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## RabbitMQ 3.8.2
RabbitMQ `3.8.2` is a maintenance release.
### Erlang/OTP Compatibility Notes
This release [**requires Erlang/OTP 21.3**](https://www.rabbitmq.com/which-erlang.html) or later.
`22.x` series is recommended.
[Provisioning Latest Erlang Releases](https://www.rabbitmq.com/which-erlang.html#erlang-repositories) explains
what package repositories and tools can be used to provision latest patch versions of Erlang `21.3.x` and `22.x`.
### Compatibility Notes
#### Upgrading to Erlang 21.x or Later Versions
When upgrading to this release from `3.7.6` or an older version, extra care has to be taken.
Since CLI tools from RabbitMQ releases older than 3.7.7 will fail on Erlang 21 or later,
RabbitMQ **must be upgraded at the same time as Erlang**. Alternatively the node can be upgraded
to `3.7.18` first, then Erlang 21.x or 22.x, then to RabbitMQ 3.8.x.
#### Upgrade Doc Guides and Change Log
See [3.8.0 release notes](https://github.com/rabbitmq/rabbitmq-server/releases/tag/v3.8.0) upgrade
and compatibility notes first if upgrading from an earlier release.
See the [Upgrading guide](https://www.rabbitmq.com/upgrade.html) for general documentation on upgrades
and [RabbitMQ change log](https://www.rabbitmq.com/changelog.html) for release notes of other releases.
### Getting Help
Any questions about this release, upgrades or RabbitMQ in general are welcome on the
[RabbitMQ mailing list](https://groups.google.com/forum/#!forum/rabbitmq-users).
## Changes
### Core Server
#### Enhancements
* Raft implementation optimizations.
GitHub issues: [rabbitmq/ra#137](https://github.com/rabbitmq/ra/pull/137), [rabbitmq/ra#148](https://github.com/rabbitmq/ra/pull/148)
* Quorum queue optimization: enables local (not going through the leader) delivery from Raft followers
when appropriate and safe.
GitHub issues: [rabbitmq/rabbitmq-server#2146](https://github.com/rabbitmq/rabbitmq-server/pull/2146), [rabbitmq/ra#132](https://github.com/rabbitmq/ra/pull/132)
* If `x-queue-type` argument is not provided at queue declaration time, the type is assumed to be `classic`
instead of missing.
GitHub issue: [rabbitmq/rabbitmq-common#341](https://github.com/rabbitmq/rabbitmq-common/issues/341)
* Quorum queue consumer timeout now can be configured using new style configuration file:
``` ini
# Hard timeout for quorum queue consumer acknowledgemnts of two minutes
consumer_timeout = 120000
```
GitHub issue: [rabbitmq/rabbitmq-server#2163](https://github.com/rabbitmq/rabbitmq-server/pull/2163)
#### Bug Fixes
* A quorum queue could produce an empty Raft log segment if node is killed at a particular moment in time,
which would prevent the node from successfully recovering the log after restart.
GitHub issues: [rabbitmq/ra#138](https://github.com/rabbitmq/ra/pull/138)
* Quorum queue consumer count metric could be duplicated when reported via HTTP API or to a Prometheus scraper.
GitHub issue: [rabbitmq/rabbitmq-server#2176](https://github.com/rabbitmq/rabbitmq-server/pull/2176)
### CLI Tools
#### Enhancements
* It is now possible to [export and import definitions]() without the use of plugins with
`rabbitmqctl export_definitions` and `rabbitmqctl import_definitions`:
``` sh
# export as a JSON file
rabbitmqctl export_definitions /path/to/target.file.json
# export as JSON to standard output and pipe to jq
rabbitmqctl export_definitions "-" | jq
# export as a compressed Erlang term file
rabbitmqctl export_definitions /path/to/target.file --format=erlang
# learn more
rabbitmqctl help export_definitions
```
``` sh
# import from a JSON file
rabbitmqctl import_definitions /path/to/target.file.json
# import JSON from standard input
cat /path/to/definitions.json | rabbitmqctl import_definitions "-"
# import from a compressed Erlang term file
rabbitmqctl import_definitions /path/to/target.file --format=erlang
# learn more
rabbitmqctl help import_definitions
```
GitHub issue: [rabbitmq/rabbitmq-management#749](https://github.com/rabbitmq/rabbitmq-management/issues/749)
* Entities with `amq.*` prefixes are now skipped during import instead of producing an error.
GitHub issue: [rabbitmq/rabbitmq-server#2170](https://github.com/rabbitmq/rabbitmq-server/issues/2170)
#### Bug Fixes
* `rabbitmqctl await_startup` failed with an exception when RabbitMQ application was stopped but the
runtime (Erlang VM) was running.
GitHub issue: [rabbitmq/rabbitmq-server#2158](https://github.com/rabbitmq/rabbitmq-server/issues/2158)
### Management Plugin
#### Bug Fixes
* Definition import via HTTP API could fail in if performed via HTTP API (but not management UI)
and contained operator policies.
GitHub issue: [rabbitmq/rabbitmq-management#751](https://github.com/rabbitmq/rabbitmq-management/issues/751)
#### Enhancements
* Metric aggregation optimizations.
GitHub issue: [rabbitmq/rabbitmq-management-agent#84](https://github.com/rabbitmq/rabbitmq-management-agent/pull/84)
### MQTT Plugin
#### Enhancements
* Throughput improvements ranging from 14 to 60 percent depending on workload.
GitHub issue: [rabbitmq/rabbitmq-server#2168](https://github.com/rabbitmq/rabbitmq-server/issues/2168)
* Throughput improvements and reduced CPU usage but slightly higher per connection RAM footprint.
GitHub issues: [rabbitmq/rabbitmq-mqtt#216](https://github.com/rabbitmq/rabbitmq-mqtt/pull/216), [rabbitmq/rabbitmq-mqtt#217](https://github.com/rabbitmq/rabbitmq-mqtt/pull/217)
#### Bug Fixes
* Client ID tracker could produce an empty Raft log segment if node is killed at a particular moment in time,
which would prevent the node from successfully recovering the log after restart.
GitHub issues: [rabbitmq/discussions#4](https://github.com/rabbitmq/discussions/issues/4), [rabbitmq/ra#138](https://github.com/rabbitmq/ra/pull/138)
* Last Will messages that use QoS 2 will now be downgraded to QoS 1 just like with "regular" published messages.
GitHub issue: [rabbitmq/rabbitmq-mqtt#214](https://github.com/rabbitmq/rabbitmq-mqtt/issues/214)
### AMQP 1.0 Plugin
#### Enhancements
* Throughput improvements.
GitHub issue: [rabbitmq/rabbitmq-server#2168](https://github.com/rabbitmq/rabbitmq-server/issues/2168)
### STOMP Plugin
#### Enhancements
* Throughput improvements.
GitHub issue: [rabbitmq/rabbitmq-server#2168](https://github.com/rabbitmq/rabbitmq-server/issues/2168)
### Web STOMP Plugin
#### Enhancements
* Clients now can authenticate using an x.509 (TLS) certificate.
GitHub issue: [rabbitmq/rabbitmq-web-stomp#116](https://github.com/rabbitmq/rabbitmq-web-stomp/issues/116)
### Prometheus Plugin
* A small number of queue metrics were not read from the metric store correctly.
GitHub issue: [rabbitmq/rabbitmq-prometheus#19](https://github.com/rabbitmq/rabbitmq-prometheus/issues/19)
## Source code archives
**Warning**: The source code archive provided by GitHub only contains the source of the broker,
not the plugins or the client libraries. Please download the archive named `rabbitmq-server-3.8.2.tar.xz`.
|
