support static stability in instance metadata credential provider (#4049)

* support static stability in EC2 credential provider

* update test files eslintrc version

* add changelog

* update the error message

Author: AllanZhengYP

.changes/next-release/feature-EC2MetadataCredentials-f20878a4.json

@@ -0,0 +1,5 @@
+{
+  "type": "feature",
+  "category": "EC2MetadataCredentials",
+  "description": "Allow EC2MetadataCredentials to extend the existing expiration when EC2 Metadata Service returns expired credentials or failure response."
+}

lib/config-base.d.ts

@@ -83,6 +83,7 @@ export interface HTTPOptions {
 export interface Logger {
     write?: (chunk: any, encoding?: string, callback?: () => void) => void
     log?: (...messages: any[]) => void;
+    warn?: (...message: any[]) => void;
 }
 export interface ParamValidation {
     /**

lib/credentials/ec2_metadata_credentials.d.ts

@@ -1,21 +1,31 @@
 import {Credentials} from '../credentials';
+import {Logger} from '../config-base';
+
 export class EC2MetadataCredentials extends Credentials {
-		/**
-		 * Creates credentials from the metadata service on an EC2 instance.
-		 * @param {object} options - Override the default (1s) timeout period.
-		 */
-		constructor(options?: EC2MetadataCredentialsOptions);
-	}
-    interface EC2MetadataCredentialsOptions {
-        httpOptions?: {
-            /**
-             * Timeout in milliseconds.
-             */
-            timeout?: number
-            /**
-            * Connection timeout in milliseconds.
-            */
-           connectTimeout?: number
-        }
-        maxRetries?: number
+    /**
+     * Creates credentials from the metadata service on an EC2 instance.
+     * @param {object} options - Override the default (1s) timeout period.
+     */
+    constructor(options?: EC2MetadataCredentialsOptions);
+
+    /**
+     * The original expiration of the current credential. In case of AWS
+     * outage, the EC2 metadata will extend expiration of the existing
+     * credential.
+     */
+    originalExpiration?: Date;
+}
+interface EC2MetadataCredentialsOptions {
+    httpOptions?: {
+        /**
+         * Timeout in milliseconds.
+         */
+        timeout?: number
+        /**
+        * Connection timeout in milliseconds.
+        */
+        connectTimeout?: number
     }
+    maxRetries?: number
+    logger?: Logger
+}

lib/credentials/ec2_metadata_credentials.js

@@ -18,15 +18,27 @@ require('../metadata_service');
  * AWS.config.credentials = new AWS.EC2MetadataCredentials({
  *   httpOptions: { timeout: 5000 }, // 5 second timeout
  *   maxRetries: 10, // retry 10 times
- *   retryDelayOptions: { base: 200 } // see AWS.Config for information
+ *   retryDelayOptions: { base: 200 }, // see AWS.Config for information
+ *   logger: console // see AWS.Config for information
  * });
+ * ```
  *
  * If your requests are timing out in connecting to the metadata service, such
  * as when testing on a development machine, you can use the connectTimeout
  * option, specified in milliseconds, which also defaults to 1 second.
- * ```
+ *
+ * If the requests failed or returns expired credentials, it will
+ * extend the expiration of current credential, with a warning message. For more
+ * information, please go to:
+ * https://docs.aws.amazon.com/sdkref/latest/guide/feature-static-credentials.html
+ *
+ * @!attribute originalExpiration
+ *   @return [Date] The optional original expiration of the current credential.
+ *   In case of AWS outage, the EC2 metadata will extend expiration of the
+ *   existing credential.
  *
  * @see AWS.Config.retryDelayOptions
+ * @see AWS.Config.logger
  *
  * @!macro nobrowser
  */
@@ -44,7 +56,7 @@ AWS.EC2MetadataCredentials = AWS.util.inherit(AWS.Credentials, {
        options.httpOptions);
 
     this.metadataService = new AWS.MetadataService(options);
-    this.metadata = {};
+    this.logger = options.logger || AWS.config && AWS.config.logger;
   },
 
   /**
@@ -62,6 +74,13 @@ AWS.EC2MetadataCredentials = AWS.util.inherit(AWS.Credentials, {
    */
   defaultMaxRetries: 3,
 
+  /**
+   * The original expiration of the current credential. In case of AWS
+   * outage, the EC2 metadata will extend expiration of the existing
+   * credential.
+   */
+  originalExpiration: undefined,
+
   /**
    * Loads the credentials from the instance metadata service
    *
@@ -84,24 +103,62 @@ AWS.EC2MetadataCredentials = AWS.util.inherit(AWS.Credentials, {
   load: function load(callback) {
     var self = this;
     self.metadataService.loadCredentials(function(err, creds) {
-      if (!err) {
-        var currentTime = AWS.util.date.getDate();
-        var expireTime = new Date(creds.Expiration);
-        if (expireTime < currentTime) {
-          err = AWS.util.error(
-            new Error('EC2 Instance Metadata Serivce provided expired credentials'),
-            { code: 'EC2MetadataCredentialsProviderFailure' }
-          );
+      if (err) {
+        if (self.hasLoadedCredentials()) {
+          self.extendExpirationIfExpired();
+          callback();
         } else {
-          self.expired = false;
-          self.metadata = creds;
-          self.accessKeyId = creds.AccessKeyId;
-          self.secretAccessKey = creds.SecretAccessKey;
-          self.sessionToken = creds.Token;
-          self.expireTime = expireTime;
+          callback(err);
         }
+      } else {
+        self.setCredentials(creds);
+        self.extendExpirationIfExpired();
+        callback();
       }
-      callback(err);
     });
+  },
+
+  /**
+   * Whether this credential has been loaded.
+   * @api private
+   */
+  hasLoadedCredentials: function hasLoadedCredentials() {
+    return this.AccessKeyId && this.secretAccessKey;
+  },
+
+  /**
+   * if expired, extend the expiration by 15 minutes base plus a jitter of 5
+   * minutes range.
+   * @api private
+   */
+  extendExpirationIfExpired: function extendExpirationIfExpired() {
+    if (this.needsRefresh()) {
+      this.originalExpiration = this.originalExpiration || this.expireTime;
+      this.expired = false;
+      var nextTimeout = 15 * 60 + Math.floor(Math.random() * 5 * 60);
+      var currentTime = AWS.util.date.getDate().getTime();
+      this.expireTime = new Date(currentTime + nextTimeout * 1000);
+      // TODO: add doc link;
+      this.logger.warn('Attempting credential expiration extension due to a '
+          + 'credential service availability issue. A refresh of these '
+          + 'credentials will be attempted again at ' + this.expireTime
+          + '\nFor more information, please visit: https://docs.aws.amazon.com/sdkref/latest/guide/feature-static-credentials.html');
+    }
+  },
+
+  /**
+   * Update the credential with new credential responded from EC2 metadata
+   * service.
+   * @api private
+   */
+  setCredentials: function setCredentials(creds) {
+    var currentTime = AWS.util.date.getDate().getTime();
+    var expireTime = new Date(creds.Expiration);
+    this.expired = currentTime >= expireTime ? true : false;
+    this.metadata = creds;
+    this.accessKeyId = creds.AccessKeyId;
+    this.secretAccessKey = creds.SecretAccessKey;
+    this.sessionToken = creds.Token;
+    this.expireTime = expireTime;
   }
 });

test/.eslintrc

@@ -1,6 +1,6 @@
 {
     "extends": "../.eslintrc",
     "parserOptions": {
-        "ecmaVersion": 8
+        "ecmaVersion": 9
     }
 }