Shawn created HADOOP-18346:
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Summary: Suggest to update the IP address of ConnectionId when
server of Connection got updated
Key: HADOOP-18346
URL: https://issues.apache.org/jira/browse/HADOOP-18346
Project: Hadoop Common
Issue Type: Improvement
Components: hdfs-client
Affects Versions: 3.3.1
Reporter: Shawn
When use ProtobufRpcEngine to get RPC proxy, we apply the InetSocketAddress
addr, and this address is then kept in the ConnectionId (see
[here|https://github.com/apache/hadoop/blob/rel/release-3.3.1/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/ProtobufRpcEngine.java#L139]
and
[here|https://github.com/apache/hadoop/blob/rel/release-3.3.1/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/Client.java#L1681]).
When the destination IP of the connection changes, we have code to update the
server variable in the connection (see
[here|https://github.com/apache/hadoop/blob/rel/release-3.3.1/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/Client.java#L641]).
This makes the retry of the connection to succeed.
However, the above logic only temporary fix the connection. After the RPC call
of the client, the connection will be closed. Next time when we use the same
proxy to do the RPC call, we will again to fail the first connection and
succeed the second one after the server IP got updates.
My suggestion is to not only update the server variable in the connection, but
also update the address of the ConnectionId in the Invoker. This way, we can
reuse the proxy with the latest IP address.
The use case for this is: in Apache ozone project, we initialize the RPC proxy
with a fixed InetSocketAddress (for example, datanode needs to set up the RPC
proxy to scm). But if lately the server IP changes (e.g. in k8s, the IP of a
pod is very likely to change), every time the proxy needs two calls (1st fails
and the 2nd succeeds with the updated IP). By using the above solution, we can
eliminate this issue.
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