Persist check state for TTL checks #1009
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LGTM! |
ryanuber
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Jun 8, 2015
Persist check state for TTL checks
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Awesome! Thanks!
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TTL checks work on the assumption that there is an external app calling in to Consul to "ping" the check, keeping it healthy. During a Consul restart, the current behavior is to re-register the check directly into a pre-determined state. This can leave the TTL-based checks in an undesirable state for an extended period of time, depending on the TTL.
This change persists the last submitted status into the data directory. The check status, output, and an expiration timestamp are all written to disk, and restored on later agent starts. During startup, if the persisted status is still "fresh" enough (the expiration timer is based on the TTL of the check), the state and output are restored and registered as the initial status of the check.
I think we could do something similar for the other check types, but since Consul has the ability to actively run those checks, we might solve it in a different way.
Fixes #1001