Commits on Jan 24, 2022

1. kvserver: de-flake TestProtectedTimestamps …

   Fixed cockroachdb#75020. This test makes use of an "upsert-until-backpressure"
   primitive, where it continually writes blobs to a scratch table
   configured with a lower max range size (1<<18 from the default of
   512<<20) until it experiences replica backpressure. Before cockroachdb#73876 (when
   using the system config span), the splitting off of the scratch table's
   ranges happened near instantly after the creation of the table itself.
   This changed slightly with the span configs infrastructure, where
   there's more of asynchrony built in and ranges may appear after a while
   longer.
   
   The test previously started upserting as soon as it created the table,
   being able to implicitly rely on the tight synchrony of already having
   the table's ranges carved out. This comes when deciding to record a
   replica's largest previous max range size -- something we only do if the
   replica's current size is larger than the new limit (see
   (*Replica).SetSpanCnfig). When we weren't upserting until the range
   applied the latest config, this was not possible. With span configs and
   its additional asynchrony, this assumption no longer held. It was
   possible then for the range to accept writes larger than the newest max
   range size, which unintentionally (for this test at least) triggers an
   escape hatch where we avoid backpressure when lowering a range's max
   size below its current size (cockroachdb#46863).
   
   The failure is easy to repro. This test runs in ~8s, and with the
   following we were reliably seeing timeouts where the test was waiting
   for backpressure to kick in (but it never did because of the escape
   hatch).
   
       dev test pkg/kv/kvserver \
         -f TestProtectedTimestamps -v --show-logs \
         --timeout 300s --ignore-cache --count 10
   
   De-flaking this test is simple -- we just wait for the table's replicas
   to apply the latest config before issuing writes to it.
   
   Release note: None

   

   irfansharif committed Jan 24, 2022
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