recycle the fastboot instance after 1k requests

README.md

@@ -137,6 +137,7 @@ The supported options are:
  - `enabled`: defaults to `environment === 'production'` so that `prember` only runs during production builds.
  - `indexFile`: defaults to `"index.html"`. This is the name we will give to each of the files we create during pre-rendering.
  - `emptyFile`: defaults to `"_empty.html"`. This is where we will put a copy of your empty `index.html` as it was before any pre-rendering.
+ - `requestsPerFastboot`: defaults to `1000`. This tells prember how many requests to pass to a single fastboot instance before creating a new one. This can be useful for memory management.
 
 ## Using a custom URL discovery function
 

lib/prerender.js

@@ -15,7 +15,7 @@ const port = 7784;
 class Prerender extends Plugin {
   constructor(
     builtAppTree,
-    { urls, indexFile, emptyFile, fastbootOptions },
+    { urls, indexFile, emptyFile, fastbootOptions, requestsPerFastboot },
     ui,
     plugins,
     rootURL
@@ -31,11 +31,14 @@ class Prerender extends Plugin {
     this.port = port;
     this.host = `localhost:${port}`;
     this.fastbootOptions = fastbootOptions || {};
+    this.requestsPerFastboot = requestsPerFastboot || 1000;
+    this.app = undefined;
+    this.visitCounter = 0;
   }
 
-  async listUrls(app, protocol, host) {
+  async listUrls(protocol, host) {
     let visit = async (url) => {
-      return this._visit(app, protocol, host, url);
+      return this._visit(protocol, host, url);
     };
 
     if (typeof this.urls === 'function') {
@@ -109,22 +112,16 @@ class Prerender extends Plugin {
       JSON.stringify(pkg)
     );
 
-    let app = new FastBoot(
-      Object.assign({}, this.fastbootOptions, {
-        distPath: this.inputPaths[0],
-      })
-    );
-
     let expressServer = express()
       .use(this.rootURL, express.static(this.inputPaths[0]))
       .listen(this.port);
 
     let hadFailures = false;
 
-    for (let url of await this.listUrls(app, this.protocol, this.host)) {
+    for (let url of await this.listUrls(this.protocol, this.host)) {
       try {
         hadFailures =
-          !(await this._prerender(app, this.protocol, this.host, url)) ||
+          !(await this._prerender(this.protocol, this.host, url)) ||
           hadFailures;
       } catch (err) {
         hadFailures = true;
@@ -141,7 +138,19 @@ class Prerender extends Plugin {
     }
   }
 
-  async _visit(app, protocol, host, url) {
+  async _visit(protocol, host, url) {
+    // keep track of calls to visit so we know when we can recycle the fastboot instance
+    this.visitCounter++;
+
+    if (!this.app || this.visitCounter > this.requestsPerFastboot) {
+      this.visitCounter = 0;
+      this.app = new FastBoot(
+        Object.assign({}, this.fastbootOptions, {
+          distPath: this.inputPaths[0],
+        })
+      );
+    }
+
     let opts = {
       request: {
         url,
@@ -154,11 +163,11 @@ class Prerender extends Plugin {
         },
       },
     };
-    return await app.visit(url, opts);
+    return await this.app.visit(url, opts);
   }
 
-  async _prerender(app, protocol, host, url) {
-    let page = await this._visit(app, protocol, host, url);
+  async _prerender(protocol, host, url) {
+    let page = await this._visit(protocol, host, url);
     if (page.statusCode === 200) {
       let html = await page.html();
       await this._writeFile(url, html);