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HBase, mail # dev - Stream-of-consciousness notes from HBase BoF presentations


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Re: Stream-of-consciousness notes from HBase BoF presentations
yuzhihong@... 2012-06-16, 00:40
Thanks for the write up, Dave.

W.r.t. Slide 6 in J-D's talk, hbase-5699 would allow HLog's to be grouped by table, avoiding the issue to slow updating tables.

Cheers

On Jun 15, 2012, at 9:07 AM, Dave Wang <[EMAIL PROTECTED]> wrote:

> Please fill out if I missed anything, thanks.
>
> Schema thoughts - Ian
> * Build typed schema into HBase somehow?
> ** Easier for app developers
> * Idea of hashing schema into each row, perhaps have a system-level table
> for schema descriptions
>
> Performance tidbits - JD (slides at
> http://www.slideshare.net/jdcryans/performance-bof12)
>
> Write path:
> * Too much write contention (flattening out)
> ** increase memstore size
> ** rely only on memstore lower limit, but don't ever hit upper limit if
> possible
> ** HBASE-3484
> * Memstore vs. HLog size - make sure hlogs are not forcing flushes
> ** ideal is hlog.blocksize * maxlogs == just a bit above memstore.lowerLimit
> ** New balancer in trunk has balancer with weighted read vs. write requests
> * Too many regions/families - don't hit the global memstore size
> ** means global memstore size will already be reached before flush size, so
> many small files being flushed (bad)
> * write to many families with different data sizes
> ** flush size is based on region, not family
> ** HBASE-3149 about fixing this.
> * HLog compression (4608)
> ** breaks replication (5778)
> ** benefits with keys to values ratio is high (counters), since it doesn't
> compress the values
>
> Read path:
> * current LRU is sometimes better, sometimes worse.  Other algorithms may
> beat this (e.g. 2Q) in some cases.
> * make sure working data set fits in block cache of course
> * evictions start happening at 85% (DEFAULT_ACCEPTABLE_FACTOR) and evict
> down to 75% (DEFAULT_MIN_FACTOR).  Too aggressive.  Try 95% and 90%.
> * disable blockcache if you have a highly random read pattern.  disable per
> family, not throughout RS, since meta blocks (leaf, bloom) are really hot
> and you want BC on for those.
> * slabcache - double-caches everything, not flexible with regards to block
> sizes, doesn't help that much with GC since by default BC is 25% of heap by
> default.  Most heap is used by memstores.
> * GC issues tend to be caused by memstores and IPC queues (default 1000
> entries, lots of data sitting in there not processed yet sometimes)
> See Charlie Hunt's book re: GC walkthrough.  There's 20% of so of the heap
> just for HBase internals (compactions, etc.) BTW.
> ** GC topic is tough for general prescription, since JVMs change, garbage
> collectors change.
> * Overall heap size: 20-32 GB.
> * Turn on bloom filters (row) in 0.92+.  Should be on by default.
>
> Metrics and UI - Elliott - slides at
> http://www.slideshare.net/eclark00/hbase-birds-of-a-feather-metrics-ui
> * per-region metrics in 0.94
> ** on by default but need to turn on NullContextWithUpdateThread
> ** There's a patch to tcollector for OpenTSDB
> * JMX JSON: /jmx web page.  Info server needs to be running
> * New UI for master in trunk.
>
> Region load - Eugene
> * Uses d3 - Javascript library for making charts - used this to create bar
> graphs for regions/RS load
> * Streaming data possible - moving graphs with this
>
> HBase integration testing - Andy
> * Bigtop - Do for Hadoop what Debian did for Linux
> * gives you build and packaging infrastructure with RPM and DEBs
> * Deployment - puppet
> * Integration test - iTest
> * iTest has helper functions, shell-outs for test scripting
> * HBASE-6201 - mvn verify -> iTest -> MiniCluster and/or actual cluster
> * Automate the RC testing matrix into this
> * Add long-running ingestion tests and chaos monkeys - LoadTestTool, YCSB,
> GoraCI, Gremlins
> * Add full system application test cases, Kerberos setup/usage helper
> functions to iTest
>
> Benchpress - Marshall
> * Programmatic load ingestion tool
> * posting JSON to HTTP
> * unzip tarball, run shell script
> * Open source soon with Apache license
>
> Snapshots - Jesse
> * HBASE-6255