[cli] detect number of CPU cores

* use nproc to detect number of cores
  - nproc correctly detects limits set by docker

CHANGELOG.md

@@ -24,6 +24,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - Fix lua docs formatting in the CORS policy [PR #530](https://github.com/3scale/apicast/pull/530)
 - `post_action` phase not being called in the policy_chain [PR #539](https://github.com/3scale/apicast/pull/539)
 - Failing to execute `libexec/boot` on some systems [PR #544](https://github.com/3scale/apicast/pull/544)
+- Detect number of CPU cores in containers by using `nproc` [PR #554](https://github.com/3scale/apicast/pull/554)
 
 ## Changed
 

gateway/config/production.lua

@@ -1,5 +1,4 @@
 return {
-    worker_processes = 'auto',
     master_process = 'on',
     lua_code_cache = 'on',
 }

gateway/src/apicast/cli/command/start.lua

@@ -179,7 +179,7 @@ local function configure(cmd)
     cmd:flag("-d --daemon", "Daemonize.")
     cmd:option("-w --workers",
         "Number of worker processes to start.",
-        resty_env.value('APICAST_WORKERS') or 1)
+        resty_env.value('APICAST_WORKERS') or Environment.default_config.worker_processes)
     cmd:option("-p --pid", "Path to the PID file.")
     cmd:mutex(
         cmd:flag('-b --boot',

gateway/src/apicast/cli/environment.lua

@@ -6,6 +6,7 @@
 local pl_path = require('pl.path')
 local resty_env = require('resty.env')
 local linked_list = require('apicast.linked_list')
+local util = require('apicast.util')
 local setmetatable = setmetatable
 local loadfile = loadfile
 local pcall = pcall
@@ -40,6 +41,13 @@ local function parse_nameservers()
     end
 end
 
+local function cpus()
+    -- TODO: support /sys/fs/cgroup/cpuset/cpuset.cpus
+    -- see https://github.com/sclorg/rhscl-dockerfiles/blob/ff912d8764af9a41096e63064bbc325395afa608/rhel7.sti-base/bin/cgroup-limits#L55-L75
+    local nproc = util.system('nproc')
+    return tonumber(nproc)
+end
+
 
 local _M = {}
 ---
@@ -58,6 +66,7 @@ _M.default_config = {
     ca_bundle = resty_env.value('SSL_CERT_FILE'),
     policy_chain = require('apicast.policy_chain').default(),
     nameservers = parse_nameservers(),
+    worker_processes = cpus() or 'auto',
     package = {
         path = package.path,
         cpath = package.cpath,