Blank screen failure caused by inaccessible remote zqd

[philrz]

This issue was originally identified by @orochford. My repro is using GA Brim tagged v0.18.0 talking to GA zqd tagged v0.22.0.

First I need to start a remote zqd and populate it with a Space. In my case I started Brim in a Linux VM in VirtualBox and imported a pcap. I used ps to grab the zqd command line that Brim had started, then quit the app and restarted zqd standalone by modifying the command line to drop the localhost from the -l parameter and remove the -brimfd from the end. Hence:

/usr/lib/brim/resources/app/zdeps/zqd listen -l :9867 -data /home/phil/.config/Brim/data/spaces -config /home/phil/.config/Brim/zqd-config.yaml -zeekrunner /usr/lib/brim/resources/app/zdeps/zeek/zeekrunner

I have a port forwarding rule configured in VirtualBox such that localhost:9999 gets forwarded to port 9867 in the VM.

Now from the local Brim desktop on my Mac, I connect successfully to the remote zqd via localhost:9999, click the Space name to see its contents, then quit the app.

Now I stop the remote zqd and relaunch the app. I get the white screen with DevTools console showing:

[philrz]

In a group discussion today it was noted that this class of "blank screen" issues would ideally be addressed by changing the app's behavior such that it doesn't touch the network until after the app is fully rendered. This would allow for operations such as deleting the config for a Connection that's gone forever. If the fix for this particular issue does not cover the general case, I'll open a new issue at the same time this one gets closed as a reminder to cover that general case.

[philrz]

Verified in Brim commit a563c51 talking to zqd commit e26ffa3.

Following the original repro steps as shown in the attached video, now after I quit my Brim app and restart it after stopping the remote zqd, instead of a white screen I'm shown a "Connection Error" screen along with a message "Unable to connect to service" in the Space picker. I can click to my functioning local zqd without a problem. I can also click the "Retry" button and witness the spinner & failed attempt if it's still down (shown here) or if it's back up it will successfully reconnect and show the Space contents (tested, but not captured in the video).

Verify.mov.zip

Thanks @mason-fish!