[pgpool-general: 8755] Re: ERROR unable to flush data to frontend

[Tatsuo Ishii]

Hi,

> Greetings,
> 
> We are getting this error message "ERROR: unable to flush data to frontend"
> sporadically in our environments, across several micro service applications
> running under K8s.
> 
> ~~
> 2023-05-08 23:15:00.558: console pid 3290292: ERROR:  unable to flush data
> to frontend
> ~~
> 
> I'm attaching an extract from our logs as an example.
> 
> I have found one or two older posts mentioning that this was an issue
> with the client disconnecting abruptly, thus pgpool is unable to
> communicate with the client and reports this error - is this correct?
> 
> Any recommendations on how to diagnose (and hopefully fix) this issue would
> be greatly appreciated.

>From the log:

2023-05-08 22:31:38.947: console pid 3338613: LOG:  Sync message from frontend.
2023-05-08 22:31:38.947: console pid 3338613: DEBUG:  processing command complete
2023-05-08 22:31:38.947: console pid 3338613: DETAIL:  set transaction state to T
2023-05-08 22:31:40.932: console pid 3338613: LOG:  Query message from frontend.
2023-05-08 22:31:40.933: console pid 3338613: DETAIL:  query: "DISCARD ALL"
2023-05-08 22:31:40.933: console pid 3338613: DEBUG:  decide where to send the query
2023-05-08 22:31:40.933: console pid 3338613: DETAIL:  destination = 3 for query= "DISCARD ALL"
2023-05-08 22:31:40.933: console pid 3338613: DEBUG:  waiting for query response
2023-05-08 22:31:40.933: console pid 3338613: DETAIL:  waiting for backend:1 to complete the query
2023-05-08 22:31:40.933: console pid 3338613: ERROR:  unable to flush data to frontend

Assuming you enable log_client_messages, it seems the client did not
send a "terminate message" before disconnecting to pgpool.

(because if it did so, we should have seen "LOG: Terminate message
from frontend." in the log).

I suggest you to fix the client so that it sends terminate message
before disconnecting pgpool.

Best reagards,
--
Tatsuo Ishii
SRA OSS LLC
English: http://www.sraoss.co.jp/index_en/
Japanese:http://www.sraoss.co.jp