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Date: Tue, 11 May 2010 09:31:27 -0700
Message-ID: <AANLkTimZH02gdOkVgLJEMI0VIQ_t5rUWO5cKdicJbQ_f@mail.gmail.com>
Subject: Re: connection.isMasterRunning()
From: Jean-Daniel Cryans <jdcryans@apache.org>
To: hbase-dev@hadoop.apache.org
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Check if in Zookeeper the znode /hbase/master is there. You can easily
do this by using
org.apache.hadoop.hbase.zookeeper.ZooKeeperWrapper.readMasterAddressOrThrow=
().
This method isn't static, you have to create your own instance.

J-D

On Tue, May 11, 2010 at 5:38 AM, Al Lias <al.lias@gmx.de> wrote:
> Am 29.03.2010 23:35, schrieb Ted Yu:
>> https://issues.apache.org/jira/browse/HBASE-2391 has been filed.
>>
>> We call HBaseAdmin.isMasterRunning() to see if client has connection wit=
h
>> HBase. If there is a working alternative, we'd love to use it.
>>
>
> Just to catch up on this....what is the recommended way to
> programmatically check if Hbase is up (say on 0.20.4)?
>
> Thx,
>
> =A0 =A0 =A0 =A0Al
>
>> ...
>> On Mon, Mar 29, 2010 at 2:25 PM, Jean-Daniel Cryans <jdcryans@apache.org=
>wrote:
>>
>>> I think this method wasn't updated when we moved to Zookeeper (since
>>> in pre-0.20, dead master =3D dead cluster), also looking at when this i=
s
>>> called, I only see it from HMerge and HBaseAdmin.isMasterRunning()...
>>> which in turn isn't called anywhere in the java code (I think we call
>>> it in the shell tho).
>>>
>>> So we should first consider if this method is useful at all, and if so
>>> then what would be the best fix. For example, if you run a HMerge
>>> while the master is down but the region servers are up, you're going
>>> to end up with something wrong since it expects hbase to be completely
>>> down.
>>>
>>> Can you open a jira to continue discussions there?
>>>
>>> Thx!
>>>
>>> J-D
>>>
>>> On Mon, Mar 29, 2010 at 2:01 PM, Ted Yu <yuzhihong@gmail.com> wrote:
>>>> Hi,
>>>> While going over TableServers.isMasterRunning() in HConnectionManager,=
 I
>>> see
>>>> this:
>>>> =A0 =A0public boolean isMasterRunning() {
>>>> =A0 =A0 =A0if (this.master =3D=3D null) {
>>>> =A0 =A0 =A0 =A0try {
>>>> =A0 =A0 =A0 =A0 =A0getMaster();
>>>>
>>>> =A0 =A0 =A0 =A0} catch (MasterNotRunningException e) {
>>>> =A0 =A0 =A0 =A0 =A0return false;
>>>> =A0 =A0 =A0 =A0}
>>>> =A0 =A0 =A0}
>>>> =A0 =A0 =A0return true;
>>>> =A0 =A0}
>>>> When isMasterRunning() is called the first time, if master is obtained
>>>> successfully, master field would contain reference to HMasterInterface=
.
>>>> Subsequent calls to isMasterRunning() wouldn't throw
>>>> MasterNotRunningException even if master server stops responding to
>>> clients.
>>>>
>>>> I think master.isMasterRunning() should be called if master isn't null=
.
>>>>
>>>> Regards
>>>>
>>>
>>
>
>