Merge pull request #1071 from appsignal/unregister-probe

Allow probes to be unregistered

.changesets/unregister-probes.md

@@ -0,0 +1,6 @@
+---
+bump: "patch"
+type: "change"
+---
+
+Allow unregistering minutely probes. Use `Appsignal::Probes.unregister` to unregister probes registered with `Appsignal::Probes.register` if you do not need a certain probe, including default probes.

lib/appsignal/probes.rb

@@ -43,6 +43,11 @@ def internal_register(name, probe)
         probes[name] = probe
       end
 
+      # @api private
+      def unregister(name)
+        probes.delete(name)
+      end
+
       # @api private
       def each(&block)
         probes.each(&block)
@@ -128,9 +133,10 @@ def probes
       #   # "started" # Printed on Appsignal::Probes.start
       #   # "called" # Repeated every minute
       #
-      # @param name [Symbol/String] Name of the probe. Can be used with {[]}.
-      #   This name will be used in errors in the log and allows overwriting of
-      #   probes by registering new ones with the same name.
+      # @param name [Symbol/String] Name of the probe. Can be used with
+      #   {ProbeCollection#[]}. This name will be used in errors in the log and
+      #   allows overwriting of probes by registering new ones with the same
+      #   name.
       # @param probe [Object] Any object that listens to the `call` method will
       #   be used as a probe.
       # @return [void]
@@ -140,6 +146,26 @@ def register(name, probe)
         initialize_probe(name, probe) if started?
       end
 
+      # Unregister a probe that's registered with {register}.
+      # Can also be used to unregister automatically registered probes by the
+      # gem.
+      #
+      # @example Unregister probes
+      #   # First register a probe
+      #   Appsignal::Probes.register :my_probe, lambda {}
+      #
+      #   # Then unregister a probe if needed
+      #   Appsignal::Probes.unregister :my_probe
+      #
+      # @param name [Symbol/String] Name of the probe used to {register} the
+      #   probe.
+      # @return [void]
+      def unregister(name)
+        probes.unregister(name)
+
+        uninitialize_probe(name)
+      end
+
       # @api private
       def start
         stop
@@ -228,6 +254,12 @@ def initialize_probe(name, probe)
         logger.debug error.backtrace.join("\n")
       end
 
+      def uninitialize_probe(name)
+        mutex.synchronize do
+          probe_instances.delete(name)
+        end
+      end
+
       def dependencies_present?(probe)
         return true unless probe.respond_to? :dependencies_present?
 

spec/lib/appsignal/probes_spec.rb

@@ -72,9 +72,7 @@ def call
     let(:log) { log_contents(log_stream) }
     before do
       Appsignal.internal_logger = test_logger(log_stream)
-      # Speed up test time
-      allow(Appsignal::Probes).to receive(:initial_wait_time).and_return(0.001)
-      allow(Appsignal::Probes).to receive(:wait_time).and_return(0.001)
+      speed_up_tests!
     end
 
     describe ".started?" do
@@ -261,6 +259,35 @@ def call
     end
   end
 
+  describe ".unregister" do
+    let(:log_stream) { StringIO.new }
+    let(:log) { log_contents(log_stream) }
+    before do
+      Appsignal.internal_logger = test_logger(log_stream)
+      speed_up_tests!
+    end
+
+    it "does not call the initialized probe after unregistering" do
+      probe1_calls = 0
+      probe2_calls = 0
+      probe1 = lambda { probe1_calls += 1 }
+      probe2 = lambda { probe2_calls += 1 }
+      Appsignal::Probes.register :probe1, probe1
+      Appsignal::Probes.register :probe2, probe2
+      Appsignal::Probes.start
+      wait_for("enough probe1 calls") { probe1_calls >= 2 }
+      wait_for("enough probe2 calls") { probe2_calls >= 2 }
+
+      Appsignal::Probes.unregister :probe2
+      probe1_calls = 0
+      probe2_calls = 0
+      # Check the probe 1 calls to make sure the probes have been called before
+      # testing if the unregistered probe has not been called
+      wait_for("enough probe1 calls") { probe1_calls >= 2 }
+      expect(probe2_calls).to eq(0)
+    end
+  end
+
   describe ".stop" do
     before do
       allow(Appsignal::Probes).to receive(:initial_wait_time).and_return(0.001)
@@ -411,6 +438,19 @@ def call
       end
     end
 
+    describe "#unregister" do
+      it "removes the probe from the collection" do
+        expect(Appsignal::Probes).to receive(:probes).and_return(collection)
+
+        probe = lambda {}
+        silence { collection.register :my_probe, probe }
+        expect(collection[:my_probe]).to eql(probe)
+
+        silence { collection.unregister :my_probe }
+        expect(collection[:my_probe]).to be_nil
+      end
+    end
+
     describe "#each" do
       it "loops over the registered probes" do
         probe = lambda {}
@@ -423,4 +463,10 @@ def call
       end
     end
   end
+
+  # Speed up test time by decreasing wait times in the probes mechanism
+  def speed_up_tests!
+    allow(Appsignal::Probes).to receive(:initial_wait_time).and_return(0.001)
+    allow(Appsignal::Probes).to receive(:wait_time).and_return(0.001)
+  end
 end