Azkaban源碼閱讀之AzkabanApplication

Azkaban是一個Hadoop批處理調度器，可以通過訪問其前台展示頁面來進行部署、運行job等操作。

//IndexServlet.java    @Override    protected void doPost(HttpServletRequest req, HttpServletResponse resp)            throws ServletException, IOException {        /* set runtime properties from request and response */        super.setRuntimeProperties(req, resp);        AzkabanApplication app = getApplication();        String action = getParam(req, "action");        if ("loadjobs".equals(action)) {        resp.setContentType("application/json");        String folder = getParam(req, "folder");        resp.getWriter().print(getJSONJobsForFolder(app.getAllFlows(), folder));        resp.getWriter().flush();        return;        }        else if("unschedule".equals(action)) {            String jobid = getParam(req, "job");            app.getScheduleManager().removeScheduledJob(jobid);        } else if("cancel".equals(action)) {            cancelJob(app, req);        } else if("schedule".equals(action)) {            String redirect = scheduleJobs(app, req, resp);            if (!redirect.isEmpty()) {            resp.sendRedirect(redirect);            return;            }        } else {            throw new ServletException("Unknown action: " + action);        }        resp.sendRedirect(req.getContextPath());    }

看檔案名稱就可以看出了這個是整個系統啟動並執行源頭，一切從這裡開始. . . . . . .

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AzkabanApplication中是一系列用於整個系統初始化的代碼，接下來就來看一下吧~

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    public AzkabanApplication(List<File> jobDirs, File logDir, File tempDir, boolean enableDevMode) throws IOException {        this._jobDirs = Utils.nonNull(jobDirs);        this._logsDir = Utils.nonNull(logDir);        this._tempDir = Utils.nonNull(tempDir);        if(!this._logsDir.exists())            this._logsDir.mkdirs();        if(!this._tempDir.exists())            this._tempDir.mkdirs();        for(File jobDir: _jobDirs) {            if(!jobDir.exists()) {                logger.warn("Job directory " + jobDir + " does not exist. Creating.");                jobDir.mkdirs();            }        }        if(jobDirs.size() < 1)            throw new IllegalArgumentException("No job directory given.");        /**         * 載入預設的屬性檔案         * 實際上只用.properties為尾碼的檔案         */        Props defaultProps = PropsUtils.loadPropsInDirs(_jobDirs, ".properties", ".schema");        /**         * 主要功能就是載入HADOOP_HOME         */        _baseClassLoader = getBaseClassloader();        String defaultTimezoneID = defaultProps.getString(DEFAULT_TIMEZONE_ID, null);        if (defaultTimezoneID != null) {        DateTimeZone.setDefault(DateTimeZone.forID(defaultTimezoneID));        TimeZone.setDefault(TimeZone.getTimeZone(defaultTimezoneID));        }                /**         * 由於Azkaban支援鎖shezhi,在這裡進行鎖管理的初始化         */        NamedPermitManager permitManager = getNamedPermitManager(defaultProps);        /**         * 初始化Azkaban支援的job類型         */        JobWrappingFactory factory = new JobWrappingFactory(                permitManager,                new ReadWriteLockManager(),                _logsDir.getAbsolutePath(),                "java",                new ImmutableMap.Builder<String, Class<? extends Job>>()                 .put("java", JavaJob.class)                 .put("command", ProcessJob.class)                 .put("javaprocess", JavaProcessJob.class)                 .put("pig", PigProcessJob.class)                 .put("propertyPusher", NoopJob.class)                 .put("python", PythonJob.class)                 .put("ruby", RubyJob.class)                 .put("script", ScriptJob.class).build());        _hdfsUrl = defaultProps.getString("hdfs.instance.url", null);        _jobManager = new JobManager(factory,                                     _logsDir.getAbsolutePath(),                                     defaultProps,                                     _jobDirs,                                     _baseClassLoader);        _mailer = new Mailman(defaultProps.getString("mail.host", "localhost"),                              defaultProps.getString("mail.user", ""),                              defaultProps.getString("mail.password", ""));        String failureEmail = defaultProps.getString("job.failure.email", null);        String successEmail = defaultProps.getString("job.success.email", null);        int schedulerThreads = defaultProps.getInt("scheduler.threads", 50);        _instanceName = defaultProps.getString(INSTANCE_NAME, "");                final File initialJobDir = _jobDirs.get(0);        File schedule = getScheduleFile(defaultProps, initialJobDir);        File backup = getBackupFile(defaultProps, initialJobDir);        File executionsStorageDir = new File(                defaultProps.getString("azkaban.executions.storage.dir", initialJobDir.getAbsolutePath() + "/executions")        );        if (! executionsStorageDir.exists()) executionsStorageDir.mkdirs();        /**         * 獲得上次啟動Azkaban時執行的最大jobId         */        long lastExecutionId = getLastExecutionId(executionsStorageDir);        logger.info(String.format("Using path[%s] for storing executions.", executionsStorageDir));        logger.info(String.format("Last known execution id was [%s]", lastExecutionId));        final ExecutableFlowSerializer flowSerializer = new DefaultExecutableFlowSerializer();        final ExecutableFlowDeserializer flowDeserializer = new DefaultExecutableFlowDeserializer(_jobManager, factory);        FlowExecutionSerializer flowExecutionSerializer = new FlowExecutionSerializer(flowSerializer);        FlowExecutionDeserializer flowExecutionDeserializer = new FlowExecutionDeserializer(flowDeserializer);        /**         * 初始化管理工作流程的緩衝,預設將cache大小設定為1000         * 這裡是整個初始化過程中的重點!!!         */        _allFlows = new CachingFlowManager(                new RefreshableFlowManager(                        _jobManager,                        flowExecutionSerializer,                        flowExecutionDeserializer,                         executionsStorageDir,                        lastExecutionId                ),                defaultProps.getInt("azkaban.flow.cache.size", 1000)        );        _jobManager.setFlowManager(_allFlows);        _jobExecutorManager = new JobExecutorManager(        _allFlows,         _jobManager,         _mailer,         failureEmail,         successEmail,        schedulerThreads        );                this._schedulerManager = new ScheduleManager(_jobExecutorManager, new LocalFileScheduleLoader(schedule, backup));        /* set predefined log url prefix         */        String server_url = defaultProps.getString("server.url", null) ;        if (server_url != null) {            if (server_url.endsWith("/"))            _jobExecutorManager.setRuntimeProperty(AppCommon.DEFAULT_LOG_URL_PREFIX, server_url + "logs?file=" );            else             _jobExecutorManager.setRuntimeProperty(AppCommon.DEFAULT_LOG_URL_PREFIX, server_url + "/logs?file=" );        }        this._velocityEngine = configureVelocityEngine(enableDevMode);    }

這部分將系統所需的各個部分，各個屬性都進行了初始化的操作。

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http://blog.csdn.net/zhang__bing/article/details/8721834