[
https://issues.apache.org/jira/browse/HDFS-8696?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14654263#comment-14654263
]
Jun Yin commented on HDFS-8696:
-------------------------------
good catch, actually we use V3 which Xiaobing sent by email.
The dfs.webhdfs.server.worker.threads was something taht old patch left in the
config file, it has no effect with the latest patch I think.
> Reduce the variances of latency of WebHDFS
> ------------------------------------------
>
> Key: HDFS-8696
> URL: https://issues.apache.org/jira/browse/HDFS-8696
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: webhdfs
> Affects Versions: 2.7.0
> Reporter: Xiaobing Zhou
> Assignee: Xiaobing Zhou
> Attachments: HDFS-8696.1.patch, HDFS-8696.2.patch, HDFS-8696.3.patch
>
>
> There is an issue that appears related to the webhdfs server. When making two
> concurrent requests, the DN will sometimes pause for extended periods (I've
> seen 1-300 seconds), killing performance and dropping connections.
> To reproduce:
> 1. set up a HDFS cluster
> 2. Upload a large file (I was using 10GB). Perform 1-byte reads, writing
> the time out to /tmp/times.txt
> {noformat}
> i=1
> while (true); do
> echo $i
> let i++
> /usr/bin/time -f %e -o /tmp/times.txt -a curl -s -L -o /dev/null
> "http://<namenode>:50070/webhdfs/v1/tmp/bigfile?op=OPEN&user.name=root&length=1";
> done
> {noformat}
> 3. Watch for 1-byte requests that take more than one second:
> tail -F /tmp/times.txt | grep -E "^[^0]"
> 4. After it has had a chance to warm up, start doing large transfers from
> another shell:
> {noformat}
> i=1
> while (true); do
> echo $i
> let i++
> (/usr/bin/time -f %e curl -s -L -o /dev/null
> "http://<namenode>:50070/webhdfs/v1/tmp/bigfile?op=OPEN&user.name=root");
> done
> {noformat}
> It's easy to find after a minute or two that small reads will sometimes
> pause for 1-300 seconds. In some extreme cases, it appears that the
> transfers timeout and the DN drops the connection.
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
