tcpsock:setkeepalive

Hello, I'm trying to deal with websockets and want to set unlimited keepalive to socket. In nginx.conf lua_socket_keepalive_timeout 180m; does not affect. In code sock:settimeout works well, but sock:setkeepalive says, that there is not such method in sock, i.e sock:setkeepalive == nil. Why? Pleese write in docs what is maximum timeout. Thanks for great work!

[agentzh]

@Romaboy Please ensure your ngx_lua module or OpenResty is up to date. If it is indeed the latest, please provide a self-contained and minimal example that we can easily reproduce the issue on our side. Thank you.

I had updated everything this morning, so I'm very and very happy that now can control pub/sub with semaphore. 3 hours of timeout is quite enough. But setkeepalive wasn't appear. In "content_by_lua" (moonscript):
print require('inspect') ngx.req.socket true
describes this table as:
{
<userdata 1>,
= <1>{
__index = <table 1>,
receive = <function 1>,
receiveuntil = <function 2>,
send = <function 3>,
settimeout = <function 4>
}
}

[agentzh]

@Romaboy Okay, I see what is going on here. There is no setkeepalive for downstream cosockets. The NGINX core handles downstream keepalive according to the HTTP protocol automatically.

@agentzh User subscribe to some channel, and new message in channel will be appear in any moment, maybe after hour, maybe won't appeat at all, so how is it possible to open suitable socket "upstream" with setkeepalive? Would be good to write few words in docks about 'downstream", "upstream", cause it's little confusing.

No, maybe problem is that I read not very carefully or bad english undestending, there is someting about downstream.

[agentzh]

@Romaboy These are nginx terms. "downstream" means the direction towards the client side while "upstream" means the direction towards backend (or origin).

@agentzh I've been thinking for long time how to do usable websockets among several workers and now have idea! What if get data from downstream such as user IP and other necessary data, then convert it into string (json or just separate with comma) and save into shared.dict, then in another request when some db row is added or changed check for subscribers in that shared dict, for each of those create ngx.socket.tcp (that is upstream, as I understood) with those saved IPs and send changed rows to subscribers? How do you think, is it possible? Another words, is it possible to fill ngx.socket.tcp with data from downstream only using lua primitives?

[agentzh]

@Romaboy I think you need ngx.semaphore for this:

https://github.com/openresty/lua-resty-core/blob/master/lib/ngx/semaphore.md#readme

@agentzh yes, I had made chat with semphores, that was small victory, but want some more: such chat won't be run with few workers, and if there is eight CPU on server only one would be run, it's confusing... Now I see only two ways: 1) somehow deserialize connection into string, save to dict and then serialize it into new connection on other requests. But seems that is impossible
2) Save changed data with channel to dict and then somehow ask all workers to read them and send to subscribers. Maybe it's possible to iterate workers? I don't understand why there are ngx.worker.pid, ngx.worker.count, ngx.worker.id if there is no way to use them for iteration. Or switching. Or tie one location to one worker. I think bridge between them would be very important feature for whole project.

[agentzh]

@Romaboy There are two approaches here for inter-worker synchronization:

1. use the shared memory queues to dispatch messages across nginx workers: feature: add api in shdict: lpush, lpop, rpush, rpop, llen #586

   This feature is expected to get merged into the mainline version soon. Each worker can have a background light thread (initiated by init_worker_by_lua + ngx.timer.at) that repeatedly dispatch messages between the current worker and the shared queues.

2. use cosocket's listen() and accept() APIs to allow each worker to listen on a different unix domain socket. And the workers can talk to each other through such local socket pairs directly. And I know a developer is actively working on the listen() and accept() methods right now.

Hope it helps.

@agentzh

Each worker can have a background light thread (initiated by init_worker_by_lua + ngx.timer.at) that repeatedly dispatch messages between the current worker and the shared queues.

while true do *check dict* end
infinite loop, okay, best solution for now