Paul Baclace created WHIRR-693:
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Summary: Control order of actions with waves of
whirr.instance-templates
Key: WHIRR-693
URL: https://issues.apache.org/jira/browse/WHIRR-693
Project: Whirr
Issue Type: Bug
Components: core
Reporter: Paul Baclace
Priority: Critical
A cluster can be specified with "waves" by supporting an optional suffix on
whirr.instance-templates property in order to provide *running* base-level
services (like ZK or a master-master mysql) to another layer of services during
the configuration phase. This enables storing cluster-wide information in
zookeeper or doing db creation beforehand.
An example of a two "wave" (avoiding "phase" which already has a meaning)
cluster:
whirr.instance-templates.0=1 zookeeper, 2 zookeeper, 4 noop
The .0 templates run like normal during "whirr launch-cluster" and then, during
the same Whirr run, the .1 template is applied as a modification of the same
cluster so that new host instances are not allocated:
whirr.instance-templates.1=1 my-master, 2 my-gateway, 4 my-worker
In the second wave, instance provisioning is inhibited, the instance-templates
must have the same number of commas and same sequence of leading numbers, and a
role is only allowed to appear in one wave.
Here is another example:
whirr.instance-templates.0=1 mysql-master+zookeeper, 1
mysql-master+zookeeper,4 noop
whirr.instance-templates.1=1 hadoop-namenode+hadoop-jobtracker, 1
hbase-master+hadoop-secondarynn,4
hadoop-tasktracker+hadoop-datanode+hbase-regionserver
In the first wave, the two mysql-masters form a multi-master ensemble which
keeps state information about the setup in the Whirr process (much like
ZooKeeperCluster.getHosts(cluster) informs services/hbase of the quorum).
In the second wave, nodes are not allocated (BootstrapClusterAction.doAction()
is inhibited if instances already exist), but all phases for
LaunchClusterCommand, including beforeBootstrap() and afterBootstrap()
callbacks, are executed. If other whirr.cli.command.*Command are run, they
would see a combined whirr.instance-templates that works like normal.
Obviously, there would be no reason to limit this to 2 waves, but I do not
expect more than 10 waves to be useful, so the pattern could enable a suffix of
"\.[0-9]".
Instead of WHIRR-221 which aims to specify a single global order for service
startup, the wave format has the advantage that it relies on the implicit
synchronization barriers at phases already supported by Whirr, and state
generated by a wave is available to later waves.
Conceptually, this merely splits the whirr.instance-templates into waves of
(bootstrap,install,configure,start). If no .[0-9] suffixes are present, then
Whirr would behave just like normal.
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