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ratelimiting.md

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Extensions - Rate Limiting

Table of Contents

Introduction

Out workflows can execute numerous downstream services. Rate limiting can be used to protect these downstream services from flooding. In addition, rate limiting can help us keep our cost at a desired rate in cases where downstream service invocations have an associated cost factor.

Extension Definition

Parameter Description Type Required
extensionid Unique extension Id (default is 'workflow-kpi-extension') string yes
singleInstance Rate limits per single workflow instance object no
allInstances Rate limits per all workflow instances object no

Single Instance Definition

Parameter Description Type Required
maxActionsPerSecond Sets the rate limiting on number of actions that can be executed per second. Notice that the number is represented as number type, so that you can set it to less than 1 if needed. For example, set the number to 0.1 means you want workflow actions should be executed once every 10 seconds. Default zero value means 'unlimited' number no
maxConcurrentActions Maximum number of actions that can be executed in parallel string no
maxProducedEventsPerSecond Sets the rate limiting on number of events that can be produced per second. Notice that the number is represented as number type, so that you can set it to less than 1 if needed. For example, set the number to 0.1 means workflow can produce events once every 10 seconds. Default zero value means 'unlimited' string no
maxStates Maximum number of workflow states that should be executed. Default is zero, meaning unlimited. string no
maxTransitions Maximum number of workflow transitions that should be executed. Default is zero, meaning unlimited. string no

All Instances Definition

Parameter Description Type Required
maxActionsPerSecond Sets the rate limiting on number of actions that can be executed per second. Notice that the number is represented as number type, so that you can set it to less than 1 if needed. For example, set the number to 0.1 means you want workflow actions should be executed once every 10 seconds. Default zero value means 'unlimited' number no
maxConcurrentActions Maximum number of actions that can be executed in parallel string no
maxProducedEventsPerSecond Sets the rate limiting on number of events that can be produced per second. Notice that the number is represented as number type, so that you can set it to less than 1 if needed. For example, set the number to 0.1 means workflow can produce events once every 10 seconds. Default zero value means 'unlimited' string no
maxStates Maximum number of workflow states that should be executed. Default is zero, meaning unlimited. string no
maxTransitions Maximum number of workflow transitions that should be executed. Default is zero, meaning unlimited. string no

Example

The following example shows a workflow definition on the left and an associated sample Rate Limiting extension definition on the right. We assume that our extensions definition yaml is located in a resource accessible via URI: file://myextensions/ratelimiting.yml.

Workflow Rate Limiting Extension 
id: processapplication
name: Process Application
version: '1.0.0'
specVersion: '0.8'
extensions:
  - extensionId: workflow-ratelimiting-extension
    path: file://myextensions/ratelimiting.yml
start: ProcessNewApplication
states:
  - name: ProcessNewApplication
    type: event
    onEvents:
      - eventRefs:
          - ApplicationReceivedEvent
        actions:
          - functionRef: processApplicationFunction
          - functionRef: acceptApplicantFunction
          - functionRef: depositFeesFunction
    end:
      produceEvents:
        - eventRef: NotifyApplicantEvent
functions:
  - name: processApplicationFunction
    operation: file://myservice.json#process
  - name: acceptApplicantFunction
    operation: file://myservice.json#accept
  - name: depositFeesFunction
    operation: file://myservice.json#deposit
events:
  - name: ApplicationReceivedEvent
    type: application
    source: "/applications/new"
  - name: NotifyApplicantEvent
    type: notifications
    source: "/applicants/notify"
 
extensionid: workflow-ratelimiting-extension
singleInstance:
  maxActionsPerSecond: 0.1
  maxConcurrentActions: 200
  maxProducedEventsPerSecond: 2
  maxStates: '1000'
  maxTransitions: '1000'
allInstances:
  maxActionsPerSecond: 1
  maxConcurrentActions: 500
  maxProducedEventsPerSecond: 20
  maxStates: '10000'
  maxTransitions: '10000'