When fetching node alloc assignments, be defensive against a stale read before
killing local nodes allocs.
The bug is when both client and servers are restarting and the client requests
the node allocation for the node, it might get stale data as server hasn't
finished applying all the restored raft transaction to store.
Consequently, client would kill and destroy the alloc locally, just to fetch it
again moments later when server store is up to date.
The bug can be reproduced quite reliably with single node setup (configured with
persistence). I suspect it's too edge-casey to occur in production cluster with
multiple servers, but we may need to examine leader failover scenarios more closely.
In this commit, we only remove and destroy allocs if the removal index is more
recent than the alloc index. This seems like a cheap resiliency fix we already
use for detecting alloc updates.
A more proper fix would be to ensure that a nomad server only serves
RPC calls when state store is fully restored or up to date in leadership
transition cases.
I noticed that `watchNodeUpdates()` almost immediately after
`registerAndHeartbeat()` calls `retryRegisterNode()`, well after 5
seconds.
This call is unnecessary and made debugging a bit harder. So here, we
ensure that we only re-register node for new node events, not for
initial registration.
Tons left to do and lots of churn:
1. No state saving
2. No shutdown or gc
3. Removed AR factory *for now*
4. Made all "Config" structs local to the package they configure
5. Added allocID to GC to avoid a lookup
Really hating how many things use *structs.Allocation. It's not bad
without state saving, but if AllocRunner starts updating its copy things
get racy fast.
This PR removes deepcopying of the job attached to the allocation in the
alloc runner. This operation is called very often so removing reflect
from the code path and the potentially large number of mallocs need to
create a job reduced memory and cpu pressure.
