Combine serverless with artillery and you get serverless-artillery for instant, cheap, and easy performance testing at scale.
Latest commit 8db7fd0 Sep 20, 2018

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Combine serverless with artillery and you get serverless-artillery (a.k.a. serverless-artillery) for instant, cheap, and easy performance testing at scale.

We were motivated to create this project in order to facilitate moving performance testing earlier and more frequently into our CI/CD pipelines such that the question wasn't 'whether...' but 'why wouldn't...' ' automatically (acceptance and) perf test your system every time you check in?'.

If you would like a more detailed walk through of motivations, setup, and usage, please consider taking a look at the workshop that was initially presented at the Serverless Conference, London 2016: Load testing an ApiGateway endpoint? You may want to use the artillery-plugin-aws-sigv4. Want to record your results in InfluxDb? You may want to use artillery-plugin-influxdb. Want to record your results without setting up a database? You may want to use artillery-plugin-cloudwatch.


We assume you have node.js (v4 or better) installed. Likewise you should have the serverless framework (v1.0+) either installed globally or available in the local node_modules.

npm install -g serverless-artillery

Docker Installation

The post installation causes permission issues when installing in a Docker image. To successfully install in Docker make sure to add the following to your Dockerfile before the serverless and serverless-artillery install. Refer to the sample Dockerfile.

ENV NPM_CONFIG_PREFIX=/home/node/.npm-global
ENV PATH=$PATH:/home/node/.npm-global/bin

Quick Start & Finish

$ slsart deploy   // and then
$ slsart invoke   // repeat as desired, before...
$ slsart remove

Deeper Dive

$ slsart deploy                  // If not already deployed.

// create a custom test against your service with a 10 second duration and 3 RPS:
$ slsart script -e -d 10 -r 3

// run acceptance tests
$ slsart invoke -a               // iterate on editing `./script.yml` and invoking as desired, before...

// run performance tests
$ slsart invoke

$ slsart remove

Note that you may need to define AWS_PROFILE to declare the AWS credentials to use and perhaps HTTP_PROXY in order to escape your corporate proxy. See the Serverless Framework docs or the workshop for details of how to set your system up for successful deployment, invocation, and removal.

More advanced use cases

Use arbitrary script files

$ slsart -p /my/path/to/my.other.script.yml

Generate a customizable script on the CLI (hit with 10 requests per second, scaling up to 25 requests per second over 60 seconds)

$ slsart script -e -d 60 -r 10 -t 25

Generate a local copy of the function that can be edited and redeployed with your changed settings. This enables more advanced configurations of the function to send load against VPC hosted services, use CSV files to specify variables in your URLs (hint: put your csv in the same directory as your serverless.yml and redeploy), or other non-default use cases. Similarly, you'll want to do this if you need to alter hard-coded limits. See for function configuration related documentation. See for script configuration related documentation.

$ slsart configure
$ nano serverless.yml
$ nano handler.js

Detailed Usage

$ slsart --help
  deploy     Deploy a default version of the function that will execute your
             Artillery scripts.  See
             for reference.
  invoke     Invoke your function with your Artillery script.  Will prefer a
             script given by `-d`, `--data`, `-p`, or `--path` over a
             `script.[yml|json]` file in the current directory over the default
             script.  Invocation mode will default to "performance" but adding
             the `-a` flag will run the script in "acceptance" mode.  See
             for reference.
  remove     Remove the function and the associated resources created for or by
             it.  See
             for reference.
  script     Create a local Artillery script so that you can customize it for
             your specific load requirements.  See for
  configure  Create a local copy of the deployment assets for modification and
             deployment.  See for documentation.

  --help         Show help                                             [boolean]
  --version      Show version number                                   [boolean]
  -D, --debug    Execute the command in debug mode.  It will be chatty about
                 what it is happening in the code.
  -V, --verbose  Execute the command in verbose mode.  It will be chatty about
                 what it is attempting to accomplish.



$ slsart deploy --help

slsart deploy

See for further supported options.


$ slsart invoke --help

slsart invoke

  -a, --acceptance  Execute the script in acceptance mode.  It will execute each
                    flow once, reporting failures.
  -d, --data        A stringified script to execute
  -p, --path        A path to the file containing the script to execute
  --si, --stdIn     Have serverless read the event to invoke the remote function
                    with from the "standard in" stream
  --jo, --jsonOnly  Only write JSON to console.log to facilitate piping the
                    invocation result into a tool such as jq

See for further supported options.

Removed Flags:
  -s, --script      In order to support the full CLI experience of the Serverless 
                    Framework, a collision between this flag and the -s/--stage
                    flags of those frameworks had to be resovled.  These flags
                    are thereby invalidated and will be rejected.

Reserved Flags:
-t, --type          serverless-artillery calculates, based on your HTTP timeout
                    settings, the expected completion of your script and sets
                    the invocation type appropriately.  Dropping a 
                    RequestResponse connection can trigger function retries for
                    triple the load and you will not receive a report directly
                    from an Event invocation type.
-f, --function      serverless-artillery provides the function and its
                    implementation.  If you want an arbitrary function, please
                    consider using the Serverless Framework, you'll be much

Unsupported Flags:
--raw               serverless-artillery, having provided the function implementation
                    knows that it only supports JSON, stending raw strings is
                    unsupported.  If you have altered the function to accept other
                    data, you probably already know the Serverless Framework and
                    are using it.  Why are you trying this flag in that case?


$ slsart remove --help

slsart remove

See for further supported options.


$ slsart script --help

slsart script

  -e, --endpoint  The endpoint to load with traffic.                    [string]
  -d, --duration  The duration, in seconds, to load the given endpoint. [number]
  -r, --rate      The rate, in requests per second, at which to load the given
                  endpoint.                                             [number]
  -t, --rampTo    The rate to adjust towards away from the given rate, in
                  requests per second at which to load the given endpoint.
  -o, --out       The file to output the generated script in to.        [string]


$ slsart configure

slsart configure

Script Customization

$ mkdir myCustomLoadTest    // Make your own test directory
$ cd myCustomLoadTest
$ slsart script             // Use slsart to get basic files
$ nano script.yml           // Edit event.json to change test endpoint

Modify the script.yml file to point at your own endpoint with the load profile that you want to test your application with. See for documentation on scripts.

For example, change the script to target your service:

  target: ""
  - flow:
    - get:
        url: "/your/path"

and up the duration of the test to one minute and provide more load:

    - duration: 60      # Duration of test in seconds
      arrivalRate: 100  # Starting rate (requests per second)
      rampTo: 200       # Ending rate (RPS at end of test duration)

Then invoke the function with your script again using:

$ slsart invoke

Now you can create a copy of the test, edit that copy, and invoke the function with it.

$ cp script.yml trafficSpike.yml
$ nano trafficSpike.yml

Update the load spec... Then invoke it!

$ slsart invoke -p trafficSpike.yml

Acceptance Mode

Find defects before performance testing! Acceptance mode runs each flow in your script exactly once and reports the results.

To use:

Add -a to invoke command:

$ slsart invoke -a

To run exclusively in acceptance mode, hard code the mode into your script:

  mode: acceptance

note: 'acceptance' may be abbreviated to 'acc' in the script

Scripts running in acceptance mode do not require a phases array in the config section of the script but it is expected that performance tests will be run in this mode (via the -a flag) and have them anyway.

For the purposes of facilitating the use of this tool in a CI/CD pipeline, if any of the acceptance tests fail to successfully complete, the process will exit with a non-zero exit code.

Reserved Flags

The flags -t, --type, -f, and --function are reserved for serverless-artillery use. They cannot be supplied on the command line.

The -t and --type flags are reserved because the tool uses the script you provide it to cacluate whether an Event or RequestResponse invocation type is more appropriate. If that argument was supplied, a user might have an expectation-behavior mismatch.

The -f and --function flags are reserved because a part of the value that serverless-artillery provides is the automated definition of the function providing load testing and thereby a necessarily strong opinion of the name that function was given.

Unsupported Flags

The flag --raw is unsupported because, while arbitrary functions can accept strings, a string does not comprise a valid artillery script.

Function Customization

Sometimes you need to customize your load testing function. Sometimes occassionally becomes all the times. The endpoints you need to slam are in the VPC or you need to separate out various versions of the load testing function in order to maintain least privilege. Perhaps you really want to draw from a data payload to feed IDs into the endpoints you will be hitting. We welcome you to:

slsart configure

This command gives you a copy of the Serverless service artifacts used to create and deploy your load testing function. As such, you have free reign!

!!! Note that any time you make modifications you must execute slsart deploy to have them applied !!!

Deployment and Settings Customization

Open up the serverless.yml you just created. It will contain the default Serverless Framework service definition. The Serverless Framework helps coalesce the specification of Lambda and various other serverless technologies in an easy to manage and maintain format. Add a vpc attribute (docs) with subnetIds and securityGroupIds sub-attributes to target your VPC protected endpoints. Add custom IAM rights (docs) to the service to maintain least privilege. You can use payloads by adding the payload to your lambda directory and adding the payload configuration to your script (docs).

Full documentation of what is in the serverless.yml and the options you have available can be found at

Load Test Execution Customization (

The script allows you to add plugins for various capabilities. Load testing an ApiGateway endpoint? You may want to use the artillery-plugin-aws-sigv4. Want to record your results in InfluxDb? You may want to use artillery-plugin-influxdb. Docs for plugin use and configuration are available from those projects and from artillery-core's plugin docs.

Script Splitting Customization

The following controls are available in the default deployed function. That said, the defaults are good and you generally won't need them until you have gotten deeper into implementation which is why we've put off mentioning until now. If you define a _split attribute within the script, the values of that object will be used to alter the splitting of your script.

  _split: {
    maxScriptDurationInSeconds: 86400,  # Default listed.  Hard-coded max is 518400
    maxChunkDurationInSeconds: 240,     # Default listed.  Hard-coded max is 285
    maxScriptRequestsPerSecond: 5000,   # Default listed.  Hard-coded max is 50000
    maxChunkRequestsPerSecond: 25,      # Default listed.  Hard-coded max is 500
    timeBufferInMilliseconds: 15000,    # Default listed.  Hard-coded max is 30000

See the [Splitting and Distribution Logic Customization](#Splitting and Distribution Logic Customization) section for an in depth discussion of how splitting is implemented and what you control with these parameters as well as the concerns involved in making decisions about them. See the comments in ~/lambda/handler.js for detailed documentation of the semantics the code has with regard to them (search for 'const constants'). By the way, you now have the source code to change those hard-coded limits and can change them at will if you so desire - we wanted to provide a margin of safety and guardrails but not restrictions.

Debugging and Tracing Behavior Customization

There are two primary tools for debugging and tracing the function and how it splits and executes the task it has been given. Define the following in your script:

  _trace: true,
  _simulation: true,


The first causes the code to report the actions it is taking with your script and the chunks that it breaks your script into. Expect statements such as this:

scheduling self invocation for 1234567890123 in 2345678901234 with a 3456789012345 ms delay

This would be produced by the following:

console.log(`scheduling self invocation for ${event._genesis} in ${event._start} with a ${timeDelay} ms delay`);

There are definitions that will help you understand these statements. In the code you will see _genesis, _start, now, and timeDelay:

_genesis: the datetime stamp immediately taken by the function that received the original script. _genesis is added to the original script so that all child function executions of the original handler have a datetime stamp of when the original "load execution request" was received. If you are not running many load tests simultaneously then this can serve as a unique ID for the current load execution. This can be useful for correlation. An improvement could include adding a unique factor to avoid collisions in such usage.
_start: the datetime stamp immediately taken by the current function that is executing on either the original script or a chunk of that original script. This allows relative time reporting and evaluation with a function execution.
now: the datetime stamp taken when the log entry was produced.
timeDelay: a time delta (in milliseconds) between the current time of the current function and when it has scheduled to take the action reported in the current log entry.

This mode is very useful in identifying what the system is doing or where something is going wrong. #bugs-happen


Setting the _simulation attribute to a truthy value will cause the function to split the script without taking action on the script. Functionally, this comprises splitting the given script into pieces without invoking functions to handle the split chunks and/or execute the load described by those chunks. Concretely, when it comes time to invoke new function instances for distributing the load, it simply invokes (or schedules an invokation of) itself. Likewise, when it comes time to invoke the artillery-core entry point for generating load from the chunk, it instead invokes the simulation shim that reports what would have been executed and immediately completes.

This mode, in combination with _trace related behavior is very helpful in debugging script splitting behavior and identifying what the logic declares should occur.

Splitting and Distribution Logic Customization

You've got the code. Have at! Have fun and consider contributing improvements back into the tool. Thank you!

Some helpful notions used in the code and discussion of them follows...


In fact, an artillery script is composed of a number of phases which occur one after the other. Each of these phases has its own duration and maximum load. The duration is straightforwardly how long the phase lasts. The maximum load of the phase is the maximum Requests Per Second (RPS) that are declared for the entirety of that phase (e.g. a phase declaring a ramp from 0 to 500 RPS {or 500 to 0} has a maximum load of 500 RPS). Phases are declared in serial in order to provide warming or not as appropriate for the load testing scenario that iterests you.

The duration of the script is the sum of the durations of its phases. The maximum load of the script is the maximum RPS that any of its phases declares.


The splitting of a script comprises taking "chunks" off of the script.

First, we take chunks from the script by duration. This is driven by the maximum duration of the underlying function as a service (FaaS) provider that we are using. For AWS Lambda, this is currently 5 minutes. However, we need to allow for cold starts and as such must provide a buffer of time before we begin the execution of any specific load job. Following the execution of a load job, the artillery-core framework calculates a summary and invokes custom analyzers (via the plugin capabilities it offers). As a result, a tailing buffer is also needed to ensure execution can properly complete.

The result is a script chunk that can be executed within the duration limited period the FaaS provider allows (no guarantees yet exist on whether a single function can execute the demanded load). This chunk will be called the script for referential simplicity. We also may have a remainder script that must be executed by a new function instance as the current splitting function nears its timeout.

Next, we take chunks from the script by maximum load. This is driven by the maximum requests per second that a single execution of the underlying function as a service (FaaS) provider is capable of pushing with high fidelity. For AWS Lambda (with the default 1024 MB configuration), we found 25 RPS to be a good level. This is lower than the absolute ceiling that Lambda is capable of pushing for a reason. First, each connection will be a separate opened and closed socket. Second, if we are producing too many connections, we can be in the middle of making a request when we receive the response of a separate request. Given that this is implemented in nodejs, we have one thread and that means the timestamping of the receipt of that response is artificially and incorrectly delayed. We found that at RPS above 25 we observed an increase in the volatility of observed latencies. That written, if you do not intend to record your latencies, then you could bump this up to the limit of the FaaS service (i.e. _split.maxChunkRequestsPerSecond = 300 or so). If you don't care about having separate sockets per request, you can alter that with artillery configuration as well.

Anyway... The result is a script chunk that is less than the limited period and also executable by a single function instance. Therefore, we invoke a single function with the chunk to execute it.


Wait. There's a general pattern here of distributed load execution!


We know!

We're excited too!

We've already begun writing a plugin-driven generalization of this pattern. Any task that a declaration can be provided for which itself can be executed in parallel and broken into parallelizable chunks can be driven using this capabiltiy.

Watch for that effort here:

We expect to retro-fit this project with the serverless-star project as its first use case and proof-of-not-a-painful-waste-of-our-time-ness™.


  1. for documentation about how to define your load shape, volume, targets, inputs, et cetera
  2. for documentation about how to create a custom function configuration
  3. serverless-artillery README for documentation on the use of this tool
  4. serverless-star Next generation implementation and generalization of the arbitrarily wide work distribution capability