Michael Ho created IMPALA-6907:
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Summary: Update
Key: IMPALA-6907
URL: https://issues.apache.org/jira/browse/IMPALA-6907
Project: IMPALA
Issue Type: Bug
Components: Distributed Exec
Affects Versions: Impala 2.11.0, Impala 2.10.0, Impala 2.9.0, Impala 3.0,
Impala 2.12.0
Reporter: Michael Ho
Assignee: Michael Ho
Currently, {{ImpalaServer::MembershipCallback()}} will remove stale connections
to hosts which were removed from the cluster membership.
{noformat}
while (loc_entry != query_locations_.end()) {
if (current_membership.find(loc_entry->first) ==
current_membership.end()) {
unordered_set<TUniqueId>::const_iterator query_id =
loc_entry->second.begin();
// Add failed backend locations to all queries that ran on that
backend.
for(; query_id != loc_entry->second.end(); ++query_id) {
vector<TNetworkAddress>& failed_hosts =
queries_to_cancel[*query_id];
failed_hosts.push_back(loc_entry->first);
}
exec_env_->impalad_client_cache()->CloseConnections(loc_entry->first); <<<-----
{noformat}
However, it's relies on checking against {{query_locations_}} which is
populated only when the Impalad node acts as a coordinator. With the support
for executor only configuration for Impalad nodes, {{query_locations_}} will be
empty for executor only Impalad nodes so {{ImpalaServer::MembershipCallback()}}
will not remove stale connections to hosts removed from cluster. This may cause
stale connections to stay in connection cache for extended period of time,
leading to query failure after the removed hosts rejoined the cluster as the
stale connections are used.
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