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backport-2.1: kv: try next replica on RangeNotFoundError #31250

Merged
merged 5 commits into from
Oct 12, 2018
Merged

backport-2.1: kv: try next replica on RangeNotFoundError #31250

merged 5 commits into from
Oct 12, 2018

Commits on Oct 12, 2018

  1. roachtest: print output on failure in election test 

    This was hiding the output if the invocation itself failed, which is
when you wanted it most.

Release note: None
    @tbg
    tbg committed Oct 12, 2018
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  2. kv: improve a trace event about descriptor eviction 

    Release note: None
    @tbg
    tbg committed Oct 12, 2018
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  3. storage: report optional StoreID with RangeNotFoundError 

    Release note: None
    @tbg
    tbg committed Oct 12, 2018
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  4. kv: try next replica on RangeNotFoundError 

    Previously, if a Batch RPC came back with a RangeNotFoundError,
we would immediately stop trying to send to more replicas, evict the
range descriptor, and start a new attempt after a back-off.

This new attempt could end up using the same replica, so if the
RangeNotFoundError persisted for some amount of time, so would the
unsuccessful retries for requests to it as DistSender doesn't
aggressively shuffle the replicas.

It turns out that there are such situations, and the
election-after-restart roachtest spuriously hit one of them:

1. new replica receives a preemptive snapshot and the ConfChange
2. cluster restarts
3. now the new replica is in this state until the range wakes
   up, which may not happen for some time.
4. the first request to the range runs into the above problem

@nvanbenschoten: I think there is an issue to be filed about the
tendency of DistSender to get stuck in unfortunate configurations.

Fixes cockroachdb#30613.

Release note (bug fix): Avoid repeatedly trying a replica that was found
to be in the process of being added.
    @tbg
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  5. kv: cache leaseholder on successful response 

    Whenever a successful response is received from an RPC that we know has
to contact the leaseholder to succeed, update the leaseholder cache.

The immediate motivation for this is to be able to land the preceding
commits, which greatly exacerbated (as in, added a much faster failure
mode to)

```
make stress PKG=./pkg/sql/logictest TESTS=TestPlannerLogic/5node-dist/distsql_interleaved_join
```

However, the change is one we've wanted to make for a while; our caching
and in particular the eviction of leaseholders has been deficient
essentially ever since it was first introduced.

Touches cockroachdb#31068.

Release note: None
    @tbg
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