[Postgres-xc-developers] Analysis of "GTM error, could not obtain snapshot" (found 3 bugs in GTM proxy)

[Masataka S. <pg...@gm...>]

Hi,

I looked into an error message "GTM error, could not obtain snapshot".
The root cause was very simple, but I found another 2 bugs on the way
of analysis.

I explain the summary of bugs and attached patches.

01_fix_error_target:
 When GTM proxy received an error response to a command, GTM proxy
reported error using an unrelated connection to the command. Because
proxy_main.c:ProcessResponse uses ereport function and it is
internally use GetMyThreadInfo->thr_conn, but thr_conn is not set
correctly.

02_fix_backend_proxy_id:
 When Postgres-XC disconnected connection to GTM proxy, GTM proxy
reports it to GTM by MSG_BACKEND_DISCONNECT. The message must have
 It could snuff out GTXID from the snapshot, and it is the root cause
of the subject.

03_fix_commit_rollback_status:
 TXN_COMMIT_RESULT / TXN_ROLLBACK_RESULT should have a gxid and a
status, but GTM Proxy sends it without a status.


I want to commit these patches tomorrow.
I'm sorry but please notice me quickly if you have a comment to the patches.

Regards