by Bozho | Mar 17, 2017 | Aggregated, API design, Developer tips, timeouts
Many libraries wrap some external communication. Be it a REST-like API, a message queue, a database, a mail server or something else. And therefore you have to have some timeout – for connecting, for reading, writing or idling. And sadly, many libraries have their default timeouts set to “0” or “-1” which means “infinity”. And that is a very useless and even harmful default. There isn’t a practical use case where you’d want to hang on forever waiting for a resource. And there are tons of situations where this can happen, e.g. the other end gets stuck. In the past 3 months I had 2 libraries that have a default timeout of “infinity” and that eventually lead to production problems because we’ve forgotten to configure them properly. Sometimes you even don’t see the problem, until a thread pool gets exhausted. So, I have a request to API/library designers (as I’ve done before – against property maps and encoding other than UTF-8). Never have “infinity” as a default timeout. Your library will thus cause lots of production issues. Also note that it’s sometimes an underlying HTTP client (or Socket) that doesn’t have a reasonable default – it’s still your job to fix that when wrapping it. What default should you provide? Reasonable. 5 seconds maybe? You may (rightly) say you don’t want to impose an arbitrary timeout on your users. In that case I have a better proposal: Explicitly require a timeout for building your “client” (because these libraries are most often clients for some external system). E.g. Client.create(url, credentials, timeout). And fail if no timeout is provided. That makes...
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