Copyright	(C) 2026 Edward Kmett
License	UPL-1.0 AND BSD-3-Clause
Maintainer	Edward Kmett <ekmett@gmail.com>
Stability	experimental
Portability	GHC FFI; THC runtime services or native fallback implementation
Safe Haskell	Trustworthy
Language	Haskell2010

THC.GC

Description

JVM-wide collector statistics. These queries neither force a collection nor enable monitoring. Values are independently sampled and cumulative.

Synopsis

data Available a
- = Available a
- | Unsupported
- | Disabled
- | Denied
- | Unavailable
data CollectorStats = CollectorStats {
- collectorName :: Available String
- collectionCount :: Available Word64
- collectionMilliseconds :: Available Word64
}
collectors :: IO (Available [CollectorStats])

Documentation

data Available a Source #

An absent metric is not zero. Queries never enable JVM-wide monitoring. fmap transforms a genuine value and preserves every non-value status:

>>> fmap (+ 1) (Available (41 :: Int))
Available 42
>>> fmap (+ 1) (Disabled :: Available Int)
Disabled
>>> map (fmap (+ 1)) [Unsupported, Disabled, Denied, Unavailable :: Available Int]
[Unsupported,Disabled,Denied,Unavailable]

Constructors

Available a	A genuine value; its scope is specified by the query.
Unsupported	The runtime or provider does not implement this service.
Disabled	Supported, but its instrumentation or sink is switched off.
Denied	The current context or host security policy forbids access.
Unavailable	Normally supported, but no value is currently available.

Instances

Instances details

Functor Available #
Instance details Defined in THC.Runtime.Types Methods fmap :: (a -> b) -> Available a -> Available b # (<$) :: a -> Available b -> Available a #
Eq a => Eq (Available a) #
Instance details Defined in THC.Runtime.Types Methods (==) :: Available a -> Available a -> Bool # (/=) :: Available a -> Available a -> Bool #
Ord a => Ord (Available a) #
Instance details Defined in THC.Runtime.Types Methods compare :: Available a -> Available a -> Ordering # (<) :: Available a -> Available a -> Bool # (<=) :: Available a -> Available a -> Bool # (>) :: Available a -> Available a -> Bool # (>=) :: Available a -> Available a -> Bool # max :: Available a -> Available a -> Available a # min :: Available a -> Available a -> Available a #
Show a => Show (Available a) #
Instance details Defined in THC.Runtime.Types Methods showsPrec :: Int -> Available a -> ShowS # show :: Available a -> String # showList :: [Available a] -> ShowS #

data CollectorStats Source #

One JVM collector's name and cumulative counters, each independently available. A collector can disappear or decline to expose a counter.

Constructors

CollectorStats
Fields collectorName :: Available String collectionCount :: Available Word64 collectionMilliseconds :: Available Word64 Approximate elapsed collection time, not pause time or CPU time.

Instances

Instances details

Eq CollectorStats #
Instance details Defined in THC.GC Methods (==) :: CollectorStats -> CollectorStats -> Bool # (/=) :: CollectorStats -> CollectorStats -> Bool #
Show CollectorStats #
Instance details Defined in THC.GC Methods showsPrec :: Int -> CollectorStats -> ShowS # show :: CollectorStats -> String # showList :: [CollectorStats] -> ShowS #

collectors :: IO (Available [CollectorStats]) Source #

Enumerate collectors. Individual optional/invalidated counters retain their own status. An empty available list is different from no JVM support.