Jordan Pittier 980d65f586 Swift: Optionally start only the necessary services ...

Currently Devstack starts all Swift services, including those
in charge of "consistency convergence" (remember Swift is eventually
consistent), data scrubbing, hard-deletion (*-reaper services)
cleanup.

But when running with Replication Factor 1 some of those services
are not needed at all. Besides, the fonctionnalities provided by
some of these services are not tested at all (neither in Tempest
nor in Swift functional tests).

Thus, in light of saving some Mo of RAM, this patch introduces a config
flag to start only a minimal set of Swift services, just what's required
to make all of our current tests pass.

The default value for this new config flag is set to start all services,
that is to maintain Devstack's current behavior.

For sake of completeness, here is the list of services that are not
going to be started is the config flag is toggled, and the associated RSS
according to our peakmem_tracker

40004  swift-object-replicator /etc/swift/object-server/1.conf
34320  swift-container-replicator /etc/swift/container-server/1.conf
33584  swift-object-auditor /etc/swift/object-server/1.conf
33328  swift-object-reconstructor /etc/swift/object-server/1.conf
31936  swift-object-updater /etc/swift/object-server/1.conf
31492  swift-account-reaper /etc/swift/account-server/1.conf
31076  swift-account-replicator /etc/swift/account-server/1.conf
29540  swift-container-updater /etc/swift/container-server/1.conf
29220  swift-account-auditor /etc/swift/account-server/1.conf
29036  swift-container-auditor /etc/swift/container-server/1.conf

So we are looking at saving at most ~350Mo of RAM (could be less
because RSS doesn't account for shared memory).

A follow-up patch will soon be proposed in devstack-gate to not run
those additional services in our Gate jobs.

Change-Id: I8a0d03ac0296a74e38efd185beb8513866eaf0c4

2017-03-29 13:26:52 +02:00

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