It is well known that UNIX sockets are faster than TCP over loopback.
E.g. on my machine according to lmbench[1] they have ~ 2 times
lower latency and ~ 2-3 times more throughput compared to TCP over
loopback:
*Local* Communication latencies in microseconds - smaller is better
---------------------------------------------------------------------
Host OS 2p/0K Pipe AF UDP RPC/ TCP RPC/ TCP
ctxsw UNIX UDP TCP conn
--------- ------------- ----- ----- ---- ----- ----- ----- ----- ----
teco Linux 4.2.0-1 13.8 29.2 26.8 45.0 47.9 48.5 55.5 45.
*Local* Communication bandwidths in MB/s - bigger is better
-----------------------------------------------------------------------------
Host OS Pipe AF TCP File Mmap Bcopy Bcopy Mem Mem
UNIX reread reread (libc) (hand) read write
--------- ------------- ---- ---- ---- ------ ------ ------ ------ ---- -----
teco Linux 4.2.0-1 1084 4353 1493 2329.1 3720.7 1613.8 1109.2 3402 1404.
The same ratio usually holds for servers.
Also UNIX sockets, since they reside on filesystem, besides being faster with
less latency, have one another nice property: access permissions to them are
managed the same way access to files is.
Because of lower latencies and higher throughput - for performance reasons, and
for easier security, it makes sense to interconnect services on one machine via
UNIX sockets and talk via TCP only to outside world.
All internal services inside GitLab can talk to each other via UNIX socket
already and only gitlab-shell was missing support to talk to Unicorn via UNIX
socket.
Let's teach gitlab-shell to talk via UNIX sockets.
[1] http://www.bitmover.com/lmbench/
~~~~
In this patch we
- add URI::HTTPUNIX to handle http+unix:// URI scheme
- add Net::HTTPUNIX to handle "connect via unix socket and then talk http"
- adjust GitlabNet#http_client_for() accordingly
- adjust documentation in config.yml.example
The http+unix:// scheme is not reinvented anew: the idea about its structure is
quite logical an was already established at least in requests-unixsocket python
package:
http://fixall.online/theres-no-need-to-reinvent-the-wheelhttpsgithubcommsabramorequests-unixsocketurl/241810/
https://github.com/msabramo/requests-unixsocket