Erik Krogen created HDFS-14442:
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Summary: Disagreement between HAUtil.getAddressOfActive and
RpcInvocationHandler.getConnectionId
Key: HDFS-14442
URL: https://issues.apache.org/jira/browse/HDFS-14442
Project: Hadoop HDFS
Issue Type: Bug
Affects Versions: 3.3.0
Reporter: Erik Krogen
While working on HDFS-14245, we noticed a discrepancy in some proxy-handling
code.
The description of {{RpcInvocationHandler.getConnectionId()}} states:
{code}
/**
* Returns the connection id associated with the InvocationHandler instance.
* @return ConnectionId
*/
ConnectionId getConnectionId();
{code}
It does not make any claims about whether this connection ID will be an active
proxy or not. Yet in {{HAUtil}} we have:
{code}
/**
* Get the internet address of the currently-active NN. This should rarely be
* used, since callers of this method who connect directly to the NN using the
* resulting InetSocketAddress will not be able to connect to the active NN if
* a failover were to occur after this method has been called.
*
* @param fs the file system to get the active address of.
* @return the internet address of the currently-active NN.
* @throws IOException if an error occurs while resolving the active NN.
*/
public static InetSocketAddress getAddressOfActive(FileSystem fs)
throws IOException {
if (!(fs instanceof DistributedFileSystem)) {
throw new IllegalArgumentException("FileSystem " + fs + " is not a DFS.");
}
// force client address resolution.
fs.exists(new Path("/"));
DistributedFileSystem dfs = (DistributedFileSystem) fs;
DFSClient dfsClient = dfs.getClient();
return RPC.getServerAddress(dfsClient.getNamenode());
}
{code}
Where the call {{RPC.getServerAddress()}} eventually terminates into
{{RpcInvocationHandler#getConnectionId()}}, via {{RPC.getServerAddress()}} ->
{{RPC.getConnectionIdForProxy()}} ->
{{RpcInvocationHandler#getConnectionId()}}. {{HAUtil}} appears to be making an
incorrect assumption that {{RpcInvocationHandler}} will necessarily return an
_active_ connection ID. {{ObserverReadProxyProvider}} demonstrates a
counter-example to this, since the current connection ID may be pointing at,
for example, an Observer NameNode.
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