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https://issues.apache.org/jira/browse/HBASE-1204?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12683162#action_12683162
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stack commented on HBASE-1204:
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Nitay, this should be close, right?
> 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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