.class)
                   .createGauge("uptime", "oap server start up time", MetricsTag.EMPTY_KEY, MetricsTag.EMPTY_VALUE)
                   // Set uptime to second
                   .setValue(System.currentTimeMillis() / 1000d);

            if (RunningMode.isInitMode()) {
                log.info("OAP starts up in init mode successfully, exit now...");
                System.exit(0);
            }
        } catch (Throwable t) {
            log.error(t.getMessage(), t);
            System.exit(1);
        }
    }
}

OAPServerStartUp

package org.apache.skywalking.oap.server.starter;

// OAP Start class 
public class OAPServerStartUp {
    public static void main(String[] args) {
        OAPServerBootstrap.start();
    }
}

With Skywalking OAP Start the process analysis module loading mechanism

Sequence diagram

file

Source file :OAPServerStartUp.sdt

Case study : Enclosure load analysis

The configuration file

from application.yml The configuration file , It can be seen that .

Modules are defined in a three-tier structure :

  • first floor : Module definition name
  • The second floor : Provide module name / selector
  • The third level : The module provides configuration information / selector The selected module provides configuration
storage:
  selector: ${SW_STORAGE:h2}
  elasticsearch:
    nameSpace: ${SW_NAMESPACE:""}
    clusterNodes: ${SW_STORAGE_ES_CLUSTER_NODES:localhost:9200}
    # etc...
  elasticsearch7:
    nameSpace: ${SW_NAMESPACE:""}
    clusterNodes: ${SW_STORAGE_ES_CLUSTER_NODES:localhost:9200}
    # etc...
  h2:
    driver: ${SW_STORAGE_H2_DRIVER:org.h2.jdbcx.JdbcDataSource}
    url: ${SW_STORAGE_H2_URL:jdbc:h2:mem:skywalking-oap-db;DB_CLOSE_DELAY=-1}
    # etc...
  mysql:
    properties:
      jdbcUrl: ${SW_JDBC_URL:"jdbc:mysql://localhost:3306/swtest"}
      dataSource.user: ${SW_DATA_SOURCE_USER:root}
      dataSource.password: ${SW_DATA_SOURCE_PASSWORD:root@1234}
      # etc...
  tidb:
    properties:
      jdbcUrl: ${SW_JDBC_URL:"jdbc:mysql://localhost:4000/tidbswtest"}
      dataSource.user: ${SW_DATA_SOURCE_USER:root}
      dataSource.password: ${SW_DATA_SOURCE_PASSWORD:""}
      # etc...
  influxdb:
    url: ${SW_STORAGE_INFLUXDB_URL:http://localhost:8086}
    user: ${SW_STORAGE_INFLUXDB_USER:root}
    password: ${SW_STORAGE_INFLUXDB_PASSWORD:}
    # etc...

Load the configuration

after org.apache.skywalking.oap.server.starter.config.ApplicationConfigLoader#load Call to , org.apache.skywalking.oap.server.starter.OAPServerBootstrap#start Get all the modules that need to be loaded , This includes enclosures .

stay org.apache.skywalking.oap.server.starter.config.ApplicationConfigLoader#selectConfig Also through storage.selector=h2 , The enclosure only retains h2 Configuration information :

storage:
    h2:
    driver: ${SW_STORAGE_H2_DRIVER:org.h2.jdbcx.JdbcDataSource}
    url: ${SW_STORAGE_H2_URL:jdbc:h2:mem:skywalking-oap-db;DB_CLOSE_DELAY=-1}
    # etc...

Preparation stage

stay org.apache.skywalking.oap.server.library.module.ModuleManager#init in , adopt SPI Loaded the module definition object , The definition classes corresponding to the enclosure are as follows :

PS: You can see that a lot of Service  Interface

package org.apache.skywalking.oap.server.core.storage;

import org.apache.skywalking.oap.server.core.storage.cache.INetworkAddressAliasDAO;
import org.apache.skywalking.oap.server.core.storage.management.UITemplateManagementDAO;
import org.apache.skywalking.oap.server.core.storage.profile.IProfileTaskLogQueryDAO;
import org.apache.skywalking.oap.server.core.storage.profile.IProfileTaskQueryDAO;
import org.apache.skywalking.oap.server.core.storage.profile.IProfileThreadSnapshotQueryDAO;
import org.apache.skywalking.oap.server.core.storage.query.IAggregationQueryDAO;
import org.apache.skywalking.oap.server.core.storage.query.IAlarmQueryDAO;
import org.apache.skywalking.oap.server.core.storage.query.IBrowserLogQueryDAO;
import org.apache.skywalking.oap.server.core.storage.query.ILogQueryDAO;
import org.apache.skywalking.oap.server.core.storage.query.IMetadataQueryDAO;
import org.apache.skywalking.oap.server.core.storage.query.IMetricsQueryDAO;
import org.apache.skywalking.oap.server.core.storage.query.ITopNRecordsQueryDAO;
import org.apache.skywalking.oap.server.core.storage.query.ITopologyQueryDAO;
import org.apache.skywalking.oap.server.core.storage.query.ITraceQueryDAO;
import org.apache.skywalking.oap.server.library.module.ModuleDefine;

/**
 * StorageModule provides the capabilities(services) to interact with the database. With different databases, this
 * module could have different providers, such as currently, H2, MySQL, ES, TiDB.
 */
public class StorageModule extends ModuleDefine {

    public static final String NAME = "storage";

    public StorageModule() {
        super(NAME);
    }

    @Override
    public Class[] services() {
        return new Class[]{
                IBatchDAO.class,
                StorageDAO.class,
                IHistoryDeleteDAO.class,
                INetworkAddressAliasDAO.class,
                ITopologyQueryDAO.class,
                IMetricsQueryDAO.class,
                ITraceQueryDAO.class,
                IMetadataQueryDAO.class,
                IAggregationQueryDAO.class,
                IAlarmQueryDAO.class,
                ITopNRecordsQueryDAO.class,
                ILogQueryDAO.class,
                IProfileTaskQueryDAO.class,
                IProfileTaskLogQueryDAO.class,
                IProfileThreadSnapshotQueryDAO.class,
                UITemplateManagementDAO.class,
                IBrowserLogQueryDAO.class
        };
    }
}

It also calls org.apache.skywalking.oap.server.library.module.ModuleDefine#prepare Enter the preparation stage

        String[] moduleNames = applicationConfiguration.moduleList();
        ServiceLoader<ModuleDefine> moduleServiceLoader = ServiceLoader.load(ModuleDefine.class);
        ServiceLoader<ModuleProvider> moduleProviderLoader = ServiceLoader.load(ModuleProvider.class);

        LinkedList<String> moduleList = new LinkedList<>(Arrays.asList(moduleNames));
        for (ModuleDefine module : moduleServiceLoader) {
            for (String moduleName : moduleNames) {
                if (moduleName.equals(module.name())) {
                    module.prepare(this, applicationConfiguration.getModuleConfiguration(moduleName), moduleProviderLoader);
                    loadedModules.put(moduleName, module);
                    moduleList.remove(moduleName);
                }
            }
        }

stay org.apache.skywalking.oap.server.library.module.ModuleDefine#prepare Through the incoming configuration , Only match the modules selected in the configuration file to provide objects .

        for (ModuleProvider provider : moduleProviderLoader) {
            if (!configuration.has(provider.name())) {
                continue;
            }

            if (provider.module().equals(getClass())) {
                if (loadedProvider == null) {
                    loadedProvider = provider;
                    loadedProvider.setManager(moduleManager);
                    loadedProvider.setModuleDefine(this);
                } else {
                    throw new DuplicateProviderException(this.name() + " module has one " + loadedProvider.name() + "[" + loadedProvider.getClass().getName() 
                                                         + "] provider already, " + provider.name() + "[" + provider.getClass().getName() + "] is defined as 2nd provider.");
                }
            }

        }

        if (loadedProvider == null) {
            throw new ProviderNotFoundException(this.name() + " module no provider found.");
        }

        LOGGER.info("Prepare the {} provider in {} module.", loadedProvider.name(), this.name());
        try {
            copyProperties(loadedProvider.createConfigBeanIfAbsent(), configuration.getProviderConfiguration(loadedProvider.name()), this.name(), loadedProvider.name());
        } catch (IllegalAccessException e) {
            throw new ModuleConfigException(this.name() + " module config transport to config bean failure.", e);
        }
        loadedProvider.prepare();

for example “ The configuration file ” A section selected h2 , Then the loaded provider class is org.apache.skywalking.oap.server.storage.plugin.jdbc.h2.H2StorageProvider

its prepare The method is as follows , You can see : Registered all StorageModule Declarative Service Interface

    @Override
    public void prepare() throws ServiceNotProvidedException, ModuleStartException {
        Properties settings = new Properties();
        settings.setProperty("dataSourceClassName", config.getDriver());
        settings.setProperty("dataSource.url", config.getUrl());
        settings.setProperty("dataSource.user", config.getUser());
        settings.setProperty("dataSource.password", config.getPassword());
        h2Client = new JDBCHikariCPClient(settings);

        this.registerServiceImplementation(IBatchDAO.class, new H2BatchDAO(h2Client));
        this.registerServiceImplementation(
            StorageDAO.class,
            new H2StorageDAO(
                getManager(), h2Client, config.getMaxSizeOfArrayColumn(), config.getNumOfSearchableValuesPerTag())
        );

        this.registerServiceImplementation(
            INetworkAddressAliasDAO.class, new H2NetworkAddressAliasDAO(h2Client));

        this.registerServiceImplementation(ITopologyQueryDAO.class, new H2TopologyQueryDAO(h2Client));
        this.registerServiceImplementation(IMetricsQueryDAO.class, new H2MetricsQueryDAO(h2Client));
        this.registerServiceImplementation(
            ITraceQueryDAO.class, new H2TraceQueryDAO(
                getManager(),
                h2Client,
                config.getMaxSizeOfArrayColumn(),
                config.getNumOfSearchableValuesPerTag()
            ));
        this.registerServiceImplementation(IBrowserLogQueryDAO.class, new H2BrowserLogQueryDAO(h2Client));
        this.registerServiceImplementation(
            IMetadataQueryDAO.class, new H2MetadataQueryDAO(h2Client, config.getMetadataQueryMaxSize()));
        this.registerServiceImplementation(IAggregationQueryDAO.class, new H2AggregationQueryDAO(h2Client));
        this.registerServiceImplementation(IAlarmQueryDAO.class, new H2AlarmQueryDAO(h2Client));
        this.registerServiceImplementation(
            IHistoryDeleteDAO.class, new H2HistoryDeleteDAO(h2Client));
        this.registerServiceImplementation(ITopNRecordsQueryDAO.class, new H2TopNRecordsQueryDAO(h2Client));
        this.registerServiceImplementation(
            ILogQueryDAO.class,
            new H2LogQueryDAO(
                h2Client,
                getManager(),
                config.getMaxSizeOfArrayColumn(),
                config.getNumOfSearchableValuesPerTag()
            )
        );

        this.registerServiceImplementation(IProfileTaskQueryDAO.class, new H2ProfileTaskQueryDAO(h2Client));
        this.registerServiceImplementation(IProfileTaskLogQueryDAO.class, new H2ProfileTaskLogQueryDAO(h2Client));
        this.registerServiceImplementation(
            IProfileThreadSnapshotQueryDAO.class, new H2ProfileThreadSnapshotQueryDAO(h2Client));
        this.registerServiceImplementation(UITemplateManagementDAO.class, new H2UITemplateManagementDAO(h2Client));
    }

Start-up phase

stay org.apache.skywalking.oap.server.library.module.ModuleManager#init By calling org.apache.skywalking.oap.server.library.module.BootstrapFlow#start Enter start-up phase

    void start(
        ModuleManager moduleManager) throws ModuleNotFoundException, ServiceNotProvidedException, ModuleStartException {
        for (ModuleProvider provider : startupSequence) {
            LOGGER.info("start the provider {} in {} module.", provider.name(), provider.getModuleName());
            provider.requiredCheck(provider.getModule().services());

            provider.start();
        }
    }

for example “ The configuration file ” A section selected h2 , Then the loaded provider class is org.apache.skywalking.oap.server.storage.plugin.jdbc.h2.H2StorageProvider

its start The method is as follows , You can see : start-up h2client And monitor ModelCreator

    @Override
    public void start() throws ServiceNotProvidedException, ModuleStartException {
        final ConfigService configService = getManager().find(CoreModule.NAME)
                                                        .provider()
                                                        .getService(ConfigService.class);
        final int numOfSearchableTracesTags = configService.getSearchableTracesTags().split(Const.COMMA).length;
        if (numOfSearchableTracesTags * config.getNumOfSearchableValuesPerTag() > config.getMaxSizeOfArrayColumn()) {
            throw new ModuleStartException("Size of searchableTracesTags[" + numOfSearchableTracesTags
                                               + "] * numOfSearchableValuesPerTag[" + config.getNumOfSearchableValuesPerTag()
                                               + "] > maxSizeOfArrayColumn[" + config.getMaxSizeOfArrayColumn()
                                               + "]. Potential out of bound in the runtime.");
        }
        final int numOfSearchableLogsTags = configService.getSearchableLogsTags().split(Const.COMMA).length;
        if (numOfSearchableLogsTags * config.getNumOfSearchableValuesPerTag() > config.getMaxSizeOfArrayColumn()) {
            throw new ModuleStartException("Size of searchableLogsTags[" + numOfSearchableLogsTags
                                               + "] * numOfSearchableValuesPerTag[" + config.getNumOfSearchableValuesPerTag()
                                               + "] > maxSizeOfArrayColumn[" + config.getMaxSizeOfArrayColumn()
                                               + "]. Potential out of bound in the runtime.");
        }

        MetricsCreator metricCreator = getManager().find(TelemetryModule.NAME)
                                                   .provider()
                                                   .getService(MetricsCreator.class);
        HealthCheckMetrics healthChecker = metricCreator.createHealthCheckerGauge(
            "storage_h2", MetricsTag.EMPTY_KEY, MetricsTag.EMPTY_VALUE);
        h2Client.registerChecker(healthChecker);
        try {
            h2Client.connect();

            H2TableInstaller installer = new H2TableInstaller(
                h2Client, getManager(), config.getMaxSizeOfArrayColumn(), config.getNumOfSearchableValuesPerTag());
            getManager().find(CoreModule.NAME).provider().getService(ModelCreator.class).addModelListener(installer);
        } catch (StorageException e) {
            throw new ModuleStartException(e.getMessage(), e);
        }
    }

Notification stage after completion

stay org.apache.skywalking.oap.server.library.module.ModuleManager#init By calling org.apache.skywalking.oap.server.library.module.BootstrapFlow#notifyAfterCompleted Enter the post completion notification stage

    void notifyAfterCompleted() throws ServiceNotProvidedException, ModuleStartException {
        for (ModuleProvider provider : startupSequence) {
            provider.notifyAfterCompleted();
        }
    }

for example “ The configuration file ” A section selected h2 , Then the loaded provider class is org.apache.skywalking.oap.server.storage.plugin.jdbc.h2.H2StorageProvider

its notifyAfterCompleted The method is as follows , You can see : There's nothing to do

    @Override
    public void notifyAfterCompleted() throws ServiceNotProvidedException, ModuleStartException {

    }

H2StorageProvider Complete source code

package org.apache.skywalking.oap.server.storage.plugin.jdbc.h2;

// etc...

/**
 * H2 Storage provider is for demonstration and preview only. I will find that haven't implemented several interfaces,
 * because not necessary, and don't consider about performance very much.
 * <p>
 * If someone wants to implement SQL-style database as storage, please just refer the logic.
 */
@Slf4j
public class H2StorageProvider extends ModuleProvider {

    private H2StorageConfig config;
    private JDBCHikariCPClient h2Client;

    public H2StorageProvider() {
        config = new H2StorageConfig();
    }

    @Override
    public String name() {
        return "h2";
    }

    @Override
    public Class<? extends ModuleDefine> module() {
        return StorageModule.class;
    }

    @Override
    public ModuleConfig createConfigBeanIfAbsent() {
        return config;
    }

    @Override
    public void prepare() throws ServiceNotProvidedException, ModuleStartException {
        Properties settings = new Properties();
        settings.setProperty("dataSourceClassName", config.getDriver());
        settings.setProperty("dataSource.url", config.getUrl());
        settings.setProperty("dataSource.user", config.getUser());
        settings.setProperty("dataSource.password", config.getPassword());
        h2Client = new JDBCHikariCPClient(settings);

        this.registerServiceImplementation(IBatchDAO.class, new H2BatchDAO(h2Client));
        this.registerServiceImplementation(
            StorageDAO.class,
            new H2StorageDAO(
                getManager(), h2Client, config.getMaxSizeOfArrayColumn(), config.getNumOfSearchableValuesPerTag())
        );

        this.registerServiceImplementation(
            INetworkAddressAliasDAO.class, new H2NetworkAddressAliasDAO(h2Client));

        this.registerServiceImplementation(ITopologyQueryDAO.class, new H2TopologyQueryDAO(h2Client));
        this.registerServiceImplementation(IMetricsQueryDAO.class, new H2MetricsQueryDAO(h2Client));
        this.registerServiceImplementation(
            ITraceQueryDAO.class, new H2TraceQueryDAO(
                getManager(),
                h2Client,
                config.getMaxSizeOfArrayColumn(),
                config.getNumOfSearchableValuesPerTag()
            ));
        this.registerServiceImplementation(IBrowserLogQueryDAO.class, new H2BrowserLogQueryDAO(h2Client));
        this.registerServiceImplementation(
            IMetadataQueryDAO.class, new H2MetadataQueryDAO(h2Client, config.getMetadataQueryMaxSize()));
        this.registerServiceImplementation(IAggregationQueryDAO.class, new H2AggregationQueryDAO(h2Client));
        this.registerServiceImplementation(IAlarmQueryDAO.class, new H2AlarmQueryDAO(h2Client));
        this.registerServiceImplementation(
            IHistoryDeleteDAO.class, new H2HistoryDeleteDAO(h2Client));
        this.registerServiceImplementation(ITopNRecordsQueryDAO.class, new H2TopNRecordsQueryDAO(h2Client));
        this.registerServiceImplementation(
            ILogQueryDAO.class,
            new H2LogQueryDAO(
                h2Client,
                getManager(),
                config.getMaxSizeOfArrayColumn(),
                config.getNumOfSearchableValuesPerTag()
            )
        );

        this.registerServiceImplementation(IProfileTaskQueryDAO.class, new H2ProfileTaskQueryDAO(h2Client));
        this.registerServiceImplementation(IProfileTaskLogQueryDAO.class, new H2ProfileTaskLogQueryDAO(h2Client));
        this.registerServiceImplementation(
            IProfileThreadSnapshotQueryDAO.class, new H2ProfileThreadSnapshotQueryDAO(h2Client));
        this.registerServiceImplementation(UITemplateManagementDAO.class, new H2UITemplateManagementDAO(h2Client));
    }

    @Override
    public void start() throws ServiceNotProvidedException, ModuleStartException {
        final ConfigService configService = getManager().find(CoreModule.NAME)
                                                        .provider()
                                                        .getService(ConfigService.class);
        final int numOfSearchableTracesTags = configService.getSearchableTracesTags().split(Const.COMMA).length;
        if (numOfSearchableTracesTags * config.getNumOfSearchableValuesPerTag() > config.getMaxSizeOfArrayColumn()) {
            throw new ModuleStartException("Size of searchableTracesTags[" + numOfSearchableTracesTags
                                               + "] * numOfSearchableValuesPerTag[" + config.getNumOfSearchableValuesPerTag()
                                               + "] > maxSizeOfArrayColumn[" + config.getMaxSizeOfArrayColumn()
                                               + "]. Potential out of bound in the runtime.");
        }
        final int numOfSearchableLogsTags = configService.getSearchableLogsTags().split(Const.COMMA).length;
        if (numOfSearchableLogsTags * config.getNumOfSearchableValuesPerTag() > config.getMaxSizeOfArrayColumn()) {
            throw new ModuleStartException("Size of searchableLogsTags[" + numOfSearchableLogsTags
                                               + "] * numOfSearchableValuesPerTag[" + config.getNumOfSearchableValuesPerTag()
                                               + "] > maxSizeOfArrayColumn[" + config.getMaxSizeOfArrayColumn()
                                               + "]. Potential out of bound in the runtime.");
        }

        MetricsCreator metricCreator = getManager().find(TelemetryModule.NAME)
                                                   .provider()
                                                   .getService(MetricsCreator.class);
        HealthCheckMetrics healthChecker = metricCreator.createHealthCheckerGauge(
            "storage_h2", MetricsTag.EMPTY_KEY, MetricsTag.EMPTY_VALUE);
        h2Client.registerChecker(healthChecker);
        try {
            h2Client.connect();

            H2TableInstaller installer = new H2TableInstaller(
                h2Client, getManager(), config.getMaxSizeOfArrayColumn(), config.getNumOfSearchableValuesPerTag());
            getManager().find(CoreModule.NAME).provider().getService(ModelCreator.class).addModelListener(installer);
        } catch (StorageException e) {
            throw new ModuleStartException(e.getMessage(), e);
        }
    }

    @Override
    public void notifyAfterCompleted() throws ServiceNotProvidedException, ModuleStartException {

    }

    @Override
    public String[] requiredModules() {
        return new String[] {CoreModule.NAME};
    }
}

summary

Skywalking The module mechanism provided is very well designed , At work , If there are more than one N choose 1 Scene , We can learn from its design .

Reference documents

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https://chowdera.com/2021/10/20211002145413006w.html

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