feat: add tenant-id to structured log message

Author: Ramisa Alam

src/InvokeContext.js

@@ -9,7 +9,7 @@
 'use strict';
 
 const assert = require('assert').strict;
-let { setCurrentRequestId } = require('./LogPatch');
+let { setCurrentRequestId, setCurrentTenantId } = require('./LogPatch');
 
 const INVOKE_HEADER = {
   ClientContext: 'lambda-runtime-client-context',
@@ -35,11 +35,19 @@ module.exports = class InvokeContext {
     return id;
   }
 
+  /**
+   * The tenantId for this request.
+   */
+  get tenantId() {
+    return this.headers[INVOKE_HEADER.TenantId];
+  }
+
   /**
    * Push relevant invoke data into the logging context.
    */
   updateLoggingContext() {
     setCurrentRequestId(this.invokeId);
+    setCurrentTenantId(this.tenantId);
   }
 
   /**

src/LogPatch.js

@@ -28,13 +28,23 @@ const jsonErrorReplacer = (_, value) => {
   return value;
 };
 
-function formatJsonMessage(requestId, timestamp, level, ...messageParams) {
+function formatJsonMessage(
+  requestId,
+  timestamp,
+  level,
+  tenantId,
+  ...messageParams
+) {
   let result = {
     timestamp: timestamp,
     level: level.name,
     requestId: requestId,
   };
 
+  if (tenantId != undefined && tenantId != null) {
+    result.tenantId = tenantId;
+  }
+
   if (messageParams.length === 1) {
     result.message = messageParams[0];
     try {
@@ -65,6 +75,13 @@ let _currentRequestId = {
   set: (id) => (global[REQUEST_ID_SYMBOL] = id),
 };
 
+/* Use a unique symbol to provide global access without risk of name clashes. */
+const TENANT_ID_SYMBOL = Symbol.for('aws.lambda.runtime.tenantId');
+let _currentTenantId = {
+  get: () => global[TENANT_ID_SYMBOL],
+  set: (id) => (global[TENANT_ID_SYMBOL] = id),
+};
+
 /**
  * Write logs to stdout.
  */
@@ -82,7 +99,15 @@ let logTextToStdout = (level, message, ...params) => {
 let logJsonToStdout = (level, message, ...params) => {
   let time = new Date().toISOString();
   let requestId = _currentRequestId.get();
-  let line = formatJsonMessage(requestId, time, level, message, ...params);
+  let tenantId = _currentTenantId.get();
+  let line = formatJsonMessage(
+    requestId,
+    time,
+    level,
+    tenantId,
+    message,
+    ...params,
+  );
   line = line.replace(/\n/g, '\r');
   process.stdout.write(line + '\n');
 };
@@ -125,10 +150,12 @@ let logJsonToFd = function (logTarget) {
     let date = new Date();
     let time = date.toISOString();
     let requestId = _currentRequestId.get();
+    let tenantId = _currentTenantId.get();
     let enrichedMessage = formatJsonMessage(
       requestId,
       time,
       level,
+      tenantId,
       message,
       ...params,
     );
@@ -239,6 +266,7 @@ let _patchConsole = () => {
 
 module.exports = {
   setCurrentRequestId: _currentRequestId.set,
+  setCurrentTenantId: _currentTenantId.set,
   patchConsole: _patchConsole,
   structuredConsole: structuredConsole,
 };

test/unit/LogPatchTest.js

@@ -415,9 +415,38 @@ describe('The multiline log patch', () => {
         );
         receivedMessage.should.have.property('level', logFunctions[fIdx][1]);
         receivedMessage.should.have.property('requestId', EXPECTED_ID);
+        receivedMessage.should.not.have.property('tenantId');
       }
     });
 
+    it('should format messages with tenant id as json correctly', () => {
+      const EXPECTED_TENANT_ID = 'tenantId';
+      LogPatch.setCurrentTenantId(EXPECTED_TENANT_ID);
+
+      for (let fIdx = 0; fIdx < logFunctions.length; fIdx++) {
+        logFunctions[fIdx][0]('structured logging with tenant id');
+        let receivedMessage = telemetryTarget.readLine(
+          logFunctions[fIdx][1],
+          'JSON',
+        );
+        receivedMessage = JSON.parse(receivedMessage);
+
+        receivedMessage.should.have.property('timestamp');
+        let receivedTime = new Date(receivedMessage.timestamp);
+        let now = new Date();
+        assert(now >= receivedTime && now - receivedTime <= 1000);
+
+        receivedMessage.should.have.property(
+          'message',
+          'structured logging with tenant id',
+        );
+        receivedMessage.should.have.property('level', logFunctions[fIdx][1]);
+        receivedMessage.should.have.property('requestId', EXPECTED_ID);
+        receivedMessage.should.have.property('tenantId', EXPECTED_TENANT_ID);
+      }
+      LogPatch.setCurrentTenantId(undefined);
+    });
+
     it('should filter messages correctly', () => {
       const loglevelSettings = [
         undefined,