Summary: | Iteration over a view on a synchronized collection without obtaining a lock on the collection | ||
---|---|---|---|
Product: | JMeter - Now in Github | Reporter: | Bob Atkey <bob> |
Component: | Main | Assignee: | JMeter issues mailing list <issues> |
Status: | REOPENED --- | ||
Severity: | major | CC: | p.mouawad, ttaolu |
Priority: | P3 | Keywords: | APIBug, FAQ, NeedsReleaseNote |
Version: | 5.0 | ||
Target Milestone: | JMETER_5.0 | ||
Hardware: | PC | ||
OS: | Linux | ||
Attachments: |
Jmeter Test Error When Itr next and remove
Slow down recoverRunningVersion to show problems Slow down recoverRunningVersion to show problems sl Slow down recoverRunningVersion to show problems |
Description
Bob Atkey
2013-11-28 16:44:13 UTC
I wrote:
> We are also planning to use this finding as an example of Android-related
> concurrency mistakes in an article about ThreadSafe.
Obviously, "Android-related" was a mistake here. I meant to write "Java-related". Sorry about that.
Thanks for report, I was wondering why your tool does not also report line 456: return new PropertyIteratorImpl(propMap.values()); Did you report all findings of your tool or only some examples ? > Thanks for report, I was wondering why your tool does not also report line 456: > return new PropertyIteratorImpl(propMap.values()); Actually, our tool doesn't report the instance on line 456 because it doesn't look into the implementation of PropertyIteratorImpl while analysing the AbstractTestElement class. Therefore, it doesn't realise that everything that is passed in will have .iterator() called on it. This is certainly something that we will look at adding to ThreadSafe in the future. Thanks! > Did you report all findings of your tool or only some examples ? I only reported two examples of findings that I thought looked interesting. If I get more time soon I will report the rest of the interesting looking reports that ThreadSafe gives. Created PR for the example identified in this issue: https://github.com/apache/jmeter/pull/260 Are there any more that the tool found (in the latest code) which should be addressed? As far as I can see, the syncrhonizedMap was added in attempt to fix https://bz.apache.org/bugzilla/show_bug.cgi?id=16304 The latest reply suggests that the synchronization did not help. So I do not see much reason to complicate code. I don't think it would hurt, yet I see no reason how it would help. (In reply to Vladimir Sitnikov from comment #5) > As far as I can see, the syncrhonizedMap was added in attempt to fix > https://bz.apache.org/bugzilla/show_bug.cgi?id=16304 > The latest reply suggests that the synchronization did not help. > > So I do not see much reason to complicate code. > I don't think it would hurt, yet I see no reason how it would help. Thanks Felix for digging, interesting indeed. A question for you, I have a doubt. In my understanding, calling synchronized in monothreaded call has a cost: http://stackoverflow.com/questions/973518/are-synchronized-methods-slower-in-single-threaded-applications Do you confirm this from benchmarks you did ? (In reply to Vladimir Sitnikov from comment #5) > As far as I can see, the syncrhonizedMap was added in attempt to fix > https://bz.apache.org/bugzilla/show_bug.cgi?id=16304 > The latest reply suggests that the synchronization did not help. > > So I do not see much reason to complicate code. > I don't think it would hurt, yet I see no reason how it would help. It does say the problem still exists in the comment yet the issue was set to resolved. Maybe we should remove the synchronizedMap as we are accessing it in an unsafe way anyway - or just comment the code and close this bz. Created attachment 38216 [details]
Jmeter Test Error When Itr next and remove
public void recoverRunningVersion() {
Iterator iter = this.propMap.entrySet().iterator();
while(iter.hasNext()) {
Entry<String, JMeterProperty> entry = (Entry)iter.next();
JMeterProperty prop = (JMeterProperty)entry.getValue();
if (this.isTemporary(prop)) {
iter.remove();
this.clearTemporary(prop);
} else {
prop.recoverRunningVersion(this);
}
}
this.emptyTemporary();
}
For the 10 slave Linux machines used in the test environment, each 10 thread is 100 concurrent, and most of them report an error.ConcurrentModificationException, The sampler is a downloaded soap sampler. Most of the machines report this error. The script includes two CSV config and some listeners. I don't know whether the component is used incorrectly or where there is a problem. I haven't found the problem for a day, Some people say that problem is 'recycle on EOF' set by CSV config is false. Is it the problem caused by soap sampler, but there is no error when running locally in windows os @TaoLu, could you please share the script that reproduces the issue? Created attachment 38218 [details] Slow down recoverRunningVersion to show problems I think we have to use a lock around the clean-up of the temporary properties like Graham did. With the attached patch I can reproduce an overlap in the recoverRunningVersion method between more than one thread. The exceptions (with are for example: 2022-03-08 21:23:14,089 WARN o.a.j.t.AbstractTestElement: Recover in different threads: [Thread[Thread-33,6,main], Thread[Thread-19,6,main]]; Element: org.apache.jmeter.sampler.DebugSampler@7ea357f0 java.lang.RuntimeException: Thread mismatch >-------at org.apache.jmeter.testelement.AbstractTestElement.recoverRunningVersion(AbstractTestElement.java:511) ~[ApacheJMeter_core.jar:5.5-SNAPSHOT] >-------at org.apache.jmeter.threads.SamplePackage.recoverRunningVersion(SamplePackage.java:126) ~[ApacheJMeter_core.jar:5.5-SNAPSHOT] >-------at org.apache.jmeter.threads.TestCompiler.done(TestCompiler.java:123) ~[ApacheJMeter_core.jar:5.5-SNAPSHOT] >-------at org.apache.jmeter.threads.JMeterThread.executeSamplePackage(JMeterThread.java:593) ~[ApacheJMeter_core.jar:5.5-SNAPSHOT] >-------at org.apache.jmeter.threads.JMeterThread.processSampler(JMeterThread.java:501) ~[ApacheJMeter_core.jar:5.5-SNAPSHOT] >-------at org.apache.jmeter.threads.JMeterThread.run(JMeterThread.java:268) ~[ApacheJMeter_core.jar:5.5-SNAPSHOT] >-------at java.lang.Thread.run(Thread.java:748) ~[?:1.8.0_201] 2022-03-08 21:23:14,579 WARN o.a.j.t.AbstractTestElement: Recover in different threads: [Thread[Thread-34,6,main], Thread[Thread-20,6,main]]; Element: org.apache.jmeter.sampler.DebugSampler@521c345a java.lang.RuntimeException: Thread mismatch >-------at org.apache.jmeter.testelement.AbstractTestElement.recoverRunningVersion(AbstractTestElement.java:511) ~[ApacheJMeter_core.jar:5.5-SNAPSHOT] >-------at org.apache.jmeter.threads.SamplePackage.recoverRunningVersion(SamplePackage.java:126) ~[ApacheJMeter_core.jar:5.5-SNAPSHOT] >-------at org.apache.jmeter.threads.TestCompiler.done(TestCompiler.java:123) ~[ApacheJMeter_core.jar:5.5-SNAPSHOT] >-------at org.apache.jmeter.threads.JMeterThread.executeSamplePackage(JMeterThread.java:593) ~[ApacheJMeter_core.jar:5.5-SNAPSHOT] >-------at org.apache.jmeter.threads.JMeterThread.processSampler(JMeterThread.java:501) ~[ApacheJMeter_core.jar:5.5-SNAPSHOT] >-------at org.apache.jmeter.threads.JMeterThread.run(JMeterThread.java:268) ~[ApacheJMeter_core.jar:5.5-SNAPSHOT] >-------at java.lang.Thread.run(Thread.java:748) ~[?:1.8.0_201] 2022-03-08 21:23:14,590 WARN o.a.j.t.AbstractTestElement: Recover in different threads: [Thread[Thread-35,6,main], Thread[Thread-30,6,main], Thread[Thread-21,6,main], Thread[Thread-16,6,main]]; Element: org.apache.jmeter.control.LoopController@4b4d66fb java.lang.RuntimeException: Thread mismatch >-------at org.apache.jmeter.testelement.AbstractTestElement.recoverRunningVersion(AbstractTestElement.java:511) ~[ApacheJMeter_core.jar:5.5-SNAPSHOT] >-------at org.apache.jmeter.control.LoopController.reInitialize(LoopController.java:203) ~[ApacheJMeter_core.jar:5.5-SNAPSHOT] >-------at org.apache.jmeter.control.LoopController.nextIsNull(LoopController.java:157) ~[ApacheJMeter_core.jar:5.5-SNAPSHOT] >-------at org.apache.jmeter.control.GenericController.next(GenericController.java:170) ~[ApacheJMeter_core.jar:5.5-SNAPSHOT] >-------at org.apache.jmeter.control.LoopController.next(LoopController.java:134) ~[ApacheJMeter_core.jar:5.5-SNAPSHOT] >-------at org.apache.jmeter.threads.AbstractThreadGroup.next(AbstractThreadGroup.java:99) ~[ApacheJMeter_core.jar:5.5-SNAPSHOT] >-------at org.apache.jmeter.threads.JMeterThread.run(JMeterThread.java:303) ~[ApacheJMeter_core.jar:5.5-SNAPSHOT] >-------at java.lang.Thread.run(Thread.java:748) ~[?:1.8.0_201] Forget my last comment for now, as I forgot to remove the thread from the stack. Created attachment 38219 [details] Slow down recoverRunningVersion to show problems Now a working version of the "slow" recoverRunningVersion method. When the threads are removed at the end (in my simple test plan) one Test Element is getting flagged, only. 2022-03-08 21:55:40,771 WARN o.a.j.t.AbstractTestElement: Recover in different threads: [Thread[Thread-53,6,main], Thread[Thread-54,6,main]]; Element: org.apache.jmeter.reporters.ResultCollector@42f6fa63 java.lang.RuntimeException: Thread mismatch >-------at org.apache.jmeter.testelement.AbstractTestElement.recoverRunningVersion(AbstractTestElement.java:513) ~[ApacheJMeter_core.jar:5.5-SNAPSHOT] >-------at org.apache.jmeter.threads.SamplePackage.recoverRunningVersion(SamplePackage.java:110) ~[ApacheJMeter_core.jar:5.5-SNAPSHOT] >-------at org.apache.jmeter.threads.SamplePackage.recoverRunningVersion(SamplePackage.java:120) ~[ApacheJMeter_core.jar:5.5-SNAPSHOT] >-------at org.apache.jmeter.threads.TestCompiler.done(TestCompiler.java:123) ~[ApacheJMeter_core.jar:5.5-SNAPSHOT] >-------at org.apache.jmeter.threads.JMeterThread.executeSamplePackage(JMeterThread.java:593) ~[ApacheJMeter_core.jar:5.5-SNAPSHOT] >-------at org.apache.jmeter.threads.JMeterThread.processSampler(JMeterThread.java:501) ~[ApacheJMeter_core.jar:5.5-SNAPSHOT] >-------at org.apache.jmeter.threads.JMeterThread.run(JMeterThread.java:268) ~[ApacheJMeter_core.jar:5.5-SNAPSHOT] >-------at java.lang.Thread.run(Thread.java:748) ~[?:1.8.0_201] The code for ResultCollector explicitly mentions, that it has to be thread-safe (which recoverRunningVersion is not). So maybe, we can make it for ResultCollector thread-safe instead of all? But on the other hand, if we obtain a lock for a single thread, it is not that expensive any more. So I think we could try to add it. Created attachment 38220 [details]
sl
Created attachment 38221 [details]
Slow down recoverRunningVersion to show problems
Adding more debug output (size of the temporary properties), it does look like ResultCollector has no temporary properties and should not be the culprit.
So, the question is, which Element is it and where does the concurrent access comes from?
@TaoLu, are you using a third party plugin? What elements do you use apart from CSV Data Source? How big are your CSV sources, how many elements do they have?
For comparison I did a simple test plan (dummy sampler + csv data source) with 2000 threads. First time with additional locking and second time without. The numbers are not that different: (with locking) $ ./bin/jmeter -t LAST -n Creating summariser <summary> Created the tree successfully using /home/felix/jmeter-tests/csv-thread-mismatch.jmx Starting standalone test @ Tue Mar 08 22:29:44 CET 2022 (1646774984565) Waiting for possible Shutdown/StopTestNow/HeapDump/ThreadDump message on port 4445 summary + 889238 in 00:00:15 = 58664.6/s Avg: 0 Min: 0 Max: 26 Err: 0 (0.00%) Active: 2000 Started: 2000 Finished: 0 summary + 2046430 in 00:00:30 = 68214.3/s Avg: 0 Min: 0 Max: 21 Err: 0 (0.00%) Active: 2000 Started: 2000 Finished: 0 summary = 2935668 in 00:00:45 = 65008.8/s Avg: 0 Min: 0 Max: 26 Err: 0 (0.00%) summary + 2015928 in 00:00:30 = 67197.6/s Avg: 0 Min: 0 Max: 20 Err: 0 (0.00%) Active: 2000 Started: 2000 Finished: 0 summary = 4951596 in 00:01:15 = 65882.5/s Avg: 0 Min: 0 Max: 26 Err: 0 (0.00%) summary + 2011866 in 00:00:30 = 67062.2/s Avg: 0 Min: 0 Max: 18 Err: 0 (0.00%) Active: 2000 Started: 2000 Finished: 0 summary = 6963462 in 00:01:45 = 66219.0/s Avg: 0 Min: 0 Max: 26 Err: 0 (0.00%) summary + 1128224 in 00:00:17 = 65874.0/s Avg: 0 Min: 0 Max: 27 Err: 0 (0.00%) Active: 0 Started: 2000 Finished: 2000 summary = 8091686 in 00:02:02 = 66170.7/s Avg: 0 Min: 0 Max: 27 Err: 0 (0.00%) Tidying up ... @ Tue Mar 08 22:31:47 CET 2022 (1646775107127) ... end of run (without locking): $ ./bin/jmeter -t LAST -n Creating summariser <summary> Created the tree successfully using /home/felix/jmeter-tests/csv-thread-mismatch.jmx Starting standalone test @ Tue Mar 08 22:32:12 CET 2022 (1646775132163) Waiting for possible Shutdown/StopTestNow/HeapDump/ThreadDump message on port 4445 summary + 1197546 in 00:00:18 = 68232.4/s Avg: 0 Min: 0 Max: 27 Err: 0 (0.00%) Active: 2000 Started: 2000 Finished: 0 summary + 2029381 in 00:00:30 = 67670.8/s Avg: 0 Min: 0 Max: 26 Err: 0 (0.00%) Active: 2000 Started: 2000 Finished: 0 summary = 3226927 in 00:00:48 = 67878.1/s Avg: 0 Min: 0 Max: 27 Err: 0 (0.00%) summary + 1888713 in 00:00:30 = 62957.1/s Avg: 0 Min: 0 Max: 23 Err: 0 (0.00%) Active: 2000 Started: 2000 Finished: 0 summary = 5115640 in 00:01:18 = 65974.2/s Avg: 0 Min: 0 Max: 27 Err: 0 (0.00%) summary + 1769647 in 00:00:30 = 58988.2/s Avg: 0 Min: 0 Max: 28 Err: 0 (0.00%) Active: 2000 Started: 2000 Finished: 0 summary = 6885287 in 00:01:48 = 64025.4/s Avg: 0 Min: 0 Max: 28 Err: 0 (0.00%) summary + 977769 in 00:00:14 = 67736.0/s Avg: 0 Min: 0 Max: 16 Err: 0 (0.00%) Active: 0 Started: 2000 Finished: 2000 summary = 7863056 in 00:02:02 = 64464.5/s Avg: 0 Min: 0 Max: 28 Err: 0 (0.00%) Tidying up ... @ Tue Mar 08 22:34:14 CET 2022 (1646775254435) ... end of run This issue has been migrated to GitHub: https://github.com/apache/jmeter/issues/3279 |