runutil

Overview ¶

Package runutil provides helpers to advanced function scheduling control like repeat or retry.

It's very often the case when you need to excutes some code every fixed intervals or have it retried automatically. To make it reliably with proper timeout, you need to carefully arrange some boilerplate for this. Below function does it for you.

For repeat executes, use Repeat:

err := runutil.Repeat(10*time.Second, stopc, func() error {
	// ...
})

Retry starts executing closure function f until no error is returned from f:

err := runutil.Retry(10*time.Second, stopc, func() error {
	// ...
})

For logging an error on each f error, use RetryWithLog:

err := runutil.RetryWithLog(logger, 10*time.Second, stopc, func() error {
	// ...
})

Another use case for runutil package is when you want to close a `Closer` interface. As we all know, we should close all implements of `Closer`, such as *os.File. Commonly we will use:

defer closer.Close()

The problem is that Close() usually can return important error e.g for os.File the actual file flush might happen (and fail) on `Close` method. It's important to *always* check error. Thanos provides utility functions to log every error like those, allowing to put them in convenient `defer`:

defer runutil.CloseWithLogOnErr(logger, closer, "log format message")

For capturing error, use CloseWithErrCapture:

var err error
defer runutil.CloseWithErrCapture(&err, closer, "log format message")

// ...

If Close() returns error, err will capture it and return by argument.

The rununtil.Exhaust* family of functions provide the same functionality but they take an io.ReadCloser and they exhaust the whole reader before closing them. They are useful when trying to use http keep-alive connections because for the same connection to be re-used the whole response body needs to be exhausted.