Middlewares

Middlewares are functions that allow you to customize some step of the request pipeline, such as Routing, Authentication, Throttling and so on.

Tree Gateway support different kinds of middleware:

• Filter - run before the request pipeline and decide if the request should or not be processed;
• Cors - you can define white and black lists, specific rules and so on for handle cor requests;
• Request and Response interceptors - allow you to customize your requests and responses information, such as headers, content body and others;
• Throttling - allow you to create a custom way to identify the source of your requests, to be used by the rate limit engine;
• Authentication - allows you to instantiate any passportjs strategy to satisfy a custom authentication method;
• Service Discovery - Integrate a service discovery provider, like consul, to your request pipeline to define the target of your service requests;
• Circuit Breaker - allows you to customize actions whenever some circuit breaker event occurs, such as 'open', 'close' or 'rejected'.
• Error Handler - allow you to customize all error messages.
• Request Logger - allow you to customize waht to do with your logs collected during requests processing.

When defining a middleware, you must create a .js file that exports the middleware function, like:

module.exports = function (request, response) {
  return req.query.denyParam !== '1';
};

Sometimes, your middlewares can need to receive parameters to be initialized. Those middlewares need to:

• be exported as a function that receives the option parameter and return the initialized middleware.
• have a property factory=1exported too.

Example:

module.exports = function(options) {
  return function (request, response) {
    return options.allowedValues.indexOf(req.query.denyParam) < 0;
  };
};
module.exports.factory = true;