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https://issues.apache.org/jira/browse/FLUME-1045?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13235479#comment-13235479
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Inder SIngh commented on FLUME-1045:
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Proposed Solution
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Sink triggered spooling
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A sink going down/all sinks go down in a failover policy setup triggers
spooling of data from the channel to local disk. As and when there is a
successful commit from the channel to one of the sinks a de-spool is triggered
from local disk to channel.
Proposed Implementation
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1. SpooledFailoverSinkProcessor – extending from FailoverSinkProcessor.
Capabilities include triggering spool(), despool() when the sink go down and
comes up respectively.
Some more design choices & assumptions
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1. Persist avro serialized objects in local disk which preserves data & headers.
2. Use channel based transaction semantics while spooling to avoid any data
loss.
3. Spool location is configurable for each SinkGroup controlled by “spool-dir".
Event’s will be spooled in batches controlled by “spool-batch-size “ Spool
files will be rolled over after they reach a size controlled by
“spoolfile-size”.
4. Validation to avoid misconfiguration of overlapping spool locations across
SinkGroups.
5. De-spooling happens one file at a time to avoid the complexity of persisting
offsets in the first cut.
> Proposal to support disk based spooling
> ---------------------------------------
>
> Key: FLUME-1045
> URL: https://issues.apache.org/jira/browse/FLUME-1045
> Project: Flume
> Issue Type: New Feature
> Affects Versions: v1.0.0
> Reporter: Inder SIngh
> Priority: Minor
> Labels: patch
>
> 1. Problem Description
> A sink being unavailable at any stage in the pipeline causes it to back-off
> and retry after a while. Channel's associated with such sinks start buffering
> data with the caveat that if you are using a memory channel it can result in
> a domino effect on the entire pipeline. There could be legitimate down times
> eg: HDFS sink being down for name node maintenance, hadoop upgrades.
> 2. Why not use a durable channel (JDBC, FileChannel)?
> Want high throughput and support sink down times as a first class use-case.
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