[HDFS-16565] DataNode holds a large number of CLOSE_WAIT connections that are not released

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Duplicate
• Affects Version/s: 3.3.0
• Component/s: datanode, ec

Environment

CentOS Linux release 7.5.1804 (Core)

• Assignee: Unassigned
• Reporter: JiangHua Zhu
• Created: 29/Apr/22 08:52
• Updated: 19/Jul/22 02:35
• Resolved: 18/May/22 02:25

Description

There is a strange phenomenon here, DataNode holds a large number of connections in CLOSE_WAIT state and does not release.
netstat -na | awk '/^tcp/ {++S[$NF]} END

{for(a in S) print a, S[a]}

'
LISTEN 20
CLOSE_WAIT 17707
ESTABLISHED 1450
TIME_WAIT 12

It can be found that the connections with the CLOSE_WAIT state have reached 17k and are still growing. View these CLOSE_WAITs through the lsof command, and get the following phenomenon:
lsof -i tcp | grep -E 'CLOSE_WAIT|COMMAND'

It can be seen that the reason for this phenomenon is that Socket#close() is not called correctly, and DataNode interacts with other nodes as Client.

Issue Links

• is related to: HDFS-15709 EC: Socket file descriptor leak in StripedBlockChecksumReconstructor