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From Shalin Shekhar Mangar <>
Subject Re: ZK related startup fixes -- pre-review requested?
Date Wed, 17 Feb 2016 20:21:09 GMT
Hi Scott,

Those all sound very important fixes. I skimmed the changes and they
all look good to me. I think the ZkController changes are
straightforward. The leader election changes should get some more eyes
(maybe Mark Miller can chime in) but please do open the jira issues
(preferably separate ones for easier review+commit).


On Mon, Feb 15, 2016 at 1:59 PM, Scott Blum <> wrote:
> Hi folks (paticularly Erick and Shalin),
> Before I go through the cycle of creating JIRAs and requesting formal
> review, I wondered if I could get some feedback on some work I've been doing
> to allow SolrCloud to startup faster and more reliably.
> Problems:
> 1) Quickly restarting a node makes leader election unreliable; the existing
> ZK node hasn't yet disappeared and confuses the current logic.  I believe I
> have fixed this and simplified the logic.  This affects overseer election.
> 2) ZkController.publishAndWaitForDownStates() occurs before overseer
> election.  That means if there is currently no overseer, there is ironically
> no one to actually service the down state changes it's waiting on.  This
> particularly affects a single-node cluster such as you might run locally for
> development.
> 3) Audited our current implementations of process(WatchedEvent) for
> consistency and handling edge cases.
> 4) Simplified DistributedMap; there's a whole lot more API surface area and
> implementation machinery than we're using.
> Code is here:
> The individual commits might be informative.
> Would some some feedback, and if these seem reasonable I'll open one or more
> JIRAs and rebase the changes to trunk.
> Thanks!
> Scott

Shalin Shekhar Mangar.

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