Problem: We pass grpc context down to applier in readonly serializable txn. This context can be cancelled for example due to timeout. This will trigger panic.

Solution: provide different error handler for readonly serializable txn.

fixes https://github.com/etcd-io/etcd/issues/14110

Please read https://github.com/etcd-io/etcd/blob/main/CONTRIBUTING.md#contribution-flow.

Please sign off the commit.

Codecov Report

Merging #14149 (99f9260) into main (4977877) will decrease coverage by 0.15%. The diff coverage is 63.15%.

@@            Coverage Diff             @@
##             main   #14149      +/-   ##
==========================================
- Coverage   75.42%   75.26%   -0.16%     
==========================================
  Files         456      456              
  Lines       36919    36926       +7     
==========================================
- Hits        27846    27793      -53     
- Misses       7340     7394      +54     
- Partials     1733     1739       +6     

Flag	Coverage Δ
all	75.26% <63.15%> (-0.16%)	:arrow_down:

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
server/etcdserver/txn/txn.go	90.11% <53.33%> (-0.56%)	:arrow_down:
server/etcdserver/api/v3rpc/grpc.go	91.42% <100.00%> (ø)
server/storage/mvcc/kvstore_txn.go	79.12% <100.00%> (ø)
client/v3/namespace/watch.go	87.87% <0.00%> (-6.07%)	:arrow_down:
client/v3/leasing/cache.go	87.22% <0.00%> (-4.45%)	:arrow_down:
client/v3/experimental/recipes/double_barrier.go	71.87% <0.00%> (-3.13%)	:arrow_down:
client/v3/retry_interceptor.go	64.54% <0.00%> (-2.73%)	:arrow_down:
client/v3/concurrency/election.go	79.68% <0.00%> (-2.35%)	:arrow_down:
raft/storage.go	91.66% <0.00%> (-1.86%)	:arrow_down:
server/etcdserver/api/v3rpc/watch.go	86.91% <0.00%> (-1.68%)	:arrow_down:
... and 11 more

Help us with your feedback. Take ten seconds to tell us how you rate us.

@ahrtr @ptabor updated PR with alternative version of the test that uses reflection to check the name of the caller function and cancel context for rangeKeys. Added more comments about test setup. Addressed other small comments.

The only thing that isn't done is migration to new client interface (comment). If this approach looks good, I'll try the new client for main and keep this version for 3.5

@ahrtr this is ready for review with unit tests instead of integration

Thanks @spzala

Great work! @lavacat