Sounds good.
Just opened ACCUMULO-4684 for docs.
On 7/24/17 2:13 PM, Adam J. Shook wrote:
Thanks, Josh. As this is our stage cluster, we aren't too worried about
the missing data; I just want to clean up the metadata so the queue
looks better. I'll take the back-fill approach and see how that goes.
--Adam
On Mon, Jul 24, 2017 at 1:55 PM, Josh Elser <[email protected]
<mailto:[email protected]>> wrote:
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
