zookeeper配置中心实战--solrcloud zookeeper配置中心原理及源码分析

程序的发展，需要引入集中配置：

• 随着程序功能的日益复杂，程序的配置日益增多：各种功能的开关、参数的配置、服务器的地址……
• 并且对配置的期望也越来越高，配置修改后实时生效，灰度发布，分环境、分集群管理配置，完善的权限、审核机制……
• 并且随着采用分布式的开发模式，项目之间的相互引用随着服务的不断增多，相互之间的调用复杂度成指数升高，每次投产或者上线新的项目时苦不堪言，因此需要引用配置中心治理。

有哪些开源配置中心

1. spring-cloud/spring-cloud-config
   https://github.com/spring-cloud/spring-cloud-config
   spring出品，可以和spring cloud无缝配合

2. 淘宝 diamond
   https://github.com/takeseem/diamond
   已经不维护

3. disconf
   https://github.com/knightliao/disconf
   java开发，蚂蚁金服技术专家发起，业界使用广泛

4. ctrip apollo
   https://github.com/ctripcorp/apollo/
   Apollo（阿波罗）是携程框架部门研发的开源配置管理中心，具备规范的权限、流程治理等特性。

配置中心的实现方式可以使用数据库如mysql，可以使用缓存数据如redis，mongodb等，也可以使用zookeeper，zookeeper的watcher特性使它天然具有配置中心的属性。

1.solr zookeeper配置中心搭建(windows环境)

　　1.1 下载solr 

　　下载最新的solr https://lucene.apache.org/solr/mirrors-solr-latest-redir.html

　　我此时下载的最新版本为 solr-7.7.0.zip

　　解压到本地目录

　　E:demosolr-7.7.0

       1.2 启动solr

  　　CMD进入bin目录下，执行 solr.cmd start -e cloud

　　 按照提示创建solr cloud实例和分片和collection:

　　techproducts

，详细参考官方文档：https://lucene.apache.org/solr/guide/7_6/solr-tutorial.html

　　　回到E:demosolr-7.7.0目录，CMD执行导入数据命令： 

　　java -jar -Dc=techproducts -Dauto exampleexampledocspost.jar exampleexampledocs*　

       1.3  访问admin 

           http://localhost:8983

         查看内置zookeeper状态

       

 　　创建了一个9983端口的zk实例

    1.4 使用ZooInspector监控查看

运行脚本

@echo off
cd D:softwarezookeeper-3.4.6ooInspectoruild
d:
Java -Dfile.encoding=UTF-8 -jar zookeeper-dev-ZooInspector.jar

2.配置中心文件的上传，下载功能实现

   本文仅实现上传功能，下载功能由读者自行实现

  2.1 上传配置文件：进入E:demosolr-7.7.0/bin目录，CMD执行

solr.cmd zk cp ../LICENSE.txt zk:/test/LICENSE.txt -z localhost:9983

此时在zk下面创建了一个test目录，目录下面有一个license.txt节点，数据即为license.txt文件内容。

 2.2 源码分析

   用记事本打开solr.cmd命令，找到parse_zk_args参数的地方，发现解析完zk参数就启动了运行zk命令方法run_zk

:run_zk
IF "!ZK_OP!"=="" (
  set "ERROR_MSG=Invalid command specified for zk sub-command"
  goto zk_short_usage
)

IF "!ZK_HOST!"=="" (
  set "ERROR_MSG=Must specify -z zkHost"
  goto zk_short_usage
)

IF "!ZK_OP!"=="-upconfig" (
  set ZK_OP="upconfig"
)
IF "!ZK_OP!"=="-downconfig" (
  set ZK_OP="downconfig"
)

IF "!ZK_OP!"=="upconfig" (
  IF "!CONFIGSET_NAME!"=="" (
    set ERROR_MSG="-n option must be set for upconfig"
    goto zk_short_usage
  )
  IF "!CONFIGSET_DIR!"=="" (
    set ERROR_MSG="The -d option must be set for upconfig."
    goto zk_short_usage
  )
  "%JAVA%" %SOLR_SSL_OPTS% %AUTHC_OPTS% %SOLR_ZK_CREDS_AND_ACLS% -Dsolr.install.dir="%SOLR_TIP%" ^
  -Dlog4j.configurationFile="file:///%DEFAULT_SERVER_DIR%
esourceslog4j2-console.xml" ^
  -classpath "%DEFAULT_SERVER_DIR%solr-webappwebappWEB-INFlib*;%DEFAULT_SERVER_DIR%libext*" ^
  org.apache.solr.util.SolrCLI !ZK_OP! -confname !CONFIGSET_NAME! -confdir !CONFIGSET_DIR! -zkHost !ZK_HOST! %ZK_VERBOSE%^
  -configsetsDir "%SOLR_TIP%/server/solr/configsets"
) ELSE IF "!ZK_OP!"=="downconfig" (
  IF "!CONFIGSET_NAME!"=="" (
    set ERROR_MSG="-n option must be set for downconfig"
    goto zk_short_usage
  )
  IF "!CONFIGSET_DIR!"=="" (
    set ERROR_MSG="The -d option must be set for downconfig."
    goto zk_short_usage
  )
  "%JAVA%" %SOLR_SSL_OPTS% %AUTHC_OPTS% %SOLR_ZK_CREDS_AND_ACLS% -Dsolr.install.dir="%SOLR_TIP%" ^
  -Dlog4j.configurationFile="file:///%DEFAULT_SERVER_DIR%
esourceslog4j2-console.xml" ^
  -classpath "%DEFAULT_SERVER_DIR%solr-webappwebappWEB-INFlib*;%DEFAULT_SERVER_DIR%libext*" ^
  org.apache.solr.util.SolrCLI !ZK_OP! -confname !CONFIGSET_NAME! -confdir !CONFIGSET_DIR! -zkHost !ZK_HOST! %ZK_VERBOSE%
) ELSE IF "!ZK_OP!"=="cp" (
  IF "%ZK_SRC%"=="" (
    set ERROR_MSG="<src> must be specified for 'cp' command"
    goto zk_short_usage
  )
  IF "%ZK_DST%"=="" (
    set ERROR_MSG=<dest> must be specified for 'cp' command"
    goto zk_short_usage
  )
  IF NOT "!ZK_SRC:~0,3!"=="zk:" (
    IF NOT "!%ZK_DST:~0,3!"=="zk:" (
      set ERROR_MSG="At least one of src or dst must be prefixed by 'zk:'"
      goto zk_short_usage
  )
  )
  "%JAVA%" %SOLR_SSL_OPTS% %AUTHC_OPTS% %SOLR_ZK_CREDS_AND_ACLS% -Dsolr.install.dir="%SOLR_TIP%" ^
  -Dlog4j.configurationFile="file:///%DEFAULT_SERVER_DIR%
esourceslog4j2-console.xml" ^
  -classpath "%DEFAULT_SERVER_DIR%solr-webappwebappWEB-INFlib*;%DEFAULT_SERVER_DIR%libext*" ^
  org.apache.solr.util.SolrCLI !ZK_OP! -zkHost !ZK_HOST! -src !ZK_SRC! -dst !ZK_DST! -recurse !ZK_RECURSE! %ZK_VERBOSE%
) ELSE IF "!ZK_OP!"=="mv" (
  IF "%ZK_SRC%"=="" (
    set ERROR_MSG="<src> must be specified for 'mv' command"
    goto zk_short_usage
  )
  IF "%ZK_DST%"=="" (
    set ERROR_MSG="<dest> must be specified for 'mv' command"
    goto zk_short_usage
  )
  "%JAVA%" %SOLR_SSL_OPTS% %AUTHC_OPTS% %SOLR_ZK_CREDS_AND_ACLS% -Dsolr.install.dir="%SOLR_TIP%" ^
  -Dlog4j.configurationFile="file:///%DEFAULT_SERVER_DIR%
esourceslog4j2-console.xml" ^
  -classpath "%DEFAULT_SERVER_DIR%solr-webappwebappWEB-INFlib*;%DEFAULT_SERVER_DIR%libext*" ^
  org.apache.solr.util.SolrCLI !ZK_OP! -zkHost !ZK_HOST! -src !ZK_SRC! -dst !ZK_DST! %ZK_VERBOSE%
) ELSE IF "!ZK_OP!"=="rm" (
  IF "%ZK_SRC"=="" (
    set ERROR_MSG="Zookeeper path to remove must be specified when using the 'rm' command"
    goto zk_short_usage
  )
  "%JAVA%" %SOLR_SSL_OPTS% %AUTHC_OPTS% %SOLR_ZK_CREDS_AND_ACLS% -Dsolr.install.dir="%SOLR_TIP%" ^
  -Dlog4j.configurationFile="file:///%DEFAULT_SERVER_DIR%
esourceslog4j2-console.xml" ^
  -classpath "%DEFAULT_SERVER_DIR%solr-webappwebappWEB-INFlib*;%DEFAULT_SERVER_DIR%libext*" ^
  org.apache.solr.util.SolrCLI !ZK_OP! -zkHost !ZK_HOST! -path !ZK_SRC! -recurse !ZK_RECURSE! %ZK_VERBOSE%
) ELSE IF "!ZK_OP!"=="ls" (
  IF "%ZK_SRC"=="" (
    set ERROR_MSG="Zookeeper path to remove must be specified when using the 'ls' command"
    goto zk_short_usage
  )
  "%JAVA%" %SOLR_SSL_OPTS% %AUTHC_OPTS% %SOLR_ZK_CREDS_AND_ACLS% -Dsolr.install.dir="%SOLR_TIP%" ^
  -Dlog4j.configurationFile="file:///%DEFAULT_SERVER_DIR%
esourceslog4j2-console.xml" ^
  -classpath "%DEFAULT_SERVER_DIR%solr-webappwebappWEB-INFlib*;%DEFAULT_SERVER_DIR%libext*" ^
  org.apache.solr.util.SolrCLI !ZK_OP! -zkHost !ZK_HOST! -path !ZK_SRC! -recurse !ZK_RECURSE! %ZK_VERBOSE%
) ELSE IF "!ZK_OP!"=="mkroot" (
  IF "%ZK_SRC"=="" (
    set ERROR_MSG="Zookeeper path to create must be specified when using the 'mkroot' command"
    goto zk_short_usage
  )
  "%JAVA%" %SOLR_SSL_OPTS% %AUTHC_OPTS% %SOLR_ZK_CREDS_AND_ACLS% -Dsolr.install.dir="%SOLR_TIP%" ^
  -Dlog4j.configurationFile="file:///%SOLR_SERVER_DIR%
esourceslog4j2-console.xml" ^
  -classpath "%DEFAULT_SERVER_DIR%solr-webappwebappWEB-INFlib*;%DEFAULT_SERVER_DIR%libext*" ^
  org.apache.solr.util.SolrCLI !ZK_OP! -zkHost !ZK_HOST! -path !ZK_SRC! %ZK_VERBOSE%
) ELSE (
  set ERROR_MSG="Unknown zk option !ZK_OP!"
  goto zk_short_usage
)
goto done

红色即为zk cp命令时执行 

org.apache.solr.util.SolrCLI类

 不同的命令，使用不同的Tool类

 // Creates an instance of the requested tool, using classpath scanning if necessary
  private static Tool newTool(String toolType) throws Exception {
    if ("healthcheck".equals(toolType))
      return new HealthcheckTool();
    else if ("status".equals(toolType))
      return new StatusTool();
    else if ("api".equals(toolType))
      return new ApiTool();
    else if ("create_collection".equals(toolType))
      return new CreateCollectionTool();
    else if ("create_core".equals(toolType))
      return new CreateCoreTool();
    else if ("create".equals(toolType))
      return new CreateTool();
    else if ("delete".equals(toolType))
      return new DeleteTool();
    else if ("config".equals(toolType))
      return new ConfigTool();
    else if ("run_example".equals(toolType))
      return new RunExampleTool();
    else if ("upconfig".equals(toolType))
      return new ConfigSetUploadTool();
    else if ("downconfig".equals(toolType))
      return new ConfigSetDownloadTool();
    else if ("rm".equals(toolType))
      return new ZkRmTool();
    else if ("mv".equals(toolType))
      return new ZkMvTool();
    else if ("cp".equals(toolType))
      return new ZkCpTool();
    else if ("ls".equals(toolType))
      return new ZkLsTool();
    else if ("mkroot".equals(toolType))
      return new ZkMkrootTool();
    else if ("assert".equals(toolType))
      return new AssertTool();
    else if ("utils".equals(toolType))
      return new UtilsTool();
    else if ("auth".equals(toolType))
      return new AuthTool();

cp执行ZkCpTool的runImpl方法

    protected void runImpl(CommandLine cli) throws Exception {
      raiseLogLevelUnlessVerbose(cli);
      String zkHost = getZkHost(cli);
      if (zkHost == null) {
        throw new IllegalStateException("Solr at " + cli.getOptionValue("solrUrl") +
            " is running in standalone server mode, cp can only be used when running in SolrCloud mode.
");
      }

      try (SolrZkClient zkClient = new SolrZkClient(zkHost, 30000)) {
        echoIfVerbose("
Connecting to ZooKeeper at " + zkHost + " ...", cli);
        String src = cli.getOptionValue("src");
        String dst = cli.getOptionValue("dst");
        Boolean recurse = Boolean.parseBoolean(cli.getOptionValue("recurse"));
        echo("Copying from '" + src + "' to '" + dst + "'. ZooKeeper at " + zkHost);

        boolean srcIsZk = src.toLowerCase(Locale.ROOT).startsWith("zk:");
        boolean dstIsZk = dst.toLowerCase(Locale.ROOT).startsWith("zk:");

        String srcName = src;
        if (srcIsZk) {
          srcName = src.substring(3);
        } else if (srcName.toLowerCase(Locale.ROOT).startsWith("file:")) {
          srcName = srcName.substring(5);
        }

        String dstName = dst;
        if (dstIsZk) {
          dstName = dst.substring(3);
        } else {
          if (dstName.toLowerCase(Locale.ROOT).startsWith("file:")) {
            dstName = dstName.substring(5);
          }
        }
        zkClient.zkTransfer(srcName, srcIsZk, dstName, dstIsZk, recurse);
      } catch (Exception e) {
        log.error("Could not complete the zk operation for reason: " + e.getMessage());
        throw (e);
      }
    }

调用SolrZkClient的zkTransfer

  public void zkTransfer(String src, Boolean srcIsZk, 
                         String dst, Boolean dstIsZk,
                         Boolean recurse) throws SolrServerException, KeeperException, InterruptedException, IOException {
    ZkMaintenanceUtils.zkTransfer(this, src, srcIsZk, dst, dstIsZk, recurse);
  }

实现由ZkMaintenanceUtils来做

 /**
   * Copy between local file system and Zookeeper, or from one Zookeeper node to another,
   * optionally copying recursively.
   *
   * @param src     Source to copy from. Both src and dst may be Znodes. However, both may NOT be local
   * @param dst     The place to copy the files too. Both src and dst may be Znodes. However both may NOT be local
   * @param recurse if the source is a directory, reccursively copy the contents iff this is true.
   * @throws SolrServerException  Explanatory exception due to bad params, failed operation, etc.
   * @throws KeeperException      Could not perform the Zookeeper operation.
   * @throws InterruptedException Thread interrupted
   */
  public static void zkTransfer(SolrZkClient zkClient, String src, Boolean srcIsZk,
                         String dst, Boolean dstIsZk, 
                         Boolean recurse) throws SolrServerException, KeeperException, InterruptedException, IOException {

    if (srcIsZk == false && dstIsZk == false) {
      throw new SolrServerException("One or both of source or destination must specify ZK nodes.");
    }

    // Make sure -recurse is specified if the source has children.
    if (recurse == false) {
      if (srcIsZk) {
        if (zkClient.getChildren(src, null, true).size() != 0) {
          throw new SolrServerException("Zookeeper node " + src + " has children and recurse is false");
        }
      } else if (Files.isDirectory(Paths.get(src))) {
        throw new SolrServerException("Local path " + Paths.get(src).toAbsolutePath() + " is a directory and recurse is false");
      }
    }

    if (dstIsZk && dst.length() == 0) {
      dst = "/"; // for consistency, one can copy from zk: and send to zk:/
    }
    dst = normalizeDest(src, dst, srcIsZk, dstIsZk);

    // ZK -> ZK copy.
    if (srcIsZk && dstIsZk) {
      traverseZkTree(zkClient, src, VISIT_ORDER.VISIT_PRE, new ZkCopier(zkClient, src, dst));
      return;
    }

    //local -> ZK copy
    if (dstIsZk) {
      uploadToZK(zkClient, Paths.get(src), dst, null);
      return;
    }

    // Copying individual files from ZK requires special handling since downloadFromZK assumes the node has children.
    // This is kind of a weak test for the notion of "directory" on Zookeeper.
    // ZK -> local copy where ZK is a parent node
    if (zkClient.getChildren(src, null, true).size() > 0) {
      downloadFromZK(zkClient, src, Paths.get(dst));
      return;
    }

    // Single file ZK -> local copy where ZK is a leaf node
    if (Files.isDirectory(Paths.get(dst))) {
      if (dst.endsWith(File.separator) == false) dst += File.separator;
      dst = normalizeDest(src, dst, srcIsZk, dstIsZk);
    }
    byte[] data = zkClient.getData(src, null, null, true);
    Path filename = Paths.get(dst);
    Files.createDirectories(filename.getParent());
    log.info("Writing file {}", filename);
    Files.write(filename, data);
  }

注意：这个copy 可以是本地文件到znode之间的copy，也可以是znode之间的copy

本文以本地文档到znode之间的copy

public static void uploadToZK(SolrZkClient zkClient, final Path fromPath, final String zkPath,
                                final Pattern filenameExclusions) throws IOException {

    String path = fromPath.toString();
    if (path.endsWith("*")) {
      path = path.substring(0, path.length() - 1);
    }

    final Path rootPath = Paths.get(path);
        
    if (!Files.exists(rootPath))
      throw new IOException("Path " + rootPath + " does not exist");

    Files.walkFileTree(rootPath, new SimpleFileVisitor<Path>() {
      @Override
      public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
        String filename = file.getFileName().toString();
        if (filenameExclusions != null && filenameExclusions.matcher(filename).matches()) {
          log.info("uploadToZK skipping '{}' due to filenameExclusions '{}'", filename, filenameExclusions);
          return FileVisitResult.CONTINUE;
        }
        String zkNode = createZkNodeName(zkPath, rootPath, file);
        try {
          // if the path exists (and presumably we're uploading data to it) just set its data
          if (file.toFile().getName().equals(ZKNODE_DATA_FILE) && zkClient.exists(zkNode, true)) {
            zkClient.setData(zkNode, file.toFile(), true);
          } else {
            zkClient.makePath(zkNode, file.toFile(), false, true);
          }
        } catch (KeeperException | InterruptedException e) {
          throw new IOException("Error uploading file " + file.toString() + " to zookeeper path " + zkNode,
              SolrZkClient.checkInterrupted(e));
        }
        return FileVisitResult.CONTINUE;
      }

      @Override
      public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs) throws IOException {
        if (dir.getFileName().toString().startsWith(".")) return FileVisitResult.SKIP_SUBTREE;

        return FileVisitResult.CONTINUE;
      }
    });
  }

文件转换为byte流数据，设置到znode

  /**
   * Write file to ZooKeeper - default system encoding used.
   *
   * @param path path to upload file to e.g. /solr/conf/solrconfig.xml
   * @param file path to file to be uploaded
   */
  public Stat setData(String path, File file, boolean retryOnConnLoss) throws IOException,
      KeeperException, InterruptedException {
    log.debug("Write to ZooKeeper: {} to {}", file.getAbsolutePath(), path);
    byte[] data = FileUtils.readFileToByteArray(file);
    return setData(path, data, retryOnConnLoss);

  /**
   * Returns node's state
   */
  public Stat setData(final String path, final byte data[], final int version, boolean retryOnConnLoss)
      throws KeeperException, InterruptedException {
    if (retryOnConnLoss) {
      return zkCmdExecutor.retryOperation(() -> keeper.setData(path, data, version));
    } else {
      return keeper.setData(path, data, version);
    }
  }

具体实现为ZooKeeper本身的客户端ZooKeeper.java

  /**
     * Set the data for the node of the given path if such a node exists and the
     * given version matches the version of the node (if the given version is
     * -1, it matches any node's versions). Return the stat of the node.
     * <p>
     * This operation, if successful, will trigger all the watches on the node
     * of the given path left by getData calls.
     * <p>
     * A KeeperException with error code KeeperException.NoNode will be thrown
     * if no node with the given path exists.
     * <p>
     * A KeeperException with error code KeeperException.BadVersion will be
     * thrown if the given version does not match the node's version.
     * <p>
     * The maximum allowable size of the data array is 1 MB (1,048,576 bytes).
     * Arrays larger than this will cause a KeeperException to be thrown.
     *
     * @param path
     *                the path of the node
     * @param data
     *                the data to set
     * @param version
     *                the expected matching version
     * @return the state of the node
     * @throws InterruptedException If the server transaction is interrupted.
     * @throws KeeperException If the server signals an error with a non-zero error code.
     * @throws IllegalArgumentException if an invalid path is specified
     */
    public Stat setData(final String path, byte data[], int version)
        throws KeeperException, InterruptedException
    {
        final String clientPath = path;
        PathUtils.validatePath(clientPath);

        final String serverPath = prependChroot(clientPath);

        RequestHeader h = new RequestHeader();
        h.setType(ZooDefs.OpCode.setData);
        SetDataRequest request = new SetDataRequest();
        request.setPath(serverPath);
        request.setData(data);
        request.setVersion(version);
        SetDataResponse response = new SetDataResponse();
        ReplyHeader r = cnxn.submitRequest(h, request, response, null);
        if (r.getErr() != 0) {
            throw KeeperException.create(KeeperException.Code.get(r.getErr()),
                    clientPath);
        }
        return response.getStat();
    }

3. 小结

   1.solrcloud使用zookeeper实现了配置中心，入口函数为ZkCLI.java ，它使用命令模式内部封装了一系列命令，如：healthcheck，status，api，config，upconfig，downconfig，mv，cp，ls,mkroot等命令

   2.最终调用的是apache zookeeper本身的api，如果为文件的话，需要先转为byte流，然后存入znode节点中。

参考文献：

【1】https://www.cnblogs.com/xiaoqi/p/configserver-compair.html

【2】https://lucene.apache.org/solr/guide/7_6/solr-tutorial.html