Retrying poller initialization.

Author: tarehart

README.md

@@ -3,14 +3,15 @@
 [![npm version][npm-badge]][npm-url]
 [![Build Status - GitHub Actions][gha-badge]][gha-ci]
 
-A wrapper around @aws-sdk/client-appconfigdata to provide background polling and caching.
+This library polls AWS AppConfig on a background thread so your app has instant access to a cached version of your configuration.
+It relies on the official @aws-sdk/client-appconfigdata library to fetch the data.
 
 Although AWS seems to recommend their [simplified retrieval methods](https://docs.aws.amazon.com/appconfig/latest/userguide/appconfig-retrieving-simplified-methods.html) for fetching AppConfig, i.e. running an agent in a separate process, you may prefer to use this library:
 
 - You don't need to set up a lambda extension.
 - You easily get parity between your local development server and prod.
 - The parsed version of your config is conveniently cached.
-- You get convenient reporting of transient errors while the library works in the background to recover.
+- You get reporting of transient errors while the library works in the background to recover.
 
 ## Usage
 

__tests__/poller.test.ts

@@ -180,4 +180,46 @@ describe('Poller', () => {
       standardConfig.configParser(configValue2),
     );
   });
+
+  it('Retries start session if first one fails', async () => {
+    const configValue = 'worked once';
+
+    appConfigClientMock.on(StartConfigurationSessionCommand)
+      .rejectsOnce({
+        message: 'Failed to start',
+      })
+      .resolves({
+        InitialConfigurationToken: 'initialToken',
+      });
+
+    appConfigClientMock
+      .on(GetLatestConfigurationCommand)
+      .resolves({
+        Configuration: Uint8ArrayBlobAdapter.fromString(configValue),
+      });
+
+    const dataClient = new AppConfigDataClient();
+
+    poller = new Poller({
+      dataClient: dataClient,
+      ...standardConfig,
+    });
+
+    const initialResponse = await poller.start();
+    expect(initialResponse.error).toBeDefined();
+    expect(initialResponse.isInitiallySuccessful).toBeFalsy();
+
+    const latest = poller.getConfigurationString();
+
+    expect(latest.latestValue).toBeUndefined();
+    expect(latest.errorCausingStaleValue).toBeUndefined();
+
+    await wait(standardConfig.pollIntervalSeconds * 1000 + 100);
+
+    const updated = poller.getConfigurationObject();
+    expect(updated.errorCausingStaleValue).toBeUndefined();
+    expect(updated.latestValue).toEqual(
+      standardConfig.configParser(configValue),
+    );
+  });
 });

package.json

@@ -1,6 +1,6 @@
 {
   "name": "aws-appconfig-poller",
-  "version": "0.0.4",
+  "version": "0.0.5",
   "description": "A wrapper around @aws-sdk/client-appconfigdata to provide background polling and caching.",
   "repository": {
     "type": "git",
@@ -41,7 +41,7 @@
     "test": "jest --coverage",
     "prettier": "prettier --config .prettierrc --write .",
     "test:watch": "jest --watch",
-    "infinite": "tsc && node build/examples/infinitePoller.js"
+    "infinite": "tsc && node dist/examples/infinitePoller.js"
   },
   "author": "Tyler Arehart <tarehart@users.noreply.github.com>",
   "license": "MIT",

src/poller.ts

@@ -28,8 +28,9 @@ export interface Outcome {
 
 type PollingPhase = 'ready' | 'starting' | 'active' | 'stopped';
 
+const DEFAULT_POLL_INTERVAL_SECONDS = 60;
+
 export class Poller<T> {
-  private readonly DEFAULT_POLL_INTERVAL_SECONDS = 60;
 
   private readonly config: PollerConfig<T>;
 
@@ -130,6 +131,7 @@ export class Poller<T> {
 
       return await this.fetchLatestConfiguration();
     } catch (e) {
+      this.timeoutHandle = setTimeout(this.startPolling.bind(this), this.config.pollIntervalSeconds || DEFAULT_POLL_INTERVAL_SECONDS)
       return {
         isInitiallySuccessful: false,
         error: e,
@@ -248,7 +250,7 @@ export class Poller<T> {
     return (
       this.config.pollIntervalSeconds ||
       awsSuggestedSeconds ||
-      this.DEFAULT_POLL_INTERVAL_SECONDS
+      DEFAULT_POLL_INTERVAL_SECONDS
     );
   }
 }