eclipsesource
Memory leak
We have an application that brings up several short lived J2V8 engines a second and over a couple of days, the java process consumes more and more memory until the server becomes unresponsive. Restarting the Java process fixes the issue and frees the memory. We have monitored the heap, which looks fine, so believe there is a memory leak in either the JNI layer or the V8 instances themselves. The leak can be easily demonstrated with the following code:
public static void main(String[] args) {
while(true) {
try (V8 v8 = V8.createV8Runtime()) {}
}
}
During a run of the test I dumped the memory stats periodically.
The first memory stats just after Java launch:
Thu Sep 12 09:14:39 UTC 2019
total used free shared buff/cache available
Mem: 2002820 797368 515472 5344 689980 1045256
The last memory stats before the server became unresponsive:
Thu Sep 12 11:34:21 UTC 2019
total used free shared buff/cache available
Mem: 2002820 1898052 64968 5148 39800 7040
The memory stats after killing the Java process:
total used free shared buff/cache available
Mem: 2002820 834248 923900 5212 244672 1019236
Here are some details on the server OS and software:
OS Details
NAME="Ubuntu" VERSION="18.04.2 LTS (Bionic Beaver)" ID=ubuntu ID_LIKE=debian PRETTY_NAME="Ubuntu 18.04.2 LTS" VERSION_ID="18.04" HOME_URL="https://www.ubuntu.com/" SUPPORT_URL="https://help.ubuntu.com/" BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/" PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy" VERSION_CODENAME=bionic UBUNTU_CODENAME=bionic
J2V8 Build Output
J2V8 Version [INFO] --------------< com.eclipsesource.j2v8:j2v8_linux_x86_64 >-------------- [INFO] Building j2v8_linux_x86_64 5.1.0-SNAPSHOT
V8 Details
Version 5.4.500
Even worse, using more than one runtime sometimes causes segfaults with our application. We've opted to re-use runtimes for now. Maybe you'll have more luck with a newer version.
We cannot reuse runtime instance either. In multi-threaded environment its hard to control the thread accessing the runtime instance.
I could not fix this issue so we side stepped it by using GraalVM. The javascript engine has given us better performance than J2V8 and has much more up to date ECMAScript compliance. We are using in it a highly threaded environment and have seen no leaks. I can highly recommend it.
GraalVM doesn’t work with Android though, right?
On Thu, 10. Dec 2020 at 17:41 javabully [email protected] wrote:
I could not fix this issue so we side stepped it by using GraalVM. The javascript engine has given us better performance than J2V8 and has much more up to date ECMAScript compliance. We are using in it a highly threaded environment and have seen no leaks. I can highly recommend it.
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You can try JavaScriptCore as an alternative on Android.
Not that there are not downsides there, including that it's a C/C++ API that you need to wrap yourself for Java (unless there's an existing wrapper I'm unaware of). That said, such a wrapper isn't that hard to produce.
I like the notion of J2V8, but:
- V8 libraries aren't readily available (and are really painful to build)
- If you actually need a C/C++ API at any point, JavaScriptCore's API is straightforward
I've now done projects with both on Android. Both worked. (I didn't notice the memory leak noted here as my J2V8 runtimes while multiple are fairly long-lived.)
Currently, you have to close/release the V8 instance if you have created yourself. It's also mentioned in the Javadocs here and here.
We also have upgraded the V8 version (V8 8.3.110) in the latest J2V8 Android releases.
Elmi, any plans for making that work on a Mac? We run latest J2V8 on Android, and test on Macs. But we haven’t been able to run latest J2V8 on mac, so we are kind of stuck on ES2015.
Cheers.
On Thu, 10. Dec 2020 at 18:36 Elmi Ahmadov [email protected] wrote:
Currently, you have to close/release the V8 instance if you have created yourself. It's also mentioned in the Javadocs here https://github.com/eclipsesource/J2V8/blob/master/src/main/java/com/eclipsesource/v8/V8Object.java#L25 and here https://github.com/eclipsesource/J2V8/blob/master/src/main/java/com/eclipsesource/v8/V8Value.java#L13 .
We also have upgraded the V8 version (V8 8.3.110) in the latest J2V8 Android releases.
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Currently, I can mention about any plan but I have successfully built J2V8 for Android, Linux and macOS (PR) some time ago. I guess Android and Linux builds should still be relevant. At least, the last Github Action build was successful for them.
You can build on your local machine either with pre-build V8 library (here) or you can also build V8 locally.
If you want to build V8 locally, use the following command:
python build.py -t macos -a x64 --docker v8 j2v8cmake j2v8jni j2v8cpp j2v8optimize j2v8java j2v8test
Maybe you can apply changes for macOS locally and try.
Thanks, will give it a shot over the weekend. Cheers.
On Thu, 10. Dec 2020 at 18:49 Elmi Ahmadov [email protected] wrote:
Currently, I can mention about any plan but I have successfully built J2V8 for Android, Linux and macOS (PR https://github.com/eclipsesource/J2V8/pull/489) some time ago. I guess Android and Linux builds still should be relevant. At least, the last Github Action build was successful for them.
You can build on your local machine either with pre-build V8 library (here https://github.com/eclipsesource/J2V8/blob/master/.github/workflows/main.yml#L16) or you can also build V8 locally.
If you want to build V8 locally, use the following command:
python build.py -t linux -a x64 --docker j2v8cmake j2v8jni j2v8cpp j2v8optimize j2v8java j2v8test
Maybe you can apply changes for macOS locally and try.
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@ahmadov Yeah, it was possible to build for a Mac. Not really super intuitive, but possible. Thanks for your help.