fix(*): avoid creating multiple timers to run the same active check

lib/resty/healthcheck.lua

@@ -33,6 +33,7 @@ local ipairs = ipairs
 local table_insert = table.insert
 local table_remove = table.remove
 local string_format = string.format
+local math_max = math.max
 local ssl = require("ngx.ssl")
 local resty_timer = require "resty.timer"
 local bit = require("bit")
@@ -1200,6 +1201,32 @@ local function renew_periodic_lock(shm, key)
 end
 
 
+local function get_callback_lock(shm, key, ttl)
+  local value = shm:get(key)
+  if value == nil then
+    -- no worker is checking, try to acquire the lock
+    local ok, err = shm:add(key, true, ttl or LOCK_PERIOD)
+    if not ok then
+      if err == "exists" then
+        -- another worker got the lock before
+        return false
+      end
+
+      return nil, err
+    end
+
+    return true
+  end
+
+  return false
+end
+
+
+local function remove_callback_lock(shm, key)
+  return shm:delete(key)
+end
+
+
 --- Active health check callback function.
 -- @param self the checker object this timer runs on
 -- @param health_mode either "healthy" or "unhealthy" to indicate what check
@@ -1208,10 +1235,27 @@ local function checker_callback(self, health_mode)
     self.checker_callback_count = self.checker_callback_count + 1
   end
 
+  -- Set a callback pending lock will exist for 2x the time of the active check.
+  -- An active check should be finished within this time and next timer will be
+  -- executed to exit a pending status.
+  local callback_pending_ttl = (math_max(self.checks.active.healthy.active and
+                                         self.checks.active.healthy.interval or 0,
+                                         self.checks.active.unhealthy.active and
+                                         self.checks.active.unhealthy.interval or 0)
+                                         + self.checks.active.timeout) * 2
+
+  local callback_lock = self.CALLBACK_LOCK .. health_mode
+  -- a pending timer already exists, so skip this time
+  local ok, _ = get_callback_lock(self.shm, callback_lock, callback_pending_ttl)
+  if not ok then
+    return
+  end
+
   local list_to_check = {}
   local targets, err = fetch_target_list(self)
   if not targets then
     self:log(ERR, "checker_callback: ", err)
+    remove_callback_lock(self.shm, callback_lock)
     return
   end
 
@@ -1235,6 +1279,7 @@ local function checker_callback(self, health_mode)
 
   if not list_to_check[1] then
     self:log(DEBUG, "checking ", health_mode, " targets: nothing to do")
+    remove_callback_lock(self.shm, callback_lock)
   else
     local timer = resty_timer({
       interval = 0,
@@ -1244,10 +1289,12 @@ local function checker_callback(self, health_mode)
       expire = function()
         self:log(DEBUG, "checking ", health_mode, " targets: #", #list_to_check)
         self:active_check_targets(list_to_check)
+        remove_callback_lock(self.shm, callback_lock)
       end,
     })
     if timer == nil then
       self:log(ERR, "failed to create timer to check ", health_mode)
+      remove_callback_lock(self.shm, callback_lock)
     end
   end
 end
@@ -1614,6 +1661,7 @@ function _M.new(opts)
   self.TARGET_LIST_LOCK = SHM_PREFIX .. self.name .. ":target_list_lock"
   self.TARGET_LOCK      = SHM_PREFIX .. self.name .. ":target_lock"
   self.PERIODIC_LOCK    = SHM_PREFIX .. ":period_lock:"
+  self.CALLBACK_LOCK    = SHM_PREFIX .. self.name .. ":callback_lock:"
   -- prepare constants
   self.EVENT_SOURCE     = EVENT_SOURCE_PREFIX .. " [" .. self.name .. "]"
   self.LOG_PREFIX       = LOG_PREFIX .. "(" .. self.name .. ") "

t/with_resty-events/14-tls_active_probes.t

@@ -46,6 +46,7 @@ __DATA__
 events_module = "resty.events",
                 checks = {
                     active = {
+                        timeout = 2,
                         type = "https",
                         http_path = "/",
                         healthy  = {
@@ -60,7 +61,7 @@ events_module = "resty.events",
                 }
             })
             local ok, err = checker:add_target("104.154.89.105", 443, "badssl.com", false)
-            ngx.sleep(8) -- wait for 4x the check interval
+            ngx.sleep(16) -- wait for 4x the check interval
             ngx.say(checker:get_target_status("104.154.89.105", 443, "badssl.com"))  -- true
         }
     }
@@ -69,7 +70,7 @@ GET /t
 --- response_body
 true
 --- timeout
-15
+20
 
 === TEST 2: active probes, invalid cert
 --- http_config eval: $::HttpConfig
@@ -87,6 +88,7 @@ true
 events_module = "resty.events",
                 checks = {
                     active = {
+                        timeout = 2,
                         type = "https",
                         http_path = "/",
                         healthy  = {
@@ -101,7 +103,7 @@ events_module = "resty.events",
                 }
             })
             local ok, err = checker:add_target("104.154.89.105", 443, "wrong.host.badssl.com", true)
-            ngx.sleep(8) -- wait for 4x the check interval
+            ngx.sleep(16) -- wait for 4x the check interval
             ngx.say(checker:get_target_status("104.154.89.105", 443, "wrong.host.badssl.com"))  -- false
         }
     }
@@ -110,7 +112,7 @@ GET /t
 --- response_body
 false
 --- timeout
-15
+20
 
 === TEST 3: active probes, accept invalid cert when disabling check
 --- http_config eval: $::HttpConfig
@@ -128,6 +130,7 @@ false
 events_module = "resty.events",
                 checks = {
                     active = {
+                        timeout = 2,
                         type = "https",
                         https_verify_certificate = false,
                         http_path = "/",
@@ -143,7 +146,7 @@ events_module = "resty.events",
                 }
             })
             local ok, err = checker:add_target("104.154.89.105", 443, "wrong.host.badssl.com", false)
-            ngx.sleep(8) -- wait for 4x the check interval
+            ngx.sleep(16) -- wait for 4x the check interval
             ngx.say(checker:get_target_status("104.154.89.105", 443, "wrong.host.badssl.com"))  -- true
         }
     }
@@ -152,4 +155,4 @@ GET /t
 --- response_body
 true
 --- timeout
-15
+20

t/with_resty-events/19-timer.t

@@ -0,0 +1,93 @@
+use Test::Nginx::Socket::Lua;
+use Cwd qw(cwd);
+
+workers(1);
+
+plan tests => repeat_each() * blocks() * 2;
+
+my $pwd = cwd();
+$ENV{TEST_NGINX_SERVROOT} = server_root();
+
+our $HttpConfig = qq{
+    lua_package_path "$pwd/lib/?.lua;;";
+    lua_shared_dict test_shm 8m;
+
+    init_worker_by_lua_block {
+        local we = require "resty.events.compat"
+        assert(we.configure({
+            unique_timeout = 5,
+            broker_id = 0,
+            listening = "unix:$ENV{TEST_NGINX_SERVROOT}/worker_events.sock"
+        }))
+        assert(we.configured())
+    }
+
+    server {
+        server_name kong_worker_events;
+        listen unix:$ENV{TEST_NGINX_SERVROOT}/worker_events.sock;
+        access_log off;
+        location / {
+            content_by_lua_block {
+                require("resty.events.compat").run()
+            }
+        }
+    }
+};
+
+run_tests();
+
+__DATA__
+
+
+
+
+=== TEST 1: active probes, http node failing
+--- http_config eval
+qq{
+    $::HttpConfig
+
+    server {
+        listen 2130;
+        location = /status {
+            content_by_lua_block {
+                ngx.sleep(2)
+                ngx.exit(500);
+            }
+        }
+    }
+}
+--- config
+    location = /t {
+        content_by_lua_block {
+            local healthcheck = require("resty.healthcheck")
+            local checker = healthcheck.new({
+                name = "testing",
+                shm_name = "test_shm",
+                events_module = "resty.events",
+                type = "http",
+                checks = {
+                    active = {
+                        timeout = 1,
+                        http_path = "/status",
+                        healthy  = {
+                            interval = 0.1,
+                            successes = 3,
+                        },
+                        unhealthy  = {
+                            interval = 0.1,
+                            http_failures = 3,
+                        }
+                    },
+                }
+            })
+            local ok, err = checker:add_target("127.0.0.1", 2130, nil, true)
+            ngx.sleep(3) -- wait for some time to let the checks run
+            -- There should be no more than 3 timers running atm, but
+            -- add a few spaces for worker events
+            ngx.say(tonumber(ngx.timer.running_count()) <= 5)
+        }
+    }
+--- request
+GET /t
+--- response_body
+true

t/with_worker-events/14-tls_active_probes.t

@@ -34,6 +34,7 @@ __DATA__
                 shm_name = "test_shm",
                 checks = {
                     active = {
+                        timeout = 2,
                         type = "https",
                         http_path = "/",
                         healthy  = {
@@ -48,7 +49,7 @@ __DATA__
                 }
             })
             local ok, err = checker:add_target("104.154.89.105", 443, "badssl.com", false)
-            ngx.sleep(8) -- wait for 4x the check interval
+            ngx.sleep(16) -- wait for 4x the check interval
             ngx.say(checker:get_target_status("104.154.89.105", 443, "badssl.com"))  -- true
         }
     }
@@ -57,7 +58,7 @@ GET /t
 --- response_body
 true
 --- timeout
-15
+20
 
 === TEST 2: active probes, invalid cert
 --- http_config eval: $::HttpConfig
@@ -74,6 +75,7 @@ true
                 shm_name = "test_shm",
                 checks = {
                     active = {
+                        timeout = 2,
                         type = "https",
                         http_path = "/",
                         healthy  = {
@@ -88,7 +90,7 @@ true
                 }
             })
             local ok, err = checker:add_target("104.154.89.105", 443, "wrong.host.badssl.com", true)
-            ngx.sleep(8) -- wait for 4x the check interval
+            ngx.sleep(16) -- wait for 4x the check interval
             ngx.say(checker:get_target_status("104.154.89.105", 443, "wrong.host.badssl.com"))  -- false
         }
     }
@@ -97,7 +99,7 @@ GET /t
 --- response_body
 false
 --- timeout
-15
+20
 
 === TEST 3: active probes, accept invalid cert when disabling check
 --- http_config eval: $::HttpConfig
@@ -114,6 +116,7 @@ false
                 shm_name = "test_shm",
                 checks = {
                     active = {
+                        timeout = 2,
                         type = "https",
                         https_verify_certificate = false,
                         http_path = "/",
@@ -129,7 +132,7 @@ false
                 }
             })
             local ok, err = checker:add_target("104.154.89.105", 443, "wrong.host.badssl.com", false)
-            ngx.sleep(8) -- wait for 4x the check interval
+            ngx.sleep(16) -- wait for 4x the check interval
             ngx.say(checker:get_target_status("104.154.89.105", 443, "wrong.host.badssl.com"))  -- true
         }
     }
@@ -138,4 +141,4 @@ GET /t
 --- response_body
 true
 --- timeout
-15
+20