MultiQueue

Overview

MultiQueue is a feature that allows GreenArrow Studio to queue messages to GreenArrow Engine more efficiently. This reduces CPU and memory IO overhead.

MultiQueue is disabled by default.

Enabling MultiQueue

1. Set the /var/hvmail/control/studio.use_direct_injection.batch_size file equal to the maximum number of messages which Studio should write to the same file. For example, to set this limit to 20, run:

     echo 20 > /var/hvmail/control/studio.use_direct_injection.batch_size
   

2. Update the ram-queue’s size to be one of the options whose name ends in _multiqueue.

3. Restart Studio’s worker to apply changes:

    svc -t /service/hvmail-studio-worker
    sleep 7
    svstat /service/hvmail-studio-worker
   

Disabling MultiQueue

1. Delete MultiQueue’s configuration file:

    rm -f /var/hvmail/control/studio.use_direct_injection.batch_size
   

2. Update the ram-queue’s size to be one of the options whose name does not end in _multiqueue.

3. Restart Studio’s worker to apply changes:

    svc -t /service/hvmail-studio-worker
    sleep 7
    svstat /service/hvmail-studio-worker
   

Caveats

1. Messages will be queued in batches, and some of Engine’s reporting does not differentiate between a message batch and the messages in that batch. For example, the hvmail_status command will report each message batch as a single message.

2. When GreenArrow Engine is running at speed capacity with a fully utilized ram-queue, enabling MultiQueue will cause Studio will be able to “hog” a larger percentage of the total system capacity compared to non-Studio email sent through Engine.