Major Description
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.
Error sending fetch request (sessionId=178328175, epoch=INITIAL) to node 425: org.apache.kafka.common.errors.DisconnectException.
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:
public void connecting(String id, long now, String host, ClientDnsLookup clientDnsLookup) {
nodeState.put(id, new NodeConnectionState(ConnectionState.CONNECTING, now, this.reconnectBackoffInitMs, host, clientDnsLookup));
}
1.1.x:
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));
}
}
2.2.x:
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));
}
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).