Add functions to count object in use and objects in pool (#29)

* Add functions to count object in use and objects in pool

* Define `keytype` and `valtype` for `Pool`

* fixup! Define `keytype` and `valtype` for `Pool`

* fixup! Add functions to count object in use and objects in pool

* Bump version

* Rename in terms of "use"

* Rename `max` -> `limit`

* Docs for keytype/valtype

Project.toml

@@ -1,7 +1,7 @@
 name = "ConcurrentUtilities"
 uuid = "f0e56b4a-5159-44fe-b623-3e5288b988bb"
 authors = ["Jacob Quinn <[email protected]>"]
-version = "2.2.1"
+version = "2.3.0"
 
 [deps]
 Serialization = "9e88b42a-f829-5b0c-bbe9-9e923198166b"

src/pools.jl

@@ -4,53 +4,96 @@ export Pool, acquire, release, drain!
 import Base: acquire, release
 
 """
-    Pool{T}(max::Int=4096)
-    Pool{K, T}(max::Int=4096)
+    Pool{T}(limit::Int=4096)
+    Pool{K, T}(limit::Int=4096)
 
 A threadsafe object for managing a pool of objects of type `T`, optionally keyed by objects
-of type `K`. Objects can be requested by calling `acquire(f, pool, [key])`, where `f` is a
+of type `K`.
+
+Objects can be requested by calling `acquire(f, pool, [key])`, where `f` is a
 function that returns a new object of type `T`.
 The `key` argument is optional and can be used to lookup objects that match a certain criteria
-(a Dict is used internally, so matching is `isequal`).
+(a `Dict` is used internally, so matching is `isequal`).
 
-The `max` argument will limit the number of objects
-that can be acquired at any given time. If the limit has been reached, `acquire` will
-block until an object is returned to the pool via `release`.
+The `limit` argument will limit the number of objects that can be in use at any given time.
+If the limit has been reached, `acquire` will block until an object is released
+via `release`.
 
-By default, `release(pool, obj)` will return the object to the pool for reuse.
-`release(pool)` will return the "permit" to the pool while not returning
-any object for reuse.
+- `release(pool, obj)` will return the object to the pool for reuse.
+- `release(pool)` will decrement the number in use but not return any object for reuse.
+- `drain!` can be used to remove objects that have been returned to the pool for reuse;
+  it does *not* release any objects that are in use.
 
-`drain!` can be used to remove any cached objects for reuse, but it does *not* release
-any active acquires.
+See also `acquire`, `release`, `Pools.limit`, `Pools.in_use`, `Pools.in_pool`, `drain!`.
+The key and object types can be inspected with `keytype` and `valtype` respectively.
 """
 mutable struct Pool{K, T}
     lock::Threads.Condition
-    max::Int
+    limit::Int
     cur::Int
     keyedvalues::Dict{K, Vector{T}}
     values::Vector{T}
 
-    function Pool{K, T}(max::Int=4096) where {K, T}
+    function Pool{K, T}(limit::Int=4096) where {K, T}
         T === Nothing && throw(ArgumentError("Pool type can not be `Nothing`"))
-        x = new(Threads.Condition(), max, 0)
+        x = new(Threads.Condition(), limit, 0)
         if K === Nothing
             x.values = T[]
-            safesizehint!(x.values, max)
+            safesizehint!(x.values, limit)
         else
             x.keyedvalues = Dict{K, Vector{T}}()
         end
         return x
     end
 end
 
-Pool{T}(max::Int=4096) where {T} = Pool{Nothing, T}(max)
+Pool{T}(limit::Int=4096) where {T} = Pool{Nothing, T}(limit)
 
 safesizehint!(x, n) = sizehint!(x, min(4096, n))
 
 # determines whether we'll look up object caches in .keyedvalues or .values
 iskeyed(::Pool{K}) where {K} = K !== Nothing
 
+"""
+    keytype(::Pool)
+
+Return the type of the keys for the pool.
+If the pool is not keyed, this will return `Nothing`.
+"""
+Base.keytype(::Type{<:Pool{K}}) where {K} = K
+Base.keytype(p::Pool) = keytype(typeof(p))
+
+"""
+    valtype(::Pool)
+
+Return the type of the objects that can be stored in the pool.
+"""
+Base.valtype(::Type{<:Pool{<:Any, T}}) where {T} = T
+Base.valtype(p::Pool) = valtype(typeof(p))
+
+"""
+    Pools.limit(pool::Pool) -> Int
+
+Return the maximum number of objects permitted to be in use at the same time.
+See `Pools.in_use(pool)` for the number of objects currently in use.
+"""
+limit(pool::Pool) = Base.@lock pool.lock pool.limit
+
+"""
+    Pools.in_use(pool::Pool) -> Int
+
+Return the number of objects currently in use. Less than or equal to `Pools.limit(pool)`.
+"""
+in_use(pool::Pool) = Base.@lock pool.lock pool.cur
+
+"""
+    Pools.in_pool(pool::Pool) -> Int
+
+Return the number of objects in the pool available for reuse.
+"""
+in_pool(pool::Pool) = Base.@lock pool.lock mapreduce(length, +, values(pool.keyedvalues); init=0)
+in_pool(pool::Pool{Nothing}) = Base.@lock pool.lock length(pool.values)
+
 """
     drain!(pool)
 
@@ -72,7 +115,7 @@ end
 TRUE(x) = true
 
 @noinline keyerror(key, K) = throw(ArgumentError("invalid key `$key` provided for pool key type $K"))
-@noinline releaseerror() = throw(ArgumentError("cannot release permit when pool is empty"))
+@noinline releaseerror() = throw(ArgumentError("cannot release when no objects are in use"))
 
 # NOTE: assumes you have the lock!
 function releasepermit(pool::Pool)
@@ -92,19 +135,19 @@ The `forcenew` keyword argument can be used to force the creation of a new objec
 The `isvalid` keyword argument can be used to specify a function that will be called to determine if an object is still valid
 for reuse. By default, all objects are considered valid.
 If there are no objects available for reuse, `f` will be called to create a new object.
-If the pool is already at its maximum capacity, `acquire` will block until an object is returned to the pool via `release`.
+If the pool is already at its usage limit, `acquire` will block until an object is returned to the pool via `release`.
 """
 function Base.acquire(f, pool::Pool{K, T}, key=nothing; forcenew::Bool=false, isvalid::Function=TRUE) where {K, T}
     key isa K || keyerror(key, K)
     Base.@lock pool.lock begin
         # first get a permit
-        while pool.cur >= pool.max
+        while pool.cur >= pool.limit
             wait(pool.lock)
         end
         pool.cur += 1
         # now see if we can get an object from the pool for reuse
         if !forcenew
-            objs = iskeyed(pool) ? get!(() -> safesizehint!(T[], pool.max), pool.keyedvalues, key) : pool.values
+            objs = iskeyed(pool) ? get!(() -> safesizehint!(T[], pool.limit), pool.keyedvalues, key) : pool.values
             while !isempty(objs)
                 obj = pop!(objs)
                 isvalid(obj) && return obj
@@ -126,10 +169,10 @@ end
     release(pool::Pool{K, T}, obj::T)
     release(pool::Pool{K, T})
 
-Return an object to a `pool`, optionally keyed by the provided `key`.
+Release an object from usage by a `pool`, optionally keyed by the provided `key`.
 If `obj` is provided, it will be returned to the pool for reuse.
 Otherwise, if `nothing` is returned, or `release(pool)` is called,
-just the "permit" will be returned to the pool.
+the usage count will be decremented without an object being returned to the pool for reuse.
 """
 function Base.release(pool::Pool{K, T}, key, obj::Union{T, Nothing}=nothing) where {K, T}
     key isa K || keyerror(key, K)

test/pools.jl

@@ -1,24 +1,49 @@
-using ConcurrentUtilities, Test
+using ConcurrentUtilities.Pools, Test
 
 @testset "Pools" begin
+    pool_size = length∘Pools.values
     @testset "nonkeyed and pool basics" begin
         pool = Pool{Int}(3)
+        @test keytype(pool) === Nothing
+        @test valtype(pool) === Int
+
+        @test Pools.limit(pool) == 3
+        @test Pools.in_use(pool) == 0
+        @test Pools.in_pool(pool) == 0
+
         # acquire an object from the pool
         x1 = acquire(() -> 1, pool)
         # no existing objects in the pool, so our function was called to create a new one
         @test x1 == 1
+        @test Pools.limit(pool) == 3
+        @test Pools.in_use(pool) == 1
+        @test Pools.in_pool(pool) == 0
+
         # release back to the pool for reuse
         release(pool, x1)
+        @test Pools.in_use(pool) == 0
+        @test Pools.in_pool(pool) == 1
+
         # acquire another object from the pool
         x1 = acquire(() -> 2, pool)
         # this time, the pool had an existing object, so our function was not called
         @test x1 == 1
+        @test Pools.in_use(pool) == 1
+        @test Pools.in_pool(pool) == 0
+
         # but now there are no objects to reuse again, so the next acquire will call our function
         x2 = acquire(() -> 2, pool)
         @test x2 == 2
+        @test Pools.in_use(pool) == 2
+        @test Pools.in_pool(pool) == 0
+
         x3 = acquire(() -> 3, pool)
         @test x3 == 3
-        # the pool is now at capacity, so the next acquire will block until an object is released
+        @test Pools.in_use(pool) == 3
+        @test Pools.in_pool(pool) == 0
+
+        # the pool is now at `Pools.limit`, so the next acquire will block until an object is released
+        @test Pools.in_use(pool) == Pools.limit(pool)
         tsk = @async acquire(() -> 4, pool; forcenew=true)
         yield()
         @test !istaskdone(tsk)
@@ -28,60 +53,110 @@ using ConcurrentUtilities, Test
         x1 = fetch(tsk)
         # even though we released 1 for reuse, we passed forcenew, so our function was called to create new
         @test x1 == 4
+        @test Pools.in_use(pool) == 3
+        @test Pools.in_pool(pool) == 1
+
         # error to try and provide a key to a non-keyed pool
         @test_throws ArgumentError acquire(() -> 1, pool, 1)
+
         # release objects back to the pool
         release(pool, x1)
         release(pool, x2)
         release(pool, x3)
+        @test Pools.in_use(pool) == 0
+        @test Pools.in_pool(pool) == 4
+
         # acquire an object, but checking isvalid
         x1 = acquire(() -> 5, pool; isvalid=x -> x == 1)
         @test x1 == 1
+        @test Pools.in_use(pool) == 1
+
         # no valid objects, so our function was called to create a new one
         x2 = acquire(() -> 6, pool; isvalid=x -> x == 1)
         @test x2 == 6
-        # we have one slot left in the pool, we now throw while creating new
+        @test Pools.in_use(pool) == 2
+
+        # we have one permit left, we now throw while creating a new object
         # and we want to test that the permit isn't permanently lost for the pool
         @test_throws ErrorException acquire(() -> error("oops"), pool; forcenew=true)
+        @test Pools.in_use(pool) == 2
+
         # we can still acquire a new object
         x3 = acquire(() -> 7, pool; forcenew=true)
         @test x3 == 7
+        @test Pools.in_use(pool) == 3
+
         # release objects back to the pool
+        drain!(pool)
         release(pool, x1)
         release(pool, x2)
         release(pool, x3)
+        @test Pools.in_use(pool) == 0
+        @test Pools.in_pool(pool) == 3
+
         # try to do an invalid release
         @test_throws ArgumentError release(pool, 10)
+
         # test that the invalid release didn't push the object to our pool for reuse
         x1 = acquire(() -> 8, pool)
         @test x1 == 7
+        @test Pools.in_use(pool) == 1
+        @test Pools.in_pool(pool) == 2
         # calling drain! removes all objects for reuse
         drain!(pool)
+        @test Pools.in_use(pool) == 1
+        @test Pools.in_pool(pool) == 0
+
         x2 = acquire(() -> 9, pool)
         @test x2 == 9
+        @test Pools.in_use(pool) == 2
+        @test Pools.in_pool(pool) == 0
     end
 
     @testset "keyed pool" begin
         # now test a keyed pool
         pool = Pool{String, Int}(3)
+        @test keytype(pool) === String
+        @test valtype(pool) === Int
+
+        @test Pools.limit(pool) == 3
+        @test Pools.in_use(pool) == 0
+        @test Pools.in_pool(pool) == 0
+
         # acquire an object from the pool
         x1 = acquire(() -> 1, pool, "a")
         # no existing objects in the pool, so our function was called to create a new one
         @test x1 == 1
+        @test Pools.in_use(pool) == 1
+        @test Pools.in_pool(pool) == 0
+
         # release back to the pool for reuse
         release(pool, "a", x1)
+        @test Pools.in_use(pool) == 0
+        @test Pools.in_pool(pool) == 1
+
         # test for a different key
         x2 = acquire(() -> 2, pool, "b")
         # there's an existing object, but for a different key, so we don't reuse
         @test x2 == 2
+        @test Pools.in_use(pool) == 1
+        @test Pools.in_pool(pool) == 1
+
         # acquire another object from the pool
         x1 = acquire(() -> 2, pool, "a")
         # this time, the pool had an existing object, so our function was not called
         @test x1 == 1
+        @test Pools.in_use(pool) == 2
+        @test Pools.in_pool(pool) == 0
+
         x3 = acquire(() -> 3, pool, "a")
         @test x3 == 3
+        @test Pools.in_use(pool) == 3
+        @test Pools.in_pool(pool) == 0
+
         # the pool is now at capacity, so the next acquire will block until an object is released
         # even though we've acquired using different keys, the capacity is shared across the pool
+        @test Pools.in_use(pool) == Pools.limit(pool)
         tsk = @async acquire(() -> 4, pool, "c"; forcenew=true)
         yield()
         @test !istaskdone(tsk)
@@ -91,13 +166,27 @@ using ConcurrentUtilities, Test
         x1 = fetch(tsk)
         # even though we released 1 for reuse, we passed forcenew, so our function was called to create new
         @test x1 == 4
+        @test Pools.in_use(pool) == 3
+        @test Pools.in_pool(pool) == 1
+
         # error to try and provide an invalid key to a keyed pool
         @test_throws ArgumentError acquire(() -> 1, pool, 1)
-        # error to release an invalid key back to the pool
-        @test_throws KeyError release(pool, "z", 1)
+        @test Pools.in_use(pool) == 3
+        @test Pools.in_pool(pool) == 1
+
         # error to *not* provide a key to a keyed pool
         @test_throws ArgumentError acquire(() -> 1, pool)
+        @test Pools.in_use(pool) == 3
+        @test Pools.in_pool(pool) == 1
+
         # error to *not* provide a key when releasing to a keyed pool
         @test_throws ArgumentError release(pool)
+        @test Pools.in_use(pool) == 3
+        @test Pools.in_pool(pool) == 1
+
+        # error to release an invalid key back to the pool
+        @test_throws KeyError release(pool, "z", 1)
+        @test_broken Pools.in_use(pool) == 3
+        @test Pools.in_pool(pool) == 1
     end
 end