GEORGE LI created KAFKA-12971:
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Summary: Kakfa 1.1.x clients cache broker hostnames, client stuck
when host is swapped for the same broker.id
Key: KAFKA-12971
URL: https://issues.apache.org/jira/browse/KAFKA-12971
Project: Kafka
Issue Type: Bug
Components: clients
Affects Versions: 1.1.1, 1.1.0, 1.1.2
Reporter: GEORGE LI
Fix For: 2.1.2
There was an upgrade of kafka-client version from 0.11 to 1.1.x to fix a bug in
0.11 with too frequent consumer offset commits. Due to the Flink version, it
can be directly using latest 2.x kafka-client version.
{code}
Error sending fetch request (sessionId=178328175, epoch=INITIAL) to node 425:
org.apache.kafka.common.errors.DisconnectException.
{code}
some consumers were stuck with above messages with broker.id 425 had hardware
failures and got swapped with a different hostname.
Comparing the {{ClusterConnectionStates.connecting()}} of the 3 versions:
0.11.0.3:
{code}
public void connecting(String id, long now, String host, ClientDnsLookup
clientDnsLookup) {
nodeState.put(id, new NodeConnectionState(ConnectionState.CONNECTING,
now, this.reconnectBackoffInitMs, host, clientDnsLookup));
}
{code}
1.1.x:
{code}
public void connecting(String id, long now, String host, ClientDnsLookup
clientDnsLookup) {
if (nodeState.containsKey(id)) {
NodeConnectionState connectionState = nodeState.get(id);
connectionState.lastConnectAttemptMs = now;
connectionState.state = ConnectionState.CONNECTING;
// Move to next resolved address, or if addresses are exhausted,
mark node to be re-resolved
connectionState.moveToNextAddress();
} else {
nodeState.put(id, new
NodeConnectionState(ConnectionState.CONNECTING, now,
this.reconnectBackoffInitMs, host, clientDnsLookup));
}
}
{code}
2.2.x:
{code}
public void connecting(String id, long now, String host, ClientDnsLookup
clientDnsLookup) {
NodeConnectionState connectionState = nodeState.get(id);
if (connectionState != null && connectionState.host().equals(host)) {
connectionState.lastConnectAttemptMs = now;
connectionState.state = ConnectionState.CONNECTING;
// Move to next resolved address, or if addresses are exhausted,
mark node to be re-resolved
connectionState.moveToNextAddress();
return;
} else if (connectionState != null) {
log.info("Hostname for node {} changed from {} to {}.", id,
connectionState.host(), host);
}
// Create a new NodeConnectionState if nodeState does not already
contain one
// for the specified id or if the hostname associated with the node id
changed.
nodeState.put(id, new NodeConnectionState(ConnectionState.CONNECTING,
now,
this.reconnectBackoffInitMs, host, clientDnsLookup));
}
{code}
>From above, the {{0.11.0.3}} is just putting the node to the NodeState HashMap
>to retry with update host.
In {{1.1.x}}, it adds a logic of "caching". {{if (nodeState.containsKey(id))}},
However, if the HOSTNAME of the broker.id is swapped/changed, it never gets to
the else block to update the NodeState with the new hostname.
In {{2.2.x}}, it adds an additional check {{if (connectionState != null &&
connectionState.host().equals(host))}}, if the Hostname changed, then called
{{nodeState.put()}} to update the host.
So from above, it looks like the 1.1.x caching logic introduced a bug of not
updating the nodeState()'s host when that is changed (e..g host failure, swap
with a different hostname, but use the same broker.id).
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