Logstash Plugin

This is a Logstash input plugin for Google Pub/Sub. The plugin can subscribe to a topic and ingest messages.

The main motivation behind the development of this plugin was to ingest Stackdriver Logging messages via the Exported Logs feature of Stackdriver Logging.

It is fully free and fully open source. The license is Apache 2.0, meaning you are pretty much free to use it however you want in whatever way.

Documentation

Prerequisites

You must first create a Google Cloud Platform project and enable the the Google Pub/Sub API. If you intend to use the plugin ingest Stackdriver Logging messages, you must also enable the Stackdriver Logging API and configure log exporting to Pub/Sub. There is plentiful information on https://cloud.google.com/ to get started,

• Google Cloud Platform Projects and Overview
• Goolge Cloud Pub/Sub documentation
• Stackdriver Logging documentation

Cloud Pub/Sub

Currently, this module requires you to create a topic manually and specify it in the logstash config file. You must also specify a subscription, but the plugin will attempt to create the pull-based subscription on its own.

All messages received from Pub/Sub will be converted to a logstash event and added to the processing pipeline queue. All Pub/Sub messages will be acknowledged and removed from the Pub/Sub topic (please see more about Pub/Sub concepts).

It is generally assumed that incoming messages will be in JSON and added to the logstash event as-is. However, if a plain text message is received, the plugin will return the raw text in as raw_message in the logstash event.

Authentication

You have two options for authentication depending on where you run Logstash.

1. If you are running Logstash outside of Google Cloud Platform, then you will need to create a Google Cloud Platform Service Account and specify the full path to the JSON private key file in your config in json_key_file setting. If you don't want to upload the file and use its content as a string, then add the content of JSON private key in json_key_file_content setting. You must assign sufficient roles to the Service Account to create a subscription and to pull messages from the subscription. Learn more about GCP Service Accounts and IAM roles here:

• Google Cloud Platform IAM overview
• Creating Service Accounts overview
• Granting Roles overview

2. If you are running Logstash on a Google Compute Engine instance, you may opt to use Application Default Credentials. In this case, you will not need to specify a JSON private key file in your config.

Stackdriver Logging (optional)

If you intend to use the logstash plugin for Stackdriver Logging message ingestion, you must first manually set up the Export option to Coud Pub/Sub and the manually create the topic. Please see the more detailed instructions at, Exported Logs and ensure that the necessary permissions have also been manually configured.

Logging messages from Stackdriver Logging exported to Pub/Sub are received as JSON and converted to a logstash event as-is in this format.

Sample Configuration

Below is a copy of the included example.conf-tmpl file that shows a basic configuration for this plugin.

input {
    google_pubsub {
        # Your GCP project id (name)
        project_id => "my-project-1234"

        # The topic name below is currently hard-coded in the plugin. You
        # must first create this topic by hand and ensure you are exporting
        # logging to this pubsub topic.
        topic => "logstash-input-dev"

        # The subscription name is customizeable. The plugin will attempt to
        # create the subscription (but use the hard-coded topic name above).
        subscription => "logstash-sub"

        # If you are running logstash within GCE, it will use
        # Application Default Credentials and use GCE's metadata
        # service to fetch tokens.  However, if you are running logstash
        # outside of GCE, you will need to specify the service account's
        # JSON key file below.
        #json_key_file => "/home/erjohnso/pkey.json"
    }
}

output { stdout { codec => rubydebug } }

(stock) Documentation

Logstash provides infrastructure to automatically generate documentation for this plugin. We use the asciidoc format to write documentation so any comments in the source code will be first converted into asciidoc and then into html. All plugin documentation are placed under one central location.

• For formatting code or config example, you can use the asciidoc [source,ruby] directive
• For more asciidoc formatting tips, see the excellent reference here https://github.com/elastic/docs#asciidoc-guide

Need Help?

Need help? Try #logstash on freenode IRC or the https://discuss.elastic.co/c/logstash discussion forum.

Developing

1. Plugin Development and Testing

Code

• To get started, you'll need JRuby with the Bundler gem installed.

• You'll also need a Logstash installation to build the plugin against.

• Create a new plugin or clone and existing from the GitHub logstash-plugins organization. We also provide example plugins.

• export LOGSTASH_SOURCE=1 and point LOGSTASH_PATH to a local Logstash e.g. export LOGSTASH_PATH=/opt/local/logstash-8.7.0

• Install Ruby dependencies

bundle install

• Install Java dependencies - regenerates the lib/logstash-input-google_pubsub_jars.rb script used to load the .jar dependencies when the plugin starts.

./gradlew vendor

NOTE: This step is necessary whenever build.gradle is updated.

Test

• Update your dependencies

bundle install

• Run Ruby tests

bundle exec rspec

2. Running your unpublished Plugin in Logstash

2.1 Run in a local Logstash clone

• Edit Logstash Gemfile and add the local plugin path, for example:

gem "logstash-filter-awesome", :path => "/your/local/logstash-filter-awesome"

• Install plugin

bin/logstash-plugin install --no-verify

• Run Logstash with your plugin

bin/logstash -e 'filter {awesome {}}'

At this point any modifications to the plugin code will be applied to this local Logstash setup. After modifying the plugin, simply rerun Logstash.

2.2 Run in an installed Logstash

You can use the same 2.1 method to run your plugin in an installed Logstash by editing its Gemfile and pointing the :path to your local plugin development directory or you can build the gem and install it using:

• Build your plugin gem

gem build logstash-filter-awesome.gemspec

• Install the plugin from the Logstash home

bin/logstash-plugin install --no-verify

• Start Logstash and proceed to test the plugin

Contributing

All contributions are welcome: ideas, patches, documentation, bug reports, complaints, and even something you drew up on a napkin.

Programming is not a required skill. Whatever you've seen about open source and maintainers or community members saying "send patches or die" - you will not see that here.

It is more important to the community that you are able to contribute.

For more information about contributing, see the CONTRIBUTING file