Terminates current Nginx worker process.

Nginx master process shall spawn a new worker process thereafter.

Terminates current Nginx worker process.

Nginx master process shall not spawn a new worker process thereafter.

Returns current time as the number of seconds elapsed since UNIX epoch.

The value is taken from Nginx core, so no additional system calls get involved. On the other hand, it means that this is only safe to use from an Nginx worker's main thread, i.e. in synchronous Haskell handlers and service hooks. Be also aware that this is a small type casting hack: the value is interpreted as being of type time_t while having been actually wrapped in a bigger C struct as its first element.

Delays current thread for the specified number of seconds.

Time intervals.

Converts a time interval into seconds.

Defines a sleeping strategy.

Single-shot services should be accompanied by Nginx directive haskell_service_var_ignore_empty.

Exports a simple service with specified name and service mode.

The service expects a plain ByteString as its first argument.

Exports a simple service with specified name and service mode.

The service expects a custom type deriving Read as its first argument. For the sake of efficiency, the object of this custom type gets deserialized into a global IORef data storage on the first service run to be further accessed directly from the storage.

Exports a simple service with specified name and service mode.

The service expects a custom type deriving FromJSON as its first argument. For the sake of efficiency, the object of this custom type gets deserialized into a global IORef data storage on the first service run to be further accessed directly from the storage.

This is the "back door" into the IO monad, allowing IO computation to be performed at any time. For this to be safe, the IO computation should be free of side effects and independent of its environment.

If the I/O computation wrapped in unsafePerformIO performs side effects, then the relative order in which those side effects take place (relative to the main I/O trunk, or other calls to unsafePerformIO) is indeterminate. Furthermore, when using unsafePerformIO to cause side-effects, you should take the following precautions to ensure the side effects are performed as many times as you expect them to be. Note that these precautions are necessary for GHC, but may not be sufficient, and other compilers may require different precautions:

• Use {-# NOINLINE foo #-} as a pragma on any function foo that calls unsafePerformIO. If the call is inlined, the I/O may be performed more than once.
• Use the compiler flag -fno-cse to prevent common sub-expression elimination being performed on the module, which might combine two side effects that were meant to be separate. A good example is using multiple global variables (like test in the example below).
• Make sure that the either you switch off let-floating (-fno-full-laziness), or that the call to unsafePerformIO cannot float outside a lambda. For example, if you say: f x = unsafePerformIO (newIORef []) you may get only one reference cell shared between all calls to f. Better would be f x = unsafePerformIO (newIORef [x]) because now it can't float outside the lambda.

It is less well known that unsafePerformIO is not type safe. For example:

    test :: IORef [a]
    test = unsafePerformIO $ newIORef []

    main = do
            writeIORef test [42]
            bang <- readIORef test
            print (bang :: [Char])

This program will core dump. This problem with polymorphic references is well known in the ML community, and does not arise with normal monadic use of references. There is no easy way to make it impossible once you use unsafePerformIO. Indeed, it is possible to write coerce :: a -> b with the help of unsafePerformIO. So be careful!