add vuex store and federation layer for api calls

frontend/src/neigbors.js

@@ -0,0 +1,48 @@
+class NeighborsCache {
+    constructor() {
+        //this._max_age = 1000 * 60 * 60; // 1 hour
+        //this._max_age = 1000 * 60 * 5; // 5 minutes
+        this._max_age = 1000 * 15; // 15 seconds
+        this._cache = JSON.parse(localStorage.getItem('neighbor-cache')) || {};
+    }
+
+    reachable(domain) {
+        console.log('reachable neighbor ' + domain)
+        if (domain in this._cache) {
+            delete this._cache[domain];
+            localStorage.setItem('neighbor-cache', JSON.stringify(this._cache));
+        }
+    }
+
+    unreachable(domain) {
+        console.log('unreachable neighbor ' + domain)
+        this._cache[domain] = {time: Date.now()};
+        localStorage.setItem('neighbor-cache', JSON.stringify(this._cache));
+    }
+
+    queryUnreachable(domain) {
+        //return false if unreachable
+        if (domain in this._cache) {
+            if (this._cache[domain].time > Date.now() - this._max_age) {
+                console.log('skip unreachable neighbor ' + domain + ' ' + Math.ceil(
+                    Date.now()/1000 - this._cache[domain].time/1000) + 's/' + Math.ceil(this._max_age/1000) + 's')
+                return true
+            } else {
+                delete this._cache[domain];
+                localStorage.setItem('neighbor-cache', JSON.stringify(this._cache));
+            }
+        }
+        return false;
+    }
+
+    list() {
+        return Object.entries(this._cache).map(([domain, elem]) => {
+            return {
+                domain: domain,
+                time: elem.time
+            }
+        })
+    }
+}
+
+export default NeighborsCache;