Simple RFC2616-compliant caching proxy server

npm install fishback
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Fishback is a simple NodeJS-powered caching HTTP proxy.

As well as supporting different caching backends, the design lends itself to filtering and processing the headers of both requests and responses. (For example, changing Cache-Control headers.) It is not well-suited to transforming request or response bodies, though it can be integrated into systems that do provide this feature.

Fishback tries hard to be RFC2616 compliant (and many of the slightly unusual features like only-if-cached and max-stale are supported), but there's probably some things it doesn't do completely correctly. (Though any variation from RFC2616 should be considered a bug.)


var fishback = require("../lib/fishback");
var http = require("http");

var proxy = fishback.createProxy(new fishback.Client("localhost", 9000));
proxy.on("newRequest", function (req) {
    console.log(req.method + " " + req.url);
proxy.on("newResponse", function (res) {
    res.setHeader("cache-control", "public, max-age=3600");


console.log("Listening on port 8000, and proxying to localhost:9000");

For more, see the examples directory.


$ npm install fishback


Fishback is heavily event based, and it relies heavily on the four event emitters http.ServerRequest, http.ServerResponse, http.ClientRequest and http.ClientResponse.

In contrast to most NodeJS "middleware" systems (including Connect), Fishback itself does not contain a web server. Instead, Fishback provides a handler for http.Server's 'request' event.


  • fishback.Handler client - probably a fishback.Client

Convenience function for creating a simple proxy from a client.

fishback.createCachingProxy(cache, client)

  • fishback.Handler cache - probably one of the cache backends
  • fishback.Handler client - probably a fishback.Client

Convenience function for creating a proxy from a cache and client.

Class: fishback.Handler(...)

"Abstract" base class for all handlers. All the classes below (the HTTP client that does real requests, the various cache backends, and the Fishback class that ties them together) are derived from this class.

Event: 'newRequest'

function (serverRequest) { }

  • http.ServerRequest serverRequest

Emitted when a new request has been received. (At the point the event is emitted, only headers are available, though you can of course arrange to listen to other events.)

Event: 'newResponse'

function (serverResponse) { }

  • http.ServerResponse serverResponse

Emitted when a new response is being sent. (At the point the event is emitted, only headers are available. Because of limitations in the http.ServerResponse API (write() does not fire any events), it is not possible to observe any "write" events.)

cache.request(serverRequest, serverResponse)

  • http.ServerRequest serverRequest
  • http.ServerResponse serverResponse

Processes a request/response pair.

If unable to handle the request (e.g. resource is not cached), serverRequest will emit the reject event.

If request is accepted (i.e. the handler is writing to serverResponse), serverResponse will emit the endHead event when headers have been set on the response.

(If overriding this method, note that the handler must ensure that if a request is rejected, any handlers that may subsequently be invoked are actually able to fulfill the request! The most important implication of this constraint is that if the request method is not GET, it must be rejected immediately (synchronously). If the method is GET, the request can be rejected asynchronously since subsequent handlers do not need any information from data events they would otherwise have missed).)


  • http.ClientResponse clientResponse

Process a client response.

This is really only useful for caching handlers--it allows them to populate their caches from responses to any real HTTP requests that are issued.

(For example, fishback.createCachingProxy() arranges things so that if the cache handler fires a reject event, a "real" HTTP request to be issued; the response from this request is then passed to the cache.)

Class: fishback.Fishback(list)

Derived from fishback.Handler.

  • list an array of fishback.Handler objects

The last object in list is assumed to be a real HTTP client that will never reject a request. The other objects can reject requests.

Class: fishback.Client(backend_hostname, backend_port, http)

Derived from fishback.Handler.

  • backend_hostname - e.g. 'localhost'
  • backend_port - e.g. 80
  • http - object with a request() method, such as require('http')

Does a real HTTP request.

Class: fishback.Memory()

Derived from fishback.Handler.

Caching backend.

Class: fishback.MongoDb()

Derived from fishback.Handler.


  • There's no HTTPS support.
  • If the proxy server is able to read from the origin faster than the client can receive data, content needs to be buffered, either by node or the kernel. (This can be fixed by backing off when write() returns false, and resuming only when the "drain" event is triggered. This is only likely to be a problem if you're streaming very large files through node.)
  • ETags (and must-revalidate) are not supported. (You don't get incorrect results; you just need retrieve the entire resource from the origin each time.)

See Also

If you're only after a proxy (rather than a caching proxy), node-http-proxy may be more suitable.


Michael Stillwell

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