JobScheduler調度器過程（JobSchedulerService的啓動過程）

 

JobSchedulerService啓動過程，最主要工做是從jobs.xml文件收集全部的jobs，放入到JobStore的成員變量mJobSet，轉成jobinfo。

 

JobScheduler服務啓動

2.1 startOtherServices

[-> SystemServer.java]

private void startOtherServices() { ... mSystemServiceManager.startService(JobSchedulerService.class); ... } 

該方法先初始化JSS，而後再調用其onStart()方法。

 

2.2 JobSchedulerService

[-> JobSchedulerService.java]

JobSchedulerService {
    List<StateController> mControllers;
    final JobHandler mHandler;
    final JobSchedulerStub mJobSchedulerStub;
    final JobStore mJobs;
    ...

    public JobSchedulerService(Context context) { super(context); mControllers = new ArrayList<StateController>(); mControllers.add(ConnectivityController.get(this)); mControllers.add(TimeController.get(this)); mControllers.add(IdleController.get(this)); mControllers.add(BatteryController.get(this)); mControllers.add(AppIdleController.get(this)); //建立主線程的looper[見小節2.3] mHandler = new JobHandler(context.getMainLooper()); //建立binder服務端[見小節2.4] mJobSchedulerStub = new JobSchedulerStub(); //[見小節2.5] mJobs = JobStore.initAndGet(this); } public void onStart() { publishBinderService(Context.JOB_SCHEDULER_SERVICE, mJobSchedulerStub); } } 

建立了5個不一樣的StateController，分別添加到mControllers。

類型	說明
ConnectivityController	註冊監聽網絡鏈接狀態的廣播
TimeController	註冊監聽job時間到期的廣播
IdleController	註冊監聽屏幕亮/滅,dream進入/退出,狀態改變的廣播
BatteryController	註冊監聽電池是否充電,電量狀態的廣播
AppIdleController	監聽app是否空閒

接下來,以ConnectivityController爲例,說一說相應Controller的建立過程, 其餘Controller也基本相似.

 

 

2.2.1 ConnectivityController

[-> ConnectivityController.java]

public class ConnectivityController extends StateController implements ConnectivityManager.OnNetworkActiveListener { public static ConnectivityController get(JobSchedulerService jms) { synchronized (sCreationLock) { if (mSingleton == null) { //單例模式 mSingleton = new ConnectivityController(jms, jms.getContext()); } return mSingleton; } } private ConnectivityController(StateChangedListener stateChangedListener, Context context) { super(stateChangedListener, context); //註冊監聽網絡鏈接狀態的廣播，且採用BackgroundThread線程 IntentFilter intentFilter = new IntentFilter(); intentFilter.addAction(ConnectivityManager.CONNECTIVITY_ACTION); mContext.registerReceiverAsUser( mConnectivityChangedReceiver, UserHandle.ALL, intentFilter, null, BackgroundThread.getHandler()); ConnectivityService cs = (ConnectivityService)ServiceManager.getService(Context.CONNECTIVITY_SERVICE); if (cs != null) { if (cs.getActiveNetworkInfo() != null) { mNetworkConnected = cs.getActiveNetworkInfo().isConnected(); } mNetworkUnmetered = mNetworkConnected && !cs.isActiveNetworkMetered(); } } } 

當監聽到CONNECTIVITY_ACTION廣播，onReceive方法的執行位於「android.bg」線程。

 

 

2.3 JSS.JobHandler

[-> JobSchedulerService.java ::JobHandler]

public class JobSchedulerService extends com.android.server.SystemService implements StateChangedListener, JobCompletedListener { private class JobHandler extends Handler { public JobHandler(Looper looper) { super(looper); } public void handleMessage(Message message) { synchronized (mJobs) { //當系統啓動到phase 600，則mReadyToRock=true. if (!mReadyToRock) { return; } } switch (message.what) { case MSG_JOB_EXPIRED: ... case MSG_CHECK_JOB: ... } maybeRunPendingJobsH(); removeMessages(MSG_CHECK_JOB); } 

JobHandler採用的是system_server進程的主線程Looper，也就是該過程運行在主線程。

 

 

2.4 JobSchedulerStub

[-> JobSchedulerService.java ::JobSchedulerStub]

final class JobSchedulerStub extends IJobScheduler.Stub { ... } 

JobSchedulerStub做爲實現接口IJobScheduler的binder服務端。

 

 

2.5 JS.initAndGet

[-> JobStore.java]

static JobStore initAndGet(JobSchedulerService jobManagerService) { synchronized (sSingletonLock) { if (sSingleton == null) { //[見小節2.6] sSingleton = new JobStore(jobManagerService.getContext(), Environment.getDataDirectory()); } return sSingleton; } }

 

2.6 建立JobStore

[-> JobStore.java]

public class JobStore { final ArraySet<JobStatus> mJobSet; private final Handler mIoHandler = IoThread.getHandler(); ... private JobStore(Context context, File dataDir) { mContext = context; mDirtyOperations = 0; File systemDir = new File(dataDir, "system"); File jobDir = new File(systemDir, "job"); jobDir.mkdirs(); // 建立/data/system/job/jobs.xml mJobsFile = new AtomicFile(new File(jobDir, "jobs.xml")); mJobSet = new ArraySet<JobStatus>(); //[見小節2.7.1] readJobMapFromDisk(mJobSet); } } 

該方法會建立job目錄以及jobs.xml文件, 以及從文件中讀取全部的JobStatus。

 

 

 

2.7 xml解析

2.7.1 ReadJobMapFromDiskRunnable

[-> JobStore.java]

private class ReadJobMapFromDiskRunnable implements Runnable { private final ArraySet<JobStatus> jobSet; ReadJobMapFromDiskRunnable(ArraySet<JobStatus> jobSet) { this.jobSet = jobSet; } public void run() { List<JobStatus> jobs; FileInputStream fis = mJobsFile.openRead(); synchronized (JobStore.this) { jobs = readJobMapImpl(fis); //[見小節2.7.2] if (jobs != null) { for (int i=0; i<jobs.size(); i++) { this.jobSet.add(jobs.get(i)); } } } fis.close(); } } 

此處mJobsFile即是/data/system/job/jobs.xml。

 

 

2.7.2 readJobMapImpl

[-> JobStore.java]

private List<JobStatus> readJobMapImpl(FileInputStream fis) throws XmlPullParserException, IOException { XmlPullParser parser = Xml.newPullParser(); parser.setInput(fis, StandardCharsets.UTF_8.name()); ... String tagName = parser.getName(); if ("job-info".equals(tagName)) { final List<JobStatus> jobs = new ArrayList<JobStatus>(); ... eventType = parser.next(); do { //讀取每個 <job/> if (eventType == XmlPullParser.START_TAG) { tagName = parser.getName(); if ("job".equals(tagName)) { //[見小節2.7.3] JobStatus persistedJob = restoreJobFromXml(parser); if (persistedJob != null) { jobs.add(persistedJob); } } } eventType = parser.next(); } while (eventType != XmlPullParser.END_DOCUMENT); return jobs; } return null; } 

從文件jobs.xml中讀取並建立JobStatus，而後添加到mJobSet.

 

 

2.7.3 restoreJobFromXml

[-> JobStore.java]

private JobStatus restoreJobFromXml(XmlPullParser parser) throws XmlPullParserException, IOException { JobInfo.Builder jobBuilder; int uid; //建立用於獲取jobInfo的Builder[見小節2.7.4] jobBuilder = buildBuilderFromXml(parser); jobBuilder.setPersisted(true); uid = Integer.valueOf(parser.getAttributeValue(null, "uid")); ... buildConstraintsFromXml(jobBuilder, parser); //讀取常量 //讀取job執行的兩個時間點：delay和deadline Pair<Long, Long> elapsedRuntimes = buildExecutionTimesFromXml(parser); ... //[見小節2.8] return new JobStatus(jobBuilder.build(), uid, elapsedRuntimes.first, elapsedRuntimes.second); }

 

2.7.4 buildBuilderFromXml

[-> JobStore.java]

private JobInfo.Builder buildBuilderFromXml(XmlPullParser parser) throws NumberFormatException { int jobId = Integer.valueOf(parser.getAttributeValue(null, "jobid")); String packageName = parser.getAttributeValue(null, "package"); String className = parser.getAttributeValue(null, "class"); ComponentName cname = new ComponentName(packageName, className); //[見小節2.7.5] return new JobInfo.Builder(jobId, cname); } 

建立的JobInfo對象，記錄着任務的jobid, package, class。

 

 

2.7.5 建立JobInfo

[-> JobInfo.java]

public class JobInfo implements Parcelable { public static final class Builder { public Builder(int jobId, ComponentName jobService) { mJobService = jobService; mJobId = jobId; } public JobInfo build() { mExtras = new PersistableBundle(mExtras); return new JobInfo(this); //建立JobInfo } } }

 

2.8 建立JobStatus

[-> JobStatus.java]

public JobStatus(JobInfo job, int uId, long earliestRunTimeElapsedMillis, long latestRunTimeElapsedMillis) { this(job, uId, 0); this.earliestRunTimeElapsedMillis = earliestRunTimeElapsedMillis; this.latestRunTimeElapsedMillis = latestRunTimeElapsedMillis; } private JobStatus(JobInfo job, int uId, int numFailures) { this.job = job; this.uId = uId; this.name = job.getService().flattenToShortString(); this.tag = "*job*/" + this.name; this.numFailures = numFailures; } 

JobStatus對象記錄着任務的jobId, ComponentName, uid以及標籤和失敗次數信息。

 

 

2.9 JSS.onBootPhase

public void onBootPhase(int phase) { if (PHASE_SYSTEM_SERVICES_READY == phase) { //階段500，則開始註冊package和use移除的廣播監聽 final IntentFilter filter = new IntentFilter(Intent.ACTION_PACKAGE_REMOVED); filter.addDataScheme("package"); getContext().registerReceiverAsUser( mBroadcastReceiver, UserHandle.ALL, filter, null, null); final IntentFilter userFilter = new IntentFilter(Intent.ACTION_USER_REMOVED); userFilter.addAction(PowerManager.ACTION_DEVICE_IDLE_MODE_CHANGED); getContext().registerReceiverAsUser( mBroadcastReceiver, UserHandle.ALL, userFilter, null, null); mPowerManager = (PowerManager)getContext().getSystemService(Context.POWER_SERVICE); } else if (phase == PHASE_THIRD_PARTY_APPS_CAN_START) { synchronized (mJobs) { mReadyToRock = true; mBatteryStats = IBatteryStats.Stub.asInterface(ServiceManager.getService( BatteryStats.SERVICE_NAME)); for (int i = 0; i < MAX_JOB_CONTEXTS_COUNT; i++) { //建立JobServiceContext對象 mActiveServices.add( new JobServiceContext(this, mBatteryStats, getContext().getMainLooper())); } ArraySet<JobStatus> jobs = mJobs.getJobs(); for (int i=0; i<jobs.size(); i++) { JobStatus job = jobs.valueAt(i); for (int controller=0; controller<mControllers.size(); controller++) { mControllers.get(controller).deviceIdleModeChanged(mDeviceIdleMode); mControllers.get(controller).maybeStartTrackingJob(job); } } //[見小節3.8] mHandler.obtainMessage(MSG_CHECK_JOB).sendToTarget(); } } } 

對於低內存的設備，則只建立一個建立JobServiceContext對象；不然建立3個該對象。

 

 

2.9.1 建立JobServiceContext

[-> JobServiceContext.java]

JobServiceContext(JobSchedulerService service, IBatteryStats batteryStats, Looper looper) {
    this(service.getContext(), batteryStats, service, looper); } JobServiceContext(Context context, IBatteryStats batteryStats, JobCompletedListener completedListener, Looper looper) { mContext = context; mBatteryStats = batteryStats; mCallbackHandler = new JobServiceHandler(looper); mCompletedListener = completedListener; mAvailable = true; } 

此處的JobServiceHandler採用的是system_server進程的主線程。

 

 

2.10 小結

1. JSS.JobHandler運行在system_server進程的主線程；
2. JobServiceContext.JobServiceHandler運行在system_server進程的主線程；
3. JobSchedulerStub做爲實現接口IJobScheduler的binder服務端；
4. JobStore：其成員變量mIoHandler運行在」android.io」線程；
5. JobStatus：從/data/system/job/jobs.xml文件中讀取每一個JobInfo,再解析成JobStatus對象，添加到mJobSet。