Add vm.system_counts measurements with atom, port, process limits (#79)

Author: studzien

README.md

@@ -9,7 +9,7 @@ Allows to periodically collect measurements and dispatch them as Telemetry event
 
   * `[vm, memory]` - contains the total memory, process memory, and all other keys in `erlang:memory/0`
   * `[vm, total_run_queue_lengths]` - returns the run queue lengths for CPU and IO schedulers. It contains the `total`, `cpu` and `io` measurements
-  * `[vm, system_counts]` - returns the current process, atom and port count as per `erlang:system_info/1`
+  * `[vm, system_counts]` - returns the current process, atom and port count as well as their respective limits as per `erlang:system_info/1`
   * `[vm, persistent_term]` - number of terms and memory byte size for `persistent_term`
 
 You can directly consume those events after adding `telemetry_poller` as a dependency.

examples/TelemetryPollerVM.ex

@@ -64,7 +64,10 @@ defmodule TelemetryPollerVM do
         "-------------\n" <>
         "  atom_count: #{event_measurements.atom_count}\n" <>
         "  port_count: #{event_measurements.port_count}\n" <>
-        "  process_count: #{event_measurements.process_count}\n"
+        "  process_count: #{event_measurements.process_count}\n" <>
+        "  atom_limit: #{event_measurements.atom_limit}\n" <>
+        "  port_limit: #{event_measurements.port_limit}\n" <>
+        "  process_limit: #{event_measurements.process_limit}\n"
     )
   end
 end

examples/telemetry_poller_vm.erl

@@ -77,18 +77,27 @@ handle([vm, system_counts], EventMeasurements, _EventMetadata, _HandlerConfig) -
     #{
         atom_count := AtomCount,
         port_count := PortCount,
-        process_count := ProcessCount
+        process_count := ProcessCount,
+        atom_limit := AtomLimit,
+        port_limit := PortLimit,
+        process_limit := ProcessLimit
     } = EventMeasurements,
     % Do something with the measurements
     io:format(
         "system_counts~n"
         "-------------~n"
         "  atom_count: ~p~n"
         "  port_count: ~p~n"
-        "  process_count: ~p~n~n",
+        "  process_count: ~p~n"
+        "  atom_limit: ~p~n"
+        "  port_limit: ~p~n"
+        "  process_limit: ~p~n~n",
         [
             AtomCount,
             PortCount,
-            ProcessCount
+            ProcessCount,
+            AtomLimit,
+            PortLimit,
+            ProcessLimit
         ]
     ).

src/telemetry_poller.erl

@@ -83,6 +83,9 @@ The measurement includes:
   * `process_count` - the number of processes currently existing at the local node
   * `atom_count` - the number of atoms currently existing at the local node
   * `port_count` - the number of ports currently existing at the local node
+  * `process_limit` - the maximum number of processes allowed at the local node
+  * `atom_limit` - the maximum number of atoms allowed at the local node
+  * `port_limit` - the maximum number of ports allowed at the local node
 
 ### Persistent term (since 1.2.0)
 

src/telemetry_poller_builtin.erl

@@ -46,10 +46,16 @@ system_counts() ->
     ProcessCount = erlang:system_info(process_count),
     AtomCount = erlang:system_info(atom_count),
     PortCount = erlang:system_info(port_count),
+    ProcessLimit = erlang:system_info(process_limit),
+    AtomLimit = erlang:system_info(atom_limit),
+    PortLimit = erlang:system_info(port_limit),
     telemetry:execute([vm, system_counts], #{
         process_count => ProcessCount,
         atom_count => AtomCount,
-        port_count => PortCount
+        port_count => PortCount,
+        process_limit => ProcessLimit,
+        atom_limit => AtomLimit,
+        port_limit => PortLimit
     }).
 
 -spec persistent_term() -> ok.

test/telemetry_poller_SUITE.erl

@@ -128,7 +128,8 @@ dispatches_system_counts(_Config) ->
   {ok, _Poller} = telemetry_poller:start_link([{measurements, [system_counts]},{period, 100}]),
   HandlerId = attach_to([vm, system_counts]),
   receive
-    {event, [vm, system_counts], #{process_count := _, atom_count := _, port_count := _}, _} ->
+    {event, [vm, system_counts], #{process_count := _, atom_count := _, port_count := _,
+                                   process_limit := _, atom_limit := _, port_limit := _}, _} ->
       telemetry:detach(HandlerId),
       ?assert(true)
   after