ja30278 / tripwire

Break out from scripts blocking the node.js event loop

Tripwire

Tripwire allows node.js applications to termiante execution of scripts that block the node.js event loop. For example, you can break out from infinite loops like while(true). This functionality is useful if you are executing untrusted code within your node.js process.

Tripwire contains a native extension of node.js and currently supports Windows, Mac, and Linux. I do take contributions.

Install with:

npm install tripwire

Then in your application, you can put a limit on the total amout of CPU time (kernel and user mode combined) the event loop is blocked before the execution of the script is terminated:

var tripwire = require('tripwire');

process.on('uncaughtException', function (e) {
  console.log('The event loop was blocked for longer than 2000 milliseconds');
  process.exit(1);
});

// set the limit of execution time to 2000 milliseconds
tripwire.resetTripwire(2000);

// execute code that will block the event loop for longer
while(true);

// clear the tripwire (in this case this code is never reached)
tripwire.clearTripwire();

When the event loop is blocked for longer than the time specified in the call to resetTripwire, tripwire will terminate execution of the script. Node.js will subsequently execute the uncaughtException handler if one is registered. The exception passed to uncaughtException handler will be null in that case. In order to determine whether the exception was indeed caused by tripwire, an optional context can be established during a call to resetTripwire and retrtieved with a call to getContext. The getContext will return undefined if the tripwire had not been triggered.

var tripwire = require('tripwire');

process.on('uncaughtException', function (e) {
  if (undefined === tripwire.getContext())
    console.log('The exception was not caused by tripwire.');
  else
    console.log('The event loop was blocked for longer than 2000 milliseconds');
  process.exit(1);
});

// set the limit of execution time to 2000 milliseconds
var context = { someData: "foobar" };
tripwire.resetTripwire(2000, context);

For more samples, see here.

Running tests

There are a few mocha tests included that you can run with

mocha -R list

Building

On OSX and Linux, the native component is built at installation time.

On Windows, the native component is included in the repository and not built during npm install tripwire.

You can rebuild the native component using node-gyp. Currently the native component can be compiled on Windows, Mac, and Linux (I do take contributions).

On Windows:

node-gyp configure build
copy build\Release\tripwire.node lib\native\win32\4.0\ia32\