Loader (loader v0.2.0)
Loader
is a load-generating library that allows you to define arbitrary distributions of arbitrary work via mathematical functions and small structs.
These distributions, called LoadProfile
s, can be paired up with a WorkSpec
and executed to generate load, and gather statistics from a client's perspective.
example
Example
Let's assume there is some service at http://website.io/public/api
, and we want to generate some simple, uniform load against that service.
alias Loader.{LoadProfile, WorkResponse, WorkSpec}
uniform_one_minute_profile =
LoadProfile.new(%{
target_running_time: 60,
function: &LoadProfile.Curves.uniform(&1, 10) # y = 10
})
service_call_spec = %WorkSpec{
task: fn ->
Finch.build(:get, "http://website.io/public/api", [])
|> Finch.request(MyApp.Finch)
end,
is_success?: fn %WorkResponse{data: res} ->
case res do
{:ok, _any} -> true
_any -> false
end
end
}
Loader.execute_profile(uniform_one_minute_profile, service_call_spec)
The above example will generate a uniform 10 requests/ second against our imaginary service. We could also write additional load profiles, and run them concurrently to generate constructive interference!
linear_one_minute_profile =
LoadProfile.new(%{
target_running_time: 60,
function: &LoadProfile.Curves.linear(&1, 1.5, 5) # y = 1.5x + 5
})
sine_wave_one_minute_profile =
LoadProfile.new(%{
target_running_time: 60,
function: fn x -> 5 * (:math.sin(x) + 1) end # y = 5 * (sin(x) + 1)
})
Loader.execute_profiles([
{uniform_one_minute_profile, service_call_spec},
{linear_one_minute_profile, service_call_spec},
{sine_wave_one_minute_profile, service_call_spec},
])
Visualized, this second example would produce load on the service as shown, where x
is in seconds and y
is requests/ second:

telemetry
Telemetry
Loader
emits the following telemetry events:
[:loader, :load_profile_execution, :start]
- emitted whenLoader.execute_profile/2
orLoader.execute_profiles/1
is called.[:loader, :load_profile_execution, :stop]
- emitted when aLoadProfile
has been fully emitted, regardless of the number of successes or failures of individual tasks[:loader, :task, :start]
- emitted when the:task
callback from aLoader.WorkSpec
is invoked[:loader, :task, :stop]
- emitted when the:task
callback from aLoader.WorkSpec
is invoked[:loader, :task, :exception]
- emitted if there is an uncaught exception while invoking the:task
callback from aLoader.WorkSpec
See the documentation for the Loader.Telemetry
module for more information.
installation
Installation
The package can be installed by adding loader
to your list of dependencies in mix.exs
:
def deps do
[
{:loader, "~> 0.2.0"}
]
end
The docs can be found at https://hexdocs.pm/loader.
Link to this section Summary
Functions
Execute tasks based on the work_spec
, scheduled based on the parameters in the load_profile
Execute several LoadProfile
s simultaneously, each with their supplied WorkSpec
Link to this section Functions
execute_profile(load_profile, work_spec)
@spec execute_profile(Loader.LoadProfile.t(), Loader.WorkSpec.t()) :: DynamicSupervisor.on_start_child()
Execute tasks based on the work_spec
, scheduled based on the parameters in the load_profile
execute_profiles(profile_spec_pairs)
@spec execute_profiles([{Loader.LoadProfile.t(), Loader.WorkSpec.t()}]) :: [ DynamicSupervisor.on_start_child() ]
Execute several LoadProfile
s simultaneously, each with their supplied WorkSpec