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Storage drivers options
Storage back ends
The Message service supports several different storage back ends
(storage drivers) for storing management information, messages and their
metadata. The recommended storage back end is MongoDB. For information
on how to specify the storage back ends, see zaqar-drivers.
When the storage back end is chosen, the corresponding back-end
options become active. For example, if Redis is chosen as the management
storage back end, the options in
[drivers:management_store:redis] section become active.
Storage layer pipelines
A pipeline is a set of stages needed to process a request. When a new
request comes to the Message service, first it goes through the
transport layer pipeline and then through one of the storage layer
pipelines depending on the type of operation of each particular request.
For example, if the Message service receives a request to make a
queue-related operation, the storage layer pipeline will be
queue pipeline. The Message service always has the actual
storage controller as the final storage layer pipeline stage.
By setting the options in the [storage] section of
zaqar.conf, you can add additional stages to these storage
layer pipelines:
- Claim pipeline
- Message pipeline with built-in stage available to
use:
zaqar.notification.notifier- sends notifications to the queue subscribers on each incoming message to the queue, in other words, enables notifications functionality.
- Queue pipeline
- Subscription pipeline
The storage layer pipelines options are empty by default, because additional stages can affect the performance of the Message service. Depending on the stages, the sequence in which the option values are listed does matter or not.
You can add external stages to the storage layer pipelines. For information how to write and add your own external stages, see Writing stages for the storage pipelines tutorial.
Options
The following tables detail the available options: