[CORL-281] Metrics (#2298)

* feat: iunitial metrics implementation

* fix: graphql endpoint was throwing errors.

* feat: add metrics env variables to readme

src/core/server/graph/common/extensions/LoggerExtension.ts

@@ -1,9 +1,4 @@
-import {
-  DocumentNode,
-  ExecutionArgs,
-  GraphQLError,
-  OperationDefinitionNode,
-} from "graphql";
+import { ExecutionArgs, GraphQLError } from "graphql";
 import {
   EndHandler,
   GraphQLExtension,
@@ -12,33 +7,13 @@ import {
 import now from "performance-now";
 
 import CommonContext from "talk-server/graph/common/context";
+import { getOperationMetadata } from "./helpers";
 
 export function logError(ctx: CommonContext, err: GraphQLError) {
   ctx.logger.error({ err }, "graphql query error");
 }
 
 export class LoggerExtension implements GraphQLExtension<CommonContext> {
-  private getOperationMetadata(doc: DocumentNode) {
-    if (doc.kind === "Document") {
-      const operationDefinition = doc.definitions.find(
-        ({ kind }) => kind === "OperationDefinition"
-      ) as OperationDefinitionNode | undefined;
-      if (operationDefinition) {
-        let operationName: string | undefined;
-        if (operationDefinition.name) {
-          operationName = operationDefinition.name.value;
-        }
-
-        return {
-          operationName,
-          operation: operationDefinition.operation,
-        };
-      }
-    }
-
-    return {};
-  }
-
   public executionDidStart(o: {
     executionArgs: ExecutionArgs;
   }): EndHandler | void {
@@ -55,7 +30,7 @@ export class LoggerExtension implements GraphQLExtension<CommonContext> {
         o.executionArgs.contextValue.logger.debug(
           {
             responseTime,
-            ...this.getOperationMetadata(o.executionArgs.document),
+            ...getOperationMetadata(o.executionArgs.document),
           },
           "graphql query"
         );

src/core/server/graph/common/extensions/MetricsExtension.ts

@@ -0,0 +1,51 @@
+import { ExecutionArgs } from "graphql";
+import { EndHandler, GraphQLExtension } from "graphql-extensions";
+import now from "performance-now";
+import { Counter, Histogram } from "prom-client";
+
+import CommonContext from "talk-server/graph/common/context";
+import { getOperationMetadata } from "./helpers";
+
+export interface MetricsExtensionOptions {
+  executedGraphQueriesTotalCounter: Counter;
+  graphQLExecutionTimingsHistogram: Histogram;
+}
+
+export class MetricsExtension implements GraphQLExtension<CommonContext> {
+  private options: MetricsExtensionOptions;
+
+  constructor(options: MetricsExtensionOptions) {
+    this.options = options;
+  }
+
+  public executionDidStart(o: {
+    executionArgs: ExecutionArgs;
+  }): EndHandler | void {
+    // Only try to log things if the context is provided.
+    if (o.executionArgs.contextValue) {
+      // Grab the start time so we can calculate the time it takes to execute
+      // the graph query.
+      const startTime = now();
+      return () => {
+        // Compute the end time.
+        const responseTime = Math.round(now() - startTime);
+
+        // Get the request metadata.
+        const { operation, operationName } = getOperationMetadata(
+          o.executionArgs.document
+        );
+
+        if (operation && operationName) {
+          // Increment the graph query value, tagging with the name of the query.
+          this.options.executedGraphQueriesTotalCounter
+            .labels(operation, operationName)
+            .inc();
+
+          this.options.graphQLExecutionTimingsHistogram
+            .labels(operation, operationName)
+            .observe(responseTime);
+        }
+      };
+    }
+  }
+}

src/core/server/graph/common/extensions/helpers.ts

@@ -0,0 +1,22 @@
+import { DocumentNode, OperationDefinitionNode } from "graphql";
+
+export function getOperationMetadata(doc: DocumentNode) {
+  if (doc.kind === "Document") {
+    const operationDefinition = doc.definitions.find(
+      ({ kind }) => kind === "OperationDefinition"
+    ) as OperationDefinitionNode | undefined;
+    if (operationDefinition) {
+      let operationName: string | undefined;
+      if (operationDefinition.name) {
+        operationName = operationDefinition.name.value;
+      }
+
+      return {
+        operationName,
+        operation: operationDefinition.operation,
+      };
+    }
+  }
+
+  return {};
+}

src/core/server/graph/common/extensions/index.ts

@@ -1,2 +1,3 @@
 export * from "./ErrorWrappingExtension";
 export * from "./LoggerExtension";
+export * from "./MetricsExtension";