The default metric source, used when a specific metric source is not specified.

This may itself be nil, in which case default no-op behavior will occur.

Increments a counter metric by a numeric amount (which should be positive).

Returns nil.

Finds or creates a counter metric with the given metric name.

Returns a function used to increment the counter. Invoked with no arguments, increments the counter by 1, or with a single numeric argument, increments the counter by that amount.

Creates a gauge that obtains its metric values from value-fn, which must return a number. Does nothing if a gauge with that name already exists.

Returns nil.

Creates a histogram (sometimes called a distribution summary), which tracks the number of events and a dimension for each event; internally, distributes different events to various bucket ranges, yielding a histogram of sizes of the event; a comment example is to use a histogram to track the size of incoming requests or outgoing responses.

Returns a function that records the dimension of an event.

Increments a counter metric by 1.

Returns nil.

Obtains and starts a timer, then executes the body adding a (try … finally) block to stop the timer, using the *default-metric-source*.

Variant of timed when using a specific metric source.

Creates a timer and return the timer’s trigger function. Invoking the trigger starts tracking execution duration, and returns another function that stops the timer and records the elapsed duration.

The stop timer function is idempotent; only the first call records a duration.

Internally, timers measure elapsed nanosecond time.