Sean Chow created HDFS-15402:
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Summary: Requesting http jmx metrics leads to too much CLOSE-WAIT
on datanode
Key: HDFS-15402
URL: https://issues.apache.org/jira/browse/HDFS-15402
Project: Hadoop HDFS
Issue Type: Bug
Components: metrics
Affects Versions: 3.1.3
Reporter: Sean Chow
We access {{http://127.0.0.1:50075/jmx}} to get datanode metrics
periodically. But there is too much CLOSE-WAIT socket state that lead the
normal webhdfs request failed.
{code:java}
$ ss -ant|grep 127.0.0.1:50075 |grep CLOSE-WAIT |head -10
CLOSE-WAIT 122 0 127.0.0.1:50075 127.0.0.1:37296
CLOSE-WAIT 122 0 127.0.0.1:50075 127.0.0.1:26499
CLOSE-WAIT 122 0 127.0.0.1:50075 127.0.0.1:47470
CLOSE-WAIT 122 0 127.0.0.1:50075 127.0.0.1:42852
CLOSE-WAIT 122 0 127.0.0.1:50075 127.0.0.1:40281
$ ss -ant|grep 127.0.0.1:50075 |grep CLOSE-WAIT | wc -l
6729
lsof -i:37296
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
java 101015 hdfs 3044u IPv4 271157177 0t0 TCP localhost:50075->localhost:37296
(CLOSE_WAIT)
{code}
The pid 101015 is the datanode's process id.
I use {{cdh6.1.1}} and {{apache-hadoop-3.1.3}} in my production, and both of
them have the same issue. When the metric retriving script stop, the number of
CLOSE-WAIT does not increase anymore.
The version apache-hadoop-2.9.2 does not have this issue with the same
retriving metric script.
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