Amogh Margoor created IMPALA-10812:
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Summary: [DOCS] RPC to submit query getting stuck for AWS NLB
forever.
Key: IMPALA-10812
URL: https://issues.apache.org/jira/browse/IMPALA-10812
Project: IMPALA
Issue Type: Bug
Reporter: Amogh Margoor
Initial RPC to submit a query and fetch the query handle can take quite long
time to return as it can do various operations for planning and submission that
involve executing Catalog Operations like Rename, Alter Table Recover
partition that can take time on tables with many
partitions([https://github.com/apache/impala/blob/1231208da7104c832c13f272d1e5b8f554d29337/be/src/exec/catalog-op-executor.cc#L92]).
Attached is the profile of one such DDL query.
These RPCs are:
1. Beeswax:
[https://github.com/apache/impala/blob/b28da054f3595bb92873433211438306fc22fbc7/be/src/service/impala-beeswax-server.cc#L57]
2. HS2:
[https://github.com/apache/impala/blob/b28da054f3595bb92873433211438306fc22fbc7/be/src/service/impala-hs2-server.cc#L462]
One of the side effects of such RPC taking long time is that clients such as
impala-shell using AWS NLB can get stuck for ever. The reason is NLB tracks and
closes connections after 350s and cannot be configured. But after closing the
connection it doesn;t send TCP RST to the client. Only when client tries to
send data or packets NLB issues back TCP RST to indicate connection is not
alive. Documentation is here:
[https://docs.aws.amazon.com/elasticloadbalancing/latest/network/network-load-balancers.html#connection-idle-timeout].
Hence the impala-shell waiting for RPC to return gets stuck indefinitely.
Hence, we may need to evaluate techniques for RPCs to return query handle after
# Creating Driver:
https://github.com/apache/impala/blob/b28da054f3595bb92873433211438306fc22fbc7/be/src/service/impala-server.cc#L1150
# Register Query:
[https://github.com/apache/impala/blob/b28da054f3595bb92873433211438306fc22fbc7/be/src/service/impala-server.cc#L1168]
and execute later parts of RPC asynchronously in different thread without
blocking the RPC. That way clients can get query handle and poll for it for
state and results.
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