[jira] [Commented] (HADOOP-10282) Create a FairCallQueue: a multi-level call queue which schedules incoming calls and multiplexes outgoing calls

["Arpit Agarwal (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HADOOP-10282?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14032924#comment-14032924 ] 

Arpit Agarwal commented on HADOOP-10282:
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Hi Chris, all the Jiras HADOOP-10279, HADOOP-10281 and HADOOP-10282 just add new files.

How are they meant to plugin to the existing code? Perhaps I forgot some context on the changes so if this is described elsewhere, can you just give me a pointer?

Thanks!

> Create a FairCallQueue: a multi-level call queue which schedules incoming calls and multiplexes outgoing calls
> --------------------------------------------------------------------------------------------------------------
>
>                 Key: HADOOP-10282
>                 URL: https://issues.apache.org/jira/browse/HADOOP-10282
>             Project: Hadoop Common
>          Issue Type: Sub-task
>            Reporter: Chris Li
>            Assignee: Chris Li
>         Attachments: HADOOP-10282.patch
>
>
> The FairCallQueue ensures quality of service by altering the order of RPC calls internally. 
> It consists of three parts:
> 1. a Scheduler (`HistoryRpcScheduler` is provided) which provides a priority number from 0 to N (0 being highest priority)
> 2. a Multi-level queue (residing in `FairCallQueue`) which provides a way to keep calls in priority order internally
> 3. a Multiplexer (`WeightedRoundRobinMultiplexer` is provided) which provides logic to control which queue to take from
> Currently the Mux and Scheduler are not pluggable, but they probably should be (up for discussion).
> This is how it is used:
> // Production
> 1. Call is created and given to the CallQueueManager
> 2. CallQueueManager requests a `put(T call)` into the `FairCallQueue` which implements `BlockingQueue`
> 3. `FairCallQueue` asks its scheduler for a scheduling decision, which is an integer e.g. 12
> 4. `FairCallQueue` inserts Call into the 12th queue: `queues.get(12).put(call)`
> // Consumption
> 1. CallQueueManager requests `take()` or `poll()` on FairCallQueue
> 2. `FairCallQueue` asks its multiplexer for which queue to draw from, which will also be an integer e.g. 2
> 3. `FairCallQueue` draws from this queue if it has an available call (or tries other queues if it is empty)
> Additional information is available in the linked JIRAs regarding the Scheduler and Multiplexer's roles.



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