[[upgrading-logstash]]
== Upgrading Logstash

[IMPORTANT]
===========================================
Before upgrading Logstash:

* Consult the <<breaking-changes,breaking changes>> docs.
* Read the <<releasenotes>>.
* Test upgrades in a development environment before upgrading your production cluster.

While upgrading Logstash:

* If you use {monitoring}, you must re-use the data directory when you
upgrade Logstash. Otherwise, the Logstash node is assigned a new persistent UUID
and becomes a new node in the monitoring data.
===========================================

If you're upgrading other products in the stack, also read the
{stack-ref}/index.html[Elastic Stack Installation and Upgrade Guide]. 

See the following topics for information about upgrading Logstash:

* <<upgrading-using-package-managers>>
* <<upgrading-using-direct-download>>
* <<upgrading-minor-versions>>
* <<upgrading-logstash-7.0>>
* <<upgrading-logstash-pqs>>

[[upgrading-using-package-managers]]
=== Upgrading Using Package Managers

This procedure uses <<package-repositories,package managers>> to upgrade Logstash.

1. Shut down your Logstash pipeline, including any inputs that send events to Logstash.
2. Using the directions in the <<package-repositories>> section, update your repository
links to point to the 7.x repositories.
3. Run the `apt-get upgrade logstash` or `yum update logstash` command as appropriate for your operating system.
4. Test your configuration file with the `logstash --config.test_and_exit -f <configuration-file>` command. Configuration options for
some Logstash plugins have changed in the 7.x release.
5. Restart your Logstash pipeline after you have updated your configuration file.

[[upgrading-using-direct-download]]
=== Upgrading Using a Direct Download

This procedure downloads the relevant Logstash binaries directly from Elastic.

1. Shut down your Logstash pipeline, including any inputs that send events to Logstash.
2. Download the https://www.elastic.co/downloads/logstash[Logstash installation file] that matches your host environment.
3. Unpack the installation file into your Logstash directory.
4. Test your configuration file with the `logstash --config.test_and_exit -f <configuration-file>` command. 
Configuration options for
some Logstash plugins have changed in the 7.x release.
5. Restart your Logstash pipeline after updating your configuration file.



[[upgrading-minor-versions]]
=== Upgrading between minor versions

As a general rule, you can upgrade between minor versions (for example, 7.x to
7.y, where x < y) by simply installing the new release and restarting {ls}. 
{ls} typically maintains backwards compatibility for configuration
settings and exported fields. Please review the
<<releasenotes,release notes>> for potential exceptions.

Upgrading between non-consecutive major versions (5.x to 7.x, for example) is not
supported.

[[upgrading-logstash-pqs]]
=== Upgrading with the Persistent Queue Enabled

If you have the persistent queue (PQ) enabled, please read the section that applies
for your upgrade scenario.

* If you are upgrading from version 6.2.x or earlier, we recommend that you
<<drain-pq,drain the persistent queue>> before you upgrade.

* If you are upgrading from version 6.3.0 or later, see
<<upgrading-logstash-pqs-6.3>> for information.

[float]
[[drain-pq]]
==== Drain the Persistent Queue (version 6.2.x and earlier)

The following applies only if you are upgrading from Logstash version 6.2.x or
earlier with the persistent queue (PQ) enabled.

We strive to maintain backward compatibility within a given major release. 
Serialization issues in Logstash 6.2.x and earlier required us to break
that compatibility in version 6.3.0 to ensure correctness of operation. For more
technical details, please check our tracking github issue for this
matter, https://github.com/elastic/logstash/issues/9494[#9494].

We strongly recommend that you drain or delete
the persistent queue before you upgrade from version 6.2.x and earlier.

To drain the queue:
 
. In the logstash.yml file, set `queue.drain:true`.
. Restart Logstash for this setting to take effect. 
. Shutdown Logstash (using CTRL+C or SIGTERM), and wait for the queue to empty.

When the queue is empty:

. Complete the upgrade.
. Restart Logstash.

We have resolved issues with data incompatibilities for version 6.3 and later. 
These steps won’t be required for future upgrades.

[float]
[[upgrading-logstash-pqs-6.3]]
==== Upgrading from version 6.3 (and later) with Persistent Queues Enabled 

Upgrading Logstash with persistent queues enabled is supported. The persistent
queue directory is self-contained and can be read by a new Logstash instance
running the same pipeline. You can safely shut down the original Logstash
instance, spin up a new instance, and set `path.queue` in the `logstash.yml`
<<logstash-settings-file,settings file>> to point to the original queue directory.
You can also use a mounted drive to make this workflow easier.

Keep in mind that only one Logstash instance can write to `path.queue`. You
cannot have the original instance and the new instance writing to the queue at
the same time.

[[upgrading-logstash-7.0]]
=== Upgrading Logstash to 7.0

Before upgrading Logstash, remember to read the <<breaking-changes,breaking
changes>> docs and the <<releasenotes>>.

If you are installing Logstash with other components in the Elastic Stack, also see the
{stack-ref}/index.html[Elastic Stack installation and upgrade documentation].

NOTE: Upgrading between non-consecutive major versions (5.x to 7.x, for example) is not
supported. We recommend that you upgrade to 6.x, and then upgrade to 7.x.

==== When to Upgrade

Fresh installations can and should start with the same version across the Elastic Stack.

Elasticsearch 7.0 does not require Logstash 7.0. An Elasticsearch 7.0 cluster
will happily receive data from earlier versions of Logstash via the default
HTTP communication layer. This provides some flexibility to decide when to
upgrade Logstash relative to an Elasticsearch upgrade. It may or may not be
convenient for you to upgrade them together, and it is not required to be done
at the same time as long as Elasticsearch is upgraded first.

You should upgrade in a timely manner to get the performance improvements that come with Logstash 7.0, but do so in
the way that makes the most sense for your environment.

==== When Not to Upgrade

If any Logstash plugin that you require is not compatible with Logstash 7.0, then you should wait until it is ready
before upgrading.

Although we make great efforts to ensure compatibility, Logstash 7.0 is not completely backwards compatible. As noted
in the Elastic Stack upgrade guide, Logstash 7.0 should not be upgraded before Elasticsearch 7.0. This is both
practical and because some Logstash 7.0 plugins may attempt to use features of Elasticsearch 7.0 that did not exist
in earlier versions. For example, if you attempt to send the 7.x template to a cluster before Elasticsearch 7.0, then 
all indexing likely fail. If you use your own custom template with Logstash,
then this issue can be ignored.
