| pgpool-II 4.0.1 Documentation | |||
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Pgpool-II allows read query load balancing. It is enabled by default. To see the effect, let's use pgbench -S command.
$ pgbench -p 11000 -c 10 -S -T 10 test
starting vacuum...end.
transaction type: <builtin: select only>
scaling factor: 1
query mode: simple
number of clients: 10
number of threads: 1
duration: 10 s
number of transactions actually processed: 148044
latency average = 0.676 ms
tps = 14802.897506 (including connections establishing)
tps = 14810.213749 (excluding connections establishing)
$ psql -p 11000 -c "show pool_nodes" test
node_id | hostname | port | status | lb_weight | role | select_cnt | load_balance_node | replication_delay
---------+----------+-------+--------+-----------+---------+------------+-------------------+-------------------
0 | /tmp | 11002 | up | 0.500000 | primary | 75152 | true | 0
1 | /tmp | 11003 | up | 0.500000 | standby | 72893 | false | 0
(2 rows)
"select_cnt" column shows how many SELECT are dispatched to each node. Since with the default configuration, Pgpool-II tries to dispatch equal number of SELECT, the column shows almost same numbers.
Pgpool-II offers more sophisticated strategy for load balancing. See Section 5.7 for more details.