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From N Keywal <nkey...@gmail.com>
Subject Re: HBaseClient recovery from .META. server power down
Date Tue, 10 Jul 2012 17:12:34 GMT
Thanks for the jira.
The client can be connected to multiple RS, depending on the rows is
working on. So yes it's initial, but it's a dynamic initial :-).
This said there is a retry on error...

On Tue, Jul 10, 2012 at 6:46 PM, Suraj Varma <svarma.ng@gmail.com> wrote:
> I will create a JIRA ticket ...
> The only side-effect I could think of is ... if a RS is having a GC of
> a few seconds, any _new_ client trying to connect would get connect
> failures. So ... the _initial_ connection to the RS is what would
> suffer from a super-low setting of the ipc.socket.timeout. This was my
> read of the code.
> So - was hoping to get a confirmation if this is the only side effect.
> Again - this is on the client side - I wouldn't risk doing this on the
> cluster side ...
> --Suraj
> On Mon, Jul 9, 2012 at 9:44 AM, N Keywal <nkeywal@gmail.com> wrote:
>> Hi,
>> What you're describing -the 35 minutes recovery time- seems to match
>> the code. And it's a bug (still there on trunk). Could you please
>> create a jira for it? If you have the logs it even better.
>> Lowering the ipc.socket.timeout seems to be an acceptable partial
>> workaround. Setting it to 10s seems ok to me. Lower than this... I
>> don't know.
>> N.
>> On Mon, Jul 9, 2012 at 6:16 PM, Suraj Varma <svarma.ng@gmail.com> wrote:
>>> Hello:
>>> I'd like to get advice on the below strategy of decreasing the
>>> "ipc.socket.timeout" configuration on the HBase Client side ... has
>>> anyone tried this? Has anyone had any issues with configuring this
>>> lower than the default 20s?
>>> Thanks,
>>> --Suraj
>>> On Mon, Jul 2, 2012 at 5:51 PM, Suraj Varma <svarma.ng@gmail.com> wrote:
>>>> By "power down" below, I mean powering down the host with the RS that
>>>> holds the .META. table. (So - essentially, the host IP is unreachable
>>>> and the RS/DN is gone.)
>>>> Just wanted to clarify my below steps ...
>>>> --S
>>>> On Mon, Jul 2, 2012 at 5:36 PM, Suraj Varma <svarma.ng@gmail.com> wrote:
>>>>> Hello:
>>>>> We've been doing some failure scenario tests by powering down a .META.
>>>>> holding region server host and while the HBase cluster itself recovers
>>>>> and reassigns the META region and other regions (after we tweaked down
>>>>> the default timeouts), our client apps using HBaseClient take a long
>>>>> time to recover.
>>>>> hbase-0.90.6 / cdh3u4 / JDK 1.6.0_23
>>>>> Process:
>>>>> 1) Apply load via client app on HBase cluster for several minutes
>>>>> 2) Power down the region server holding the .META. server
>>>>> 3) Measure how long it takes for cluster to reassign META table and
>>>>> for client threads to re-lookup and re-orient to the lesser cluster
>>>>> (minus the RS and DN on that host).
>>>>> What we see:
>>>>> 1) Client threads spike up to maxThread size ... and take over 35 mins
>>>>> to recover (i.e. for the thread count to go back to normal) - no calls
>>>>> are being serviced - they are all just backed up on a synchronized
>>>>> method ...
>>>>> 2) Essentially, all the client app threads queue up behind the
>>>>> HBaseClient.setupIOStreams method in oahh.ipc.HBaseClient
>>>>> (http://grepcode.com/file/repo1.maven.org/maven2/org.apache.hbase/hbase/0.90.2/org/apache/hadoop/hbase/ipc/HBaseClient.java#312).
>>>>> http://tinyurl.com/7js53dj
>>>>> After taking several thread dumps we found that the thread within this
>>>>> synchronized method was blocked on
>>>>>    NetUtils.connect(this.socket, remoteId.getAddress(), getSocketTimeout(conf));
>>>>> Essentially, the thread which got the lock would try to connect to the
>>>>> dead RS (till socket times out), retrying, and then the next thread
>>>>> gets in and so forth.
>>>>> Solution tested:
>>>>> -------------------
>>>>> So - the ipc.HBaseClient code shows ipc.socket.timeout default is 20s.
>>>>> We dropped this down to a low number (1000 ms,  100 ms, etc) and the
>>>>> recovery was much faster (in a couple of minutes).
>>>>> So - we're thinking of setting the HBase client side hbase-site.xml
>>>>> with an ipc.socket.timeout of 100ms. Looking at the code, it appears
>>>>> that this is only ever used during the initial "HConnection" setup via
>>>>> the NetUtils.connect and should only ever be used when connectivity to
>>>>> a region server is lost and needs to be re-established. i.e it does
>>>>> not affect the normal "RPC" actiivity as this is just the connect
>>>>> timeout.
>>>>> Am I reading the code right? Any thoughts on how whether this is too
>>>>> low for comfort? (Our internal tests did not show any errors during
>>>>> normal operation related to timeouts etc ... but, I just wanted to run
>>>>> this by the experts.).
>>>>> Note that this above timeout tweak is only on the HBase client side.
>>>>> Thanks,
>>>>> --Suraj

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