[pgpool-general: 3134] vacuum analyze caused node degeneration

[Sean Hogan]

Hi,

Recently during a test event we had an unexpected node degeneration, and 
I need to provide some reasonable explanation of why it happened.  Our 
system is two pgpool-II 3.3.3 nodes fronting two PostgreSQL 9.2.7 nodes.

We selected a table in pgAdmin3 and ran VACUUM with the ANALYZE option.  
Auto-vacuum is enabled on the database so the manual vacuum is a bit 
nonsensical, but I still didn't expect a failure.

The logging tells the story:

2014-08-19 13:56:53 LOG:   pid 7375: pool_send_and_wait: Error or notice 
message from backend: : DB node id: 0 backend pid: 7404 statement: 
VACUUM VERBOSE ANALYZE sch.tbl message: vacuuming "sch.tbl"
2014-08-19 13:56:53 LOG:   pid 7375: pool_send_and_wait: Error or notice 
message from backend: : DB node id: 1 backend pid: 314 statement: VACUUM 
VERBOSE ANALYZE sch.tbl message: vacuuming "sch.tbl"
2014-08-19 13:56:53 ERROR: pid 7375: read_kind_from_backend: 1 th kind C 
does not match with master or majority connection kind N
2014-08-19 13:56:53 ERROR: pid 7375: kind mismatch among backends. 
Possible last query was: "VACUUM VERBOSE ANALYZE sch.tbl" kind details 
are: 0[N: "pg_toast_170592198": found 0 removable, 0 nonremovable row 
versions in 0 out of 0 pages] 1[C]
2014-08-19 13:56:53 LOG:   pid 7375: degenerate_backend_set: 1 fail over 
request from pid 7375

Web searches for potential causes were not helpful.  Any ideas why node 
1 would just say "command completed" without all the other information 
garbage that came from node 0?

Thanks for any assistance,

Sean
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