Java troubleshooting series: Java Web requests are dead, unable to respond, and threads are full

zenfery 2021-01-05 16:57:43
java troubleshooting series java web


Remember a Java Web A situation in which service requests are dead , The reason is that the request thread pool is full of deadlocks , Unable to receive new request . The following is the troubleshooting process of this problem :

1、 An instance failed to respond to the website alarm , Find the corresponding instance , Manual curl Request interface , Unable to respond .

2、 Use jps Command to find the process number of the corresponding process .

3、 Use jstat see GC Is it still in normal operation , Full command :jstat -gcutil 1624 1s, every other 1s Print once memory and gc situation , Here's the picture :
image.png
As you can see from the figure above, there is basically no change in memory , Not now GC, On the one hand, it shows that the process basically does not carry out any tasks ; On the other hand, it can also reflect JVM It's not completely dead , Still alive ( There's a small change in memory ). Take a look at the back gc situation , Here's the picture :
image.png
Basically, we can see that we had a GC, Column YGC One more time than the last picture .

4、 Reuse jmap -heap 1647 confirm JVM There's no pressure on memory , Here's the picture :
image.png

5、 Take a look at the threads jstack -l 1647 > jstack-20201224.log , And output the results to a file , Easy to check . Open the file and find that there are a lot of qtp The thread named for the beginning , Statistics , Here's the picture :
image.png
After the check , Because the project uses jetty Containers , This is the name of the thread in the request thread pool , Obviously , Threads are full , And don't release . Take a look at the normal JVM What are examples like ?
image.png
Number of threads 28 individual . Confirm the state of the exception thread again :
image.png

6、 Open the file of view thread just exported , Find out the specific reason why the thread cannot be released , Here's the picture :
image.png
You can see that it's because the thread is blocked in BasicFuture.get() method , And then you can see that your code is called in ProcessTaskQueryResultService.java Of 198 That's ok , Here's the picture :
image.png
You can see that the code uses Apache Of httpasyncclient Asynchronous calls to Libraries , return Future, If the request is abnormal , Here is the request for a relatively large response result , Interfaces are resource intensive , It's not responding , Will always be blocked in Future.get() It's about , The best way is to set the timeout for getting the results , As shown in the example above .

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https://javamana.com/2020/12/20201231011139375n.html

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