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From Todd Lipcon <t...@cloudera.com>
Subject Hackathon notes 3/21/2011
Date Sat, 26 Mar 2011 05:49:29 GMT
Dear HBase developers,

Last Monday, several HBase contributors met up at the StumbleUpon offices
for a bit of a hackathon. We spent the beginning of the day discussing a few
general topics, and then from about 11am through 7pm or so most of us
hunkered down to hacking on various projects. I was the secretary for the
morning, so here are the notes. Please excuse any typos or if I got your
name wrong - I was never cut out for stenography.

Thanks to those who came, and special thanks to the folks at StumbleUpon for
space, food, and beer!

 - Upcoming releases:
   - 0.90.2 - when to release? a few bugs
   - 0.91.x - - should we do one?
   - 0.92.0 - when and what?
 - Next user group meetup?
 - Upcoming features:
   - Rolling restart improvements?
   - Online config change
   - Security and build issues
   - Distributed splitting
 - Maybe produce some code today! (power through above, then work on
respective priorities)



 - Stack @ StumbleUpon
 - Todd @ Cloudera
 - Elliot @ NGMoco - using 0.89 in prod, 0.90.1 about to be rolled out
 - Ted Yu from CarrierIQ
 - Liyin and Nicolas from Facebook, using 0.89 for messaging product
 - Benoit from SU - TSDB
 - Mingjie, Eugene, Gary from TrendMicro - using some internal build
which is like trunk (security + coprocessors frankenbuild)
 - JD from SU
 - Prakash Khemani from FB - his group is on 0.90 - increment heavy workload
   - has a patch for distributed splitting
   - if a server goes down, takes 10-15 minutes to catch up, so wants
to reduce that time window
 - Marc, independent consultant with MetaMarkets right now - 0.90.1
"pseudo prdoction" work
 - Ryan from StumbleUpon


 - next week? (week of 3/28?)
   - there are some bugs that need ot be fixed still
   - candidate end of this week, then some time for testing
 - Stack has volunteered to be release manager

 - should we do it?
   - people seem to think yes
   - but we shouldn't put much effort into testing these pre-release
   - there are a lot of interesting things in trunk that people might
want to play with

 - JD would like to have something more than alpha quality in time
for Hadoop Summit (3rd or 4th week of June)
 - What are pending items?
   - Coprocessors
   - Online schema changes? Makes Coprocessors more useful
   - HBASE-1502 - removing heartbeats
   - HBASE-2856 - ACID fixes
   - Distributed splitting
 - Time based or feature based? we want to try doing really time based
 - May 1st for first release candidate

Next meetup:
 - some time in April? in south bay?

 - Rolling restart: Stack working on it
 - Online schema edit? FB finds it a pain point but Nicolas not sure
where it ranks on their priority list
 - Online config changes?
 - Online schema change is probably more important than online config
change, since config change can be done with rolling restart
   - For co-processors, we need to attack some classloading issues
before online schema change can really reload coprocessor

Security and build:
 - Security code has been isolated as much as possible:
   - two separate layers:
     - RPC layer does secure RPC - pluggable RPC implementation and
subclassing for HBaseServer and Client classes
     - Loadable coprocessors for auth
 - But building is difficult - need to build against a secure Hadoop
in order to do this
   - conditional build step? maven module?
 - Stack and Gary will look into how to build and release this:
   - maybe Maven profiles? modules?
   - separate jar to be added to classpath with stuff that depends on

Distributed splitting:
 - HLogSplitter code is pretty different on FB's 0.90 branch
 - But most stuff plugs easily into trunk
 - Same interface:
   - call splitLog with server name
   - master uses SplitLogManager - puts log splitting tasks in ZK
   - each RS has SplitLogWorkers - watch for tasks, race to grab them in ZK
   - each RS splits logs one at a time
   - RS pings the master on the tasks as it splits them
   - master can preempt a task away from a worker
   - when master comes up it needs to grab orphanned tasks
 - some unit tests done, but hasn't been substantially tested on real
 - Current splitting does batching - multiple input logs go to one
output file per region
   - new splitting creates 3-4x as many files for recovered.edits
   - this is OK - we already handle this with seqids
 - If whole cluster goes down, something like MapReduce makes more sense
 - this feature is targeted towards single-RS failure
   - currently seeing downtime of 10 minutes when RS goes down
   - FB has various internal scripts/tools ("HyperShell") that let
them do the full-cluster-failure case efficiently, but they don't have
a clean way of open sourcing it
   - Maybe we can build something like this with hbase-regionservers.sh

What are we working on:
 - Todd - maybe making YCSB runnable as integration test
 - Stack - rolling restart? with Nicolas's help perhaps
 - Marc - add some new cases to hbck
 - Ryan - maybe porting RPC to Thrift?
   - wants to resolve the meta-in-ZK ticket as "wontfix"
 - Prakash - distributed splitting
 - JD - fix bugs he saw over the weekend
 - Gary - work on splitting out security build (maven pom file fun)
 - Eugene: ZK-938 - kerberos stuff for ZooKeeper (necessary for HBase
   - or maybe just fix some open bugs in HBase
 - Mingjie: open bugs for secure HBase (Access Control related)
 - Benoit: busy working on StumbleUpon stuff - mostly just observing
 - Nicolas: multithreaded compactions - needs to be refactored and cleaned
   - they have very big storefiles (10GB+) so their compactions take 1hr+
   - or just talking to people about stuff - easier than IRC
 - Liyin - add ability to do ZK miniclusters with multiple ZKs
 - Ted - working on pending patches / testing
 - Elliot: HBASE-3541 - HBase rest multigets

Todd Lipcon
Software Engineer, Cloudera

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