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From "Nitay Joffe (JIRA)" <j...@apache.org>
Subject [jira] Work started: (HBASE-1204) Ensure there is always at least one server.X line in ZooKeeper conf/zoo.cfg
Date Wed, 18 Mar 2009 20:55:50 GMT

     [ https://issues.apache.org/jira/browse/HBASE-1204?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Work on HBASE-1204 started by Nitay Joffe.

> Ensure there is always at least one server.X line in ZooKeeper conf/zoo.cfg
> ---------------------------------------------------------------------------
>
>                 Key: HBASE-1204
>                 URL: https://issues.apache.org/jira/browse/HBASE-1204
>             Project: Hadoop HBase
>          Issue Type: Improvement
>            Reporter: Nitay Joffe
>            Assignee: Nitay Joffe
>         Attachments: hbase-1204.patch
>
>
> This is needed so that we can get rid of the "hbase.master" property from the configuration
XML.
> From HBASE-1145:
> There is a bit of an issue regarding getting rid of the "hbase.master" property in hbase-site.xml.
Currently, anybody in HBase needing ZooKeeper parses the server.X lines out of conf/zoo.cfg
to know how to connect to ZooKeeper. If there are no server.X lines, it means we are running
a single instance ZooKeeper on the master server. To find that server, we use the "hbase.master"
property in hbase-site.xml.
> After discussing it with Andrew Purtell and Michael Stack, we came up with the following:
> We have three cases:
> 1) "local" mode. All servers/clients are on localhost.
> 2) Distributed operation with single instance ZooKeeper running on master host.
> 3) Distributed operation with distributed ZooKeeper running.
> To fix these cases (1 and 2) and allow us to remove the "hbase.master" property from
hbase-site.xml, we need to make sure there is _always_ a server.X line with the master's address
in the zoo.cfg. Even when you're running a single instance ZooKeeper on the master server,
there should be a single server.X line with the master's address.
> To avoid adding a lot of configuration headache on the user, we want to have the default
conf/zoo.cfg have a sensible default for the single server master hostname case. We suggest
shipping a new ZooKeeper jar with ZOOKEEPER-279 patched in, and using the variable substitution
to inject the master hostname into zoo.cfg. For example, our new zoo.cfg would look something
like:
> {code}
> # The number of milliseconds of each tick
> tickTime=2000
> # The number of ticks that the initial 
> # synchronization phase can take
> initLimit=10
> # The number of ticks that can pass between 
> # sending a request and getting an acknowledgement
> syncLimit=5
> # the directory where the snapshot is stored.
> dataDir=${hbase.tmp.dir}/zookeeper
> # the port at which the clients will connect
> clientPort=2181 
> server.0=${master.address.hostname}:2888:3888
> {code}
> The "master.address.hostname" is a new property being added to the hbase-site.xml during
this period while we transition users to ZooKeeper. If the property is not set, we will use
gethostname() to fill in the variable and produce copious warning messages that it may not
work and the user should either fill in that variable in hbase-site.xml, or edit zoo.cfg by
hand.

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