Documentation

Plugins

Condition Development

Declaring Condition

Approach is quite similar to Policy

Code of url-match condition:

// content of conditions/url-match.js file
module.exports = {
  name: 'url-match',
  schema: {
    $id: 'http://express-gateway.io/schemas/conditions/url-match.json',
    type: 'object',
    properties: {
      expected: {
        type: 'string'
      }
    },
    required: ['expected']
  },
  handler: conditionConfig => req => conditionConfig.expected === req.url
};

• name - Name of the condition, this is how it can be referenced in pipeline
• schema - JSON Schema of the condition; it will be used to validate the data passed in.
• handler - Function that returns true\false. The function accepts ExpressJS Request object and condition parameters. And conditionParams is all configuration options in the pipeline for this condition

Condition Params

Let say you have pipeline defined as:

pipelines:
  apiPipeline:
    apiEndpoints:
      - api
    policies:
      - example:
          -
            condition:
                name: 'url-match'
                expected: '/test'
            action:  # everything under the action will be actionParams
              baseUrl: 'https://example.com'

In this case during request example policy will only be executed in url-match condition is met. And inside the condition conditionParams will be

{
    "expected": "/test"
}

Exporting Condition with plugin

This is done in manifest.js init function

module.exports = {
  version: '1.2.0',
  init: function (pluginContext) {
     const condition = require('./conditions/url-match.js')
     pluginContext.registerCondition(condition)
  }
}

Condition registration and execution sequence

Condition has 2 major components:

• pluginContext.registerCondition - to register the condition as part of plugin
• function (req, conditionConfig) => true/false - handler function

pluginContext.registerCondition

• Executes at Express Gateway start. Before pipeline engine and before http server start.
• Executes only one time

function (req, conditionConfig) => true/false Handler

• Executes on each request in current pipeline. If not matched will prevent policy from being fired