Family{C}: use n-tuples for label names and values.

docs/src/index.md

@@ -167,8 +167,8 @@ See <https://prometheus.io/docs/concepts/data_model/#metric-names-and-labels> fo
 
 ```@docs
 Prometheus.Family{C}(::String, ::String, ::Any; kwargs...) where C
-Prometheus.labels(::Prometheus.Family, ::Vector{String})
-Prometheus.remove(::Prometheus.Family, ::Vector{String})
+Prometheus.labels(::Prometheus.Family{C, N}, ::NTuple{N, String}) where {C, N}
+Prometheus.remove(::Prometheus.Family{C, N}, ::NTuple{N, String}) where {C, N}
 Prometheus.clear(::Prometheus.Family)
 ```
 

src/Prometheus.jl

@@ -355,12 +355,12 @@ end
 # Family{<:Collector} <: Collector #
 ####################################
 
-struct LabelNames
-    labelnames::Vector{String}
+struct LabelNames{N}
+    labelnames::NTuple{N, String}
 end
 
-struct LabelValues
-    labelvalues::Vector{String}
+struct LabelValues{N}
+    labelvalues::NTuple{N, String}
 end
 function Base.hash(l::LabelValues, h::UInt)
     h = hash(0x94a2d04ee9e5a55b, h) # hash("Prometheus.LabelValues") on Julia 1.9.3
@@ -373,20 +373,20 @@ function Base.:(==)(l1::LabelValues, l2::LabelValues)
     return l1.labelvalues == l2.labelvalues
 end
 
-struct Family{C} <: Collector
+struct Family{C, N} <: Collector
     metric_name::String
     help::String
-    labelnames::LabelNames
-    children::Dict{LabelValues, C}
+    labelnames::LabelNames{N}
+    children::Dict{LabelValues{N}, C}
     lock::ReentrantLock
 
     function Family{C}(
-            metric_name::String, help::String, labelnames::Vector{String};
+            metric_name::String, help::String, labelnames::NTuple{N, String};
             registry::Union{CollectorRegistry, Nothing}=DEFAULT_REGISTRY,
-        ) where C
-        children = Dict{LabelValues, C}()
+        ) where {C, N}
+        children = Dict{LabelValues{N}, C}()
         lock = ReentrantLock()
-        family = new(metric_name, help, LabelNames(labelnames), children, lock)
+        family = new{C, N}(metric_name, help, LabelNames(labelnames), children, lock)
         if registry !== nothing
             register(registry, family)
         end
@@ -403,7 +403,7 @@ label values encountered a new collector of type `C <: Collector` will be create
 **Arguments**
  - `name :: String`: the name of the family metric.
  - `help :: String`: the documentation for the family metric.
- - `labelnames :: Vector{String}`: the label names.
+ - `labelnames :: Tuple{String, ...}`: the label names.
 
 **Keyword arguments**
  - `registry :: Prometheus.CollectorRegistry`: the registry in which to register the
@@ -433,7 +433,7 @@ function metric_names(family::Family)
 end
 
 """
-    Prometheus.labels(family::Family{C}, labelvalues::Vector{String}) where C
+    Prometheus.labels(family::Family{C}, labelvalues::Tuple{String, ...}) where C
 
 Return the collector of type `C` from the family corresponding to the labels given by
 `labelvalues`.
@@ -444,7 +444,7 @@ Return the collector of type `C` from the family corresponding to the labels giv
     matter (below 100ns for some basic benchmarks) but it is safe to cache the returned
     collector if required.
 """
-function labels(family::Family{C}, labelvalues::Vector{String}) where C
+function labels(family::Family{C, N}, labelvalues::NTuple{N, String}) where {C, N}
     collector = @lock family.lock get!(family.children, LabelValues(labelvalues)) do
         C(family.metric_name, family.help; registry=nothing)
     end
@@ -452,7 +452,7 @@ function labels(family::Family{C}, labelvalues::Vector{String}) where C
 end
 
 """
-    Prometheus.remove(family::Family, labelvalues::Vector{String})
+    Prometheus.remove(family::Family, labelvalues::Tuple{String, ...})
 
 Remove the collector corresponding to `labelvalues`. Effectively this resets the collector
 since [`Prometheus.labels`](@ref) will recreate the collector when called with the same
@@ -461,7 +461,7 @@ label names.
 !!! note
     This method invalidates cached collectors for the label names.
 """
-function remove(family::Family, labelvalues::Vector{String})
+function remove(family::Family{<:Any, N}, labelvalues::NTuple{N, String}) where N
     @lock family.lock delete!(family.children, LabelValues(labelvalues))
     return
 end

src/gc_collector.jl

@@ -46,12 +46,12 @@ function collect!(metrics::Vector, ::GCCollector)
     push!(metrics,
         Metric(
             "counter", "julia_gc_alloc_total", "Total number of allocations (calls to malloc, realloc, etc)",
-            LabelNames(["type"]),
+            LabelNames(("type",)),
             [
-                Sample(nothing, LabelValues(["bigalloc"]), gc_num.bigalloc),
-                Sample(nothing, LabelValues(["malloc"]), gc_num.malloc),
-                Sample(nothing, LabelValues(["poolalloc"]), gc_num.poolalloc),
-                Sample(nothing, LabelValues(["realloc"]), gc_num.realloc),
+                Sample(nothing, LabelValues(("bigalloc",)), gc_num.bigalloc),
+                Sample(nothing, LabelValues(("malloc",)), gc_num.malloc),
+                Sample(nothing, LabelValues(("poolalloc",)), gc_num.poolalloc),
+                Sample(nothing, LabelValues(("realloc",)), gc_num.realloc),
             ],
         ),
         Metric(
@@ -72,10 +72,10 @@ function collect!(metrics::Vector, ::GCCollector)
         ),
         Metric(
             "counter", "julia_gc_collections_total", "Total number of calls to garbage collection",
-            LabelNames(["type"]),
+            LabelNames(("type",)),
             [
-                Sample(nothing, LabelValues(["full"]), gc_num.full_sweep),
-                Sample(nothing, LabelValues(["minor"]), gc_num.pause - gc_num.full_sweep),
+                Sample(nothing, LabelValues(("full",)), gc_num.full_sweep),
+                Sample(nothing, LabelValues(("minor",)), gc_num.pause - gc_num.full_sweep),
             ],
         ),
     )

src/process_collector.jl

@@ -121,10 +121,10 @@ function collect!(metrics::Vector, procc::ProcessCollector)
             proc_cpu_seconds = Metric(
                 "counter", "process_cpu_seconds_total",
                 "Total CPU time (user and system mode) in seconds.",
-                LabelNames(["mode"]),
+                LabelNames(("mode",)),
                 [
-                    Sample(nothing, LabelValues(["system"]), stime),
-                    Sample(nothing, LabelValues(["user"]), utime),
+                    Sample(nothing, LabelValues(("system",)), stime),
+                    Sample(nothing, LabelValues(("user",)), utime),
                 ],
             )
             push!(metrics, proc_cpu_seconds)

test/runtests.jl

@@ -151,9 +151,9 @@ end
 
 @testset "Prometheus.LabelNames and Prometheus.LabelValues" begin
     # Custom hashing
-    v1 = Prometheus.LabelValues(["foo", "bar"])
-    v2 = Prometheus.LabelValues(["foo", "bar"])
-    v3 = Prometheus.LabelValues(["foo", "baz"])
+    v1 = Prometheus.LabelValues(("foo", "bar"))
+    v2 = Prometheus.LabelValues(("foo", "bar"))
+    v3 = Prometheus.LabelValues(("foo", "baz"))
     @test hash(v1) == hash(v2)
     @test hash(v1) != hash(v3)
     @test v1 == v2
@@ -167,20 +167,20 @@ end
     empty!(Prometheus.DEFAULT_REGISTRY.collectors)
     c = Prometheus.Family{Collector}(
         "http_requests", "Number of HTTP requests.",
-        ["endpoint", "status_code"],
+        ("endpoint", "status_code"),
     )
     @test c in Prometheus.DEFAULT_REGISTRY.collectors
     r = Prometheus.CollectorRegistry()
     c = Prometheus.Family{Collector}(
         "http_requests", "Number of HTTP requests.",
-        ["endpoint", "status_code"];
+        ("endpoint", "status_code");
         registry = r,
     )
     @test c in r.collectors
     @test length(c.children) == 0
     # Prometheus.labels(...), Prometheus.remove(...), Prometheus.clear()
-    l1 = ["/foo/", "200"]
-    l2 = ["/bar/", "404"]
+    l1 = ("/foo/", "200")
+    l2 = ("/bar/", "404")
     @test Prometheus.labels(c, l1) === Prometheus.labels(c, l1)
     @test Prometheus.labels(c, l2) === Prometheus.labels(c, l2)
     @test length(c.children) == 2
@@ -207,8 +207,8 @@ end
     @test metric.help == c.help
     @test length(metric.samples) == 2
     s1, s2 = metric.samples[1], metric.samples[2]
-    @test s1.labels.labelvalues == ["/bar/", "404"]
-    @test s2.labels.labelvalues == ["/foo/", "200"]
+    @test s1.labels.labelvalues == ("/bar/", "404")
+    @test s2.labels.labelvalues == ("/foo/", "200")
     @test s1.value == 3
     @test s2.value == 3
     # Prometheus.expose_metric(...)
@@ -227,14 +227,14 @@ end
     r = Prometheus.CollectorRegistry()
     c = Prometheus.Family{Prometheus.Summary}(
         "http_request_time", "Time to process requests.",
-        ["endpoint", "status_code"];
+        ("endpoint", "status_code");
         registry = r,
     )
     @test c in r.collectors
     @test length(c.children) == 0
     # Prometheus.inc(...)
-    l1 = ["/foo/", "200"]
-    l2 = ["/bar/", "404"]
+    l1 = ("/foo/", "200")
+    l2 = ("/bar/", "404")
     @test Prometheus.labels(c, l1) === Prometheus.labels(c, l1)
     @test Prometheus.labels(c, l2) === Prometheus.labels(c, l2)
     @test length(c.children) == 2
@@ -262,8 +262,8 @@ end
     @test metric.help == c.help
     @test length(metric.samples) == 4
     s1, s2, s3, s4 = metric.samples
-    @test s1.labels.labelvalues == s2.labels.labelvalues == ["/bar/", "404"]
-    @test s3.labels.labelvalues == s4.labels.labelvalues == ["/foo/", "200"]
+    @test s1.labels.labelvalues == s2.labels.labelvalues == ("/bar/", "404")
+    @test s3.labels.labelvalues == s4.labels.labelvalues == ("/foo/", "200")
     @test s1.value == 2   # _count
     @test s2.value == 6.4 # _sum
     @test s3.value == 2   # _count