Commit Graph

6 Commits

Author SHA1 Message Date
Armon Dadgar 6b9ace19cf consul: Collect useful session metrics 2015-01-02 22:46:51 +05:30
Armon Dadgar 4d0903f781 consul: Adding more tests for session TTLs 2014-12-12 21:42:59 -08:00
Armon Dadgar 990ad02f83 consul: Minor cleanups 2014-12-12 15:43:34 -08:00
Atin Malaviya 5a76929ba4 Fixed clearSessionTimer, created invalidateSession, added invalid TTL test 2014-12-11 05:34:31 -05:00
Atin Malaviya 8369b77204 Clean up code based on feedback from armon 2014-12-10 20:49:06 -05:00
Atin Malaviya b623af776b Consul Session TTLs
The design of the session TTLs is based on the Google Chubby approach
(http://research.google.com/archive/chubby-osdi06.pdf). The Session
struct has an additional TTL field now. This attaches an implicit
heartbeat based failure detector. Tracking of heartbeats is done by
the current leader and not persisted via the Raft log. The implication
of this is during a leader failover, we do not retain the last
heartbeat times.

Similar to Chubby, the TTL represents a lower-bound. Consul promises
not to terminate a session before the TTL has expired, but is allowed
to extend the expiration past it. This enables us to reset the TTL on
a leader failover. The TTL is also extended when the client does a
heartbeat. Like Chubby, this means a TTL is extended on creation,
heartbeat or failover.

Additionally, because we must account for time requests are in transit
and the relative rates of clocks on the clients and servers, Consul
will take the conservative approach of internally multiplying the TTL
by 2x. This helps to compensate for network latency and clock skew
without violating the contract.

Reference: https://docs.google.com/document/d/1Y5-pahLkUaA7Kz4SBU_mehKiyt9yaaUGcBTMZR7lToY/edit?usp=sharing
2014-12-07 12:38:22 -05:00