Ahsan Hadi's presentation from PG Con 2014 in Ottawa

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pgpool-II load testing
Muhammad Usama
May 7, 2014

2. © 2014 EnterpriseDB Corporation. All rights reserved. 2
Goals and objectives

Stress testing

Load balancing / Statement Routing testing

Performance testing compared with PG running
on single machine

Cluster stability testing

3. © 2014 EnterpriseDB Corporation. All rights reserved. 3
Hardware/Software configuration

Large amazon instances (15GB Ram with 4 2.5GHz
intel Xeon)

PostgreSQL 9.3.2

pgpool-II version 3.3.3

Pgbench (benchmarking tool)

75% read and 25% write load (workload)

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Pgpool Cluster setup

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pgbench script (read intensive)
set nbranches :scale
set ntellers 10 * :scale
set naccounts 100000 * :scale
setrandom aid 1 :naccounts
setrandom bid 1 :nbranches
setrandom tid 1 :ntellers
setrandom delta -5000 5000
BEGIN;
UPDATE pgbench_accounts SET abalance = abalance + :delta WHERE aid = :aid;
SELECT abalance FROM pgbench_accounts WHERE aid = :aid;
UPDATE pgbench_tellers SET tbalance = tbalance + :delta WHERE tid = :tid;
UPDATE pgbench_branches SET bbalance = bbalance + :delta WHERE bid = :bid;
INSERT INTO pgbench_history (tid, bid, aid, delta, mtime) VALUES (:tid, :bid, :aid, :delta,
CURRENT_TIMESTAMP);
END;

6. © 2014 EnterpriseDB Corporation. All rights reserved. 6
pgbench script cont…
setrandom aid 1 :naccounts
SELECT abalance FROM pgbench_accounts WHERE aid = :aid;
setrandom aid 1 :naccounts
SELECT abalance FROM pgbench_accounts WHERE aid = :aid;
setrandom aid 1 :naccounts
SELECT abalance FROM pgbench_accounts WHERE aid = :aid;
setrandom aid 1 :naccounts
SELECT abalance FROM pgbench_accounts WHERE aid = :aid;
setrandom aid 1 :naccounts
SELECT abalance FROM pgbench_accounts WHERE aid = :aid;
setrandom aid 1 :naccounts
SELECT abalance FROM pgbench_accounts WHERE aid = :aid;
setrandom aid 1 :naccounts
SELECT abalance FROM pgbench_accounts WHERE aid = :aid;
setrandom aid 1 :naccounts
SELECT abalance FROM pgbench_accounts WHERE aid = :aid;
setrandom aid 1 :naccounts
SELECT abalance FROM pgbench_accounts WHERE aid = :aid;

7. © 2014 EnterpriseDB Corporation. All rights reserved. 7
Test methodology

Automated test script

Performs fresh initdb for every test & executes each test
3 times

20 min run for each test

Test with 300, 1000 and 2000 scale factors

Median value of tps

Ensures repeatable results

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1000 Clients with 1000 and 2000 SF

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300 Clients with 300,1000,2000 SF

10. © 2014 EnterpriseDB Corporation. All rights reserved. 10
100 Clients with 100,300,1000,2000 SF

11. © 2014 EnterpriseDB Corporation. All rights reserved. 11

Horizontal read scalability. Addition of read replicas
increase performance for large size databases.

Better performance when database size increases then
memory. No performance gain for smaller databases which
fits in memory

Writes go to primary server and reads are load balanced
across the replicas.

Performance is not so good with prepared protocol.
Doesn't crash but gives negligible performance gain.