feat(cli): add 'drain' CLI command to set /status/ready to 503

bin/kong

@@ -31,6 +31,7 @@ local cmds = {
   roar = true,
   hybrid = true,
   vault = true,
+  drain = true,
 }
 
 -- unnecessary to inject nginx directives for these simple cmds
@@ -42,6 +43,7 @@ local skip_inject_cmds = {
   quit = true,
   health = true,
   hybrid = true,
+  drain = true,
 }
 
 for k in pairs(cmds) do

changelog/unreleased/kong/feat-kong-drain-cmd.yml

@@ -0,0 +1,3 @@
+message: Add the `kong drain` CLI command to make the `/status/ready` endpoint return `503 Service Unavailable` response.
+type: feature
+scope: CLI Command

kong-3.9.0-0.rockspec

@@ -146,6 +146,7 @@ build = {
     ["kong.cmd.vault"] = "kong/cmd/vault.lua",
     ["kong.cmd.version"] = "kong/cmd/version.lua",
     ["kong.cmd.hybrid"] = "kong/cmd/hybrid.lua",
+    ["kong.cmd.drain"] = "kong/cmd/drain.lua",
     ["kong.cmd.utils.log"] = "kong/cmd/utils/log.lua",
     ["kong.cmd.utils.kill"] = "kong/cmd/utils/kill.lua",
     ["kong.cmd.utils.env"] = "kong/cmd/utils/env.lua",

kong/cmd/drain.lua

@@ -0,0 +1,88 @@
+local http = require "resty.luasocket.http"
+local print = print
+local fmt = string.format
+
+local conf_loader = require "kong.conf_loader"
+local pl_path = require "pl.path"
+local log = require "kong.cmd.utils.log"
+local json_encode = require("cjson.safe").encode
+
+local function execute(args)
+  log.disable()
+
+  -- only to retrieve the default prefix or use given one
+  local conf = assert(conf_loader(args.conf, {
+    prefix = args.prefix
+  }))
+
+  if pl_path.exists(conf.kong_env) then
+    -- load <PREFIX>/kong.conf containing running node's config
+    conf = assert(conf_loader(conf.kong_env))
+  end
+
+  log.enable()
+
+  if #conf.status_listeners == 0 then
+    print("No status listeners found in configuration.")
+    return
+  end
+
+  local status_listener = conf.status_listeners[1]
+
+  local scheme = "http"
+  if status_listener.ssl then
+    scheme = "https"
+  end
+
+  local url = scheme .. "://" .. status_listener.ip .. ":" .. status_listener.port .. "/status/ready"
+
+  local httpc = http.new()
+  httpc:set_timeout(1000)
+
+
+  local res, err = httpc:request_uri(url, {
+    method = "POST",
+    headers = {
+        ["Content-Type"] = "application/json"
+    },
+    body = json_encode({
+      status = "draining"
+    }),
+    -- we don't need to verify the SSL certificate for this request
+    ssl_verify = false,
+  })
+
+  httpc:close()
+
+  if not res then
+    print(fmt("Failed to send request to %s: %s", url, err))
+    return
+  end
+
+  if res.status ~= 204 then
+    print(fmt("Unexpected response status from %s: %d", url, res.status))
+    return
+  end
+
+  print("Kong's status successfully changed to 'draining'")
+end
+
+
+local lapp = [[
+Usage: kong drain [OPTIONS]
+
+Make status listeners(`/status/ready`) return 503 Service Unavailable.
+
+Example usage:
+ kong drain
+
+Options:
+ -c,--conf    (optional string)  configuration file
+ -p,--prefix  (optional string)  override prefix directory
+]]
+
+
+return {
+  lapp = lapp,
+  execute = execute,
+}

kong/status/ready.lua

@@ -23,6 +23,7 @@ local PLUGINS_REBUILD_COUNTER_KEY = constants.PLUGINS_REBUILD_COUNTER_KEY
 local ROUTERS_REBUILD_COUNTER_KEY = constants.ROUTERS_REBUILD_COUNTER_KEY
 local DECLARATIVE_EMPTY_CONFIG_HASH = constants.DECLARATIVE_EMPTY_CONFIG_HASH
 
+local KONG_STATUS_READY = "kong:status:ready"
 
 local function is_dbless_ready(router_rebuilds, plugins_iterator_rebuilds)
   if router_rebuilds < worker_count then
@@ -75,16 +76,16 @@ local function is_ready()
   if not ok then
     return false, "failed to connect to database"
   end
-  
+
   kong.db:close()
 
   if is_control_plane then
     return true
   end
 
-  local router_rebuilds = 
+  local router_rebuilds =
       tonumber(kong_shm:get(ROUTERS_REBUILD_COUNTER_KEY)) or 0
-  local plugins_iterator_rebuilds = 
+  local plugins_iterator_rebuilds =
       tonumber(kong_shm:get(PLUGINS_REBUILD_COUNTER_KEY)) or 0
 
   local err
@@ -102,6 +103,15 @@ end
 return {
   ["/status/ready"] = {
     GET = function(self, dao, helpers)
+      local ready = kong_shm:get(KONG_STATUS_READY)
+      if ready == nil then
+        kong_shm:set(KONG_STATUS_READY, true)
+      end
+
+      if ready == false then
+        return kong.response.exit(503, { message = "draining" })
+      end
+
       local ok, err = is_ready()
       if ok then
         ngx_log(ngx_DEBUG, "ready for proxying")
@@ -111,6 +121,15 @@ return {
         ngx_log(ngx_NOTICE, "not ready for proxying: ", err)
         return kong.response.exit(503, { message = err })
       end
+    end,
+
+    POST = function(self, dao, helpers)
+      if self.params and self.params.status == "draining" then
+        kong_shm:set(KONG_STATUS_READY, false)
+        return kong.response.exit(204)
+      end
+
+      return kong.response.exit(400)
     end
-  }
+  },
 }