Lingo.Gateway.SessionStore behaviour (Lingo v0.4.2)

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Keeps gateway sessions across restarts of the whole bot, so a redeployed bot resumes its shards instead of identifying them again.

Shards that crash or restart while the bot runs always resume; a store is only needed to carry sessions over a full stop. Give one with the :gateway option:

gateway: [session_store: {Lingo.Gateway.SessionStore.File, path: "sessions.bin"}]

The bot calls load/2 once when it starts. It calls save/3 for a shard whenever its session starts or resumes, and for every shard when the bot stops, after they've closed, with their last sequence numbers; and delete/4 when a session can't be resumed anymore. Discord keeps a session resumable for only a few minutes after its connection drops, and replays the events missed in between.

Calls come from one process per bot, one at a time, never from the shards themselves, so a slow store doesn't hold up the gateway. A store that raises is logged and otherwise ignored. Each shard is saved on its own, so the nodes of a bot split across several (see Lingo.Gateway) can share a store without overwriting each other's sessions; when they do, each node loads only the sessions of its own :ids.

A resumed session doesn't send GUILD_CREATE again, so a cache that starts empty stays without the guilds it already had: use a store with caching off, or when that's acceptable (Lingo warns when both are on).

Summary

Types

session()

One shard's session.

Callbacks

delete(bot, shard_id, shard_count, opts)

Forgets a shard's session.

load(bot, opts)

Returns the sessions saved for the bot named bot.

save(bot, session, opts)

Saves one shard's session, replacing the one saved for that shard before.

Types

session()

@type session() :: %{
  shard_id: non_neg_integer(),
  shard_count: pos_integer(),
  session_id: String.t(),
  resume_gateway_url: String.t(),
  seq: non_neg_integer()
}

One shard's session.

Callbacks

delete(bot, shard_id, shard_count, opts)

@callback delete(
  bot :: term(),
  shard_id :: non_neg_integer(),
  shard_count :: pos_integer(),
  opts :: keyword()
) :: :ok

Forgets a shard's session.

load(bot, opts)

@callback load(bot :: term(), opts :: keyword()) :: [session()]

Returns the sessions saved for the bot named bot.

save(bot, session, opts)

@callback save(bot :: term(), session(), opts :: keyword()) :: :ok

Saves one shard's session, replacing the one saved for that shard before.