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https://issues.apache.org/jira/browse/DRILL-4543?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15216522#comment-15216522
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Paul Rogers commented on DRILL-4543:
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Great idea! Perhaps generalize this to a configuration stack:
* System properties (-DpropName=value)
* Env var: DRILL_PROP_NAME=value
* Drill site config: "propName": "value"
* Defaults
The idea is that items higher in order take precedence over items lower in the
order. Mesos can override values with env vars. YARN can use either env vars or
command-like args (-D...).
Then, when the values are needed by other Drill-bits, this particular Drill-bit
uses ZK to advertise its actual values as computed using the override rules.
YARN (or Mesos) can adjust ports and resources, and other Drill-bits can learn
of those customizations.
> Advertise Drill-bit ports, status, capabilities in ZooKeeper
> ------------------------------------------------------------
>
> Key: DRILL-4543
> URL: https://issues.apache.org/jira/browse/DRILL-4543
> Project: Apache Drill
> Issue Type: Improvement
> Components: Server
> Reporter: Paul Rogers
> Fix For: 2.0.0
>
>
> Today Drill uses ZooKeeper (ZK) to advertise the existence of a Drill-bit,
> providing just the host name/IP Address of the Drill-bit. All other
> information (ports, status, capabilities) are assumed to be the same across
> all Drill-bits in the cluster as specified in the Drill config file.
> Moving forward, as Drill becomes more sophisticated, Drill should advertise
> the specifics of each Drill-bit so that one Drill bit can differ from another.
> For example, when running on YARN, we need a way for Drill to gracefully shut
> down. Advertising a status of Ready or Unavailable will help. Ready is the
> normal state. Unavailable means the Drill-bit will finish in-flight queries,
> but won't accept new ones. (The actual status is a separate enhancement.)
> In a YARN cluster, Drill should take advantage of machines with more memory,
> but live with machines with less. (Perhaps some are newer, some are older or
> more heavily loaded.) Drill should use ZK to identify its available memory
> and CPUs so that the planner can use them. (Use of the info is a separate
> enhancement.)
> There may be times when two drill bits run on a single machine. If so, they
> must use separate ports. So, each Drill-bit should advertise its ports in ZK.
> For backward compatibility, the information is optional; if not present, the
> receiver should assume the information defaults to that in the config file.
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