Add ProcessMonitor#emit(metrics).

Author: samuel-williams-shopify

lib/async/service/supervisor/process_monitor.rb

@@ -67,15 +67,20 @@ def as_json
 					{ppid: @ppid, metrics: self.metrics}
 				end
 
-				# Run one iteration of the process monitor.
-				def run_once
-					metrics = self.metrics
-					
+				# Emit the process metrics.
+				#
+				# @parameter metrics [Hash] The process metrics to emit.
+				def emit(metrics)
 					# Log each process individually for better searchability in log platforms:
 					metrics.each do |process_id, general|
 						Console.info(self, "Process metrics captured.", general: general)
 					end
 				end
+				
+				# Run one iteration of the process monitor.
+				def run_once
+					self.emit(self.metrics)
+				end
 			end
 		end
 	end

releases.md

@@ -1,5 +1,9 @@
 # Releases
 
+## Unreleased
+
+  - Add `ProcessMonitor#emit(metrics)` as an override point for subclasses to consume captured process metrics (e.g. emitting StatsD gauges).
+
 ## v0.15.0
 
   - Improve robustness and error handling of default monitors and server loop, ensuring that monitor failures either completely crash the server or retry appropriately, rather than leaving the server in a broken state.

test/async/service/process_monitor.rb

@@ -18,6 +18,61 @@
 		it "defaults to the current parent process id" do
 			expect(monitor.ppid).to be == Process.ppid
 		end
+		
+		it "can be set explicitly" do
+			monitor = subject.new(ppid: 1)
+			expect(monitor.ppid).to be == 1
+		end
+	end
+	
+	with "#metrics" do
+		it "returns a hash of process metrics" do
+			metrics = monitor.metrics
+			expect(metrics).to be_a(Hash)
+			expect(metrics).not.to be(:empty?)
+		end
+	end
+	
+	with "#emit" do
+		it "logs each process" do
+			metrics = {
+				1234 => {process_id: 1234, command: "ruby"},
+				5678 => {process_id: 5678, command: "worker"},
+			}
+			
+			monitor.emit(metrics)
+			
+			expect(console_capture.records.length).to be == 2
+		end
+	end
+	
+	with "#run_once" do
+		it "captures metrics and passes them to emit" do
+			emitted = nil
+			monitor.define_singleton_method(:emit) {|metrics| emitted = metrics}
+			
+			monitor.run_once
+			
+			expect(emitted).to be_a(Hash)
+			expect(emitted).not.to be(:empty?)
+		end
+	end
+	
+	it "supports subclass overriding emit" do
+		received = nil
+		
+		subclass = Class.new(subject) do
+			define_method(:emit) do |metrics|
+				received = metrics
+				super(metrics)
+			end
+		end
+		
+		sub_monitor = subclass.new(interval: 1)
+		sub_monitor.run_once
+		
+		expect(received).to be_a(Hash)
+		expect(received).not.to be(:empty?)
 	end
 
 	with "#run" do