ratelimiter

Rate Limiter

The ratelimiter service type creates a rate limiter with specified limit. When it is used in the step, it applies limit against supplied token. If a spikeThreshold is specified then traffic will be blocked with a probability (that has an exponential decay) when a traffic spike occurs above the spikeThreshold multiple.

The available service settings are as follows:

Name	Type	Description
limit	string	Limit can be specifed in the format of "limit-period". Valid periods are 'S', 'M' & 'H' to represent Second, Minute & Hour. Example: "10-S" represents 10 request/second
spikeThreshold	decimal	Multiple above base traffic load which triggers the spike block logic. Spike blocking is disabled by default.
decayRate	decimal	Exponential decay rate for the spike blocking probability. Default .01

The available input for the request are as follows:

Name	Type	Description
token	string	Token for which rate limit has to be applied

The available response outputs are as follows:

Name	Type	Description
limitReached	bool	If the limit exceeds
limitAvailable	integer	Available limit
error	bool	If any error occured while applying the rate limit
errorMessage	string	The error message

A sample service definition is:

{
    "name": "RateLimiter",
    "description": "Rate limiter",
    "ref": "github.com/project-flogo/microgateway/activity/ratelimiter",
    "settings": {
        "limit": "5-M"
    }
}

An example step that invokes the above ratelimiter service to consume a token is:

{
    "service": "RateLimiter",
    "input": {
        "token": "=$.payload.headers.Token"
    }
}

Note: When token is not supplied or empty, service sets error to true. This can be handled by configuring token to some constant value, In this way service can be operated as global rate limiter. An example shown below:

{
    "service": "RateLimiter",
    "input": {
        "token": "MY_GLOBAL_TOKEN"
    }
}

Utilizing and extracting the response values can be seen in both a conditional evaluation:

{"if": "$.RateLimiter.outputs.limitReached == true"}

and a response handler:

{
    "if": "$.RateLimiter.outputs.limitReached == true",
    "error": true,
    "output": {
        "code": 403,
        "data": {
            "status":"Rate Limit Exceeded - The service you have requested is over the allowed limit."
        }
    }
}