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https://issues.apache.org/jira/browse/FLUME-1227?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13851768#comment-13851768
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Brock Noland commented on FLUME-1227:
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Hey, I have not participated in the review til now so sorry about this...but I
just noticed the following items which are mostly "nits" and improvements.
SpillableMemoryChannel
1. Static stuff should be at the top
2. Constructor should be directly below fields
3. String constants should be static final fields with javadoc description
4. Stuff can be final:
{noformat}
private Object queueLock = new Object();
{noformat}
TestSpillableMemoryChannel
1. Take null has a commented out assertion
2. There are locations where we expect "Exception" that should be a specific
type of exception.
3. Let's not use e.printStackTrace();
4. Places we assert boolean should have a message
5. Many missing spaces such as:
{noformat}
for (int i=0; i<count; ++i) {
{noformat}
and
{noformat}
nullsFound=count;
{noformat}
Docs
1. Please specify multiple data directories in the examples and add a note
that file channel performance will increase dramatically with multiple disks.
2. Add dual checkpoint to the examples as that is a good practice.
> Introduce some sort of SpillableChannel
> ---------------------------------------
>
> Key: FLUME-1227
> URL: https://issues.apache.org/jira/browse/FLUME-1227
> Project: Flume
> Issue Type: New Feature
> Components: Channel
> Reporter: Jarek Jarcec Cecho
> Assignee: Roshan Naik
> Attachments: 1227.patch.1, FLUME-1227.v2.patch, FLUME-1227.v5.patch,
> FLUME-1227.v6.patch, FLUME-1227.v7.patch, FLUME-1227.v8.patch,
> SpillableMemory Channel Design 2.pdf, SpillableMemory Channel Design.pdf
>
>
> I would like to introduce new channel that would behave similarly as scribe
> (https://github.com/facebook/scribe). It would be something between memory
> and file channel. Input events would be saved directly to the memory (only)
> and would be served from there. In case that the memory would be full, we
> would outsource the events to file.
> Let me describe the use case behind this request. We have plenty of frontend
> servers that are generating events. We want to send all events to just
> limited number of machines from where we would send the data to HDFS (some
> sort of staging layer). Reason for this second layer is our need to decouple
> event aggregation and front end code to separate machines. Using memory
> channel is fully sufficient as we can survive lost of some portion of the
> events. However in order to sustain maintenance windows or networking issues
> we would have to end up with a lot of memory assigned to those "staging"
> machines. Referenced "scribe" is dealing with this problem by implementing
> following logic - events are saved in memory similarly as our MemoryChannel.
> However in case that the memory gets full (because of maintenance, networking
> issues, ...) it will spill data to disk where they will be sitting until
> everything start working again.
> I would like to introduce channel that would implement similar logic. It's
> durability guarantees would be same as MemoryChannel - in case that someone
> would remove power cord, this channel would lose data. Based on the
> discussion in FLUME-1201, I would propose to have the implementation
> completely independent on any other channel internal code.
> Jarcec
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