On 7/24/17 1:44 PM, Adam J. Shook wrote:
We had some corrupt WAL blocks on our stage environment the other day
and opted to delete them. We not have some missing metadata and about
3k files pending for replication. I've dug into it a bit and noticed
that many of the WALs in the `order` queue of the replication table A)
no longer exist in HDFS and B) have no entries in the `repl` section of
the replication table.
Based on the code, if there are no entries in the `repl` section, then
the work will never be queued for completion via ZooKeeper and therefore
never finished -- does this make sense?
Yeah, that sounds about right. I'm lamenting that I never wrote up docs
for the user-manual to cover the table-schema. I should ... do that...
I think the order entry is created when the repl entry is. Would have to
dig back into code though.
What'd be the suggestion here
to proceed? I'm thinking a one-off tool to backfill the `repl` section
should do the trick, but I am wondering if this is something that should
be changed in Accumulo?
A tool to back-fill makes sense to me. I'm not sure what we could do in
Accumulo automatically. Any time there is data-loss (data gone missing
or old data coming back), Accumulo really can't do anything on its own.
As you described in your scenario, you made the conscious decision to
nuke the files with missing blocks. However, providing tools to handle
"common" failure scenarios outside of our purview sounds like a good idea.
Improving our docs around how to "re-sync" two tables being replicated
would also be great. We have the hammer via snapshot+export, just need
to be clear with the instructions.
Cheers,
--Adam
