Initiate Data Handshake on Reconnect

[PsychoLlama]

TL;DR: if you make changes when offline, they won't be propagated upon reconnection.

Gun version 0.3.998, the latest on npm.

Replicating the bug

In the examples folder, make some changes to allow other computers to connect:

todo/index.html

Naturally, localhost won't work from another computer.

// Line #14
-var gun = Gun(location.origin + '/gun');
+var gun = Gun('http://your-ip-address:8080/gun')

http.js

Allows other computers to connect via IP address.

// Line #28
-server.listen(port, ip);
+server.listen(port);

1. Open http://you-server-ip-address:8080/todo/index.html on two computers.
2. Add some todos, they should sync.
3. Take one computer offline and add some todos.
4. Take it back online and add more todos.
   You should notice that only the todos created while online were synced in real-time.
5. Refresh that browser, and the offline todos should (finally) replicate.

Props to @nevf for finding this bug!

[nevf]

@PsychoLlama Also note that todo's deleted while offline don't sync when back online.

[PsychoLlama]

@nevf thankfully that's part of the same problem, so both should be fixed at once 😅

Deletes in gun work by writing null to a field, meaning it operates on the same mechanics as writes. Fixing one should fix the other!

[PsychoLlama]

So in some cases, the websocket readyState isn't updated when the client goes offline. It seems the platform/browser combo I was testing on (chrome v54 on android) was just gracious.
The next solution that comes to mind is waiting for a server acknowledgment, but the websocket server doesn't give one (that I can tell).

[amark]

sounds like this was a great fix! Closing since the pull got merged. Please reopen if anything weird is going on.

[nevf]

@PsychoLlama @amark I've just got around to testing the latest master release "0.3.9991" and still am seeing much the same issues.

1. Start server on PC 1
2. Open Browser on PC 1 and on PC 2
3. Disable LAN on PC 1
4. Add 2 todo items on PC 1 and PC 2
5. Enable LAN on PC 1
6. PC 2 updates and shows all 4 todo items. PC1 only shows the items added therein.

I've also had issues where deleting a todo item when the LAN was disabled, which didn't update the other PC.

I'm using Win 10 on both PC's. PC 1 is on a Wired Network and PC 2 is connected via. WiFi. Chrome Version 54.0.2840.71 m

[amark]

@nevf, thanks. I had tried a similar variation the other day and it worked. We'll try to replicate and get back to you.

What's your project again? :)

[nevf]

@amark I'm not using Gun yet, just an interested bystander at this point. That said I've done a lot of database work including pushing updates out in real time using Websockets to Browsers in my Knowledge Base web app Clibu

Right now I'm especially interested in offline first, and the ability to use a fully fledged database app offline and then sync (resolving conflicts) when back online again. Which is part of the reason for testing gun in this scenario.

[PsychoLlama]

Hey @nevf, sorry not trying to hijack the conversation... in relation to the offline queuing issue, @amark helped me figure out how the websocket request/response model works in the browser, hopefully I can get a more robust fix out soon 😀

[nevf]

@PsychoLlama Great, look forward to giving it another work-out. FYI I've always been good at breaking things. ;-)

[PsychoLlama]

Haha, awesome @nevf! We need more users who break things, it helps us find the bugs :D