Add new advanced docs page on manual sharding

guides/advanced/manual_sharding.md

@@ -0,0 +1,26 @@
+# Manual Sharding
+
+Advanced users can use methods located in the `Nostrum.Shard.Supervisor` module
+to manually connect shards to the gateway as well as initiate manual disconnect
+and reconnects (attempting to `RESUME` sessions where possible).
+
+You can set the `num_shards` option in your `nostrum` application config to
+`:manual` to prevent Nostrum from automatically starting shards. You should use
+the methods in the shard supervisor such as `Nostrum.Shard.Supervisor.connect/2`
+to manually start shards if using this configuration option.
+
+## Reconnection example
+
+```elixir
+# On Node A
+iex> Nostrum.Shard.Supervisor.connect(0, 1)
+iex> resume_info = Nostrum.Shard.Supervisor.disconnect(0)
+%{shard_num: 0, ...}
+
+# On another node
+iex> Nostrum.Shard.Supervisor.reconnect(resume_info)
+```
+
+Discord will perform a best effort attempt to resume the gateway from the time
+of disconnection, relaying any missed events. Note that this can result in some
+events being missed or some events being delivered twice.

mix.exs

@@ -82,6 +82,7 @@ defmodule Nostrum.Mixfile do
       "guides/advanced/multi_node.md",
       "guides/advanced/hot_code_upgrade.md",
       "guides/advanced/gateway_compression.md",
+      "guides/advanced/manual_sharding.md",
       "guides/cheat-sheets/api.cheatmd",
       "guides/cheat-sheets/qlc.cheatmd",
       "guides/cheat-sheets/voice.cheatmd"