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From Ravi Prakash <ravihad...@gmail.com>
Subject Re: When is an hdfs-* service restart required?
Date Thu, 07 Sep 2017 22:41:52 GMT
Hi Kellen!

The first part of the configuration is a good indication of which service
you need to restart. Unfortunately the only way to be completely sure is to
read the codez. e.g. most hdfs configuration is mapped to variables in
DFSConfigKeys

$ find . -name *.java | grep -v test | xargs grep
"dfs.datanode.handler.count"
./hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSConfigKeys.java:
public static final String  DFS_DATANODE_HANDLER_COUNT_KEY =
"dfs.datanode.handler.count";

Looking at where this is used:
$ find . -name *.java | grep -v test | xargs grep
DFS_DATANODE_HANDLER_COUNT_KEY
./hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataNode.java:import
static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_DATANODE_HANDLER_COUNT_KEY;
./hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataNode.java:
getConf().getInt(DFS_DATANODE_HANDLER_COUNT_KEY,
./hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSConfigKeys.java:
public static final String  DFS_DATANODE_HANDLER_COUNT_KEY =
"dfs.datanode.handler.count";

Cheers,
Ravi


On Thu, Sep 7, 2017 at 10:46 AM, Kellen Arb <karb@comprehend.com> wrote:

> Hello,
>
> I have a seemingly simple question, to which I can't find a clear answer.
>
> Which services/node-types must be restarted for each of the configuration
> properties? For example, if I update the 'dfs.datanode.handler.count'
> property in the `hdfs-site.xml` configuration file, which services must be
> restarted? Can I get away with only restarting `datanodes`, or do I also
> need to restart `journalnodes` and/or `namenodes`, `zkfc` etc.
>
> Just looking for clarification on this issue, though it seems that
> generally the advice is "restart everythingā€¯?
>
> Thank you,
> Kellen Arb
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