[Postgres-xc-bugs] A stack trace for your investigating.

[ZhangJulian <jul...@ou...>]

Hi All,

It is hard to reproduce, just paste it here for your information.
A autovacuum process got a invalid xid, then it fell back to a local xid. But the xid can not get the related Snapshot from GTM. 
It looks a design error, but I know little about the local transaction design. Is there any document talking about it? 

===On the datanode:
(gdb) bt
#0  0x000000340b232925 in raise () from /lib64/libc.so.6
#1  0x000000340b234105 in abort () from /lib64/libc.so.6
#2  0x0000000000870fef in errfinish (dummy=0) at elog.c:566
#3  0x000000000087322f in elog_finish (elevel=22, fmt=0x8def08 "cannot abort transaction %u, it was already committed") at elog.c:1334
#4  0x00000000004cd162 in RecordTransactionAbort (isSubXact=0 '\000') at xact.c:1686
#5  0x00000000004ce48f in AbortTransaction () at xact.c:2998
#6  0x00000000004d00b8 in AbortOutOfAnyTransaction () at xact.c:4663
#7  0x0000000000883801 in ShutdownPostgres (code=0, arg=0) at postinit.c:1033
#8  0x0000000000738990 in shmem_exit (code=0) at ipc.c:221
#9  0x0000000000738892 in proc_exit_prepare (code=0) at ipc.c:181
#10 0x00000000007387f9 in proc_exit (code=0) at ipc.c:96
#11 0x00000000006f26f2 in AutoVacWorkerMain (argc=0, argv=0x0) at autovacuum.c:1566
#12 0x00000000006f258b in StartAutoVacWorker () at autovacuum.c:1464
#13 0x00000000007034f3 in StartAutovacuumWorker () at postmaster.c:5317
#14 0x0000000000702d8d in sigusr1_handler (postgres_signal_arg=10) at postmaster.c:4963
#15 <signal handler called>
#16 0x000000340b2e15c3 in __select_nocancel () from /lib64/libc.so.6
#17 0x00000000006fea75 in ServerLoop () at postmaster.c:1662
#18 0x00000000006fe411 in PostmasterMain (argc=5, argv=0x2a4b790) at postmaster.c:1369
#19 0x000000000066326d in main (argc=5, argv=0x2a4b790) at main.c:206

====Datanode Log：
postgresql-2014-07-18_105851.log:14716 pgxc 2014-07-18 11:42:39 CSTLOG:  statement: select autoanalyze_count from pg_stat_user_tables where schemaname = 'public' and relname = 'imei_historyseristatus'
postgresql-2014-07-18_105851.log:14716  2014-07-18 13:09:22 CSTLOG:  Falling back to local Xid. Was = 0, now is = 307616
postgresql-2014-07-18_105851.log:14716  2014-07-18 13:09:23 CSTERROR:  GTM error, could not obtain snapshot
postgresql-2014-07-18_105851.log:14716  2014-07-18 13:09:23 CSTPANIC:  cannot abort transaction 307616, it was already committed
postgresql-2014-07-18_105851.log:27533  2014-07-18 13:10:35 CSTLOG:  server process (PID 14716) was terminated by signal 6: Aborted

====GTM Log:
1:140085928392448:2014-07-18 13:05:19.803 CST -LOG:  Saving transaction restoration info, backed-up gxid: 308842
LOCATION:  GTM_WriteRestorePointXid, gtm_txn.c:2649
1:140085928392448:2014-07-18 13:09:23.001 CST -WARNING:  No transaction handle for gxid: 307616
LOCATION:  GTM_GXIDToHandle, gtm_txn.c:163
1:140085928392448:2014-07-18 13:09:23.020 CST -WARNING:  Invalid transaction handle: -1
LOCATION:  GTM_HandleToTransactionInfo, gtm_txn.c:213
1:140085928392448:2014-07-18 13:09:23.068 CST -ERROR:  Failed to get a snapshot
LOCATION:  ProcessGetSnapshotCommandMulti, gtm_snap.c:420
1:140085928392448:2014-07-18 13:18:44.968 CST -LOG:  Saving transaction restoration info, backed-up gxid: 310846


Thanks
Julian