This is very simple demonstration on how to limit latency impact (improve consumer experience) by switching to out-of-band/background validation connection checking for DB connections:
Test setup: laptop <-- 0ms latency --> VM { Wildfly JBoss} <-- 6ms latency --> VM { Oracle DB }, latency was simulated using linux tc netem (6ms but only one way).
Benchmark generator settings: ApacheBenchmark 2.4 launched with concurrency = 1, timeout = 5, 1000 requests to simple JSP page, test was repeated multiple times to heat caches/etc.
Middle-tier: JBoss/WildFly Core 2.0.10.Final, 100 connection pool, validation connection checker explicitly set to “SELECT 1 FROM DUAL”
Application: simple JSP page performing 1 DB CALL (1x INSERT)
with 6ms RTT with JDBC Connection Pool with default foreground connection check (actually 4 packets; 4*6 =~ 24ms):
Requests per second: 55.97 [#/sec] (mean)
Time per request: 17.867 [ms] (mean)
Time per request: 17.867 [ms] (mean, across all concurrent requests)
Transfer rate: 16.07 [Kbytes/sec] received
Connection Times (ms)
min mean[+/-sd] median max
Connect: 0 0 0.1 0 1
Processing: 13 18 9.8 16 218
Waiting: 13 17 9.8 16 218
Total: 13 18 9.8 17 218
Percentage of the requests served within a certain time (ms)
50% 17
66% 17
75% 18
80% 18
90% 19
95% 21
98% 38
99% 71
100% 218 (longest request)
with 6ms RTT with JDBC Connection Pool with background connection check (just 2 packets to DB; 2*6 =~ 12ms):
Requests per second: 100.74 [#/sec] (mean)
Time per request: 9.927 [ms] (mean)
Time per request: 9.927 [ms] (mean, across all concurrent requests)
Transfer rate: 28.92 [Kbytes/sec] received
Connection Times (ms)
min mean[+/-sd] median max
Connect: 0 0 0.1 0 1
Processing: 7 10 2.8 9 41
Waiting: 7 9 2.8 9 41
Total: 7 10 2.9 9 42
Percentage of the requests served within a certain time (ms)
50% 9
66% 10
75% 10
80% 10
90% 11
95% 13
98% 18
99% 26
100% 42 (longest request)
This demonstrated that the average consumer experience can be improved from ~18ms to ~10ms just by setting two options that move the checking “out-of-band” for business transaction processing. Of course the more times the application calls .getConnection() even transparently like with the case of JSP, the more impact of those settings.
p.s. I’ve used
<check-valid-connection-sql>select 1 from dual</check-valid-connection-sql>
in my experiment however you should be really using
<valid-connection-checker class-name="org.jboss.jca.adapters.jdbc.extensions.oracle.OracleValidConnectionChecker"/>
as it calls native OJDBC .isValid() or ping methods that perform the check even without SQL layer (smaller packets).
After new, sucessfull fresh installation of GC, I’ve taken full backup (from XEN dom0) of 01_gc VM for future purposes. I’m starting to regret that I’ve haven’t used LVM in dom0 for snapshot/fast-backup purposes…
) and so on…