Improvement: Add the ability to trim keys no longer in use from the k…

…eyedErrorHealthCheckSource (#44)

changelog/@unreleased/pr-44.v2.yml

@@ -0,0 +1,6 @@
+type: improvement
+improvement:
+  description: |-
+    Adds PurgeKeys to window.KeyedErrorSubmitter interface, allowing a caller to remove entries from a keyed window health check.
+  links:
+    - https://github.com/palantir/witchcraft-go-health/pull/44

sources/store/keyed_error_source.go

@@ -31,6 +31,9 @@ type KeyedErrorSubmitter interface {
 	// Submit stores non-nil errors by the provided key in a map; keys of submitted nil errors are
 	// deleted from the map.
 	Submit(key string, err error)
+	// PurgeKeys iterates through all currently tracked keys, calling fn on each.
+	// If fn returns true, the key will be removed from the healthcheck.
+	PurgeKeys(fn func(key string) bool)
 }
 
 // KeyedErrorHealthCheckSource tracks errors by key to compute health status. Only entries with non-nil
@@ -100,3 +103,13 @@ func (k *keyedErrorHealthCheckSource) HealthStatus(ctx context.Context) health.H
 		},
 	}
 }
+
+func (k *keyedErrorHealthCheckSource) PurgeKeys(fn func(key string) bool) {
+	k.lock.Lock()
+	defer k.lock.Unlock()
+	for keyName := range k.keyedErrors {
+		if fn(keyName) {
+			delete(k.keyedErrors, keyName)
+		}
+	}
+}

sources/store/keyed_error_source_test.go

@@ -63,3 +63,52 @@ func TestKeyedMessengerHealthStateHealthy(t *testing.T) {
 		},
 	}, keyedErrorSource.HealthStatus(context.Background()))
 }
+
+func TestKeyedMessengerHealthStateErrorAndPreserve(t *testing.T) {
+	keyedErrorSource := NewKeyedErrorHealthCheckSource("TEST", testMessage)
+	keyedErrorSource.Submit("1", werror.Error("error message 1"))
+	keyedErrorSource.Submit("2", werror.Error("error message 2"))
+	keyedErrorSource.Submit("3", nil)
+	assert.Equal(t, health.HealthStatus{
+		Checks: map[health.CheckType]health.HealthCheckResult{
+			"TEST": {
+				Message: &testMessage,
+				Params: map[string]interface{}{
+					"1": "error message 1",
+					"2": "error message 2",
+				},
+				State: health.New_HealthState(health.HealthState_ERROR),
+				Type:  "TEST",
+			},
+		},
+	}, keyedErrorSource.HealthStatus(context.Background()))
+	// Keep One Error
+	keyedErrorSource.PurgeKeys(func(key string) bool {
+		return key == "1"
+	})
+	assert.Equal(t, health.HealthStatus{
+		Checks: map[health.CheckType]health.HealthCheckResult{
+			"TEST": {
+				Message: &testMessage,
+				Params: map[string]interface{}{
+					"2": "error message 2",
+				},
+				State: health.New_HealthState(health.HealthState_ERROR),
+				Type:  "TEST",
+			},
+		},
+	}, keyedErrorSource.HealthStatus(context.Background()))
+	// Remove other
+	keyedErrorSource.PurgeKeys(func(key string) bool {
+		return key == "2"
+	})
+	assert.Equal(t, health.HealthStatus{
+		Checks: map[health.CheckType]health.HealthCheckResult{
+			"TEST": {
+				Message: &testMessage,
+				State:   health.New_HealthState(health.HealthState_HEALTHY),
+				Type:    "TEST",
+			},
+		},
+	}, keyedErrorSource.HealthStatus(context.Background()))
+}