Web Workers handling AJAX calls - optimisation overkill?

Question

I'm working with a code that handles all AJAX requests using Web Workers (when available). These workers do almost nothing more than XMLHttpRequest object handling (no extra computations). All requests created by workers are asynchronous (request.open("get",url,true)).

Recently, I got couple of issues regarding this code and I started to wonder if I should spend time fixing this or just dump the whole solution.

My research so far suggests that this code may be actually hurting performance. However, I wasn't able to find any credible source supporting this. My only two findings are:

• 2 year old jQuery feature suggestion to use web workers for AJAX calls
• this SO question that seems to ask about something a bit different (using synchronous requests in web workers vs AJAX calls)

Can someone point me to a reliable source discussing this issue? Or, are there any benchmarks that may dispel my doubts?

[EDIT] This question gets a little bit more interesting when WebWorker is also responsible for parsing the result (JSON.parse). Is asynchronous parsing improving performance?

Answer 1

I have created a proper benchmark for that on jsperf. Depending on the browser, WebWorker approach is 85-95% slower than a raw ajax call.

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Notes:

• since network response time can be different for each request, I'm testing only new XMLHttpRequest() and JSON.parse(jsonString);. There are no real AJAX calls being made.
• WebWorker setup and teardown operations are not being measured
• note that I'm testing a single request, results for webworker approach may be better for multiple simultaneous requests
• Calvin Metcalf explained to me that comparing sync and async on jsperf won't give accurate results and he created another benchmark that eliminates async overhead. Results still show that WebWorker approach is significantly slower.
• From the Reddit discussion I learned that data passed between the main page and WebWorker are copied and have to be serialized in the process. Therefore, using WebWorker for parsing only doesn't make much sense, data will have to be serialized and deserialized anyway before you can use them on the main page.