NFC: Move label names from Metric to Sample

This patch moves the label names from the Metric struct to the Sample
struct in preparation for the Histogram collector where only some of the
samples have labels.

src/Prometheus.jl

@@ -202,7 +202,7 @@ function collect!(metrics::Vector, counter::Counter)
     push!(metrics,
         Metric(
             "counter", counter.metric_name, counter.help,
-            nothing, Sample(nothing, nothing, @atomic(counter.value)),
+            Sample(nothing, nothing, nothing, @atomic(counter.value)),
         ),
     )
     return metrics
@@ -310,7 +310,7 @@ function collect!(metrics::Vector, gauge::Gauge)
     push!(metrics,
         Metric(
             "gauge", gauge.metric_name, gauge.help,
-            nothing, Sample(nothing, nothing, @atomic(gauge.value)),
+            Sample(nothing, nothing, nothing, @atomic(gauge.value)),
         ),
     )
     return metrics
@@ -381,10 +381,10 @@ end
 function collect!(metrics::Vector, summary::Summary)
     push!(metrics,
         Metric(
-            "summary", summary.metric_name, summary.help, nothing,
+            "summary", summary.metric_name, summary.help,
             [
-                Sample("_count", nothing, @atomic(summary._count)),
-                Sample("_sum", nothing, @atomic(summary._sum)),
+                Sample("_count", nothing, nothing, @atomic(summary._count)),
+                Sample("_sum", nothing, nothing, @atomic(summary._sum)),
             ]
         ),
     )
@@ -748,8 +748,9 @@ function collect!(metrics::Vector, family::Family{C}) where C
     type = prometheus_type(C)
     samples = Sample[]
     buf = Metric[]
+    label_names = family.label_names
     @lock family.lock begin
-        for (labels, child) in family.children
+        for (label_values, child) in family.children
             # collect!(...) the child, throw away the metric, but keep the samples
             child_metrics = collect!(resize!(buf, 0), child)
             length(child_metrics) != 1 && unreachable() # TODO: maybe this should be supported?
@@ -758,12 +759,12 @@ function collect!(metrics::Vector, family::Family{C}) where C
             # Unwrap and rewrap samples with the labels
             child_samples = child_metric.samples
             if child_samples isa Sample
-                push!(samples, Sample(child_samples.suffix, labels, child_samples.value))
+                push!(samples, Sample(child_samples.suffix, label_names, label_values, child_samples.value))
             else
                 @assert(child_samples isa Vector{Sample})
                 for child_sample in child_samples
                     @assert(child_sample.label_values === nothing)
-                    push!(samples, Sample(child_sample.suffix, labels, child_sample.value))
+                    push!(samples, Sample(child_sample.suffix, label_names, label_values, child_sample.value))
                 end
             end
         end
@@ -776,7 +777,7 @@ function collect!(metrics::Vector, family::Family{C}) where C
     end)
     push!(
         metrics,
-        Metric(type, family.metric_name, family.help, family.label_names, samples),
+        Metric(type, family.metric_name, family.help, samples),
     )
     return metrics
 end
@@ -788,6 +789,7 @@ end
 
 struct Sample
     suffix::Union{String, Nothing} # e.g. _count or _sum
+    label_names::Union{LabelNames, Nothing}
     label_values::Union{LabelValues, Nothing}
     value::Float64
 end
@@ -796,7 +798,6 @@ struct Metric
     type::String
     metric_name::String
     help::String
-    label_names::Union{LabelNames, Nothing}
     # TODO: Union{Tuple{Sample}, Vector{Sample}} would always make this iterable.
     samples::Union{Sample, Vector{Sample}}
 end
@@ -817,11 +818,10 @@ function expose_metric(io::IO, metric::Metric)
     print_escaped(io, metric.help, ('\\', '\n'))
     println(io)
     println(io, "# TYPE ", metric.metric_name, " ", metric.type)
-    label_names = metric.label_names
     samples = metric.samples
     if samples isa Sample
         # Single sample, no labels
-        @assert(label_names === nothing)
+        @assert(samples.label_names === nothing)
         @assert(samples.label_values === nothing)
         @assert(samples.suffix === nothing)
         val = samples.value
@@ -837,11 +837,13 @@ function expose_metric(io::IO, metric::Metric)
                 print(io, sample.suffix)
             end
             # Print potential labels
-            labels = sample.label_values
-            if label_names !== nothing && labels !== nothing
+            label_names = sample.label_names
+            label_values = sample.label_values
+            @assert((label_names === nothing) === (label_values === nothing))
+            if label_names !== nothing && label_values !== nothing
                 first = true
                 print(io, "{")
-                for (name, value) in zip(label_names.label_names, labels.label_values)
+                for (name, value) in zip(label_names.label_names, label_values.label_values)
                     first || print(io, ",")
                     print(io, name, "=\"")
                     print_escaped(io, value, ('\\', '\"', '\n'))

src/gc_collector.jl

@@ -44,40 +44,42 @@ function collect!(metrics::Vector, ::GCCollector)
     gc_live_bytes = Base.gc_live_bytes()
     # Push all the metrics
     push!(metrics,
-        Metric(
-            "counter", "julia_gc_alloc_total", "Total number of allocations (calls to malloc, realloc, etc)",
-            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),
-            ],
-        ),
+        let label_names = LabelNames(("type",))
+            Metric(
+                "counter", "julia_gc_alloc_total", "Total number of allocations (calls to malloc, realloc, etc)",
+                [
+                    Sample(nothing, label_names, LabelValues(("bigalloc",)), gc_num.bigalloc),
+                    Sample(nothing, label_names, LabelValues(("malloc",)), gc_num.malloc),
+                    Sample(nothing, label_names, LabelValues(("poolalloc",)), gc_num.poolalloc),
+                    Sample(nothing, label_names, LabelValues(("realloc",)), gc_num.realloc),
+                ],
+            )
+        end,
         Metric(
             "counter", "julia_gc_free_total", "Total number of calls to free()",
-            nothing, Sample(nothing, nothing, gc_num.freecall),
-        ),
-        Metric(
-            "counter", "julia_gc_alloc_bytes_total", "Total number of allocated bytes", nothing,
-            Sample(nothing, nothing, Base.gc_total_bytes(gc_num)),
+            Sample(nothing, nothing, nothing, gc_num.freecall),
         ),
         Metric(
-            "gauge", "julia_gc_live_bytes", "Current number of live bytes", nothing,
-            Sample(nothing, nothing, gc_live_bytes),
+            "counter", "julia_gc_alloc_bytes_total", "Total number of allocated bytes",
+            Sample(nothing, nothing, nothing, Base.gc_total_bytes(gc_num)),
         ),
         Metric(
-            "counter", "julia_gc_seconds_total", "Total time spent in garbage collection", nothing,
-            Sample(nothing, nothing, gc_num.total_time / 10^9), # [ns] to [s]
+            "gauge", "julia_gc_live_bytes", "Current number of live bytes",
+            Sample(nothing, nothing, nothing, gc_live_bytes),
         ),
         Metric(
-            "counter", "julia_gc_collections_total", "Total number of calls to garbage collection",
-            LabelNames(("type",)),
-            [
-                Sample(nothing, LabelValues(("full",)), gc_num.full_sweep),
-                Sample(nothing, LabelValues(("minor",)), gc_num.pause - gc_num.full_sweep),
-            ],
+            "counter", "julia_gc_seconds_total", "Total time spent in garbage collection",
+            Sample(nothing, nothing, nothing, gc_num.total_time / 10^9), # [ns] to [s]
         ),
+        let label_names = LabelNames(("type",))
+            Metric(
+                "counter", "julia_gc_collections_total", "Total number of calls to garbage collection",
+                [
+                    Sample(nothing, label_names, LabelValues(("full",)), gc_num.full_sweep),
+                    Sample(nothing, label_names, LabelValues(("minor",)), gc_num.pause - gc_num.full_sweep),
+                ],
+            )
+        end,
     )
     return metrics
 end

src/process_collector.jl

@@ -118,13 +118,13 @@ function collect!(metrics::Vector, procc::ProcessCollector)
         if procc.clock_ticks_per_second > 0
             utime = parse(Int, fields[14 - 2]) / procc.clock_ticks_per_second
             stime = parse(Int, fields[15 - 2]) / procc.clock_ticks_per_second
+            label_names = LabelNames(("mode",))
             proc_cpu_seconds = Metric(
                 "counter", "process_cpu_seconds_total",
                 "Total CPU time (user and system mode) in seconds.",
-                LabelNames(("mode",)),
                 [
-                    Sample(nothing, LabelValues(("system",)), stime),
-                    Sample(nothing, LabelValues(("user",)), utime),
+                    Sample(nothing, label_names, LabelValues(("system",)), stime),
+                    Sample(nothing, label_names, LabelValues(("user",)), utime),
                 ],
             )
             push!(metrics, proc_cpu_seconds)
@@ -132,16 +132,16 @@ function collect!(metrics::Vector, procc::ProcessCollector)
             starttime = parse(Int, fields[22 - 2]) / procc.clock_ticks_per_second
             proc_start_time = Metric(
                 "gauge", "process_start_time_seconds",
-                "Start time since unix epoch in seconds.", nothing,
-                Sample(nothing, nothing, starttime + procc.system_boot_time),
+                "Start time since unix epoch in seconds.",
+                Sample(nothing, nothing, nothing, starttime + procc.system_boot_time),
             )
             push!(metrics, proc_start_time)
         end
         # Virtual memory
         vsize = parse(Int, fields[23 - 2])
         proc_virtual_memory = Metric(
-            "gauge", "process_virtual_memory_bytes", "Virtual memory size in bytes.", nothing,
-            Sample(nothing, nothing, vsize),
+            "gauge", "process_virtual_memory_bytes", "Virtual memory size in bytes.",
+            Sample(nothing, nothing, nothing, vsize),
         )
         push!(metrics, proc_virtual_memory)
         if procc.pagesize > 0
@@ -149,8 +149,8 @@ function collect!(metrics::Vector, procc::ProcessCollector)
             rss = parse(Int, fields[24 - 2])
             proc_resident_memory = Metric(
                 "gauge", "process_resident_memory_bytes",
-                "Resident memory size (RSS) in bytes.", nothing,
-                Sample(nothing, nothing, rss * procc.pagesize),
+                "Resident memory size (RSS) in bytes.",
+                Sample(nothing, nothing, nothing, rss * procc.pagesize),
             )
             push!(metrics, proc_resident_memory)
         end
@@ -166,8 +166,8 @@ function collect!(metrics::Vector, procc::ProcessCollector)
         # Open file descriptors
         proc_open_fds = Metric(
             "gauge", "process_open_fds",
-            "Number of open file descriptors.", nothing,
-            Sample(nothing, nothing, proc_fd),
+            "Number of open file descriptors.",
+            Sample(nothing, nothing, nothing, proc_fd),
         )
         push!(metrics, proc_open_fds)
         # TODO: Maybe add maximum open fds from /proc/$(pid)/limits like the Python client
@@ -184,8 +184,8 @@ function collect!(metrics::Vector, procc::ProcessCollector)
         if rchar !== nothing
             proc_io_rchar = Metric(
                 "counter", "process_io_rchar_bytes_total",
-                "Total number of bytes read in bytes (rchar from /proc/[pid]/io).", nothing,
-                Sample(nothing, nothing, parse(Int, rchar.captures[1]::AbstractString)),
+                "Total number of bytes read in bytes (rchar from /proc/[pid]/io).",
+                Sample(nothing, nothing, nothing, parse(Int, rchar.captures[1]::AbstractString)),
             )
             push!(metrics, proc_io_rchar)
         end
@@ -193,8 +193,8 @@ function collect!(metrics::Vector, procc::ProcessCollector)
         if wchar !== nothing
             proc_io_wchar = Metric(
                 "counter", "process_io_wchar_bytes_total",
-                "Total number of bytes written in bytes (wchar from /proc/[pid]/io).", nothing,
-                Sample(nothing, nothing, parse(Int, wchar.captures[1]::AbstractString)),
+                "Total number of bytes written in bytes (wchar from /proc/[pid]/io).",
+                Sample(nothing, nothing, nothing, parse(Int, wchar.captures[1]::AbstractString)),
             )
             push!(metrics, proc_io_wchar)
         end
@@ -202,8 +202,8 @@ function collect!(metrics::Vector, procc::ProcessCollector)
         if syscr !== nothing
             proc_io_syscr = Metric(
                 "counter", "process_io_syscr_total",
-                "Total number of read I/O operations (syscalls) (syscr from /proc/[pid]/io).", nothing,
-                Sample(nothing, nothing, parse(Int, syscr.captures[1]::AbstractString)),
+                "Total number of read I/O operations (syscalls) (syscr from /proc/[pid]/io).",
+                Sample(nothing, nothing, nothing, parse(Int, syscr.captures[1]::AbstractString)),
             )
             push!(metrics, proc_io_syscr)
         end
@@ -211,8 +211,8 @@ function collect!(metrics::Vector, procc::ProcessCollector)
         if syscw !== nothing
             proc_io_syscw = Metric(
                 "counter", "process_io_syscw_total",
-                "Total number of write I/O operations (syscalls) (syscw from /proc/[pid]/io).", nothing,
-                Sample(nothing, nothing, parse(Int, syscw.captures[1]::AbstractString)),
+                "Total number of write I/O operations (syscalls) (syscw from /proc/[pid]/io).",
+                Sample(nothing, nothing, nothing, parse(Int, syscw.captures[1]::AbstractString)),
             )
             push!(metrics, proc_io_syscw)
         end
@@ -220,8 +220,8 @@ function collect!(metrics::Vector, procc::ProcessCollector)
         if read_bytes !== nothing
             proc_io_read_bytes = Metric(
                 "counter", "process_io_read_bytes_total",
-                "Total number of bytes read from the file system (read_bytes from /proc/[pid]/io).", nothing,
-                Sample(nothing, nothing, parse(Int, read_bytes.captures[1]::AbstractString)),
+                "Total number of bytes read from the file system (read_bytes from /proc/[pid]/io).",
+                Sample(nothing, nothing, nothing, parse(Int, read_bytes.captures[1]::AbstractString)),
             )
             push!(metrics, proc_io_read_bytes)
         end
@@ -229,8 +229,8 @@ function collect!(metrics::Vector, procc::ProcessCollector)
         if write_bytes !== nothing
             proc_io_write_bytes = Metric(
                 "counter", "process_io_write_bytes_total",
-                "Total number of bytes written to the file system (write_bytes from /proc/[pid]/io).", nothing,
-                Sample(nothing, nothing, parse(Int, write_bytes.captures[1]::AbstractString)),
+                "Total number of bytes written to the file system (write_bytes from /proc/[pid]/io).",
+                Sample(nothing, nothing, nothing, parse(Int, write_bytes.captures[1]::AbstractString)),
             )
             push!(metrics, proc_io_write_bytes)
         end