Phoenix.Tracker desync after connecting to node

[szlend]

When Phoenix.Tracker nodes connect for the first time, and boths nodes already hold presences, their state will not merge correctly.

Steps to reproduce

Pull https://github.com/szlend/tracker_test

Node 1

iex --sname n1 --cookie test -S mix

for n <- 1..51, do: Phoenix.Tracker.track(TrackerTest.Tracker, self(), "test", "#{inspect Node.self()}_#{n}", %{})

Node 2

iex --sname n2 --cookie test -S mix

for n <- 1..51, do: Phoenix.Tracker.track(TrackerTest.Tracker, self(), "test", "#{inspect Node.self()}_#{n}", %{})

Node.connect :"n1@your_hostname"

Both nodes

Wait a while for Phoenix.Tracker to do it's thing, then:

Phoenix.Tracker.list(TrackerTest.Tracker, "test") |> Enum.count

# Node 1
> 51

# Node 2
> 102

I can only reproduce this issue when the number of tracked presences is above 50 on each node. Looking at the debug logs, I can see one difference:

When N > 50, I get:

sending delta generation 1

When N <= 50, I get:

falling back to sending entire crdt

[chrismccord]

Thanks for the report! I will try to reproduce this and see what's going on. I have some higher item priorities to take care of first so it may take some time for me to get to this one.

[chrismccord]

@szlend I believe I've patched this issue on the cm-clouds branch. If you have time to test it out on your app under the scenarios that caused your issues, that would be extremely appreciated. Thanks!

#80

{:phoenix_pubsub, github: "phoenixframework/phoenix", branch: "cm-clouds", override: true}

[szlend]

@chrismccord This is still an issue onphoenixframework/phoenix_pubsub branch cm-clouds. Tested with the exact same steps as before.

[chrismccord]

@szlend thanks for following up! I just pushed an additional fixed for your issue. Can you retry and report back? Thanks!

[szlend]

@chrismccord Awesome, it's working now. Thanks!

[chrismccord]

I have pushed v1.0.2 with this fix. Thanks!