Limit number of simultaneous requests to the API

lib/www/client/source/package.json

@@ -9,6 +9,7 @@
   "dependencies": {
     "@deck.gl/aggregation-layers": "^9.1.13",
     "@deck.gl/geo-layers": "^9.1.13",
+    "@dougal/concurrency": "file:../../../modules/@dougal/concurrency",
     "@dougal/organisations": "file:../../../modules/@dougal/organisations",
     "@dougal/user": "file:../../../modules/@dougal/user",
     "@mdi/font": "^7.2.96",

lib/www/client/source/src/store/modules/api/actions.js

@@ -1,3 +1,4 @@
+const ConcurrencyLimiter = require('@dougal/concurrency');
 
 /** Make an API request
  *
@@ -18,6 +19,9 @@
  * to `true`).
  */
 async function api ({state, getters, commit, dispatch}, [resource, init = {}, cb, opts = {}]) {
+
+  const limiter = api.limiter || (api.limiter = new ConcurrencyLimiter(state.maxConcurrent));
+
   try {
     commit("queueRequest");
     if (init && init.hasOwnProperty("body")) {
@@ -63,7 +67,7 @@ async function api ({state, getters, commit, dispatch}, [resource, init = {}, cb
     }
 
     if (!res) {
-      res = await fetch(url, init);
+      res = await limiter.enqueue(async () => await fetch(url, init));
     }
 
     if (cache && !isCached) {

lib/www/client/source/src/store/modules/api/state.js

@@ -1,6 +1,7 @@
 const state = () => ({
   apiUrl: "/api",
-  requestsCount: 0
+  requestsCount: 0,
+  maxConcurrent: 15
 });
 
 export default state;