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Version: 4.0

Deprecated Features

Overview​

Over time, some features of RabbitMQ are not relevant anymore. Sometimes, a feature must go away to leave the room for a better replacement. Before we deorbit a feature, we follow a deprecation time window: we announce that a feature is deprecated along with the reasoning, how user should prepare for that and the estimated future version of RabbitMQ where this deprecated feature will be removed and unsupported.

Beside the public announcement, RabbitMQ has a Deprecated features subsystem that helps notify users right from the broker if they are using a feature that will be removed in the future.

You can view the list of actually deprecated features in a dedicated page.

The lifecycle of a deprecated feature​

The Deprecated features subsystem is based on the Feature flags subsystem. Therefore, much like a feature flag which goes from experimental to stable to required, a deprecated feature follow the following phases:

  1. Permitted by default. A user can continue to use the feature. They just get warnings in the logs and can use a configuration knob to start RabbitMQ as if the feature was removed for testing purpose.
  2. Denied by default. The feature is still there, but it is not usable out of the box, like if it was already removed. A user can turn it back on from the configuration.
  3. Disconnected. The feature is still present in the code, but it is compiled out in official packages. A user has to recompile RabbitMQ from source to be able to continue to use it. Note that we do not plan to use this phase very often, if ever.
  4. Removed. The code of the feature is gone and it is not possible to use it anymore. This is the equivalent of a required feature flag.

Checking if deprecated features are used​

In addition to the full list of deprecated features documented on this website, you can view the deprecated features for a specific RabbitMQ deployment using:

  • the CLI's rabbitmq-diagnostics list_deprecated_features
  • the management UI Admin > Deprecated Features panel

You can query RabbitMQ to find out if a node or cluster is actively using one or more deprecated features:

rabbitmq-diagnostics check_if_any_deprecated_features_are_used

It lists used deprecated features (if any) and exits with 0 if none are used, or non-zero if one or more deprecated features are actively used.

You can do the same using the HTTP API:

GET /api/deprecated-features/used
info

Note that the result of these queries depends on if the use of a deprecated feature can be detected or not. For instance, it is possible to detect if classic queue mirroring is used. However it is not for global QoS.

Configuring deprecated features behavior​

As described above, a user may decide to turn off a deprecated feature to test the behavior of RabbitMQ and their applications as if the feature was already removed.

# Try RabbitMQ as if the deprecated feature was gone.
deprecated_features.permit.some_deprecated_feature = false

Another user may decied to turn a denied by default deprecated feature back on to buy more time to adapt their applications while still upgrading RabbitMQ:

# Permit a deprecated feature that is denied by default.
deprecated_features.permit.some_deprecated_feature = true