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 the users of the client actively consider what is a good timeout for their usecase – without imposing anything, and most importantly – without risking stuck connections in production. Additionally, you can still present them with a “default” option, but still making them explicitly choose it. For example:

Client client = ClientBuilder.create(url) .withCredentials(credentials) .withTimeouts(Timeouts.connect(1000).read(1000)) .build(); // OR Client client = ClientBuilder.create(url) .withCredentials(credentials) .withDefaultTimeouts() .build();

The builder above should require “timeouts” to be set, and should fail if neither of the two methods was invoked. Even if you don’t provide these options, at least have a good way of specifying timeouts – some libraries require reflection to set the timeout of their underlying client.

I believe this is one of those issues that look tiny, but caus a lot of problems in the real world. And it can (and should) be solved by the library/client designers.

But since it isn’t always the case, we must make sure that timeouts are configured every time we use a 3rd party library.