horde_behavior's Introduction

HordeBehavior

Repository that helps reproduce weird behaviour of Horde.Registry.

Problem: disappearing values from Horde.Registry after spawning more than two nodes.

Expected behavior: After adding more nodes, values in the Horde.Registry from all nodes will be synced without losing any value.

Elixir: 1.13.3
horde: 0.8.7

Reproduce:

start first node

  iex --sname node1@localhost --cookie foo -S mix

start second node

  iex --sname node2@localhost --cookie foo -S mix

check state of registry on node1 - should be two processes - one per node

  nodes = [node() | Node.list()]
  Enum.map(nodes, fn node -> Horde.Registry.lookup(Registry.State, node); end)
  [[{#PID<0.276.0>, nil}], [{#PID<19886.268.0>, nil}]]

start third node

  iex --sname node3@localhost --cookie foo -S mix

check state of registry on node1 - should be three processes but there are only two processes - first and last - the middle one disappearing

  nodes = [node() | Node.list()]
  Enum.map(nodes, fn node -> Horde.Registry.lookup(Registry.State, node); end)
  [[{#PID<0.276.0>, nil}], [], [{#PID<21155.273.0>, nil}]]

Notes

I checked google and I found two issues related to it, but reading that threads didn't help me :P But maybe I missed sth.

derekkraan/horde#116
https://elixirforum.com/t/horde-dynamicsupervisor-bypasses-registry/49562
I thought that processes are adding to Horde.Registry too fast, but adding Agents manually by command below didn't help, issue still occures.

Agent.start_link(fn -> 553 end, name: {:via,iex(node2@localhost)1> Agent.start_link(fn -> 553 end, name: {:via, Horde.Registry, {Registry.State, node()}})