Question regarding maxclients param

[badraxas]

Hi, is this parameter compatible with memcached?

I'm trying to set this parameter to 1, but I can still open as many connections as I want:

  memcached:
    image: docker.dragonflydb.io/dragonflydb/dragonfly
    command: --memcached_port=11211 --cluster_mode=emulated --maxclients=1
    ports:
      - "11211:11211"
    networks:
      - network

[chakaz]

While we do support --maxclients, it's a (very) rough lower limit to how many real clients can connect. Since we use file descriptors internally, and in the limit we do not distinguish between sockets and other FDs, we don't have a real tight limit:
https://github.com/romange/helio/blob/master/util/fibers/listener_interface.cc#L398
So if you set it to 1 you will definitely not have more than 151 clients, but in reality it depends on how many threads and other operations that your server is doing (like replication, save to file, etc).

[romange]

Shahar, from reading the code, I do not think it's because of it.we just set max_clients_ right at the start.

…

On Tue, Apr 30, 2024, 9:08 PM Shahar Mike ***@***.***> wrote: While we do support --maxclients, it's a (very) rough lower limit to how many real clients can connect. Since we use file descriptors internally, and in the limit we do not distinguish between sockets and other FDs, we don't have a real tight limit: https://github.com/romange/helio/blob/master/util/fibers/listener_interface.cc#L398 So if you set it to 1 you will definitely not have more than 151 clients, but in reality it depends on how many threads and other operations that your server is doing (like replication, save to file, etc). — Reply to this email directly, view it on GitHub <#2978 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AA4BFCCOLSQC6YEACQ6B7TTY77MYDAVCNFSM6AAAAABHACQS52VHI2DSMVQWIX3LMV43SRDJONRXK43TNFXW4Q3PNVWWK3TUHM4TENZYGQ4TK> . You are receiving this because you are subscribed to this thread.Message ID: ***@***.*** com>

[chakaz]

Shahar, from reading the code, I do not think it's because of it.we just set max_clients_ right at the start.

Reading the code I linked to above, indeed it seems to only try to increase the limit and not decrease it:
https://github.com/romange/helio/blob/3545a85fcaff3e36a99db6fbc91c6e51e0280f14/util/fibers/listener_interface.cc#L407-L414

Roman, is that what you meant above? (I didn't understand your message)

[chakaz]

Thanks Roman for heading me in the right direction. I was mistaken in my above comments, sorry :)
This is indeed a bug in Dragonfly. I filed #2986 for that.