[pgpool-general: 3184] zombie connections

[Yaron Naveh]

Hi

We are struggling with the bellow issues for a long time - any help, even
partial, is highly appreciated!

We use pgpool-II 3.3.3 with 4 Postrges 9.3 nodes. We are experiencing the
following issues:

1. In the db servers I see many idle connections (processes) for a long
time (even days). "show pool_pools" does not show those connections so
pgpool is not aware of them anymore. All connections to DB come from
pg-pool so possibly it does not close the connection before killing the
child process

2. In "show pool_pools" I see many idle connections far behind their
connection_life_time and even behind their pool child_life_time. The system
was inactive for a few hours so I know for sure these connections are not
in use.

3. In "show pool_pools" I sometimes see multiple connections within the
same pool with pool_connected=1. Also, I know for a fact that those client
processes were killed a long time ago.


Here is our config:

num_init_children=400
max_pool=5
child_life_time=300
child_max_connections=0
connection_life_time=60
client_idle_limit=300

(we have 4 backends)


This is example of multiple connections in the same child with
pool_connected=1 (how can it be?).
Also those connections are already not active for many hours (inactive
zombie connection also happens when pool_connected=0)

pool_pid  |     start_time      | pool_id | backend_id |   database    |
  username     |     create_time     | majorversion | minorversion |
pool_counter | pool_backendpid | pool_connected
 4741     | 2014-09-23 06:44:46 | 0       | 1          | DB1           |
user1            | 2014-09-23 07:15:58 | 3            | 0            | 7
         | 6911            | 1
 4741     | 2014-09-23 06:44:46 | 0       | 2          | DB1           |
user1            | 2014-09-23 07:15:58 | 3            | 0            | 7
         | 22316           | 1
 4741     | 2014-09-23 06:44:46 | 0       | 3          | DB1           |
user1            | 2014-09-23 07:15:58 | 3            | 0            | 7
         | 27441           | 1


Any idea about what can cause this is highly valuable for us (even partial
idea).

Thanks,
Yaron
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