feat(queue): added a new configuration concurrency_limit(integer, default to 1) for Queue to specify the number of delivery timers

changelog/unreleased/kong/feat-queue-concurrency-limit.yml

@@ -0,0 +1,5 @@
+message: |
+  Added a new configuration `concurrency_limit`(integer, default to 1) for Queue to specify the number of delivery timers.
+  Note that setting `concurrency_limit` to `-1` means no limit at all, and each HTTP log entry would create an individual timer for sending.
+type: feature
+scope: Core

kong/clustering/compat/removed_fields.lua

@@ -166,6 +166,7 @@ return {
     opentelemetry = {
       "traces_endpoint",
       "logs_endpoint",
+      "queue.concurrency_limit",
     },
     ai_proxy = {
       "max_request_body_size",
@@ -210,5 +211,17 @@ return {
     acl = {
       "always_use_authenticated_groups",
     },
+    http_log = {
+      "queue.concurrency_limit",
+    },
+    statsd = {
+      "queue.concurrency_limit",
+    },
+    datadog = {
+      "queue.concurrency_limit",
+    },
+    zipkin = {
+      "queue.concurrency_limit",
+    },
   },
 }

kong/tools/queue.lua

@@ -240,16 +240,18 @@ local function get_or_create_queue(queue_conf, handler, handler_conf)
 
   queue = setmetatable(queue, Queue_mt)
 
-  kong.timer:named_at("queue " .. key, 0, function(_, q)
-    while q:count() > 0 do
-      q:log_debug("processing queue")
-      q:process_once()
-    end
-    q:log_debug("done processing queue")
-    queues[key] = nil
-  end, queue)
+  if queue.concurrency_limit == 1 then
+    kong.timer:named_at("queue " .. key, 0, function(_, q)
+      while q:count() > 0 do
+        q:log_debug("processing queue")
+        q:process_once()
+      end
+      q:log_debug("done processing queue")
+      queues[key] = nil
+    end, queue)
+    queues[key] = queue
+  end
 
-  queues[key] = queue
 
   queue:log_debug("queue created")
 
@@ -314,6 +316,45 @@ function Queue.can_enqueue(queue_conf, entry)
   return _can_enqueue(queue, entry)
 end
 
+local function handle(self, entries)
+  local entry_count = #entries
+
+  local start_time = now()
+  local retry_count = 0
+  while true do
+    self:log_debug("passing %d entries to handler", entry_count)
+    local status, ok, err = pcall(self.handler, self.handler_conf, entries)
+    if status and ok == true then
+      self:log_debug("handler processed %d entries successfully", entry_count)
+      break
+    end
+
+    if not status then
+      -- protected call failed, ok is the error message
+      err = ok
+    end
+
+    self:log_warn("handler could not process entries: %s", tostring(err or "no error details returned by handler"))
+
+    if not err then
+      self:log_err("handler returned falsy value but no error information")
+    end
+
+    if (now() - start_time) > self.max_retry_time then
+      self:log_err(
+        "could not send entries due to max_retry_time exceeded. %d queue entries were lost",
+        entry_count)
+      break
+    end
+
+    -- Delay before retrying.  The delay time is calculated by multiplying the configured initial_retry_delay with
+    -- 2 to the power of the number of retries, creating an exponential increase over the course of each retry.
+    -- The maximum time between retries is capped by the max_retry_delay configuration parameter.
+    sleep(math_min(self.max_retry_delay, 2 ^ retry_count * self.initial_retry_delay))
+    retry_count = retry_count + 1
+  end
+end
+
 
 -- Delete the frontmost entry from the queue and adjust the current utilization variables.
 function Queue:delete_frontmost_entry()
@@ -387,41 +428,7 @@ function Queue:process_once()
     self.already_dropped_entries = false
   end
 
-  local start_time = now()
-  local retry_count = 0
-  while true do
-    self:log_debug("passing %d entries to handler", entry_count)
-    local status
-    status, ok, err = pcall(self.handler, self.handler_conf, batch)
-    if status and ok == true then
-      self:log_debug("handler processed %d entries successfully", entry_count)
-      break
-    end
-
-    if not status then
-      -- protected call failed, ok is the error message
-      err = ok
-    end
-
-    self:log_warn("handler could not process entries: %s", tostring(err or "no error details returned by handler"))
-
-    if not err then
-      self:log_err("handler returned falsy value but no error information")
-    end
-
-    if (now() - start_time) > self.max_retry_time then
-      self:log_err(
-        "could not send entries, giving up after %d retries.  %d queue entries were lost",
-        retry_count, entry_count)
-      break
-    end
-
-    -- Delay before retrying.  The delay time is calculated by multiplying the configured initial_retry_delay with
-    -- 2 to the power of the number of retries, creating an exponential increase over the course of each retry.
-    -- The maximum time between retries is capped by the max_retry_delay configuration parameter.
-    sleep(math_min(self.max_retry_delay, 2 ^ retry_count * self.initial_retry_delay))
-    retry_count = retry_count + 1
-  end
+  handle(self, batch)
 end
 
 
@@ -506,6 +513,21 @@ local function enqueue(self, entry)
     return nil, "entry must be a non-nil Lua value"
   end
 
+  if self.concurrency_limit == -1 then -- unlimited concurrency
+    -- do not enqueue when concurrency_limit is unlimited
+    local ok, err = kong.timer:at(0, function(premature)
+      if premature then
+        return
+      end
+      handle(self, { entry })
+    end)
+    if not ok then
+      return nil, "failed to crete timer: " .. err
+    end
+    return true
+  end
+
+
   if self:count() >= self.max_entries * CAPACITY_WARNING_THRESHOLD then
     if not self.warned then
       self:log_warn('queue at %s%% capacity', CAPACITY_WARNING_THRESHOLD * 100)
@@ -615,6 +637,11 @@ function Queue.enqueue(queue_conf, handler, handler_conf, value)
     "arg #1 (queue_conf) max_bytes must be a number or nil"
   )
 
+  assert(
+    type(queue_conf.concurrency_limit) == "number",
+    "arg #1 (queue_conf) concurrency_limit must be a number"
+  )
+
   local queue = get_or_create_queue(queue_conf, handler, handler_conf)
   return enqueue(queue, value)
 end

kong/tools/queue_schema.lua

@@ -49,5 +49,12 @@ return Schema.define {
       between = { 0.001, 1000000 }, -- effectively unlimited maximum
       description = "Maximum time in seconds between retries, caps exponential backoff."
     } },
+    { concurrency_limit = {
+      type = "integer",
+      default = 1,
+      one_of = { -1, 1 },
+      description = "The number of of queue delivery timers. -1 indicates unlimited."
+    } },
+
   }
 }

spec/01-unit/01-db/01-schema/11-declarative_config/02-process_auto_fields_spec.lua

@@ -179,6 +179,7 @@ describe("declarative config: process_auto_fields", function()
                   max_coalescing_delay = 1,
                   max_retry_delay = 60,
                   max_retry_time = 60,
+                  concurrency_limit = 1,
                 },
               }
             },
@@ -236,6 +237,7 @@ describe("declarative config: process_auto_fields", function()
                   max_coalescing_delay = 1,
                   max_retry_delay = 60,
                   max_retry_time = 60,
+                  concurrency_limit = 1,
                 },
               }
             },
@@ -353,6 +355,7 @@ describe("declarative config: process_auto_fields", function()
                         max_coalescing_delay = 1,
                         max_retry_delay = 60,
                         max_retry_time = 60,
+                        concurrency_limit = 1,
                       },
                     }
                   },
@@ -674,6 +677,7 @@ describe("declarative config: process_auto_fields", function()
                             max_coalescing_delay = 1,
                             max_retry_delay = 60,
                             max_retry_time = 60,
+                            concurrency_limit = 1,
                           },
                         }
                       }

spec/01-unit/01-db/01-schema/11-declarative_config/03-flatten_spec.lua

@@ -302,6 +302,7 @@ describe("declarative config: flatten", function()
                   max_retry_delay = 60,
                   max_retry_time = 60,
                   max_bytes = null,
+                  concurrency_limit = 1,
                 },
               }
             },
@@ -409,6 +410,7 @@ describe("declarative config: flatten", function()
                   max_retry_delay = 60,
                   max_retry_time = 60,
                   max_bytes = null,
+                  concurrency_limit = 1,
                 },
               },
               consumer = {
@@ -611,7 +613,8 @@ describe("declarative config: flatten", function()
                     max_retry_delay = 60,
                     max_retry_time = 60,
                     max_bytes = null,
-                  }
+                    concurrency_limit = 1,
+                  },
                 },
                 consumer = null,
                 created_at = 1234567890,
@@ -1128,6 +1131,7 @@ describe("declarative config: flatten", function()
                     max_retry_delay = 60,
                     max_retry_time = 60,
                     max_bytes = null,
+                    concurrency_limit = 1,
                   },
                 },
                 consumer = null,

spec/01-unit/27-queue_spec.lua

@@ -786,7 +786,7 @@ describe("plugin queue", function()
     assert.equal("One", processed[1])
     assert.equal("Three", processed[2])
     assert.match_re(log_messages, 'WARN \\[\\] queue continue-processing: handler could not process entries: .*: hard error')
-    assert.match_re(log_messages, 'ERR \\[\\] queue continue-processing: could not send entries, giving up after \\d retries.  1 queue entries were lost')  
+    assert.match_re(log_messages, 'ERR \\[\\] queue continue-processing: could not send entries due to max_retry_time exceeded. \\d queue entries were lost')
   end)
 
   it("sanity check for function Queue.is_full() & Queue.can_enqueue()", function()
@@ -799,6 +799,7 @@ describe("plugin queue", function()
       max_retry_time = 60,
       initial_retry_delay = 1,
       max_retry_delay = 60,
+      concurrency_limit = 1,
     }
 
     local function enqueue(queue_conf, entry)
@@ -836,6 +837,7 @@ describe("plugin queue", function()
       max_retry_time = 60,
       initial_retry_delay = 1,
       max_retry_delay = 60,
+      concurrency_limit = 1,
     }
 
     -- should be true if the queue does not exist
@@ -861,6 +863,7 @@ describe("plugin queue", function()
       max_retry_time = 60,
       initial_retry_delay = 1,
       max_retry_delay = 60,
+      concurrency_limit = 1,
     }
 
     -- should be true if the queue does not exist

spec/02-integration/09-hybrid_mode/09-config-compat_spec.lua

@@ -256,6 +256,7 @@ describe("CP/DP config compat transformations #" .. strategy, function()
         expected_otel_prior_35.config.traces_endpoint = nil
         expected_otel_prior_35.config.logs_endpoint = nil
         expected_otel_prior_35.config.endpoint = "http://1.1.1.1:12345/v1/trace"
+        expected_otel_prior_35.config.queue.concurrency_limit = nil
 
         do_assert(uuid(), "3.4.0", expected_otel_prior_35)
 
@@ -281,6 +282,7 @@ describe("CP/DP config compat transformations #" .. strategy, function()
         expected_otel_prior_34.config.traces_endpoint = nil
         expected_otel_prior_34.config.logs_endpoint = nil
         expected_otel_prior_34.config.endpoint = "http://1.1.1.1:12345/v1/trace"
+        expected_otel_prior_34.config.queue.concurrency_limit = nil
         do_assert(uuid(), "3.3.0", expected_otel_prior_34)
 
         -- cleanup
@@ -307,6 +309,7 @@ describe("CP/DP config compat transformations #" .. strategy, function()
         expected_zipkin_prior_35.config.header_type = "preserve"
         expected_zipkin_prior_35.config.default_header_type = "b3"
         expected_zipkin_prior_35.config.propagation = nil
+        expected_zipkin_prior_35.config.queue.concurrency_limit = nil
         do_assert(uuid(), "3.4.0", expected_zipkin_prior_35)
 
         -- cleanup
@@ -328,6 +331,7 @@ describe("CP/DP config compat transformations #" .. strategy, function()
         expected_zipkin_prior_34.config.header_type = "preserve"
         expected_zipkin_prior_34.config.default_header_type = "b3"
         expected_zipkin_prior_34.config.propagation = nil
+        expected_zipkin_prior_34.config.queue.concurrency_limit = nil
         do_assert(uuid(), "3.3.0", expected_zipkin_prior_34)
 
         -- cleanup

spec/03-plugins/03-http-log/01-log_spec.lua

@@ -338,6 +338,25 @@ for _, strategy in helpers.each_strategy() do
         }
       }
 
+      local route1_4 = bp.routes:insert {
+        hosts   = { "no_queue.test" },
+        service = service1
+      }
+
+      bp.plugins:insert {
+        route = { id = route1_4.id },
+        name     = "http-log",
+        config   = {
+          http_endpoint = "http://" .. helpers.mock_upstream_host
+            .. ":"
+            .. helpers.mock_upstream_port
+            .. "/post_log/http",
+          queue = {
+            concurrency_limit = -1,
+          },
+        }
+      }
+
       helpers.setenv(vault_env_name, vault_env_value)
 
       assert(helpers.start_kong({
@@ -638,6 +657,20 @@ for _, strategy in helpers.each_strategy() do
 
         admin_client:close()
    end)
+
+    it("should not use queue when queue.concurrency_limit is -1", function()
+      reset_log("http")
+      local res = proxy_client:get("/status/200", {
+        headers = {
+          ["Host"] = "no_queue.test"
+        }
+      })
+      assert.res_status(200, res)
+
+      local entries = get_log("http", 1)
+      assert.same("127.0.0.1", entries[1].client_ip)
+      assert.logfile().has.no.line("processing queue", true)  -- should not use queue
+    end)
   end)
 
   -- test both with a single worker for a deterministic test,