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https://issues.apache.org/jira/browse/HBASE-5162?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13210809#comment-13210809
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[email protected] commented on HBASE-5162:
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src/main/java/org/apache/hadoop/hbase/client/HTable.java
<https://reviews.apache.org/r/3930/#comment11397>
I find this a bit dubious.
This won't actually slow the client thread down, but just accumulate more
data and reduce the number of RPCs. In the end it might lead to more load on
the server, because we can deliver more puts as with fewer but larger batches.
I'd rather just rely on the server sleeping the thread for a bit (as you do
later).
src/main/java/org/apache/hadoop/hbase/client/HTable.java
<https://reviews.apache.org/r/3930/#comment11399>
What if the flusher is not null? Should we re-calculate the wait time?
src/main/java/org/apache/hadoop/hbase/client/HTable.java
<https://reviews.apache.org/r/3930/#comment11400>
If sleepTime is 0 (for example from NoServerBackoffPolicy), we should
probably not create the thread and flush right here.
(But as I said in the comment above, I'd probably not bother with this
extra thread to begin with :) )
src/main/java/org/apache/hadoop/hbase/client/HTable.java
<https://reviews.apache.org/r/3930/#comment11401>
Was this a problem before? Or only now becaue of the background thread?
src/main/java/org/apache/hadoop/hbase/client/HTable.java
<https://reviews.apache.org/r/3930/#comment11398>
This will break backwards compatibility, right? (Not saying that's not ok,
just calling it out)
I'd almost rather have the client not know about this, until we reach a bad
spot (in which case we can throw back retryable exceptions).
src/main/java/org/apache/hadoop/hbase/regionserver/MemstorePressureMonitor.java
<https://reviews.apache.org/r/3930/#comment11402>
Ah ok, this is where we gracefully delay the server thread a bit.
Seems this would need to be tweaked carefully to make it effective while
not slowing normal operations.
Should the serverPauseTime be somehow related to the amount of pressure.
I.e. wait a bit more if the pressure is higher?
Maybe the pausetime calculation should be part of the pluggable policy?
Also in the jira there was some discussion about throwing (presumably
retryable) exceptions back to the client is the pressure gets too high. That
would slow the client, without consuming server resources (beyond multiple
requests).
src/main/java/org/apache/hadoop/hbase/regionserver/StoreUtils.java
<https://reviews.apache.org/r/3930/#comment11403>
General comment: Where are we on putting/documenting these things in
hbase-defaults.xml?
- Lars
On 2012-02-16 20:45:50, Jesse Yates wrote:
bq.
bq. -----------------------------------------------------------
bq. This is an automatically generated e-mail. To reply, visit:
bq. https://reviews.apache.org/r/3930/
bq. -----------------------------------------------------------
bq.
bq. (Updated 2012-02-16 20:45:50)
bq.
bq.
bq. Review request for hbase, Michael Stack, Jean-Daniel Cryans, and Lars
Hofhansl.
bq.
bq.
bq. Summary
bq. -------
bq.
bq. Under heavy write load, HBase will create a saw-tooth pattern in accepting
writes. This is due to the I/O in minor compactions not being able to keep up
with the write load. Specifically, the memstore is attempting to flush while we
are attempting to do a minor compaction, leading to blocking _all_ writes.
Instead, we need to have the option of graceful degradation mechanism.
bq.
bq. This patch supports both a short-term,adjustable server-side write
blocking as well as client-side back-off to help alleviate temporary memstore
pressure.
bq.
bq.
bq. This addresses bug HBASE-5162.
bq. https://issues.apache.org/jira/browse/HBASE-5162
bq.
bq.
bq. Diffs
bq. -----
bq.
bq. src/main/java/org/apache/hadoop/hbase/HConstants.java 763fe89
bq. src/main/java/org/apache/hadoop/hbase/client/BackoffPolicy.java
PRE-CREATION
bq. src/main/java/org/apache/hadoop/hbase/client/HTable.java 57605e6
bq. src/main/java/org/apache/hadoop/hbase/client/MonitoredResult.java
PRE-CREATION
bq. src/main/java/org/apache/hadoop/hbase/client/NoServerBackoffPolicy.java
PRE-CREATION
bq. src/main/java/org/apache/hadoop/hbase/regionserver/HRegion.java 25cb31d
bq. src/main/java/org/apache/hadoop/hbase/regionserver/HRegionServer.java
7d7be3c
bq.
src/main/java/org/apache/hadoop/hbase/regionserver/MemstorePressureMonitor.java
PRE-CREATION
bq. src/main/java/org/apache/hadoop/hbase/regionserver/OperationStatus.java
1b94ab5
bq. src/main/java/org/apache/hadoop/hbase/regionserver/PressureMonitor.java
PRE-CREATION
bq.
src/main/java/org/apache/hadoop/hbase/regionserver/SimpleMemStorePressureMonitor.java
PRE-CREATION
bq. src/main/java/org/apache/hadoop/hbase/regionserver/StoreUtils.java
PRE-CREATION
bq. src/test/java/org/apache/hadoop/hbase/client/TestClientBackOff.java
PRE-CREATION
bq.
src/test/java/org/apache/hadoop/hbase/regionserver/TestMemStorePressureMonitor.java
PRE-CREATION
bq.
bq. Diff: https://reviews.apache.org/r/3930/diff
bq.
bq.
bq. Testing
bq. -------
bq.
bq.
bq. Thanks,
bq.
bq. Jesse
bq.
bq.
> Basic client pushback mechanism
> -------------------------------
>
> Key: HBASE-5162
> URL: https://issues.apache.org/jira/browse/HBASE-5162
> Project: HBase
> Issue Type: New Feature
> Affects Versions: 0.92.0
> Reporter: Jean-Daniel Cryans
> Fix For: 0.94.0
>
> Attachments: java_HBASE-5162.patch
>
>
> The current blocking we do when we are close to some limits (memstores over
> the multiplier factor, too many store files, global memstore memory) is bad,
> too coarse and confusing. After hitting HBASE-5161, it really becomes obvious
> that we need something better.
> I did a little brainstorm with Stack, we came up quickly with two solutions:
> - Send some exception to the client, like OverloadedException, that's thrown
> when some situation happens like getting past the low memory barrier. It
> would be thrown when the client gets a handler and does some check while
> putting or deleting. The client would treat this a retryable exception but
> ideally wouldn't check .META. for a new location. It could be fancy and have
> multiple levels of pushback, like send the exception to 25% of the clients,
> and then go up if the situation persists. Should be "easy" to implement but
> we'll be using a lot more IO to send the payload over and over again (but at
> least it wouldn't sit in the RS's memory).
> - Send a message alongside a successful put or delete to tell the client to
> slow down a little, this way we don't have to do back and forth with the
> payload between the client and the server. It's a cleaner (I think) but more
> involved solution.
> In every case the RS should do very obvious things to notify the operators of
> this situation, through logs, web UI, metrics, etc.
> Other ideas?
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