lua-long-polling

A simple long-polling server (and client) written in Lua.

source: javascript.info

Features:

• Can be used to deliver messages to multiple clients at the same time.
• Tested in a production environment
• docker ready
• You can specify predefined parameters to be added to each update object, which is useful when you want to recognize different services that send updates to the same link.
• Ability to customize the amount of data stored and the storage time (for redis) so that no garbage is stored

Uses:

• In environments where it is not possible to create a web server (e.g. in a Garry's Mod game), but getting "webhooks" is necessary
• As a single point of collecting webhooks, for example to get updates from all your Telegram bots with just one request. To do this, make https://api.telegram.org/bot$TOKEN/setWebhook?url=https://your.app/SomeS3cretP@th?this_key=and_value&will_be=merged_with_updates_sent_by_telegram&botname=some_id.
• Simple chat-like services implementations

Server API:

• GET http://your.app/anySecretPath?ts=0&sleep=10, where ts is the last update id you received from polling server. Take it as an offset. The sleep parameter is the timeout during which the connection will be kept open until a new update is available. If an update arrives within this timeout, the connection will be immediately closed with the new update in the response in the following format: {ts = 123, ok = true, updates = {your_update}}
• POST --type application/json --data {"a": "b"} http://your.app/anySecretPath?merge=me. The final update will looks like this: {"a": "b", "merge": "me"}

No authorization. With API features in mind, you can use your server as a public API, because no one client will be able to get the other's data without knowing its "secret path". It's like in blockchain.

Pro tip: If you want to use Traefik as web proxy (nginx is fine without it), you may need to configure maxIdleConnsPerHost=-1 as Traefik has a limit of active connections and disconnects the excess ones with error 500

👀 Test server: poll.def.pm. But please, don't use it in production because I can turn it off at any moment.

Usage:

# run server via docker-compose.yml
docker-compose up

# run server via docker run
docker run --env-file .env -p 3000:3000 ghcr.io/trigonim/lua-long-polling:latest

# or

# use as lib for your own server implementations
luarocks install lua-long-polling
# then (server):
# local dataprovider_obj = require("long-polling.dataproviders.localtable").new()
# local longpolling = require("long-polling").new(dataprovider_obj)
# or (client):
# local kupol = require("long-polling.client")
# local polling = kupol.new("https://poll.def.pm")
# polling:subscribe(function(updtbl) print(updtbl.key) end, nil, 30)
# polling:publish({key = "value"})

Available ENV variables for server creation

All available vars are listed in .env-example

Local development

• luarocks install lua-express
• luarocks install copas
• luarocks install lua-cjson
• luarocks install redis-lua [optional. Only if you want to use the redis dataprovider]
• git clone this rep && cd rep
• lua init.lua
• or
• docker build -t lp:latest .
• docker run --env-file .env -p 3000:3000 -v $PWD/:/app lp:latest
• or just
• docker run --env-file .env -p 3000:3000 -v $PWD/:/app ghcr.io/trigonim/lua-long-polling:latest

TODO:

• Move out redis-safe into separate repo
• Create the mysql dataprovider, using luasocket-mysql driver
• Also create the filesystem dataprovider