Fallback to using the nomad server for log streaming

Only when the client isn't accessible

ui/app/components/task-log.js

@@ -2,9 +2,11 @@ import { inject as service } from '@ember/service';
 import Component from '@ember/component';
 import { computed } from '@ember/object';
 import { run } from '@ember/runloop';
+import RSVP from 'rsvp';
 import { task } from 'ember-concurrency';
 import { logger } from 'nomad-ui/utils/classes/log';
 import WindowResizable from 'nomad-ui/mixins/window-resizable';
+import timeout from 'nomad-ui/utils/timeout';
 
 export default Component.extend(WindowResizable, {
   token: service(),
@@ -14,6 +16,8 @@ export default Component.extend(WindowResizable, {
   allocation: null,
   task: null,
 
+  useServer: false,
+
   didReceiveAttrs() {
     if (this.get('allocation') && this.get('task')) {
       this.send('toggleStream');
@@ -37,11 +41,12 @@ export default Component.extend(WindowResizable, {
 
   mode: 'stdout',
 
-  logUrl: computed('allocation.id', 'allocation.node.httpAddr', function() {
+  logUrl: computed('allocation.id', 'allocation.node.httpAddr', 'useServer', function() {
     const address = this.get('allocation.node.httpAddr');
     const allocation = this.get('allocation.id');
 
-    return `//${address}/v1/client/fs/logs/${allocation}`;
+    const url = `/v1/client/fs/logs/${allocation}`;
+    return this.get('useServer') ? url : `//${address}${url}`;
   }),
 
   logParams: computed('task', 'mode', function() {
@@ -51,9 +56,18 @@ export default Component.extend(WindowResizable, {
     };
   }),
 
-  logger: logger('logUrl', 'logParams', function() {
-    const token = this.get('token');
-    return token.authorizedRequest.bind(token);
+  logger: logger('logUrl', 'logParams', function logFetch() {
+    // If the log request can't settle in one second, the client
+    // must be unavailable and the server should be used instead
+    return url =>
+      RSVP.race([this.get('token').authorizedRequest(url), timeout(1000)]).then(
+        response => response,
+        error => {
+          this.send('failoverToServer');
+          this.get('stream').perform();
+          throw error;
+        }
+      );
   }),
 
   head: task(function*() {
@@ -100,5 +114,8 @@ export default Component.extend(WindowResizable, {
         this.get('stream').perform();
       }
     },
+    failoverToServer() {
+      this.set('useServer', true);
+    },
   },
 });

ui/app/utils/classes/log.js

@@ -1,3 +1,4 @@
+import Ember from 'ember';
 import { alias } from '@ember/object/computed';
 import { assert } from '@ember/debug';
 import Evented from '@ember/object/evented';
@@ -10,6 +11,8 @@ import PollLogger from 'nomad-ui/utils/classes/poll-logger';
 
 const MAX_OUTPUT_LENGTH = 50000;
 
+export const fetchFailure = url => () => Ember.Logger.warn(`LOG FETCH: Couldn't connect to ${url}`);
+
 const Log = EmberObject.extend(Evented, {
   // Parameters
 
@@ -74,9 +77,9 @@ const Log = EmberObject.extend(Evented, {
     const url = `${this.get('url')}?${queryParams}`;
 
     this.stop();
-    let text = yield logFetch(url).then(res => res.text());
+    let text = yield logFetch(url).then(res => res.text(), fetchFailure(url));
 
-    if (text.length > MAX_OUTPUT_LENGTH) {
+    if (text && text.length > MAX_OUTPUT_LENGTH) {
       text = text.substr(0, MAX_OUTPUT_LENGTH);
       text += '\n\n---------- TRUNCATED: Click "tail" to view the bottom of the log ----------';
     }
@@ -96,7 +99,7 @@ const Log = EmberObject.extend(Evented, {
     const url = `${this.get('url')}?${queryParams}`;
 
     this.stop();
-    let text = yield logFetch(url).then(res => res.text());
+    let text = yield logFetch(url).then(res => res.text(), fetchFailure(url));
 
     this.set('tail', text);
     this.set('logPointer', 'tail');

ui/app/utils/classes/poll-logger.js

@@ -1,6 +1,7 @@
 import EmberObject from '@ember/object';
 import { task, timeout } from 'ember-concurrency';
 import AbstractLogger from './abstract-logger';
+import { fetchFailure } from './log';
 
 export default EmberObject.extend(AbstractLogger, {
   interval: 1000,
@@ -18,7 +19,14 @@ export default EmberObject.extend(AbstractLogger, {
   poll: task(function*() {
     const { interval, logFetch } = this.getProperties('interval', 'logFetch');
     while (true) {
-      let text = yield logFetch(this.get('fullUrl')).then(res => res.text());
+      const url = this.get('fullUrl');
+      let response = yield logFetch(url).then(res => res, fetchFailure(url));
+
+      if (!response) {
+        return;
+      }
+
+      let text = yield response.text();
 
       if (text) {
         const lines = text.replace(/\}\{/g, '}\n{').split('\n');

ui/app/utils/classes/stream-logger.js

@@ -2,6 +2,7 @@ import EmberObject, { computed } from '@ember/object';
 import { task } from 'ember-concurrency';
 import TextDecoder from 'nomad-ui/utils/classes/text-decoder';
 import AbstractLogger from './abstract-logger';
+import { fetchFailure } from './log';
 
 export default EmberObject.extend(AbstractLogger, {
   reader: null,
@@ -30,7 +31,11 @@ export default EmberObject.extend(AbstractLogger, {
     let buffer = '';
 
     const decoder = new TextDecoder();
-    const reader = yield logFetch(url).then(res => res.body.getReader());
+    const reader = yield logFetch(url).then(res => res.body.getReader(), fetchFailure(url));
+
+    if (!reader) {
+      return;
+    }
 
     this.set('reader', reader);
 

ui/tests/integration/task-log-test.js

@@ -26,30 +26,33 @@ let streamPointer = 0;
 moduleForComponent('task-log', 'Integration | Component | task log', {
   integration: true,
   beforeEach() {
+    const handler = ({ queryParams }) => {
+      const { origin, offset, plain, follow } = queryParams;
+
+      let frames;
+      let data;
+
+      if (origin === 'start' && offset === '0' && plain && !follow) {
+        frames = logHead;
+      } else if (origin === 'end' && plain && !follow) {
+        frames = logTail;
+      } else {
+        frames = streamFrames;
+      }
+
+      if (frames === streamFrames) {
+        data = queryParams.plain ? frames[streamPointer] : logEncode(frames, streamPointer);
+        streamPointer++;
+      } else {
+        data = queryParams.plain ? frames.join('') : logEncode(frames, frames.length - 1);
+      }
+
+      return [200, {}, data];
+    };
+
     this.server = new Pretender(function() {
-      this.get(`http://${HOST}/v1/client/fs/logs/:allocation_id`, ({ queryParams }) => {
-        const { origin, offset, plain, follow } = queryParams;
-
-        let frames;
-        let data;
-
-        if (origin === 'start' && offset === '0' && plain && !follow) {
-          frames = logHead;
-        } else if (origin === 'end' && plain && !follow) {
-          frames = logTail;
-        } else {
-          frames = streamFrames;
-        }
-
-        if (frames === streamFrames) {
-          data = queryParams.plain ? frames[streamPointer] : logEncode(frames, streamPointer);
-          streamPointer++;
-        } else {
-          data = queryParams.plain ? frames.join('') : logEncode(frames, frames.length - 1);
-        }
-
-        return [200, {}, data];
-      });
+      this.get(`http://${HOST}/v1/client/fs/logs/:allocation_id`, handler);
+      this.get('/v1/client/fs/logs/:allocation_id', handler);
     });
   },
   afterEach() {
@@ -174,3 +177,27 @@ test('Clicking stderr switches the log to standard error', function(assert) {
     );
   });
 });
+
+test('When the client is inaccessible, task-log falls back to requesting logs through the server', function(assert) {
+  run.later(run, run.cancelTimers, 2000);
+
+  // override client response to timeout
+  this.server.get(`http://${HOST}/v1/client/fs/logs/:allocation_id`, () => [400, {}, ''], 2000);
+
+  this.setProperties(commonProps);
+  this.render(hbs`{{task-log allocation=allocation task=task}}`);
+
+  const clientUrlRegex = new RegExp(`${HOST}/v1/client/fs/logs/${commonProps.allocation.id}`);
+  assert.ok(
+    this.server.handledRequests.filter(req => clientUrlRegex.test(req.url)).length,
+    'Log request was initially made directly to the client'
+  );
+
+  return wait().then(() => {
+    const serverUrl = `/v1/client/fs/logs/${commonProps.allocation.id}`;
+    assert.ok(
+      this.server.handledRequests.filter(req => req.url.startsWith(serverUrl)).length,
+      'Log request was later made to the server'
+    );
+  });
+});