渣渣菜鸡的 ElasticSearch 源码解析 —— 启动流程(上)

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zhisheng

转载请务必注明原创地址为:http://www.54tianzhisheng.cn/2018/08/11/es-code02/

前提

上篇文章写了 ElasticSearch 源码解析 —— 环境搭建 ,其中里面说了启动 打开 server 模块下的 Elasticsearch 类:org.elasticsearch.bootstrap.Elasticsearch,运行里面的 main 函数就可以启动 ElasticSearch 了,这篇文章讲讲启动流程,因为篇幅会很多,所以分了两篇来写。

启动流程

main 方法入口

可以看到入口其实是一个 main 方法,方法里面先是检查权限,然后是一个错误日志监听器(确保在日志配置之前状态日志没有出现 error),然后是 Elasticsearch 对象的创建,然后调用了静态方法 main 方法(18 行),并把创建的对象和参数以及 Terminal 默认值传进去。静态的 main 方法里面调用 elasticsearch.main 方法。

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public static void main(final String[] args) throws Exception {         //1、入口
// we want the JVM to think there is a security manager installed so that if internal policy decisions that would be based on the
// presence of a security manager or lack thereof act as if there is a security manager present (e.g., DNS cache policy)
System.setSecurityManager(new SecurityManager() {
@Override
public void checkPermission(Permission perm) {
// grant all permissions so that we can later set the security manager to the one that we want
}
});
LogConfigurator.registerErrorListener(); //
final Elasticsearch elasticsearch = new Elasticsearch();
int status = main(args, elasticsearch, Terminal.DEFAULT); //2、调用Elasticsearch.main方法
if (status != ExitCodes.OK) {
exit(status);
}
}

static int main(final String[] args, final Elasticsearch elasticsearch, final Terminal terminal) throws Exception {
return elasticsearch.main(args, terminal); //3、command main
}

1es01

因为 Elasticsearch 类是继承了 EnvironmentAwareCommand 类,EnvironmentAwareCommand 类继承了 Command 类,但是 Elasticsearch 类并没有重写 main 方法,所以上面调用的 elasticsearch.main 其实是调用了 Command 的 main 方法,代码如下:

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/** Parses options for this command from args and executes it. */
public final int main(String[] args, Terminal terminal) throws Exception {
if (addShutdownHook()) { //利用Runtime.getRuntime().addShutdownHook方法加入一个Hook,在程序退出时触发该Hook
shutdownHookThread = new Thread(() -> {
try {
this.close();
} catch (final IOException e) {
try (
StringWriter sw = new StringWriter();
PrintWriter pw = new PrintWriter(sw)) {
e.printStackTrace(pw);
terminal.println(sw.toString());
} catch (final IOException impossible) {
// StringWriter#close declares a checked IOException from the Closeable interface but the Javadocs for StringWriter
// say that an exception here is impossible
throw new AssertionError(impossible);
}
}
});
Runtime.getRuntime().addShutdownHook(shutdownHookThread);
}

beforeMain.run();

try {
mainWithoutErrorHandling(args, terminal);//4、mainWithoutErrorHandling
} catch (OptionException e) {
printHelp(terminal);
terminal.println(Terminal.Verbosity.SILENT, "ERROR: " + e.getMessage());
return ExitCodes.USAGE;
} catch (UserException e) {
if (e.exitCode == ExitCodes.USAGE) {
printHelp(terminal);
}
terminal.println(Terminal.Verbosity.SILENT, "ERROR: " + e.getMessage());
return e.exitCode;
}
return ExitCodes.OK;
}

上面代码一开始利用一个勾子函数,在程序退出时触发该 Hook,该方法主要代码是 mainWithoutErrorHandling() 方法,然后下面的是 catch 住方法抛出的异常,方法代码如下:

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/*** Executes the command, but all errors are thrown. */
void mainWithoutErrorHandling(String[] args, Terminal terminal) throws Exception {
final OptionSet options = parser.parse(args);
if (options.has(helpOption)) {
printHelp(terminal);
return;
}
if (options.has(silentOption)) {
terminal.setVerbosity(Terminal.Verbosity.SILENT);
} else if (options.has(verboseOption)) {
terminal.setVerbosity(Terminal.Verbosity.VERBOSE);
} else {
terminal.setVerbosity(Terminal.Verbosity.NORMAL);
}
execute(terminal, options);//5、执行 EnvironmentAwareCommand 中的 execute(),(重写了command里面抽象的execute方法)
}

上面的代码从 3 ~ 14 行是解析传进来的参数并配置 terminal,重要的 execute() 方法,执行的是 EnvironmentAwareCommand 中的 execute() (重写了 Command 类里面的抽象 execute 方法),从上面那个继承图可以看到 EnvironmentAwareCommand 继承了 Command,重写的 execute 方法代码如下:

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@Override
protected void execute(Terminal terminal, OptionSet options) throws Exception {
final Map<String, String> settings = new HashMap<>();
for (final KeyValuePair kvp : settingOption.values(options)) {
if (kvp.value.isEmpty()) {
throw new UserException(ExitCodes.USAGE, "setting [" + kvp.key + "] must not be empty");
}
if (settings.containsKey(kvp.key)) {
final String message = String.format(
Locale.ROOT, "setting [%s] already set, saw [%s] and [%s]",
kvp.key, settings.get(kvp.key), kvp.value);
throw new UserException(ExitCodes.USAGE, message);
}
settings.put(kvp.key, kvp.value);
}
//6、根据我们ide配置的 vm options 进行设置path.data、path.home、path.logs
putSystemPropertyIfSettingIsMissing(settings, "path.data", "es.path.data");
putSystemPropertyIfSettingIsMissing(settings, "path.home", "es.path.home");
putSystemPropertyIfSettingIsMissing(settings, "path.logs", "es.path.logs");

execute(terminal, options, createEnv(terminal, settings));//7、先调用 createEnv 创建环境
//9、执行elasticsearch的execute方法,elasticsearch中重写了EnvironmentAwareCommand中的抽象execute方法
}

方法前面是根据传参去判断配置的,如果配置为空,就会直接跳到执行 putSystemPropertyIfSettingIsMissing 方法,这里会配置三个属性:path.data、path.home、path.logs 设置 es 的 data、home、logs 目录,它这里是根据我们 ide 配置的 vm options 进行设置的,这也是为什么我们上篇文章说的配置信息,如果不配置的话就会直接报错。下面看看 putSystemPropertyIfSettingIsMissing 方法代码里面怎么做到的:

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/** Ensure the given setting exists, reading it from system properties if not already set. */
private static void putSystemPropertyIfSettingIsMissing(final Map<String, String> settings, final String setting, final String key) {
final String value = System.getProperty(key);//获取key(es.path.data)找系统设置
if (value != null) {
if (settings.containsKey(setting)) {
final String message =
String.format(
Locale.ROOT,
"duplicate setting [%s] found via command-line [%s] and system property [%s]",
setting, settings.get(setting), value);
throw new IllegalArgumentException(message);
} else {
settings.put(setting, value);
}
}
}

执行这三个方法后:

2es02

跳出此方法,继续看会发现 execute 方法调用了方法,

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execute(terminal, options, createEnv(terminal, settings));

这里我们先看看 createEnv(terminal, settings) 方法:

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protected Environment createEnv(final Terminal terminal, final Map<String, String> settings) throws UserException {
final String esPathConf = System.getProperty("es.path.conf");//8、读取我们 vm options 中配置的 es.path.conf
if (esPathConf == null) {
throw new UserException(ExitCodes.CONFIG, "the system property [es.path.conf] must be set");
}
return InternalSettingsPreparer.prepareEnvironment(Settings.EMPTY, terminal, settings, getConfigPath(esPathConf)); //8、准备环境 prepareEnvironment
}

读取我们 ide vm options 中配置的 es.path.conf,同上篇文章也讲了这个一定要配置的,因为 es 启动的时候会加载我们的配置和一些插件。这里继续看下上面代码第 6 行的 prepareEnvironment 方法:

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public static Environment prepareEnvironment(Settings input, Terminal terminal, Map<String, String> properties, Path configPath) {
// just create enough settings to build the environment, to get the config dir
Settings.Builder output = Settings.builder();
initializeSettings(output, input, properties);
Environment environment = new Environment(output.build(), configPath);

//查看 es.path.conf 目录下的配置文件是不是 yml 格式的,如果不是则抛出一个异常
if (Files.exists(environment.configFile().resolve("elasticsearch.yaml"))) {
throw new SettingsException("elasticsearch.yaml was deprecated in 5.5.0 and must be renamed to elasticsearch.yml");
}

if (Files.exists(environment.configFile().resolve("elasticsearch.json"))) {
throw new SettingsException("elasticsearch.json was deprecated in 5.5.0 and must be converted to elasticsearch.yml");
}

output = Settings.builder(); // start with a fresh output
Path path = environment.configFile().resolve("elasticsearch.yml");
if (Files.exists(path)) {
try {
output.loadFromPath(path); //加载文件并读取配置文件内容
} catch (IOException e) {
throw new SettingsException("Failed to load settings from " + path.toString(), e);
}
}

// re-initialize settings now that the config file has been loaded
initializeSettings(output, input, properties); //再一次初始化设置
finalizeSettings(output, terminal);

environment = new Environment(output.build(), configPath);

// we put back the path.logs so we can use it in the logging configuration file
output.put(Environment.PATH_LOGS_SETTING.getKey(), environment.logsFile().toAbsolutePath().normalize().toString());
return new Environment(output.build(), configPath);
}

3es03

准备的环境如上图,通过构建的环境查看配置文件 elasticsearch.yml 是不是以 yml 结尾,如果是 yaml 或者 json 结尾的则抛出异常(在 5.5.0 版本其他两种格式过期了,只能使用 yml 格式),然后加载该配置文件并读取里面的内容(KV结构)。

跳出 createEnv 方法,我们继续看 execute 方法吧。

EnvironmentAwareCommand 类的 execute 方法代码如下:

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protected abstract void execute(Terminal terminal, OptionSet options, Environment env) throws Exception;

这是个抽象方法,那么它的实现方法在 Elasticsearch 类中,代码如下:

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@Override
protected void execute(Terminal terminal, OptionSet options, Environment env) throws UserException {
if (options.nonOptionArguments().isEmpty() == false) {
throw new UserException(ExitCodes.USAGE, "Positional arguments not allowed, found " + options.nonOptionArguments());
}
if (options.has(versionOption)) {
final String versionOutput = String.format(
Locale.ROOT,
"Version: %s, Build: %s/%s/%s/%s, JVM: %s",
Version.displayVersion(Version.CURRENT, Build.CURRENT.isSnapshot()),
Build.CURRENT.flavor().displayName(),
Build.CURRENT.type().displayName(),
Build.CURRENT.shortHash(),
Build.CURRENT.date(),
JvmInfo.jvmInfo().version());
terminal.println(versionOutput);
return;
}

final boolean daemonize = options.has(daemonizeOption);
final Path pidFile = pidfileOption.value(options);
final boolean quiet = options.has(quietOption);

// a misconfigured java.io.tmpdir can cause hard-to-diagnose problems later, so reject it immediately
try {
env.validateTmpFile();
} catch (IOException e) {
throw new UserException(ExitCodes.CONFIG, e.getMessage());
}
try {
init(daemonize, pidFile, quiet, env); //10、初始化
} catch (NodeValidationException e) {
throw new UserException(ExitCodes.CONFIG, e.getMessage());
}
}

上面代码里主要还是看看 init(daemonize, pidFile, quiet, env); 初始化方法吧。

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void init(final boolean daemonize, final Path pidFile, final boolean quiet, Environment initialEnv)
throws NodeValidationException, UserException {
try {
Bootstrap.init(!daemonize, pidFile, quiet, initialEnv); //11、执行 Bootstrap 中的 init 方法
} catch (BootstrapException | RuntimeException e) {
// format exceptions to the console in a special way
// to avoid 2MB stacktraces from guice, etc.
throw new StartupException(e);
}
}

init 方法

Bootstrap 中的静态 init 方法如下:

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static void init(
final boolean foreground,
final Path pidFile,
final boolean quiet,
final Environment initialEnv) throws BootstrapException, NodeValidationException, UserException {
// force the class initializer for BootstrapInfo to run before
// the security manager is installed
BootstrapInfo.init();

INSTANCE = new Bootstrap(); //12、创建一个 Bootstrap 实例

final SecureSettings keystore = loadSecureSettings(initialEnv);//如果注册了安全模块则将相关配置加载进来
final Environment environment = createEnvironment(foreground, pidFile, keystore, initialEnv.settings(), initialEnv.configFile()); //干之前干过的事情
try {
LogConfigurator.configure(environment); //13、log 配置环境
} catch (IOException e) {
throw new BootstrapException(e);
}
if (environment.pidFile() != null) {
try {
PidFile.create(environment.pidFile(), true);
} catch (IOException e) {
throw new BootstrapException(e);
}
}

final boolean closeStandardStreams = (foreground == false) || quiet;
try {
if (closeStandardStreams) {
final Logger rootLogger = ESLoggerFactory.getRootLogger();
final Appender maybeConsoleAppender = Loggers.findAppender(rootLogger, ConsoleAppender.class);
if (maybeConsoleAppender != null) {
Loggers.removeAppender(rootLogger, maybeConsoleAppender);
}
closeSystOut();
}

// fail if somebody replaced the lucene jars
checkLucene(); //14、检查Lucene版本

// install the default uncaught exception handler; must be done before security is initialized as we do not want to grant the runtime permission setDefaultUncaughtExceptionHandler
Thread.setDefaultUncaughtExceptionHandler(
new ElasticsearchUncaughtExceptionHandler(() -> Node.NODE_NAME_SETTING.get(environment.settings())));

INSTANCE.setup(true, environment); //15、调用 setup 方法

try {
// any secure settings must be read during node construction
IOUtils.close(keystore);
} catch (IOException e) {
throw new BootstrapException(e);
}

INSTANCE.start(); //26、调用 start 方法

if (closeStandardStreams) {
closeSysError();
}
} catch (NodeValidationException | RuntimeException e) {
// disable console logging, so user does not see the exception twice (jvm will show it already)
final Logger rootLogger = ESLoggerFactory.getRootLogger();
final Appender maybeConsoleAppender = Loggers.findAppender(rootLogger, ConsoleAppender.class);
if (foreground && maybeConsoleAppender != null) {
Loggers.removeAppender(rootLogger, maybeConsoleAppender);
}
Logger logger = Loggers.getLogger(Bootstrap.class);
if (INSTANCE.node != null) {
logger = Loggers.getLogger(Bootstrap.class, Node.NODE_NAME_SETTING.get(INSTANCE.node.settings()));
}
// HACK, it sucks to do this, but we will run users out of disk space otherwise
if (e instanceof CreationException) {
// guice: log the shortened exc to the log file
ByteArrayOutputStream os = new ByteArrayOutputStream();
PrintStream ps = null;
try {
ps = new PrintStream(os, false, "UTF-8");
} catch (UnsupportedEncodingException uee) {
assert false;
e.addSuppressed(uee);
}
new StartupException(e).printStackTrace(ps);
ps.flush();
try {
logger.error("Guice Exception: {}", os.toString("UTF-8"));
} catch (UnsupportedEncodingException uee) {
assert false;
e.addSuppressed(uee);
}
} else if (e instanceof NodeValidationException) {
logger.error("node validation exception\n{}", e.getMessage());
} else {
// full exception
logger.error("Exception", e);
}
// re-enable it if appropriate, so they can see any logging during the shutdown process
if (foreground && maybeConsoleAppender != null) {
Loggers.addAppender(rootLogger, maybeConsoleAppender);
}
throw e;
}
}

该方法主要有:

1、创建 Bootstrap 实例

2、如果注册了安全模块则将相关配置加载进来

3、创建 Elasticsearch 运行的必须环境以及相关配置, 如将 config、scripts、plugins、modules、logs、lib、bin 等配置目录加载到运行环境中

4、log 配置环境,创建日志上下文

5、检查是否存在 PID 文件,如果不存在,创建 PID 文件

6、检查 Lucene 版本

7、调用 setup 方法(用当前环境来创建一个节点)

setup 方法

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private void setup(boolean addShutdownHook, Environment environment) throws BootstrapException {
Settings settings = environment.settings();//根据环境得到配置
try {
spawner.spawnNativeControllers(environment);
} catch (IOException e) {
throw new BootstrapException(e);
}
initializeNatives(
environment.tmpFile(),
BootstrapSettings.MEMORY_LOCK_SETTING.get(settings),
BootstrapSettings.SYSTEM_CALL_FILTER_SETTING.get(settings),
BootstrapSettings.CTRLHANDLER_SETTING.get(settings));
// initialize probes before the security manager is installed
initializeProbes();
if (addShutdownHook) {
Runtime.getRuntime().addShutdownHook(new Thread() {
@Override
public void run() {
try {
IOUtils.close(node, spawner);
LoggerContext context = (LoggerContext) LogManager.getContext(false);
Configurator.shutdown(context);
} catch (IOException ex) {
throw new ElasticsearchException("failed to stop node", ex);
}
}
});
}
try {
// look for jar hell
final Logger logger = ESLoggerFactory.getLogger(JarHell.class);
JarHell.checkJarHell(logger::debug);
} catch (IOException | URISyntaxException e) {
throw new BootstrapException(e);
}
// Log ifconfig output before SecurityManager is installed
IfConfig.logIfNecessary();
// install SM after natives, shutdown hooks, etc.
try {
Security.configure(environment, BootstrapSettings.SECURITY_FILTER_BAD_DEFAULTS_SETTING.get(settings));
} catch (IOException | NoSuchAlgorithmException e) {
throw new BootstrapException(e);
}
node = new Node(environment) { //16、新建节点
@Override
protected void validateNodeBeforeAcceptingRequests(
final BootstrapContext context,
final BoundTransportAddress boundTransportAddress, List<BootstrapCheck> checks) throws NodeValidationException {
BootstrapChecks.check(context, boundTransportAddress, checks);
}
};
}

上面代码最后就是 Node 节点的创建,这篇文章就不讲 Node 的创建了,下篇文章会好好讲一下 Node 节点的创建和正式启动 ES 节点的。

总结

这篇文章主要先把大概启动流程串通,因为篇幅较多所以拆开成两篇,先不扣细节了,后面流程启动文章写完后我们再单一的扣细节。

相关文章

1、渣渣菜鸡为什么要看 ElasticSearch 源码?

2、渣渣菜鸡的 ElasticSearch 源码解析 —— 环境搭建

3、渣渣菜鸡的 ElasticSearch 源码解析 —— 启动流程(上)

4、渣渣菜鸡的 ElasticSearch 源码解析 —— 启动流程(下)

5、Elasticsearch 系列文章(一):Elasticsearch 默认分词器和中分分词器之间的比较及使用方法

6、Elasticsearch 系列文章(二):全文搜索引擎 Elasticsearch 集群搭建入门教程

7、Elasticsearch 系列文章(三):ElasticSearch 集群监控

8、Elasticsearch 系列文章(四):ElasticSearch 单个节点监控

9、Elasticsearch 系列文章(五):ELK 实时日志分析平台环境搭建

10、教你如何在 IDEA 远程 Debug ElasticSearch

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文章目录
  1. 1. 关注我
  2. 2. 前提
  3. 3. 启动流程
    1. 3.1. main 方法入口
    2. 3.2. init 方法
    3. 3.3. setup 方法
  4. 4. 总结
  5. 5. 相关文章