1. 下載原始碼

本文基於zookeeper原始碼3.6.2版本。

zookeeper的原始碼在github上（https://github.com/apache/zookeeper）

2. 找入口類

3. 啟動報錯

知道主類後，我們在idea中配置zookeeper的啟動引數。zookeeper啟動時需要一個配置檔案，我們可以從原始碼的根目錄下的conf檔案中zoo_sample.cfg複製一份改名為zoo.cfg。然後啟動main方法。

發現報如下錯誤：

    public static void main(String[] args) {
        args = new String[1];
        args[0] = "zoo.cfg";
        QuorumPeerMain main = new QuorumPeerMain();
        
 
try {
            main.initializeAndRun(args);
        } catch (IllegalArgumentException e) {
            LOG.error("Invalid arguments, exiting abnormally", e);
            //LOG.info(USAGE);
            //System.err.println(USAGE);
            ZKAuditProvider.addServerStartFailureAuditLog();
            ServiceUtils.requestSystemExit(ExitCode.INVALID_INVOCATION.getValue());
        } 
 
catch (QuorumPeerConfig.ConfigException e) {
            LOG.error("Invalid config, exiting abnormally", e);
            System.err.println("Invalid config, exiting abnormally");
            ZKAuditProvider.addServerStartFailureAuditLog();
            ServiceUtils.requestSystemExit(ExitCode.INVALID_INVOCATION.getValue());
        } catch (FileTxnSnapLog.DatadirException e) {
            LOG.error("Unable to access datadir, exiting abnormally", e);
            System.err.println("Unable to access datadir, exiting abnormally");
            ZKAuditProvider.addServerStartFailureAuditLog();
            ServiceUtils.requestSystemExit(ExitCode.UNABLE_TO_ACCESS_DATADIR.getValue());
        } catch (AdminServer.AdminServerException e) {
            LOG.error("Unable to start AdminServer, exiting abnormally", e);
            System.err.println("Unable to start AdminServer, exiting abnormally");
            ZKAuditProvider.addServerStartFailureAuditLog();
            ServiceUtils.requestSystemExit(ExitCode.ERROR_STARTING_ADMIN_SERVER.getValue());
        } catch (Exception e) {
            LOG.error("Unexpected exception, exiting abnormally", e);
            ZKAuditProvider.addServerStartFailureAuditLog();
            ServiceUtils.requestSystemExit(ExitCode.UNEXPECTED_ERROR.getValue());
        }
        LOG.info("Exiting normally");
        ServiceUtils.requestSystemExit(ExitCode.EXECUTION_FINISHED.getValue());
    }