This project aims to explore Android bugs about opened files leak.
What's open files leak? Android is based on Linux and every process in Linux (or in Android) has a limit on the number of opened files. In most Android devices, the limit is 1024.
You can use the shell command ulimit to view the limit. For example,
shell@hammerhead:/ $ ulimit -a
time(cpu-seconds) unlimited
file(blocks) unlimited
coredump(blocks) 0
data(KiB) unlimited
stack(KiB) 8192
lockedmem(KiB) 65536
nofiles(descriptors) 1024 -------> look here
processes 12281
flocks unlimited
sigpending 12281
msgqueue(bytes) 819200
maxnice 40
maxrtprio 0
resident-set(KiB) unlimited
address-space(KiB) unlimited
shell@hammerhead:/ $ ulimit --help
/system/bin/sh: ulimit: --: unknown option
/system/bin/sh: ulimit: usage: ulimit [-acdefHiLlmnpqrSstv] [value]
1|shell@hammerhead:/ $ ulimit -n
1024
You can use the shell commands run-as (or su) and lsof to view the open files of one process. For example,
shell@hammerhead:/ $ ps | grep me.ycdev.android.demo.openfilesleak
u0_a128 9473 19269 1545928 53648 ffffffff 00000000 S me.ycdev.android.demo.openfilesleak
shell@hammerhead:/ $ run-as me.ycdev.android.demo.openfilesleak
shell@hammerhead:/data/data/me.ycdev.android.demo.openfilesleak $ lsof 9473
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
me.ycdev. 9473 u0_a128 exe ??? ??? ??? ??? /system/bin/app_process32_original
me.ycdev. 9473 u0_a128 0 ??? ??? ??? ??? /dev/null
me.ycdev. 9473 u0_a128 1 ??? ??? ??? ??? /dev/null
me.ycdev. 9473 u0_a128 2 ??? ??? ??? ??? /dev/null
me.ycdev. 9473 u0_a128 3 ??? ??? ??? ??? socket:[3262494]
me.ycdev. 9473 u0_a128 4 ??? ??? ??? ??? /sys/kernel/debug/tracing/trace_marker
me.ycdev. 9473 u0_a128 5 ??? ??? ??? ??? /system/framework/framework.jar
me.ycdev. 9473 u0_a128 6 ??? ??? ??? ??? /system/framework/core-libart.jar
me.ycdev. 9473 u0_a128 7 ??? ??? ??? ??? socket:[3262595]
me.ycdev. 9473 u0_a128 8 ??? ??? ??? ??? /system/framework/framework-res.apk
me.ycdev. 9473 u0_a128 9 ??? ??? ??? ??? /dev/__properties__
me.ycdev. 9473 u0_a128 10 ??? ??? ??? ??? /dev/binder
me.ycdev. 9473 u0_a128 11 ??? ??? ??? ??? pipe:[5082666]
me.ycdev. 9473 u0_a128 12 ??? ??? ??? ??? /dev/alarm
me.ycdev. 9473 u0_a128 13 ??? ??? ??? ??? socket:[5082660]
me.ycdev. 9473 u0_a128 14 ??? ??? ??? ??? /dev/cpuctl/apps/tasks
me.ycdev. 9473 u0_a128 15 ??? ??? ??? ??? /dev/cpuctl/apps/bg_non_interactive/tasks
me.ycdev. 9473 u0_a128 16 ??? ??? ??? ??? pipe:[5082661]
me.ycdev. 9473 u0_a128 17 ??? ??? ??? ??? pipe:[5082661]
me.ycdev. 9473 u0_a128 18 ??? ??? ??? ??? pipe:[5082666]
me.ycdev. 9473 u0_a128 19 ??? ??? ??? ??? anon_inode:[eventpoll]
me.ycdev. 9473 u0_a128 20 ??? ??? ??? ??? /data/app/me.ycdev.android.demo.openfilesleak-1/base.apk
me.ycdev. 9473 u0_a128 21 ??? ??? ??? ??? pipe:[5089340]
me.ycdev. 9473 u0_a128 22 ??? ??? ??? ??? socket:[5088566]
me.ycdev. 9473 u0_a128 23 ??? ??? ??? ??? pipe:[5089340]
me.ycdev. 9473 u0_a128 24 ??? ??? ??? ??? anon_inode:[eventpoll]
me.ycdev. 9473 u0_a128 25 ??? ??? ??? ??? /dev/kgsl-3d0
me.ycdev. 9473 u0_a128 26 ??? ??? ??? ??? socket:[5082687]
me.ycdev. 9473 u0_a128 27 ??? ??? ??? ??? socket:[5082691]
me.ycdev. 9473 u0_a128 28 ??? ??? ??? ??? anon_inode:dmabuf
me.ycdev. 9473 u0_a128 29 ??? ??? ??? ??? anon_inode:dmabuf
me.ycdev. 9473 u0_a128 30 ??? ??? ??? ??? /dev/ion
me.ycdev. 9473 u0_a128 31 ??? ??? ??? ??? /dev/ion
me.ycdev. 9473 u0_a128 34 ??? ??? ??? ??? anon_inode:dmabuf
me.ycdev. 9473 u0_a128 35 ??? ??? ??? ??? anon_inode:dmabuf
me.ycdev. 9473 u0_a128 36 ??? ??? ??? ??? socket:[5082749]
me.ycdev. 9473 u0_a128 37 ??? ??? ??? ??? anon_inode:dmabuf
me.ycdev. 9473 u0_a128 38 ??? ??? ??? ??? anon_inode:dmabuf
me.ycdev. 9473 u0_a128 mem ??? 00:04 0 3262499 /dev/ashmem/dalvik-main
When your users suffer a lot of strange DB operation issues, the root cause may be "open files leak"! SQLite DB is operating on a DB file. When any DB operation happens, the DB file will be opened first. If number of the open files reaches the ulimit, then no any more file can be opened.
Also, open files leak may lead other strange issues.
There are some open files leak bugs found in Android.
In constructor of java.util.ZipFile, if the zip file is invalid, the opened file (a RandomAccessFile object) will be leaked by ZipFile. Next, there are a good news and a bad news.
The good news is that when GC happens, the RandomAccessFile object will close the leaked file. So, this issue is not a big problem in most cases. But if no GC happens, it's possible to reach the ulimit!
The bad news is that when GC happens, the leaked file will not be closed on some devices! In this case, the ulimit will be reached eventually.
Please refer the test reports section. In my test report, the opened files will be leaked in those devices with Android 4.0.x ~ 4.1.x. Bug I didn't find out the leak reason in Android source code.
Ref: https://code.google.com/p/android/issues/detail?id=66383
This leak was already fixed in Android 5.0.
When use PackageManager#getPackageArchiveInfo() to parse an invalid apk file in Android 5.0+, the opened file will be leaked.
Ref: https://code.google.com/p/android/issues/detail?id=171099
This leak is still there, waiting for fix.
When WebView is not needed any more, we can do the following things to do some clean: a) Invoke WebView.loadUrl("about:blank") to clear the WebView. b) Invoke WebView.destroy() to destroy the WebView. c) Let's GC to collect the WebView object.
Unfortunately, even though we did all the above things, before Android 5.0, the open files leak is very serious.
So, take care when you decide to use WebView.
This project use Android test cases to confirm the open files leak bugs in Android versions.
Use the following command to run the test cases (connect the device first):
[PWD: ~/work/tyc/ycdev/demos/OpenFilesLeakTest] (master)
$ ./gradlew connectedAndroidTest
| Device Brand | Device Model | Android Version | Test Result | Remark |
|---|
| Device Brand | Device Model | Android Version | Test Result | Remark |
|---|---|---|---|---|
| Nexus 5 | 5.0.1 | Pass | ||
| Nexus 6 | 5.1 | Pass | ||
| Nexus One | 2.3.3 | Pass | No SD card | |
| Galaxy Nexus | 4.3 | Pass | ||
| Galaxy Nexus | 4.1.2 | Pass | ||
| Nexus 4 | 5.0 | Pass | ||
| Huawei | H60-L02 | 4.4.2 | Pass | |
| Huawei | HUAWEI MT7-TL00 | 4.4.2 | Pass | |
| Huawei | H60-L11 | 4.4.2 | Pass | |
| Huawei | H30-U10 | 4.2.2 | Pass | |
| Samsung | SM-N9100 | 4.4.4 | Pass | |
| Samsung | GT-I9300 | 4.3 | Pass | |
| Samsung | GT-I8552 | 4.1.2 | Pass | |
| Samsung | SM-N9002 | 4.3 | Pass | |
| Samsung | SM-G9006W | 5.0 | Pass | |
| Xiaomi | MI 4W | 4.4.4 | Pass | |
| Xiaomi | MI 2SC | 4.1.1 | Pass | |
| Xiaomi | MI 3 | 4.4.2 | Pass | |
| MOTO | MT887 | 4.1.2 | Pass | |
| MOTO | XT910 | 4.0.4 | Pass | |
| OPPO | N5207 | 4.4.4 | Pass | |
| Lenovo | Lenovo K900 | 4.2.2 | Pass | |
| HTC | HTC 919d | 4.4.2 | Pass | |
| Nubia | NX505J | 4.4.2 | Pass |