Android ANR 触发原理
Posted 麦田里的守望者-Jiang
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文章目录
ANR 简介
ANR(Application Not Responding):程序无响应。在Android应用程序的主线程中,如果某个事件没有在系统规定的时间范围内执行完成,就会触发ANR。通常,ANR 会对用户的体验会产生致命的影响,因为当发生ANR时,用户不能再与应用程序进行交互。所以,我们也会统计应用程序的线上ANR率,以此来衡量一个应用程序的稳定性。ANR率 是应用程序的一个非常重要的性能指标。解决ANR 也是一个重要紧急的事情。本文主要先介绍ANR 触发原理,下一篇再介绍如何处理 ANR 问题。
ANR 触发场景
在android 系统中,触发ANR的事件场景通常有四种:
- Service Timeout:Service在特定的时间内无法处理完成
- BroadcastQueue Timeout:BroadcastReceiver在特定时间内无法处理完成
- ContentProvider Timeout:内容提供者执行超时
- inputDispatching Timeout:按键或触摸事件在特定时间内无响应。
场景 | 事件 | 时间限制 |
---|---|---|
Service | ActiveServices#SERVICE_TIMEOUT | 20s |
Service | ActiveServices#SERVICE_BACKGROUND_TIMEOUT | 200s |
BroadcastQueue | ActivityManagerService#BROADCAST_FG_TIMEOUT | 10s |
BroadcastQueue | ActivityManagerService#BROADCAST_BG_TIMEOUT | 60s |
ContentProvider | ActivityManagerService#CONTENT_PROVIDER_PUBLISH_TIMEOUT | 10s |
inputDispatching | ActivityTaskManagerService#KEY_DISPATCHING_TIMEOUT | 5s |
ANR 触发原理
文中源码基于Android API 29 Platform
这里以 Service 触发场景为例子,其他的都类似(原理类似)。要 分析 Service ANR 的原因,需要从 Service 的创建过程开始:
-
启动 Service:
ContextWrapper#startService
→ContextImpl#startService
→ContextImpl#startServiceCommon
→ActivityManagerService#startService
-
AMS 处理:
ActivityManagerService#startService
→ActiveServices#startServiceLocked
-
接下来在
ActiveServices
处理事件中,会发送一个延迟消息:startServiceLocked
→retrieveServiceLocked
→startServiceInnerLocked
→bringUpServiceLocked
→ realStartServiceLocked →bumpServiceExecutingLocked
→ scheduleServiceTimeoutLocked → 发送触发ANR的延迟消息 -
另外,在realStartServiceLocked 方法中,执行
bumpServiceExecutingLocked
方法后,紧接着就会执行app.thread.scheduleCreateService(r, r.serviceInfo, mAm.compatibilityInfoForPackage(r.serviceInfo.applicationInfo), app.getReportedProcState());
代码,也就是执行ApplicationThread
的scheduleCreateService
方法,接下来就交给ActivityThread
的handleCreateService
方法,在这个方法中就开始创建 Service,ContextImpl,Application对象,并让 Service 和 ContextImpl 关联起来,最后调用Service 的onCreate
方法,完成Service的创建。 -
在
ActivityThread
的handleCreateService
方法 最后会依次执行:ActivityManagerService#serviceDoneExecuting
→ActiveServices#serviceDoneExecutingLocked(ServiceRecord r, int type, int startId, int res)
→ ActiveServices#serviceDoneExecutingLocked(r, inDestroying, inDestroying) ,在 serviceDoneExecutingLocked方法中,执行:mAm.mHandler.removeMessages(ActivityManagerService.SERVICE_TIMEOUT_MSG, r.app);
也就是移除前面在 scheduleServiceTimeoutLocked 方法中发送的触发ANR的延迟消息。
现在先查看 scheduleServiceTimeoutLocked 方法的具体实现:
void scheduleServiceTimeoutLocked(ProcessRecord proc)
if (proc.executingServices.size() == 0 || proc.thread == null)
return;
Message msg = mAm.mHandler.obtainMessage(
ActivityManagerService.SERVICE_TIMEOUT_MSG);
msg.obj = proc;
mAm.mHandler.sendMessageDelayed(msg,
proc.execServicesFg ? SERVICE_TIMEOUT : SERVICE_BACKGROUND_TIMEOUT);
在这个方法中, 会 通过 mAm
(也就是ActivityManagerService
)的 mHandler
发送一个延迟消息。这个消息的基本参数值信息是:
mHandler
:通过子线程的 Looper 创建的一个 Handler,所以这个消息是放在子线程的消息队列中,不影响主线程。what
:ActivityManagerService.SERVICE_TIMEOUT_MSG
(值12)。delayMillis
:如果是前台服务就是SERVICE_TIMEOUT
(值20*1000豪秒),否则是SERVICE_BACKGROUND_TIMEOUT
(10 * SERVICE_TIMEOUT豪秒)。
如果 Service 成功启动,也就是在规定的 SERVICE_TIMEOUT 或 SERVICE_BACKGROUND_TIMEOUT 时间范围内执行完成该事件,就会移除掉这个延迟消息:
private void serviceDoneExecutingLocked(ServiceRecord r, boolean inDestroying,
boolean finishing)
//...省略
mAm.mHandler.removeMessages(ActivityManagerService.SERVICE_TIMEOUT_MSG, r.app);
//...省略
否则就会在ActivityManagerService
中触发这个延迟消息:
final class MainHandler extends Handler
public MainHandler(Looper looper)
super(looper, null, true);
@Override
public void handleMessage(Message msg)
switch (msg.what)
//...其它消息
case SERVICE_TIMEOUT_MSG:
mServices.serviceTimeout((ProcessRecord)msg.obj);
break;
再看 ActiveServices 的 serviceTimeout
方法:
void serviceTimeout(ProcessRecord proc)
//...收集 serviceTimeout 的一些相关的服务信息,也就是给 anrMessage 赋值
if (anrMessage != null)
proc.appNotResponding(null, null, null, null, false, anrMessage);
再看 proc(也就是 ProcessRecord) 的 appNotResponding
方法:
void appNotResponding(String activityShortComponentName, ApplicationInfo aInfo,
String parentShortComponentName, WindowProcessController parentProcess,
boolean aboveSystem, String annotation)
ArrayList<Integer> firstPids = new ArrayList<>(5);
SparseArray<Boolean> lastPids = new SparseArray<>(20);
mWindowProcessController.appEarlyNotResponding(annotation, () -> kill("anr", true));
long anrTime = SystemClock.uptimeMillis();
if (isMonitorCpuUsage())
mService.updateCpuStatsNow();
synchronized (mService)
// PowerManager.reboot() can block for a long time, so ignore ANRs while shutting down.
if (mService.mAtmInternal.isShuttingDown())
Slog.i(TAG, "During shutdown skipping ANR: " + this + " " + annotation);
return;
else if (isNotResponding())
Slog.i(TAG, "Skipping duplicate ANR: " + this + " " + annotation);
return;
else if (isCrashing())
Slog.i(TAG, "Crashing app skipping ANR: " + this + " " + annotation);
return;
else if (killedByAm)
Slog.i(TAG, "App already killed by AM skipping ANR: " + this + " " + annotation);
return;
else if (killed)
Slog.i(TAG, "Skipping died app ANR: " + this + " " + annotation);
return;
// In case we come through here for the same app before completing
// this one, mark as anring now so we will bail out.
setNotResponding(true);
// Log the ANR to the event log.
EventLog.writeEvent(EventLogTags.AM_ANR, userId, pid, processName, info.flags,
annotation);
// Dump thread traces as quickly as we can, starting with "interesting" processes.
firstPids.add(pid);
// Don't dump other PIDs if it's a background ANR
if (!isSilentAnr())
int parentPid = pid;
if (parentProcess != null && parentProcess.getPid() > 0)
parentPid = parentProcess.getPid();
if (parentPid != pid) firstPids.add(parentPid);
if (MY_PID != pid && MY_PID != parentPid) firstPids.add(MY_PID);
//1. 收集应用程序最近使用的的进程pid
for (int i = getLruProcessList().size() - 1; i >= 0; i--)
ProcessRecord r = getLruProcessList().get(i);
if (r != null && r.thread != null)
int myPid = r.pid;
if (myPid > 0 && myPid != pid && myPid != parentPid && myPid != MY_PID)
if (r.isPersistent())
firstPids.add(myPid);
if (DEBUG_ANR) Slog.i(TAG, "Adding persistent proc: " + r);
else if (r.treatLikeActivity)
firstPids.add(myPid);
if (DEBUG_ANR) Slog.i(TAG, "Adding likely IME: " + r);
else
lastPids.put(myPid, Boolean.TRUE);
if (DEBUG_ANR) Slog.i(TAG, "Adding ANR proc: " + r);
// Log the ANR to the main log.
// 2.在控制台打印ANR相关的日志,日志包含:当前进程名字,当前组件信息,当前进程id,前五个进程的相关信息,cpu信息等
StringBuilder info = new StringBuilder();
info.setLength(0);
info.append("ANR in ").append(processName);
if (activityShortComponentName != null)
info.append(" (").append(activityShortComponentName).append(")");
info.append("\\n");
info.append("PID: ").append(pid).append("\\n");
if (annotation != null)
info.append("Reason: ").append(annotation).append("\\n");
if (parentShortComponentName != null
&& parentShortComponentName.equals(activityShortComponentName))
info.append("Parent: ").append(parentShortComponentName).append("\\n");
ProcessCpuTracker processCpuTracker = new ProcessCpuTracker(true);
// don't dump native PIDs for background ANRs unless it is the process of interest
String[] nativeProcs = null;
if (isSilentAnr())
for (int i = 0; i < NATIVE_STACKS_OF_INTEREST.length; i++)
if (NATIVE_STACKS_OF_INTEREST[i].equals(processName))
nativeProcs = new String[] processName ;
break;
else
nativeProcs = NATIVE_STACKS_OF_INTEREST;
int[] pids = nativeProcs == null ? null : Process.getPidsForCommands(nativeProcs);
ArrayList<Integer> nativePids = null;
if (pids != null)
nativePids = new ArrayList<>(pids.length);
for (int i : pids)
nativePids.add(i);
// For background ANRs, don't pass the ProcessCpuTracker to
// avoid spending 1/2 second collecting stats to rank lastPids.
File tracesFile = ActivityManagerService.dumpStackTraces(firstPids,
(isSilentAnr()) ? null : processCpuTracker, (isSilentAnr()) ? null : lastPids,
nativePids);
String cpuInfo = null;
if (isMonitorCpuUsage())
mService.updateCpuStatsNow();
synchronized (mService.mProcessCpuTracker)
cpuInfo = mService.mProcessCpuTracker.printCurrentState(anrTime);
info.append(processCpuTracker.printCurrentLoad());
info.append(cpuInfo);
info.append(processCpuTracker.printCurrentState(anrTime));
Slog.e(TAG, info.toString());
if (tracesFile == null)
// There is no trace file, so dump (only) the alleged culprit's threads to the log
// 3.向进程发送放弃信号,也就是退出进程信号,这里会打印日志
Process.sendSignal(pid, Process.SIGNAL_QUIT);
StatsLog.write(StatsLog.ANR_OCCURRED, uid, processName,
activityShortComponentName == null ? "unknown": activityShortComponentName,
annotation,
(this.info != null) ? (this.info.isInstantApp()
? StatsLog.ANROCCURRED__IS_INSTANT_APP__TRUE
: StatsLog.ANROCCURRED__IS_INSTANT_APP__FALSE)
: StatsLog.ANROCCURRED__IS_INSTANT_APP__UNAVAILABLE,
isInterestingToUserLocked()
? StatsLog.ANROCCURRED__FOREGROUND_STATE__FOREGROUND
: StatsLog.ANROCCURRED__FOREGROUND_STATE__BACKGROUND,
getProcessClassEnum(),
(this.info != null) ? this.info.packageName : "");
final ProcessRecord parentPr = parentProcess != null
? (ProcessRecord) parentProcess.mOwner : null;
//4. 将这次"ANR"的进程相关信息,组件信息,cpu信息和traces文件保存到dropbox,即data/system/dropbox目录
mService.addErrorToDropBox("anr", this, processName, activityShortComponentName,
parentShortComponentName, parentPr, annotation, cpuInfo, tracesFile, null);
if (mWindowProcessController.appNotResponding(info.toString(), () -> kill("anr", true),
() ->
synchronized (mService)
mService.mServices.scheduleServiceTimeoutLocked(this);
))
return;
synchronized (mService)
// mBatteryStatsService can be null if the AMS is constructed with injector only. This
// will only happen in tests.
if (mService.mBatteryStatsService != null)
mService.mBatteryStatsService.noteProcessAnr(processName, uid);
if (isSilentAnr() && !isDebugging())
kill("bg anr", true);
return;
// Set the app's notResponding state, and look up the errorReportReceiver
makeAppNotRespondingLocked(activityShortComponentName,
annotation != null ? "ANR " + annotation : "ANR", info.toString());
// mUiHandler can be null if the AMS is constructed with injector only. This will only
// happen in tests.
//5. 交给 ActivityManagerService 处理,再交给AppErrors 处理,然后弹出程序无响应对话框
if (mService.mUiHandler != null)
// Bring up the infamous App Not Responding dialog
Message msg = Message.obtain();
msg.what = ActivityManagerService.SHOW_NOT_RESPONDING_UI_MSG;
msg.obj = new AppNotRespondingDialog.Data(this, aInfo, aboveSystem);
mService.mUiHandler.sendMessage(msg);
这个方法做的主要事情是:
- 收集应用程序最近使用的的进程 pid,只收集前五个进程 pid;
- 在控制台打印ANR相关的日志,日志包含:当前进程名字,当前组件信息,当前进程id,前五个进程的相关信息,cpu信息等;
- 向进程发送放弃信号,也就是退出进程信号,这里会打印日志;
- 通过
AtivityManagerService#addErrorToDropBox
,将这次"ANR"的进程相关信息,组件信息,cpu信息和traces文件保存到dropbox,即data/system/dropbox目录中; - 交给 ActivityManagerService 处理,再交给AppErrors 处理,然后弹出程序无响应对话框。
总结
综上,创建 Service 触发 ANR的原理就是:在创建 Service 的时候,也就是调用 Service 的 onCreate
方法前会发送一个延时消息(如果是前台服务,延时时间就是 SERVICE_TIMEOUT
(值20*1000豪秒),否则延时时间是SERVICE_BACKGROUND_TIMEOUT
(10 * SERVICE_TIMEOUT豪秒))。),如果onCreate
方法在20 /200秒内执行完成,就会移除这个延时消息,不会触发 ANR;否则就会执行这个延时消息,并触发 ANR。
inputDispatching ANR 原理
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