Plugin standard library

RoboHydra comes with a number of plugins offering functionality that, while useful in many situations, doesn’t belong in the core of RoboHydra. These plugins are always in the load path, but if you want them in your server, you must explicitly mention them in your configuration file or command-line options. The following is a description of the different available plugins and how to use them:


Sets all the appropriate headers so that all CORS requests are accepted. To use it, just load the cors plugin. If you want to accept CORS requests only for certain URL paths, you can set the corsurlpath configuration variable (by default, /.*) to the regular expression path you want.

See examples/cors/ in the distribution for a full example.


Insert an artificial delay to the requests matching the specified path (by default, all paths). Useful to simulate high-latency connections and to help reproduce certain race conditions.

Can be configured with variables delaypath, delaymillis (number of milliseconds to wait, by default 2000), and delaydisabled (if given a truthy value, it disables the delay on startup; the appropriate head can of course be attached later to enable the delay).


Simple proxy for front-end developers. It proxies requests to a given URL (eg. your internal development server) except for a list of URL paths, which will be served from local files (eg. front-end files like CSS or Javascript). This allows front-end developers to work on an application without having to install a full backend on their machines.

To use it, load the frontend-dev-proxy plugin and set its proxyurl configuration variable to the proxy target URL, and urlpath to a comma-separated list of URL paths that will be served from the local filesystem. Finally, localdir must be set to a comma-separated list of local directories to serve the URL paths from. Variables urlpath and localdir need to have the same number of elements. Assume you start RoboHydra like so:

$ robohydra -n -P frontend-dev-proxy proxyurl= \
                       urlpath=/css,/js localdir=static/css,static/js

A request to such a server to http://localhost:3000/css/project.css will be served from the local file static/css/project.css, a request to http://localhost:3000/js/vendor/lodash.js will be served from the local file static/js/vendor/lodash.js, and a request to http://localhost:3000/categories/ will be proxied to


Simple logging plugin that will save all traffic to robohydra.log in the current directory. While it doesn’t log the full contents of the response bodies; paths, headers and an excerpt of the response body are present in an easy-to-scan, plain-text form so this plugin is useful in many situations to debug problems or see traffic patterns.

To use it, simply load plugin logger anywhere. You can configure the name of the log file with the configuration variable logfilepath.

See the standard plugins screencast for more details.


Avoids any client-side caching by tweaking client request caching headers. In particular, it deletes the If-Modified-Since and If-None-Match headers and sets Cache-Control to no-cache.

By default no-caching operates on all requests, but you can limit its influence to requests to a given path by setting the nocachingpath configuration variable to that path. This can be done in the configuration file or on the command-line (eg. calling RoboHydra as robohydra your.conf nocachingpath=/foo). Note that the value of nocachingpath is interpreted as a regular expression, as it will be the value of the path property of the head that tweaks the headers.

The logger plugin is a good companion for the no-caching plugin, as it allows you to see the effects on the requests. See the standard plugins screencast for more details.


Proxies to a given URL and caches all responses to GET requests. You configure it with variables proxyurl, the URL to proxy requests to; cachedir, the directory of the cache (defaults to proxy-cache); and cachettl, the number of seconds (can be a float!) that each URL will be cached for (defaults to 5).

You most probably want to use the no-caching plugin with proxy-cache. The logger is sometimes useful, too.


Records or replays traffic. This is useful in a number of situations, like replaying certain server traffic while offline, capturing certain bug-inducing traffic to attach to a bug or test case, record some traffic to fiddle with it and replay modified versions to see what happens when a client receives broken/unusual responses from the server, etc.

To use it, load the replayer plugin and set the variable replayerurl to the URL of the site you want to record, eg. start RoboHydra as robohydra -n -P replayer replayerurl= To start recording, visit the URL /start-recording and then visit whatever URLs you want. With the configuration above, any requests to http://localhost:3000/foobar will go to The traffic will be saved in a file robohydra-replayer.json in the current directory by default, but a different filename can be specified in the trafficfilepath configuration variable or through GET parameters. Note that this traffic file is relatively easy to fiddle with, which makes it easy to make variations of the traffic for testing.

Once you have some traffic that you want to replay (recorded in the same session or simply a file you had pre-recorded in a previous session), you can replay it by visiting the URL /start-replaying. From that moment on, the recording will stop and requests to, say, http://localhost:3000/foobar will receive the response recorded for /foobar (if there was more than one response recorded for that URL, all responses will be in the traffic file and used in a round-robin fashion). Any requests made to paths that don’t have any recorded response will result with 404 Not Found.

See the standard plugins screencast for more details.

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