ablyboomer

ablyboomer is an Ably load generator for Locust written in Go, based on the boomer library.

ablyboomer defines a worker that performs the same function as a Locust worker in a distributed load test. It receives start and stop events from the Locust master, spawns the appropriate amount of users that subscribe, publish and enter Ably channels based on how ablyboomer is configured, and reports message delivery and latency statistics back to the master.

Quick Start

Follow these steps to run a simple fanout load test against the Ably service:

• Build the Docker image:

make image

• Copy .env.example to .env to store your private environment variables:

cp .env.example .env

• Set ABLY_API_KEY in .env to your Ably app key

• Start the docker-compose cluster in examples/fanout:

cd examples/fanout
docker-compose up

• Visit http://localhost:8089 in your browser and start a load test with 50 users spawning at 5 users/sec

You are now running 5 ablyboomer workers that each have 10 users subscribed to a fanout channel, and also have a single standalone worker publishing a message to the fanout channel every 1s, with message latency visible in the Locust web interface.

Building

To build ablyboomer as a local binary, run:

make build

This builds a binary at bin/ably-boomer that you can run directly:

bin/ably-boomer --help

You can also build an ablyboomer Docker image with:

make image

Which is tagged as ablyrealtime/ably-boomer:latest and can be run like the binary:

docker run --rm ablyrealtime/ably-boomer:latest --help

Config

ablyboomer can be configured either using CLI flags, environment variables or a YAML config file, with precedence going from config file -> environment variables -> CLI flags.

The path to the YAML config file defaults to ably-boomer.yaml in the current directory but can be set explicitly with the --config CLI flag:

bin/ably-boomer --config my-config.yaml

An example YAML config file for a fanout subscriber load test:

locust.host: locust.example.com
subscriber.enabled: true
subscriber.channels: fanout

Or for a standalone publisher that doesn't connect to Locust but just publishes messages to the fanout channel:

standalone.enabled: true
standalone.users: 1
standalone.spawn-rate: 1.0
publisher.enabled: true
publisher.channels: fanout
publisher.publish-interval: 1s

See bin/ably-boomer --help for a full list of config options.

User Numbering

When running more than one ablyboomer process, Redis can be used to assign a unique number to each user in the load test. For example, with Redis enabled, if you have 5 workers that each start 10 users, they will use Redis to assign numbers 1-10, 11-20, 21-30, 31-40 and 41-50.

Redis can be configured with:

redis.enable: true
redis.addr: redis-host:6379
redis.connect-timeout: 5s

Channel Config

The subscriber.channels, publisher.channels and presence.channels config options are a comma separated list of channels that a user should subscribe to, publish to or enter respectively.

These config options can include a Go template to dynamically render the names of the channels, with all the built-in functions available as well as a .UserNumber variable which is the 1-indexed number of the current user and a mod function which performs a modulo calculation between two integers.

For example, to generate a "personal" channel name that is unique to each user:

subscriber.channels: personal-{{ .UserNumber }}

Or to do the same but with left-padded zeros:

subscriber.channels: personal-{{ printf "%08d" .UserNumber }}

Or to generate a "sharded" channel name that spreads the users over a fixed set of 10 channels:

subscriber.channels: sharded-{{ mod .UserNumber 10 }}

Examples

See the examples directory for some example load tests which can be run using docker-compose.

Each example can be run by changing into the directory, running docker-compose up and visiting http://localhost:8089 in your browser:

cd examples/personal

docker-compose up

# now visit http://localhost:8089

Fanout

The fanout example simulates a single channel with a large number of subscribers.

Each user creates a single subscription.

A standalone publisher publishes 1 message per second.

Personal

The personal example simulates a large number of channels, each with one subscriber.

Each user subscribes to a channel based on their assigned number (e.g. personal-0042), and publishes a message to it every second.

Sharded

The sharded example simulates a large number of subscribers, sharded over a number of channels.

Each user subscribes to a channel using their assigned number modulo 5 (i.e. one of sharded-0, sharded-1, sharded-2, sharded-3 or sharded-5).

A standalone publisher publishes 1 message per second to each of the 5 sharded channels.

Composite

The composite example simulates both a personal scenario and a sharded scenario.

Each user subscribes to a personal channel (e.g. personal-0042), publishes a message to it every second, and also subscribes to a sharded channel (i.e. one of sharded-0, sharded-1, sharded-2, sharded-3 or sharded-5).

A standalone publisher publishes 1 message per second to each of the 5 sharded channels.

Push Fanout

The push fanout example simulates a single channel with a large number of push device subscribers.

Each user registers a push device with the ablyChannel transport which publishes messages back to a channel, and subscribes to that channel to measure latency of messages pushed to it. Each user then subscribes that push device to a single fanout channel.

A standalone publisher publishes 1 message per second to the fanout channel.

Note that running this test requires you to enable push notifications on a namespace (or to enable it in the default channel rule), and add it to the subscriber and publisher channels config options. For example, with a namespace called push:

subscriber.channels: push:fanout

publisher.channels: push:fanout

Performance Options

The test can be configured to debug performance. Options are set through environment variables.

Variable	Description	Default	Required
PERF_CPU_PROFILE_DIR	The directorty path to write the pprof cpu profile	n/a	no
PERF_CPU_S3_BUCKET	The name of the s3 bucket to upload pprof data to	n/a	no

If uploading data to s3, the s3 client is configured through the default environment as per the s3 client documentation.

The AWS_REGION must be set by either specifying the AWS_REGION environment variable or to load the environment from the configuration by setting AWS_SDK_LOAD_CONFIG=true. Credentials will be retrieved from ~/.aws and a profile can be selected by setting the AWS_PROFILE environment variable. If not using the credentials file, the settings can be provided directly through environment variables.

Variable	Description	Default	Required
AWS_REGION	The AWS region to use, i.e. us-west-2	n/a	no
AWS_SDK_LOAD_CONFIG	A boolean indicating that region should be read from config in ~/.aws	n/a	no
AWS_PROFILE	The aws profile to use in the shared credentials file	"default"	no
AWS_ACCESS_KEY_ID	The AWS access key id credential to use	n/a	no
AWS_SECRET_ACCESS_KEY	The AWS secret access key to use	n/a	no
AWS_SESSION_TOKEN	The AWS session token to use	n/a	no