Change ajax_stream to use new-line delimited JSON (#52797)

Author: chrisdavies

src/legacy/core_plugins/interpreter/public/canvas/ajax_stream/ajax_stream.test.ts

@@ -26,7 +26,7 @@ describe('ajaxStream', () => {
   it('pulls items from the stream and calls the handler', async () => {
     const handler = jest.fn(() => ({}));
     const { req, sendText, done } = mockRequest();
-    const messages = ['{ "hello": "world" }\n', '{ "tis": "fate" }\n'].map(m => `${m.length}:${m}`);
+    const messages = ['{ "hello": "world" }\n', '{ "tis": "fate" }\n'];
 
     const promise = ajaxStream('', {}, req, {
       url: '/test/endpoint',
@@ -43,12 +43,34 @@ describe('ajaxStream', () => {
     expect(handler).toHaveBeenCalledWith({ tis: 'fate' });
   });
 
+  it('handles newlines in values', async () => {
+    const handler = jest.fn(() => ({}));
+    const { req, sendText, done } = mockRequest();
+    const messages = [
+      JSON.stringify({ hello: 'wo\nrld' }),
+      '\n',
+      JSON.stringify({ tis: 'fa\nte' }),
+      '\n',
+    ];
+
+    const promise = ajaxStream('', {}, req, {
+      url: '/test/endpoint',
+      onResponse: handler,
+    });
+
+    messages.forEach(sendText);
+    done();
+
+    await promise;
+    expect(handler).toHaveBeenCalledTimes(2);
+    expect(handler).toHaveBeenCalledWith({ hello: 'wo\nrld' });
+    expect(handler).toHaveBeenCalledWith({ tis: 'fa\nte' });
+  });
+
   it('handles partial messages', async () => {
     const handler = jest.fn(() => ({}));
     const { req, sendText, done } = mockRequest();
-    const messages = ['{ "hello": "world" }\n', '{ "tis": "fate" }\n']
-      .map(m => `${m.length}:${m}`)
-      .join('');
+    const messages = ['{ "hello": "world" }\n', '{ "tis": "fate" }\n'].join('');
 
     const promise = ajaxStream('', {}, req, {
       url: '/test/endpoint',
@@ -117,7 +139,7 @@ describe('ajaxStream', () => {
   it('rejects if the payload contains invalid JSON', async () => {
     const handler = jest.fn(() => ({}));
     const { req, sendText, done } = mockRequest();
-    const messages = ['{ waut? }\n'].map(m => `${m.length}:${m}`).join('');
+    const messages = ['{ waut? }\n'].join('');
 
     const promise = ajaxStream('', {}, req, {
       url: '/test/endpoint',
@@ -130,32 +152,12 @@ describe('ajaxStream', () => {
     expect(await promise.then(() => true).catch(() => false)).toBeFalsy();
   });
 
-  it('rejects if the delim is invalid', async () => {
-    const handler = jest.fn(() => ({}));
-    const { req, sendText, done } = mockRequest();
-    const messages = '{ "hi": "there" }';
-
-    const promise = ajaxStream('', {}, req, {
-      url: '/test/endpoint',
-      onResponse: handler,
-    });
-
-    sendText(messages);
-    done();
-
-    expect(await promise.then(() => true).catch(({ message }) => message)).toMatch(
-      /invalid stream response/i
-    );
-  });
-
   it('rejects if the handler throws', async () => {
     const handler = jest.fn(() => {
       throw new Error('DOH!');
     });
     const { req, sendText, done } = mockRequest();
-    const messages = ['{ "hello": "world" }\n', '{ "tis": "fate" }\n']
-      .map(m => `${m.length}:${m}`)
-      .join('');
+    const messages = ['{ "hello": "world" }\n', '{ "tis": "fate" }\n'].join('');
 
     const promise = ajaxStream('', {}, req, {
       url: '/test/endpoint',

src/legacy/core_plugins/interpreter/public/canvas/ajax_stream/ajax_stream.ts

@@ -64,34 +64,19 @@ function processBatchResponseStream<T>(handler: BatchResponseHandler<T>) {
   return (text: string) => {
     // While there's text to process...
     while (index < text.length) {
-      // Our messages are delimited by colon: len:json
-      const delim = ':';
+      // We're using new line-delimited JSON.
+      const delim = '\n';
       const delimIndex = text.indexOf(delim, index);
-      const payloadStart = delimIndex + delim.length;
 
       // We've got an incomplete batch length
       if (delimIndex < 0) {
         return;
       }
 
-      const rawLen = text.slice(index, delimIndex);
-      const payloadLen = parseInt(rawLen, 10);
-      const payloadEnd = payloadStart + payloadLen;
-
-      // We've got an invalid batch message (e.g. one without a numeric length: prefix)
-      if (isNaN(payloadLen)) {
-        throw new Error(`Invalid stream response length: ${rawLen}`);
-      }
-
-      // We've got an incomplete batch message
-      if (text.length < payloadEnd) {
-        return;
-      }
-
-      const payload = JSON.parse(text.slice(payloadStart, payloadEnd));
+      const payload = JSON.parse(text.slice(index, delimIndex));
       handler(payload);
 
-      index = payloadEnd;
+      index = delimIndex + 1;
     }
   };
 }

src/legacy/core_plugins/interpreter/server/routes/server_functions.ts

@@ -75,16 +75,15 @@ function runServerFunctions(server: any) {
 
       // Send the initial headers.
       res.writeHead(200, {
-        'Content-Type': 'text/plain',
+        'Content-Type': 'application/x-ndjson',
         Connection: 'keep-alive',
         'Transfer-Encoding': 'chunked',
         'Cache-Control': 'no-cache',
       });
 
       // Write a length-delimited response
       const streamResult = (result: any) => {
-        const payload = JSON.stringify(result) + '\n';
-        res.write(`${payload.length}:${payload}`);
+        res.write(JSON.stringify(result) + '\n');
       };
 
       // Tries to run an interpreter function, and ensures a consistent error payload on failure.