Lettura/scrittura da un socket Unix in Ruby

Question

Sto provando a connettermi, leggere e scrivere da un socket UNIX in Ruby. È una presa di stats usata da haproxy.

Il mio codice è il seguente:

require 'socket' 
socket = UNIXSocket.new("/tmp/haproxy.stats.socket") 

# First attempt: works 

socket.puts("show stat") 

while(line = socket.gets) do 
    puts line 
end 

# Second attemp: fails 

socket.puts("show stat") 

while(line = socket.gets) do 
    puts line 
end 

Riesce la prima volta, ma al secondo tentativo fallisce. Non sono sicuro del perché.

# pxname,svname,qcur,qmax,scur,smax,slim,stot,bin,bout,dreq,dresp,ereq,econ,eresp,wretr,wredis,status,weight,act,bck,chkfail,chkdown,lastchg,downtime,qlimit,pid,iid,sid,throttle,lbtot,tracked,type,rate,rate_lim,rate_max,check_status,check_code,check_duration,hrsp_1xx,hrsp_2xx,hrsp_3xx,hrsp_4xx,hrsp_5xx,hrsp_other,hanafail,req_rate,req_rate_max,req_tot,cli_abrt,srv_abrt, 
stats,FRONTEND,,,0,0,2000,0,0,0,0,0,0,,,,,OPEN,,,,,,,,,1,1,0,,,,0,0,0,0,,,,0,0,0,0,0,0,,0,0,0,,, 
stats,BACKEND,0,0,0,0,2000,0,0,0,0,0,,0,0,0,0,UP,0,0,0,,0,22,0,,1,1,0,,0,,1,0,,0,,,,0,0,0,0,0,0,,,,,0,0, 
legacy_socket,FRONTEND,,,0,0,1000,0,0,0,0,0,0,,,,,OPEN,,,,,,,,,1,2,0,,,,0,0,0,0,,,,0,0,0,0,0,0,,0,0,0,,, 
all,FRONTEND,,,0,0,10000,0,0,0,0,0,0,,,,,OPEN,,,,,,,,,1,3,0,,,,0,0,0,0,,,,0,0,0,0,0,0,,0,0,0,,, 
socket_backend,socket,0,0,0,0,200,0,0,0,,0,,0,0,0,0,DOWN,1,1,0,0,1,22,22,,1,4,1,,0,,2,0,,0,L4CON,,0,0,0,0,0,0,0,0,,,,0,0, 
socket_backend,socket,0,0,0,0,200,0,0,0,,0,,0,0,0,0,DOWN,1,1,0,0,1,22,22,,1,4,2,,0,,2,0,,0,L4CON,,0,0,0,0,0,0,0,0,,,,0,0, 
socket_backend,socket,0,0,0,0,200,0,0,0,,0,,0,0,0,0,DOWN,1,1,0,0,1,22,22,,1,4,3,,0,,2,0,,0,L4CON,,0,0,0,0,0,0,0,0,,,,0,0, 
socket_backend,socket,0,0,0,0,200,0,0,0,,0,,0,0,0,0,DOWN,1,1,0,0,1,22,22,,1,4,4,,0,,2,0,,0,L4CON,,0,0,0,0,0,0,0,0,,,,0,0, 
socket_backend,socket,0,0,0,0,200,0,0,0,,0,,0,0,0,0,DOWN,1,1,0,0,1,22,22,,1,4,5,,0,,2,0,,0,L4CON,,0,0,0,0,0,0,0,0,,,,0,0, 
socket_backend,socket,0,0,0,0,200,0,0,0,,0,,0,0,0,0,DOWN,1,1,0,0,1,22,22,,1,4,6,,0,,2,0,,0,L4CON,,0,0,0,0,0,0,0,0,,,,0,0, 
socket_backend,socket,0,0,0,0,200,0,0,0,,0,,0,0,0,0,DOWN,1,1,0,0,1,22,22,,1,4,7,,0,,2,0,,0,L4CON,,0,0,0,0,0,0,0,0,,,,0,0, 
socket_backend,socket,0,0,0,0,200,0,0,0,,0,,0,0,0,0,DOWN,1,1,0,0,1,21,21,,1,4,8,,0,,2,0,,0,L4CON,,0,0,0,0,0,0,0,0,,,,0,0, 
socket_backend,socket,0,0,0,0,200,0,0,0,,0,,0,0,0,0,DOWN,1,1,0,0,1,21,21,,1,4,9,,0,,2,0,,0,L4CON,,0,0,0,0,0,0,0,0,,,,0,0, 
socket_backend,socket,0,0,0,0,200,0,0,0,,0,,0,0,0,0,DOWN,1,1,0,0,1,21,21,,1,4,10,,0,,2,0,,0,L4CON,,0,0,0,0,0,0,0,0,,,,0,0, 
socket_backend,BACKEND,0,0,0,0,0,0,0,0,0,0,,0,0,0,0,DOWN,0,0,0,,1,21,21,,1,4,0,,0,,1,0,,0,,,,0,0,0,0,0,0,,,,,0,0, 
api_backend,api,0,0,0,0,200,0,0,0,,0,,0,0,0,0,UP,1,1,0,0,0,22,0,,1,5,1,,0,,2,0,,0,L4OK,,0,0,0,0,0,0,0,0,,,,0,0, 
api_backend,api,0,0,0,0,1,0,0,0,,0,,0,0,0,0,UP,1,1,0,0,0,22,0,,1,5,2,,0,,2,0,,0,L4OK,,0,0,0,0,0,0,0,0,,,,0,0, 
api_backend,api,0,0,0,0,1,0,0,0,,0,,0,0,0,0,DOWN,1,1,0,0,1,21,21,,1,5,3,,0,,2,0,,0,L4CON,,0,0,0,0,0,0,0,0,,,,0,0, 
api_backend,BACKEND,0,0,0,0,0,0,0,0,0,0,,0,0,0,0,UP,2,2,0,,0,22,0,,1,5,0,,0,,1,0,,0,,,,0,0,0,0,0,0,,,,,0,0, 
www_backend,ruby-www,0,0,0,0,10000,0,0,0,,0,,0,0,0,0,UP,1,1,0,0,0,22,0,,1,6,1,,0,,2,0,,0,L4OK,,0,0,0,0,0,0,0,0,,,,0,0, 
www_backend,BACKEND,0,0,0,0,0,0,0,0,0,0,,0,0,0,0,UP,1,1,0,,0,22,0,,1,6,0,,0,,1,0,,0,,,,0,0,0,0,0,0,,,,,0,0, 

/Users/Olly/Desktop/haproxy_stats.rb:14:in `write': Broken pipe (Errno::EPIPE) 
    from /Users/Olly/Desktop/haproxy_stats.rb:14:in `puts' 
    from /Users/Olly/Desktop/haproxy_stats.rb:14 

Qual è il problema? C'è un buon riferimento all'uso dei socket UNIX e di Ruby?

Answer 1

Sembra che la connessione sia stata chiusa dopo la prima richiesta. Non penso che tu stia facendo qualcosa di sbagliato. Il socket delle statistiche HAProxy è probabilmente progettato in modo che risponda a un singolo comando e quindi chiuda la connessione.

Penso che sia necessario riconnettersi per ogni richiesta.

Se si guarda a this blog post che è sull'utilizzo HAProxy presa di statistiche con socat allora questo ha un senso perchè si reindirizza il comando show stat in socat e socat legge dalla presa fino a che non si chiude.

Answer 2

È possibile utilizzare la presa uomo. Puoi usare la classe socket proprio come faresti se fosse una funzione C.

Ho trovato pagine di manuale molto utili.

Answer 3

Olly,

HAproxy chiude la connessione dopo la prima richiesta a meno che non si utilizza il comando "prompt" (vedi http://haproxy.1wt.eu/download/1.4/doc/configuration.txt la sezione 9.2):

#!/usr/bin/env ruby                               

require 'socket'                                

socket = UNIXSocket.new("/tmp/haproxy.stats.socket")                        

# Goes interactive mode 
socket.puts("prompt")                              

# Ask statistics every second                                
while true                                 
    socket.puts("show stat")                             
    socket.each_char do |c| 
    # We had the prompt, break out                         
    break if c == '>'                              
    print c                                 
    end                                  

    sleep 1                                 
end    

Answer 4

Ho anche incontrato lo stesso problema quando uso socket.puts, è possibile utilizzare socket.write anziché socket.puts per risolvere il problema.

#!/usr/bin/evn ruby 
# -*- coding: UTF-8 -*- 

require 'rubygems' 
require 'uri' 
require 'socket' 
require 'yaml' 

SOCKET = URI.parse("/var/run/haproxy/haproxy.sock") 

def get_info 
    UNIXSocket.open(SOCKET.path) do |socket| 
    socket.write("show info;") 
    info = YAML::load socket 
    #info.each {|key, value| puts "#{key} ➤ #{value}"} 
    end 
end 

puts get_info["Uptime_sec"] 

Guardate questo gem per ulteriori informazioni, il codice sorgente è here.