Analytics beacon transport mechanism gotchas

An important component in DataHem’s measurementprotocol application is the javascript tracker that emitts hits to the AppEngine collector endpoint. It is important that the tracker emitts all defined hits, if the tracker malfunction then there is no way to recover dropped hits downstream. Like Google Analytics, the DataHem tracker supports three different transport mechanisms; ‘image’ (using an Image object), ‘xhr’ (using an XMLHttpRequest object), or ‘beacon’ using the new navigator.sendBeacon method. »