fix: concurrent requests not beeing cached

arthurfiorette · Sep 19, 2021 · 1490bfc · 1490bfc
1 parent 6e61c0d
commit 1490bfc
Show file tree

Hide file tree

Showing 3 changed files with 28 additions and 5 deletions.
diff --git a/.vscode/launch.json b/.vscode/launch.json
@@ -10,7 +10,9 @@
         "${workspaceRoot}/node_modules/jest/bin/jest.js",
         // Linux:
         // "${workspaceRoot}/node_modules/.bin/jest",
-        "--runInBand"
+        "--runInBand",
+        "--watch",
+        "request.test.ts"
       ],
       "console": "integratedTerminal",
       "internalConsoleOptions": "neverOpen",

diff --git a/src/interceptors/request.ts b/src/interceptors/request.ts
@@ -1,5 +1,5 @@
 import { AxiosCacheInstance, CacheRequestConfig } from '../axios/types';
-import { CachedResponse } from '../storage/types';
+import { CachedResponse, CachedStorageValue, LoadingStorageValue } from '../storage/types';
 import { Deferred } from '../util/deferred';
 import { CACHED_STATUS_CODE, CACHED_STATUS_TEXT } from '../util/status-codes';
 import { AxiosInterceptor } from './types';
@@ -27,10 +27,19 @@ export class CacheRequestInterceptor implements AxiosInterceptor<CacheRequestCon
     const key = this.axios.generateKey(config);
 
     // Assumes that the storage handled staled responses
-    const cache = await this.axios.storage.get(key);
+    let cache = await this.axios.storage.get(key);
 
     // Not cached, continue the request, and mark it as fetching
-    if (cache.state == 'empty') {
+    emptyState: if (cache.state == 'empty') {
+      // This if catches concurrent access to a new key.
+      // The js event loop skips in the first await statement,
+      // so the next code block will be executed both if called
+      // from two places asynchronously.
+      if (this.axios.waiting[key]) {
+        cache = (await this.axios.storage.get(key)) as CachedStorageValue | LoadingStorageValue;
+        break emptyState;
+      }
+
       // Create a deferred to resolve other requests for the same key when it's completed
       this.axios.waiting[key] = new Deferred();
 

diff --git a/test/interceptors/request.test.ts b/test/interceptors/request.test.ts
@@ -1,4 +1,5 @@
-import { mockAxios } from '../mocks/axios';
+import { StatusCodes } from '../../src';
+import { axiosMock, mockAxios } from '../mocks/axios';
 
 describe('test request interceptor', () => {
   it('tests against specified methods', async () => {
@@ -26,4 +27,15 @@ describe('test request interceptor', () => {
 
     expect(cache.state).toBe('cached');
   });
+
+  it('tests concurrent requests', async () => {
+    const axios = mockAxios();
+
+    const [resp1, resp2] = await Promise.all([axios.get(''), axios.get('')]);
+
+    expect(resp1).toHaveProperty('status', axiosMock.statusCode);
+    expect(resp1).toHaveProperty('statusText', axiosMock.statusText);
+    expect(resp2).toHaveProperty('status', StatusCodes.CACHED_STATUS_CODE);
+    expect(resp2).toHaveProperty('statusText', StatusCodes.CACHED_STATUS_TEXT);
+  });
 });