Fix race condition where stdout and stderr requests can cause a no co…

…nnection error

This would happen because a no connection error happens after the second request fails, but
that's because it's assumed the second request is to a server node. However, if a user clicks
stderr fast enough, the first and second requests are both to the client node. This changes
the logic to check if the request is to the server before deeming log streaming a total failure.

ui/app/components/task-log.js

@@ -55,6 +55,10 @@ export default Component.extend({
     // AbortControllers don't exist in IE11, so provide a mock if it doesn't exist
     const aborter = window.AbortController ? new AbortController() : new MockAbortController();
     const timing = this.useServer ? this.serverTimeout : this.clientTimeout;
+
+    // Capture the state of useServer at logger create time to avoid a race
+    // between the stdout logger and stderr logger running at once.
+    const useServer = this.useServer;
     return url =>
       RSVP.race([
         this.token.authorizedRequest(url, { signal: aborter.signal }),
@@ -65,7 +69,7 @@ export default Component.extend({
         },
         error => {
           aborter.abort();
-          if (this.useServer) {
+          if (useServer) {
             this.set('noConnection', true);
           } else {
             this.send('failoverToServer');

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

@@ -280,4 +280,49 @@ module('Integration | Component | task log', function(hooks) {
     );
     assert.ok(find('[data-test-connection-error]'), 'An error message is shown');
   });
+
+  test('When the client is inaccessible, the server is accessible, and stderr is pressed before the client timeout occurs, the no connection error is not shown', async function(assert) {
+    // override client response to timeout
+    this.server.get(
+      `http://${HOST}/v1/client/fs/logs/:allocation_id`,
+      () => [400, {}, ''],
+      allowedConnectionTime * 2
+    );
+
+    // Click stderr before the client request responds
+    run.later(() => {
+      click('[data-test-log-action="stderr"]');
+      run.later(run, run.cancelTimers, commonProps.interval * 5);
+    }, allowedConnectionTime / 2);
+
+    this.setProperties(commonProps);
+    await render(hbs`{{task-log
+      allocation=allocation
+      task=task
+      clientTimeout=clientTimeout
+      serverTimeout=serverTimeout}}`);
+
+    await settled();
+
+    const clientUrlRegex = new RegExp(`${HOST}/v1/client/fs/logs/${commonProps.allocation.id}`);
+    const clientRequests = this.server.handledRequests.filter(req => clientUrlRegex.test(req.url));
+    assert.ok(
+      clientRequests.find(req => req.queryParams.type === 'stdout'),
+      'Client request for stdout'
+    );
+    assert.ok(
+      clientRequests.find(req => req.queryParams.type === 'stderr'),
+      'Client request for stderr'
+    );
+
+    const serverUrl = `/v1/client/fs/logs/${commonProps.allocation.id}`;
+    assert.ok(
+      this.server.handledRequests
+        .filter(req => req.url.startsWith(serverUrl))
+        .find(req => req.queryParams.type === 'stderr'),
+      'Server request for stderr'
+    );
+
+    assert.notOk(find('[data-test-connection-error]'), 'An error message is shown');
+  });
 });