refactor(cmd): use resty.signal for process signaling (#11382)

* refactor(cmd): rename kong.cmd.utils.kill => kong.cmd.utils.process

There's a large refactor of this module in the pipeline, and renaming
from 'kill' to 'process' makes the API more sensible.

* refactor(cmd): rename process.is_running => process.exists

This is another name-only change ahead of some larger refactoring of the
kong.cmd.utils.process module.

* refactor(cmd): use resty.signal for process signaling

This refactors kong.cmd.utils.process to use the resty.signal library
for sending signals instead of dropping to a shell.

This comes with improvements (albeit minor) to performance and security.

* chore(cmd): remove redundant process check

* tests(helpers): fix flaky http_mock PID file test

* chore(cmd): return error on signal sending failures

bin/kong-health

@@ -3,7 +3,7 @@
 setmetatable(_G, nil)
 package.path = (os.getenv("KONG_LUA_PATH_OVERRIDE") or "") .. "./?.lua;./?/init.lua;" .. package.path
 
-local kill = require "kong.cmd.utils.kill"
+local process = require "kong.cmd.utils.process"
 local kong_default_conf = require "kong.templates.kong_defaults"
 local pl_app = require "pl.lapp"
 local pl_config = require "pl.config"
@@ -42,8 +42,7 @@ local function execute(args)
 
   print("")
   local pid_file = pl_path.join(prefix, "pids", "nginx.pid")
-  kill.is_running(pid_file)
-  assert(kill.is_running(pid_file), "Kong is not running at " .. prefix)
+  assert(process.exists(pid_file), "Kong is not running at " .. prefix)
   print("Kong is healthy at ", prefix)
 end
 

kong-3.5.0-0.rockspec

@@ -116,7 +116,7 @@ build = {
     ["kong.cmd.version"] = "kong/cmd/version.lua",
     ["kong.cmd.hybrid"] = "kong/cmd/hybrid.lua",
     ["kong.cmd.utils.log"] = "kong/cmd/utils/log.lua",
-    ["kong.cmd.utils.kill"] = "kong/cmd/utils/kill.lua",
+    ["kong.cmd.utils.process"] = "kong/cmd/utils/process.lua",
     ["kong.cmd.utils.env"] = "kong/cmd/utils/env.lua",
     ["kong.cmd.utils.migrations"] = "kong/cmd/utils/migrations.lua",
     ["kong.cmd.utils.tty"] = "kong/cmd/utils/tty.lua",

kong/cmd/health.lua

@@ -1,5 +1,5 @@
 local log = require "kong.cmd.utils.log"
-local kill = require "kong.cmd.utils.kill"
+local process = require "kong.cmd.utils.process"
 local pl_path = require "pl.path"
 local pl_tablex = require "pl.tablex"
 local pl_stringx = require "pl.stringx"
@@ -26,7 +26,7 @@ local function execute(args)
 
   local count = 0
   for k, v in pairs(pids) do
-    local running = kill.is_running(v)
+    local running = process.exists(v)
     local msg = pl_stringx.ljust(k, 12, ".") .. (running and "running" or "not running")
     if running then
       count = count + 1

kong/cmd/quit.lua

@@ -1,7 +1,7 @@
 local nginx_signals = require "kong.cmd.utils.nginx_signals"
 local conf_loader = require "kong.conf_loader"
 local pl_path = require "pl.path"
-local kill = require "kong.cmd.utils.kill"
+local process = require "kong.cmd.utils.process"
 local log = require "kong.cmd.utils.log"
 
 local function execute(args)
@@ -24,7 +24,7 @@ local function execute(args)
     log.verbose("waiting %s seconds before quitting", args.wait)
     while twait > ngx.now() do
       ngx.sleep(0.2)
-      if not kill.is_running(conf.nginx_pid) then
+      if not process.exists(conf.nginx_pid) then
         log.error("Kong stopped while waiting (unexpected)")
         return
       end
@@ -41,7 +41,7 @@ local function execute(args)
   local texp, running = tstart + math.max(args.timeout, 1) -- min 1s timeout
   repeat
     ngx.sleep(0.2)
-    running = kill.is_running(conf.nginx_pid)
+    running = process.exists(conf.nginx_pid)
     ngx.update_time()
   until not running or ngx.now() >= texp
 

kong/cmd/restart.lua

@@ -1,6 +1,6 @@
 local log = require "kong.cmd.utils.log"
 local stop = require "kong.cmd.stop"
-local kill = require "kong.cmd.utils.kill"
+local process = require "kong.cmd.utils.process"
 local start = require "kong.cmd.start"
 local pl_path = require "pl.path"
 local conf_loader = require "kong.conf_loader"
@@ -27,7 +27,7 @@ local function execute(args)
   local running
   repeat
     ngx.sleep(0.1)
-    running = kill.is_running(conf.nginx_pid)
+    running = process.exists(conf.nginx_pid)
   until not running or ngx.time() >= texp
 
   start.execute(args)

kong/cmd/start.lua

@@ -3,7 +3,7 @@ local prefix_handler = require "kong.cmd.utils.prefix_handler"
 local nginx_signals = require "kong.cmd.utils.nginx_signals"
 local conf_loader = require "kong.conf_loader"
 local kong_global = require "kong.global"
-local kill = require "kong.cmd.utils.kill"
+local process = require "kong.cmd.utils.process"
 local log = require "kong.cmd.utils.log"
 local DB = require "kong.db"
 local lfs = require "lfs"
@@ -53,7 +53,7 @@ local function execute(args)
 
   conf.pg_timeout = args.db_timeout -- connect + send + read
 
-  assert(not kill.is_running(conf.nginx_pid),
+  assert(not process.exists(conf.nginx_pid),
          "Kong is already running in " .. conf.prefix)
 
   assert(prefix_handler.prepare_prefix(conf, args.nginx_conf, nil, nil,

kong/cmd/utils/nginx_signals.lua

@@ -1,6 +1,6 @@
 local ffi = require "ffi"
 local log = require "kong.cmd.utils.log"
-local kill = require "kong.cmd.utils.kill"
+local process = require "kong.cmd.utils.process"
 local meta = require "kong.meta"
 local pl_path = require "pl.path"
 local version = require "version"
@@ -55,15 +55,17 @@ end
 
 
 local function send_signal(kong_conf, signal)
-  if not kill.is_running(kong_conf.nginx_pid) then
+  local pid = process.pid(kong_conf.nginx_pid)
+
+  if not pid or not process.exists(pid) then
     return nil, fmt("nginx not running in prefix: %s", kong_conf.prefix)
   end
 
   log.verbose("sending %s signal to nginx running at %s", signal, kong_conf.nginx_pid)
 
-  local code = kill.kill(kong_conf.nginx_pid, "-s " .. signal)
-  if code ~= 0 then
-    return nil, "could not send signal"
+  local ok, err = process.signal(pid, signal)
+  if not ok then
+    return nil, fmt("could not send signal: %s", err or "unknown error")
   end
 
   return true
@@ -143,7 +145,7 @@ function _M.start(kong_conf)
     return nil, err
   end
 
-  if kill.is_running(kong_conf.nginx_pid) then
+  if process.exists(kong_conf.nginx_pid) then
     return nil, "nginx is already running in " .. kong_conf.prefix
   end
 
@@ -205,17 +207,17 @@ end
 
 
 function _M.stop(kong_conf)
-  return send_signal(kong_conf, "TERM")
+  return send_signal(kong_conf, process.SIG_TERM)
 end
 
 
 function _M.quit(kong_conf)
-  return send_signal(kong_conf, "QUIT")
+  return send_signal(kong_conf, process.SIG_QUIT)
 end
 
 
 function _M.reload(kong_conf)
-  if not kill.is_running(kong_conf.nginx_pid) then
+  if not process.exists(kong_conf.nginx_pid) then
     return nil, fmt("nginx not running in prefix: %s", kong_conf.prefix)
   end