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From "Josh Elser (JIRA)" <>
Subject [jira] [Updated] (ACCUMULO-3232) Improve consumption of WAL header in partial replication case
Date Sun, 05 Apr 2015 05:02:33 GMT


Josh Elser updated ACCUMULO-3232:
    Fix Version/s:     (was: 1.7.0)

> Improve consumption of WAL header in partial replication case
> -------------------------------------------------------------
>                 Key: ACCUMULO-3232
>                 URL:
>             Project: Accumulo
>          Issue Type: Improvement
>          Components: replication
>            Reporter: Josh Elser
> Consider a system that is actively replicating from one instance to another. Specifically,
assume there is one WAL that is currently being replicated to the destination and the source
instance is shutdown.
> When the source instance is restarted, it will notice that the WAL has read through N
{{LogFileKey}}/{{LogFileValue}} pairs (from before it was shutdown) and while proceed past
these records to get to the data in the file which it needs to read.
> We have to re-read each of these pairs from the file because the WAL is an append-only
structure, and we can't efficiently seek to some point in the file, as we wouldn't know how
to correlate the byte offset to entries.
> As we read the WAL, in addition (or perhaps instead of) tracking the offset in the WAL,
it would be good to track the correlation of N bytes read to M records consumed which would
help us better resume replication.

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