Gollum

Gollum is a n:m multiplexer that gathers messages from different sources and broadcasts them to a set of destinations.

There are a few basic terms used throughout Gollum:

• "Consumers" read data from other services
• "Producers" write data to other services
• "Streams" route data between consumers and producers
• A "message" is a set of data passed between consumers and producers
• "Formatters" can transform the content of messages
• "Filters" can block/pass messages based on their content

Writing a custom plugin does not require you to change any additional code besides your new plugin file.

Documentation

A how-to-use documentation can be found on read the docs. Developers should use the godoc pages to get started. Plugin documentation is generated from the plugin source code. So if you feel that something is missing a look into the code may help.

Consumers (reading data)

• Console read from stdin.
• File read from a file (like tail).
• Http read http requests.
• Kafka read from a Kafka topic.
• Kinesis read from a Kinesis stream.
• Profiler Generate profiling messages.
• Proxy use in combination with a proxy producer to enable two-way communication.
• Socket read from a socket (gollum specific protocol).
• Syslogd read from a socket (syslogd protocol).
• SystemD read from the SystemD journal.

Producers (writing data)

• Console write to stdin or stdout.
• ElasticSearch write to elasticsearch via http/bulk.
• File write to a file. Supports log rotation and compression.
• Firehose write data to a Firehose stream.
• HTTPRequest HTTP request forwarder.
• InfluxDB send data to an InfluxDB server.
• Kafka write to a Kafka topic.
• Kinesis write data to a Kinesis stream.
• Null like /dev/null.
• Proxy two-way communication proxy for simple protocols.
• S3 write data to Amazon S3 stream.
• Scribe send messages to a Facebook scribe server.
• Socket send messages to a socket (gollum specific protocol).
• Spooling write messages to disk and retry them later.
• Websocket send messages to a websocket.

Streams (multiplexing)

• Broadcast send to all producers in a stream.
• Random send to a random producer in a stream.
• RoundRobin switch the producer after each send in a round robin fashion.
• Route convert streams to one or multiple others

Formatters (modifying data)

• Base64Encode encode messages to base64.
• Base64Decode decode messages from base64.
• Clear clears a message
• CollectdToInflux08 convert CollectD 0.8 data to InfluxDB compatible values.
• CollectdToInflux09 convert CollectD 0.9 data to InfluxDB compatible values.
• CollectdToInflux10 convert CollectD 0.10 data to InfluxDB compatible values.
• ExtractJSON extracts a single field from a JSON object.
• Envelope add a prefix and/or postfix string to a message.
• Forward write the message without modifying it.
• Hostname prepend the current machine's hostname to a message.
• Identifier hash the message to generate a (mostly) unique id.
• JSON write the message as a JSON object. Messages can be parsed to generate fields.
• ProcessJSON Modify fields of a JSON encoded message.
• ProcessTSV Modify fields of a TSV encoded message.
• Runlength prepend the length of the message.
• Sequence prepend the sequence number of the message.
• SplitToJSON tokenize a message and put the values into JSON fields.
• StreamName prepend the name of a stream to the payload.
• StreamRevert route a message to the previous stream (e.g. after it has been routed).
• StreamRoute route a message to another stream by reading a prefix.
• Timestamp prepend a timestamp to the message.

Filters (filtering data)

• All lets all message pass.
• JSON blocks or lets json messages pass based on their content.
• None blocks all messages.
• Rate blocks messages that go over a given messages per second rate.
• RegExp blocks or lets messages pass based on a regular expression.
• Stream blocks or lets messages pass based on their stream name.

Installation

From source

Installation from source requires the installation of the Go toolchain.
Gollum supports the Go 1.5 vendor experiment that is automatically enabled when using the provided makefile. With Go 1.6 and later you can also use go build directly without additional modifications. Builds with Go 1.4 or earlier versions are not officially supported and might require additional steps and modifications.

$ make
$ ./gollum --help

You can use the make file coming with gollum to trigger cross platform builds.
Make will produce ready to deploy .zip files with the corresponding platform builds inside the dist folder.

Usage

To test gollum you can make a local profiler run with a predefined configuration:

$ gollum -c config/profile.conf -ps -ll 3

By default this test profiles the theoretic maximum throughput of 256 Byte messages.
You can enable different producers in that config to test the write performance of these producers, too.

Configuration

Configuration files are written in the YAML format and have to be loaded via command line switch. Each plugin has a different set of configuration options which are currently described in the plugin itself, i.e. you can find examples in the GoDocs.

Commandline

-c or --config [file]

Use a given configuration file.

-h or --help

Print this help message.

-ll or --loglevel [0-3]

Set the loglevel [0-3]. Higher levels produce more messages as in 0=Errors, 1=Warnings, 2=Notes, 3=Debug.

-m or --metrics [port]

Port to use for metric queries. Set 0 to disable.

-n or --numcpu [number]

Number of CPUs to use. Set 0 for all CPUs.

-p or --pidfile [file]

Write the process id into a given file.

-pc or --profilecpu [file]

Write CPU profiler results to a given file.

-pm or --profilemem [file]

Write heap profile results to a given file.

-ps or --profilespeed

Write msg/sec measurements to log.

-r or --report

Print detailed version report and quit.

-tc or --testconfig [file]

Test a given configuration file and exit.

-tr or --trace [file]

Write trace results to a given file.

-v or --version

Print version information and quit.

Building

Mac OS X

The easiest way to install go is by using homebrew:
brew install go

Linux

Download Go from the golang website and unzip it to e.g. /usr/local/go.
You have to set the GOROOT environment variable to the folder you chose:
export GOROOT=/usr/local/go

Prerequisites

If you do not already have a GOPATH set up you need to create one.
The location is free of choice, we prefer to put it into each users home folder:

mkdir -p ~/go
export GOPATH=$(HOME)/go

You can download gollum via go get github.com/trivago/gollum or clone it directly into your GOPATH.
If you choose this way you need to download your dependencies directly from that folder

mkdir -p $(GOPATH)/src/github.com/trivago
cd $(GOPATH)/src/github.com/trivago
git clone https://github.com/trivago/gollum.git
cd gollum

Build

Building gollum is as easy as make or go build. When using Go 1.5 make sure to enable the go vendor experiment by setting export GO15VENDOREXPERIMENT=1 or use make. If you want to do cross platform builds use make all or specify one of the following platforms instead of "all":

• current build for current OS (default)
• freebsd build for FreeBSD
• linux build for Linux x64
• mac build for MacOS X
• pi build for Linux ARM
• win build for Windows

There are also supplementary targets for make:

• clean clean all artifacts created by the build process
• test run unittests
• vendor install gvt and update all dependencies
• aws build for Linux x64 and generate an Elastic Beanstalk package

If you want to use native plugins (contrib/native) you will have to enable the corresponding imports in the file contrib/loader.go. Doing so will disable the possibility to do cross-platform builds for most users.

Dockerfile

The repository contains a Dockerfile which enables you to build and run gollum inside a Docker container.

$ docker build -t trivago/gollum .
$ docker run -it --rm trivago/gollum -c config/profile.conf -ps -ll 3

To use your own configuration you could run:

$ docker run -it --rm -v /path/to/config.conf:/etc/gollum/gollum.conf:ro trivago/gollum -c /etc/gollum/gollum.conf

License

This project is released under the terms of the Apache 2.0 license.