Preserve replication job stats when jobs are re-created
Previously we made sure replication job statistics were preserved when
the jobs were started and stopped by the scheduler. However, if a db
node restarted or user re-created the job, replication stats would be
reset to 0.
Some statistics like `docs_read` and `docs_written` are perhaps not as
critical. However `doc_write_failures` is. That is the indicator that
some replication docs have not replicated to the target. Not
preserving that statistic meant users could perceive there was a data
loss during replication -- data was replicated successfully according
to the replication job with no write failures, user deletes source
database, then some times later noticed some of their data is missing.
These statistics were already logged in the checkpoint history and we
just had to initialize a stats object from them when a replication job
starts. In that initialization code we pick the highest values from
either the running scheduler or the checkpointed log. The reason is
that the running stats could be higher if say job was stopped suddenly
and failed to checkpoint but scheduler retained the data.
Fixes: #2414
4 files changed
