pgpool-II 4.7.2 Documentation
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# 1.4. Testing Load Balance

Pgpool-II allows read query load balancing. It is enabled by default. To see the effect, let's use `pgbench -S` command.

        $ ./shutdownall
        $ ./startall
        $ pgbench -p 11000 -c 10 -j 10 -S -T 60 test
        starting vacuum...end.
        transaction type: <builtin: select only>
        scaling factor: 1
        query mode: simple
        number of clients: 10
        number of threads: 10
        duration: 60 s
        number of transactions actually processed: 1086766
        latency average = 0.552 ms
        tps = 18112.487043 (including connections establishing)
        tps = 18125.572952 (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 | last_status_change
        ---------+----------+-------+--------+-----------+---------+------------+-------------------+-------------------+---------------------
        0       | /tmp     | 11002 | up     | 0.500000  | primary | 537644     | false             | 0                 | 2019-01-31 11:51:58
        1       | /tmp     | 11003 | up     | 0.500000  | standby | 548582     | true              | 0                 | 2019-01-31 11:51:58
        (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 5.8 for more details.

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