hadoop-hdds/docs/content/feature/FairCallQueue.md

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FairCallQueue
===

This document contains information for setting up the `FairCallQueue` feature with Ozone. 
In order for `FairCallQueue` to be enabled and used, 
Hadoop RPC must be used as transport protocol for OM - S3G communication. 
There is no implementation for gRPC yet.

There is a custom `IdentityProvider` implementation for Ozone that must be specified in the configuration, otherwise
there is no S3G impersonation which makes the `FairCallQueue` ineffective since it's only reading one user, 
the S3G special user instead of the S3G client user.

## Configuration

There must be a port specified to which the OM will forward any activity 
and the `FailCallQueue` and `DecayRpcScheduler` will listen to. 
Furthermore, this port will have to be part of every configuration name.

Port used for below examples : 9862

```XML
<property>
   <name>ozone.om.address</name>
   <value>OMDomain:9862</value>
</property>

<property>
    <name>ozone.om.s3.grpc.server_enabled</name>
    <value>false</value>
</property>
<property>
    <name>ozone.om.transport.class</name>
    <value>org.apache.hadoop.ozone.om.protocolPB.Hadoop3OmTransportFactory</value>
</property>

<property>
   <name>ipc.9862.callqueue.impl</name>
   <value>org.apache.hadoop.ipc.FairCallQueue</value>
</property>
<property>
   <name>ipc.9862.scheduler.impl</name>
   <value>org.apache.hadoop.ipc.DecayRpcScheduler</value>
</property>
<property>
   <name>ipc.9862.identity-provider.impl</name>
   <value>org.apache.hadoop.ozone.om.helpers.OzoneIdentityProvider</value>
</property>
<property>
   <name>ipc.9862.scheduler.priority.levels</name>
   <value>2</value>
</property>
<property>
   <name>ipc.9862.backoff.enable</name>
   <value>true</value>
</property>
<property>
   <name>ipc.9862.faircallqueue.multiplexer.weights</name>
   <value>2,1</value>
</property>
<property>
    <name>ipc.9862.decay-scheduler.thresholds</name>
    <value>50</value>
</property>
```