Elasticsearch學習總結五 elasticSearch插件機制源碼解析
一.首先看看Elasticsearch中插件是如何安裝的c++
咱們安裝好es後，若是要安裝插件須要在 /usr/local/elasticsearch/bin的目錄下使用plugin這個shell腳本，仔細看了下這個shell腳本，發現裏面主要是運行了org.elasticsearch.plugins.PluginManager這個類 exec "$JAVA" $JAVA_OPTS $ES_JAVA_OPTS -Xmx64m -Xms16m -Delasticsearch -Des.path.home="$ES_HOME" $properties -cp "$ES_HOME/lib/*" org.elasticsearch.plugins.PluginManager $argsshell
下面咱們進入PluginManager這個類中看看是如何下載安裝插件的，如何執行這個類，確定應該有個main方法吧，果然如此，下面是pluginManager的main方法less
public static void main(String[] args) {
..........
String url = null;
OutputMode outputMode = OutputMode.DEFAULT;
String pluginName = null;
TimeValue timeout = DEFAULT_TIMEOUT;
int action = ACTION.NONE;
if (args.length < 1) {
displayHelp(null);
}
try {
for (int c = 0; c < args.length; c++) {
String command = args[c];
switch (command) {
case "-u":
case "--url":
// deprecated versions:
case "url":
case "-url":
url = getCommandValue(args, ++c, "--url");
// Until update is supported, then supplying a URL implies installing
// By specifying this action, we also avoid silently failing without
// dubious checks.
action = ACTION.INSTALL;
break;
case "-v":
case "--verbose":
// deprecated versions:
case "verbose":
case "-verbose":
outputMode = OutputMode.VERBOSE;
break;
case "-s":
case "--silent":
// deprecated versions:
case "silent":
case "-silent":
outputMode = OutputMode.SILENT;
break;
case "-i":
case "--install":
// deprecated versions:
case "install":
case "-install":
pluginName = getCommandValue(args, ++c, "--install");
action = ACTION.INSTALL;
break;
case "-r":
case "--remove":
// deprecated versions:
case "remove":
case "-remove":
pluginName = getCommandValue(args, ++c, "--remove");
action = ACTION.REMOVE;
break;
case "-t":
case "--timeout":
// deprecated versions:
case "timeout":
case "-timeout":
String timeoutValue = getCommandValue(args, ++c, "--timeout");
timeout = TimeValue.parseTimeValue(timeoutValue, DEFAULT_TIMEOUT);
break;
case "-l":
case "--list":
action = ACTION.LIST;
break;
case "-h":
case "--help":
displayHelp(null);
break;
default:
displayHelp("Command [" + command + "] unknown.");
// Unknown command. We break...
System.exit(EXIT_CODE_CMD_USAGE);
}
}
} catch (Throwable e) {
displayHelp("Error while parsing options: " + e.getClass().getSimpleName() +
": " + e.getMessage());
System.exit(EXIT_CODE_CMD_USAGE);
}
上面代碼中，就是當你輸入各類命令的時候，pluginManager都會根據響應的命令觸發不一樣的動做，例如輸入./plugin list 就會顯示當前es安裝了那些插件elasticsearch
當輸入 plugin -install mobz/elasticsearch-head 命令的時候，pluginManager就會去獲取當前插件名稱， pluginName = getCommandValue(args, ++c, "--install"); 而且將 action賦值 action = ACTION.INSTALL; 當完成賦值後會繼續執行以下代碼，這部分代碼主要構造PluginManger對象，而且根據action的動做去執行相應的操做，pluginManager.downloadAndExtract(pluginName);會根據插件名稱去下載相應的插件模塊化
................
if (action > ACTION.NONE) {
int exitCode = EXIT_CODE_ERROR; // we fail unless it's reset
//構造pluginManger
PluginManager pluginManager = new PluginManager(initialSettings.v2(), url, outputMode, timeout);
switch (action) {
case ACTION.INSTALL:
try {
pluginManager.log("-> Installing " + Strings.nullToEmpty(pluginName) + "...");
pluginManager.downloadAndExtract(pluginName);//執行下載解壓任務
exitCode = EXIT_CODE_OK;
} catch (IOException e) {
exitCode = EXIT_CODE_IO_ERROR;
pluginManager.log("Failed to install " + pluginName + ", reason: " + e.getMessage());
} catch (Throwable e) {
exitCode = EXIT_CODE_ERROR;
displayHelp("Error while installing plugin, reason: " + e.getClass().getSimpleName() +
": " + e.getMessage());
}
break;
.........................
PluginManager的構造函數主要是傳入下載地址，延時時長等，下面看下downloadAndExtract下載安裝是如何工做的函數
public void downloadAndExtract(String name) throws IOException {
.....
HttpDownloadHelper downloadHelper = new HttpDownloadHelper();
boolean downloaded = false;
HttpDownloadHelper.DownloadProgress progress;
if (outputMode == OutputMode.SILENT) {
progress = new HttpDownloadHelper.NullProgress();
} else {
progress = new HttpDownloadHelper.VerboseProgress(System.out);
}
.........
if (url != null) {
URL pluginUrl = new URL(url);
log("Trying " + pluginUrl.toExternalForm() + "...");
try {
downloaded = true;
downloadHelper.download(pluginUrl, pluginFile, progress, this.timeout);
} catch (ElasticsearchTimeoutException e) {
throw e;
} catch (Exception e) {
// ignore
log("Failed: " + ExceptionsHelper.detailedMessage(e));
}
}
主要是經過構建HttpDownloadHelper 實現http下載，而且實現了一個下載進度器，這就是咱們安裝插件的時候會有一些輸出的緣由，經過downloadHelper.download(pluginUrl, pluginFile, progress, this.timeout);能夠真正的實現下載，這裏就不在贅述了，當下載完畢後，會去執行解壓和安裝的過程，在解壓文件時候越過父文件夾，將文件解壓到指定目錄，好比head文件夾中，至此下載安裝基本完畢ui
ZipFile zipFile = null;
try {
zipFile = new ZipFile(pluginFile);
boolean removeTopLevelDir = topLevelDirInExcess(zipFile);
Enumeration<? extends ZipEntry> zipEntries = zipFile.entries();
while (zipEntries.hasMoreElements()) {
ZipEntry zipEntry = zipEntries.nextElement();
if (zipEntry.isDirectory()) {
continue;
}
String zipEntryName = zipEntry.getName().replace('\\', '/');
if (removeTopLevelDir) {
zipEntryName = zipEntryName.substring(zipEntryName.indexOf('/'));
}
File target = new File(extractLocation, zipEntryName);
FileSystemUtils.mkdirs(target.getParentFile());
Streams.copy(zipFile.getInputStream(zipEntry), new FileOutputStream(target));
}
log("Installed " + name + " into " + extractLocation.getAbsolutePath());
} catch (Exception e) {
log("failed to extract plugin [" + pluginFile + "]: " + ExceptionsHelper.detailedMessage(e));
return;
} finally {
if (zipFile != null) {
try {
zipFile.close();
} catch (IOException e) {
// ignore
}
}
pluginFile.delete();
}
二. elasticSearch是如何加載插件的this
elasticsearch裏面的組件基本都是用上面的方式進行模塊化管理，elasticsearch對guice進行了簡單的封裝，經過ModulesBuilder類構建es的模塊，一個es節點確定夠包括PluginsModule插件模塊，下面咱們看下插件模塊是如何工做，加載咱們的插件的url
public class PluginsModule extends AbstractModule implements SpawnModules, PreProcessModule {
private final Settings settings;
private final PluginsService pluginsService;
public PluginsModule(Settings settings, PluginsService pluginsService) {
this.settings = settings;
this.pluginsService = pluginsService;
}
//預處理組件
public Iterable<? extends Module> spawnModules() {
List<Module> modules = Lists.newArrayList();
Collection<Class<? extends Module>> modulesClasses = pluginsService.modules();
for (Class<? extends Module> moduleClass : modulesClasses) {
modules.add(createModule(moduleClass, settings));
}
modules.addAll(pluginsService.modules(settings));
return modules;
}
..............
es中全部的組件都是繼承自AbstractModule 插件調用層次爲Modules->PluginsModule->PluginsService->XXPlugin； 都是調用void processModule(Module module)方法。 區別在於 1：PluginsModule實現的是PreProcessModule接口。 2：PluginsService是本身原本的方法。 3：XXPlugin實現的是Plugin接口。 雖然他們都有processModule方法，但不是實現的同一個類。最重要是的仍是pluginService類，它真正負責加載的插件類spa
public PluginsService(Settings settings, Environment environment) {
super(settings);
this.environment = environment;
this.checkLucene = componentSettings.getAsBoolean("check_lucene", true);
.................................忽律部分代碼
loadPluginsIntoClassLoader();
if (loadClasspathPlugins) {
tupleBuilder.addAll(loadPluginsFromClasspath(settings));
}
this.plugins = tupleBuilder.build();
// we load site plugins
ImmutableList<Tuple<PluginInfo, Plugin>> tuples = loadSitePlugins();
for (Tuple<PluginInfo, Plugin> tuple : tuples) {
sitePlugins.add(tuple.v1().getName());
}
.................................忽律部分代碼
其中loadPluginsIntoClassLoader();負責classloader加載class,加載不在當前classpath中的class，使用當前setting中的classloader,這個構造函數負責加載plugin下面的全部的插件，而且使用當前的類加載器加載。
至此，插件的下載和加載所有完成。
- 1. elasticsearch源碼分析及插件開發
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- 7. ElasticSearch學習總結（一）
- 8. Elasticsearch學習總結七 ElasticSearch中的版本控制
- 9. 一、ElasticSearch源碼學習分享：ElasticSearch版本控制
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