Support alternative Thunderstore CDN

src/App.vue

@@ -26,7 +26,6 @@
 <script lang="ts">
 import Component, { mixins } from 'vue-class-component';
 import 'bulma-steps/dist/js/bulma-steps.min.js';
-import R2Error from './model/errors/R2Error';
 import ManagerSettings from './r2mm/manager/ManagerSettings';
 import ProfileProvider from './providers/ror2/model_implementation/ProfileProvider';
 import ProfileImpl from './r2mm/model_implementation/ProfileImpl';
@@ -68,33 +67,16 @@ import UtilityMixin from './components/mixins/UtilityMixin.vue';
 
 @Component
 export default class App extends mixins(UtilityMixin) {
-
-    private errorMessage: string = '';
-    private errorStack: string = '';
-    private errorSolution: string = '';
     private settings: ManagerSettings | null = null;
-
     private visible: boolean = false;
 
-    showError(error: R2Error) {
-        this.errorMessage = error.name;
-        this.errorStack = error.message;
-        this.errorSolution = error.solution;
-        LoggerProvider.instance.Log(LogSeverity.ERROR, `[${error.name}]: ${error.message}`);
-    }
-
-    closeErrorModal() {
-        this.errorMessage = '';
-        this.errorStack = '';
-        this.errorSolution = '';
-    }
-
     async created() {
         // Use as default game for settings load.
         GameManager.activeGame = GameManager.unsetGame();
 
         this.hookThunderstoreModListRefresh();
         this.hookProfileModListRefresh();
+        await this.checkCdnConnection();
 
         const settings = await ManagerSettings.getSingleton(GameManager.activeGame);
         this.settings = settings;

src/components/mixins/UtilityMixin.vue

@@ -5,15 +5,33 @@ import Component from 'vue-class-component';
 import R2Error from '../../model/errors/R2Error';
 import GameManager from '../../model/game/GameManager';
 import Profile from '../../model/Profile';
+import CdnProvider from '../../providers/generic/connection/CdnProvider';
+import LoggerProvider, { LogSeverity } from '../../providers/ror2/logging/LoggerProvider';
 import ThunderstorePackages from '../../r2mm/data/ThunderstorePackages';
 import ProfileModList from '../../r2mm/mods/ProfileModList';
 import ApiCacheUtils from '../../utils/ApiCacheUtils';
 
 @Component
 export default class UtilityMixin extends Vue {
+    private errorMessage: string = '';
+    private errorStack: string = '';
+    private errorSolution: string = '';
     readonly REFRESH_INTERVAL = 5 * 60 * 1000;
     private tsRefreshFailed = false;
 
+    showError(error: R2Error) {
+        this.errorMessage = error.name;
+        this.errorStack = error.message;
+        this.errorSolution = error.solution;
+        LoggerProvider.instance.Log(LogSeverity.ERROR, `[${error.name}]: ${error.message}`);
+    }
+
+    closeErrorModal() {
+        this.errorMessage = '';
+        this.errorStack = '';
+        this.errorSolution = '';
+    }
+
     hookProfileModListRefresh() {
         setInterval(this.refreshProfileModList, this.REFRESH_INTERVAL);
     }
@@ -64,5 +82,21 @@ export default class UtilityMixin extends Vue {
 
         this.tsRefreshFailed = false;
     }
+
+    /**
+     * Set internal state of CdnProvider to prefer a mirror CDN if the
+     * main CDN is unreachable.
+     */
+    async checkCdnConnection() {
+        try {
+            await CdnProvider.checkCdnConnection();
+        } catch (error: unknown) {
+            if (error instanceof R2Error) {
+                this.showError(error);
+            } else {
+                console.error(error);
+            }
+        }
+    }
 }
 </script>

src/components/views/OnlineModList.vue

@@ -2,7 +2,7 @@
     <div>
         <ExpandableCard
             v-for='(key, index) in pagedModList' :key="`online-${key.getFullName()}-${index}-${settings.getContext().global.expandedCards}`"
-            :image="key.getVersions()[0].getIcon()"
+            :image="getImageUrl(key)"
             :id="index"
             :description="key.getVersions()[0].getDescription()"
             :funkyMode="funkyMode"
@@ -70,6 +70,7 @@ import DownloadModModal from './DownloadModModal.vue';
 import ManifestV2 from '../../model/ManifestV2';
 import R2Error from '../../model/errors/R2Error';
 import DonateButton from '../../components/buttons/DonateButton.vue';
+import CdnProvider from '../../providers/generic/connection/CdnProvider';
 
 @Component({
     components: {
@@ -122,6 +123,12 @@ export default class OnlineModList extends Vue {
         return mod.getCategories().join(", ");
     }
 
+    getImageUrl(tsMod: ThunderstoreMod): string {
+        return CdnProvider.replaceCdnHost(
+            tsMod.getVersions()[0].getIcon()
+        );
+    }
+
     emitError(error: R2Error) {
         this.$emit('error', error);
     }

src/model/ThunderstoreVersion.ts

@@ -1,6 +1,7 @@
 import Mod from './Mod';
 import VersionNumber from './VersionNumber';
 import ReactiveObjectConverterInterface from './safety/ReactiveObjectConverter';
+import CdnProvider from '../providers/generic/connection/CdnProvider';
 
 export default class ThunderstoreVersion extends Mod implements ReactiveObjectConverterInterface {
 
@@ -35,10 +36,10 @@ export default class ThunderstoreVersion extends Mod implements ReactiveObjectCo
     }
 
     public getDownloadUrl(): string {
-        return this.downloadUrl;
+        return CdnProvider.addCdnQueryParameter(this.downloadUrl);
     }
 
     public setDownloadUrl(url: string) {
         this.downloadUrl = url;
     }
-}
+}

src/providers/generic/connection/CdnProvider.ts

@@ -0,0 +1,63 @@
+import R2Error from '../../../model/errors/R2Error';
+import { getAxiosWithTimeouts } from '../../../utils/HttpUtils';
+import { addOrReplaceSearchParams, replaceHost } from '../../../utils/UrlUtils';
+
+const CDNS = [
+    "gcdn.thunderstore.io",
+    "hcdn-1.hcdn.thunderstore.io"
+]
+const TEST_FILE = "healthz";
+
+const CONNECTION_ERROR = new R2Error(
+    "Can't reach content delivery networks",
+    `All Thunderstore CDNs seem to be currently unreachable from
+     this computer. You can still use the mod manager, but
+     downloading mods will not work.`,
+    `Test another internet connection, if available. For example
+     using a VPN or connecting to a mobile hotspot might solve the
+     issue.`
+);
+
+export default class CdnProvider {
+    private static axios = getAxiosWithTimeouts(5000, 5000);
+    private static preferredCdn = "";
+
+    public static async checkCdnConnection() {
+        const headers = {
+            "Cache-Control": "no-cache",
+            "Pragma": "no-cache",
+            "Expires": "0",
+        };
+        const params = {"disableCache": new Date().getTime()};
+        let res;
+
+        for await (const cdn of CDNS) {
+            const url = `https://${cdn}/${TEST_FILE}`;
+
+            try {
+                res = await CdnProvider.axios.get(url, {headers, params});
+            } catch (e) {
+                continue;
+            }
+
+            if (res.status === 200) {
+                CdnProvider.preferredCdn = cdn;
+                return;
+            }
+        };
+
+        throw CONNECTION_ERROR;
+    }
+
+    public static replaceCdnHost(url: string) {
+        return CdnProvider.preferredCdn
+            ? replaceHost(url, CdnProvider.preferredCdn)
+            : url;
+    }
+
+    public static addCdnQueryParameter(url: string) {
+        return CdnProvider.preferredCdn
+            ? addOrReplaceSearchParams(url, `cdn=${CdnProvider.preferredCdn}`)
+            : url;
+    }
+}

src/r2mm/profiles/ProfilesClient.ts

@@ -1,5 +1,6 @@
 import Axios, { AxiosResponse } from 'axios';
 import R2Error from '../../model/errors/R2Error';
+import CdnProvider from '../../providers/generic/connection/CdnProvider';
 
 const getProfileUrl = (profileImportCode: string): string => {
     return `https://thunderstore.io/api/experimental/legacyprofile/get/${profileImportCode}/`;
@@ -40,7 +41,10 @@ async function createProfile(payload: string): Promise<AxiosResponse<{ key: stri
 }
 
 async function getProfile(profileImportCode: string): Promise<AxiosResponse<string>> {
-    return await Axios.get(getProfileUrl(profileImportCode));
+    const url = CdnProvider.addCdnQueryParameter(
+        getProfileUrl(profileImportCode)
+    );
+    return await Axios.get(url);
 }
 
 export const ProfileApiClient = {

src/utils/HttpUtils.ts

@@ -0,0 +1,38 @@
+import axios from "axios";
+
+const newAbortSignal = (timeoutMs: number) => {
+    const abortController = new AbortController();
+    setTimeout(() => abortController.abort(), timeoutMs);
+    return abortController.signal;
+};
+
+/**
+ * Return Axios instance with timeouts enabled.
+ * @param responseTimeout Time (in ms) the server has to generate a
+ *     response once a connection is established. Defaults to 5 seconds.
+ * @param connectionTimeout Time (in ms) the request has in total,
+ *     including opening the connection and receiving the response.
+ *     Defaults to 10 seconds.
+ * @returns AxiosInstance
+ */
+export const getAxiosWithTimeouts = (responseTimeout = 5000, connectionTimeout = 10000) => {
+    const instance = axios.create({timeout: responseTimeout});
+
+    // Use interceptors to have a fresh abort signal for each request,
+    // so the instance can be shared by multiple requests.
+    instance.interceptors.request.use((config) => {
+        config.signal = newAbortSignal(connectionTimeout);
+        return config;
+    });
+
+    return instance;
+};
+
+export const isNetworkError = (responseOrError: unknown) =>
+    responseOrError instanceof Error && responseOrError.message === "Network Error";
+
+/**
+ * Is the Error thrown by Axios request caused by a response timeout?
+ */
+export const isResponseTimeout = (error: unknown) =>
+    error instanceof Error && /timeout of (\d+)ms exceeded/i.test(error.message);

src/utils/UrlUtils.ts

@@ -0,0 +1,33 @@
+/**
+ * Append given search parameters to an URL which may or may not already
+ * have search parameters.
+ *
+ * Existing search parameters with a key present in the new parameters
+ * will be overwritten.
+ */
+export const addOrReplaceSearchParams = (url: string, paramString: string) => {
+    const newUrl = new URL(url);
+    newUrl.search = new URLSearchParams(
+        Object.assign(
+            {},
+            Object.fromEntries(newUrl.searchParams),
+            Object.fromEntries(new URLSearchParams(paramString))
+        )
+    ).toString();
+    return newUrl.href;
+}
+
+/**
+ * Replace URL host, i.e. the domain and the port number.
+ *
+ * @param url e.g. "https://thunderstore.io/foo"
+ * @param domainAndPort e.g. "thunderstore.dev" or "thunderstore.dev:8080"
+ * @returns e.g. "https://thunderstore.dev:8080/foo"
+ */
+export const replaceHost = (url: string, domainAndPort: string) => {
+    const newValues = domainAndPort.split(":");
+    const newUrl = new URL(url);
+    newUrl.hostname = newValues[0];
+    newUrl.port = newValues[1] || "";
+    return newUrl.href;
+};