rate_limit: Adds a --rate option for RPS limits

doc/admin-guide/plugins/rate_limit.en.rst

@@ -49,7 +49,13 @@ are available:
 
 .. option:: --limit
 
-   The maximum number of active client transactions.
+   The maximum number of active client transactions. This option can also be
+   used in conjunction with ``--rate``.
+
+.. option:: --rate
+
+   The acceptable rate, in transaction or connections per second, that we will
+   allow. This option can also be used in conjunction with ``--limit``.
 
 .. option:: --queue
 
@@ -140,6 +146,7 @@ and nodes are documented below.
       selector:
          - sni: test1.example.com
             limit: 1000
+            rate: 200
             queue:
                size: 1000
                max-age: 30
@@ -176,7 +183,13 @@ For the top level `selector` node, the following options are available:
 
 .. option:: limit
 
-   The maximum number of active client transactions.
+   The maximum number of active client transactions. This can also be used
+   in conjunction with the ``rate`` option.
+
+.. option:: rate
+
+   This limits the number of new sessions per second. It can be used in
+   conjunction with the ``limit`` option.
 
 .. option:: aliases
 

plugins/experimental/rate_limit/CMakeLists.txt

@@ -19,6 +19,7 @@ project(rate_limit)
 
 add_atsplugin(
   rate_limit
+  limiter.cc
   ip_reputation.cc
   rate_limit.cc
   sni_limiter.cc

plugins/experimental/rate_limit/limiter.cc

@@ -0,0 +1,94 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "limiter.h"
+
+// order must align with the above
+static const char *types[] = {
+  "sni",
+  "remap",
+};
+
+// Order should match the enum in limiter.h
+static const char *suffixes[] = {
+  "queued",
+  "rejected",
+  "expired",
+  "resumed",
+};
+
+// This function will run on the dedicated thread, until the global bucket manager is dead
+void
+BucketManager::refill_thread()
+{
+  while (_running) {
+    auto startTime = std::chrono::steady_clock::now();
+
+    {
+      std::lock_guard<std::mutex> lock(_mutex);
+
+      for (auto &bucket : _buckets) {
+        bucket->refill();
+      }
+    }
+
+    auto sleepTime = std::chrono::milliseconds(BUCKET_REFILL_INTERVAL) - (std::chrono::steady_clock::now() - startTime);
+
+    if (sleepTime > std::chrono::milliseconds(0)) {
+      std::this_thread::sleep_for(sleepTime);
+    }
+  }
+}
+
+void
+metric_helper(std::array<int, RATE_LIMITER_METRIC_MAX> &metrics, uint type, const std::string &tag, const std::string &name,
+              const std::string &prefix)
+{
+  std::string metric_prefix = prefix;
+
+  metric_prefix.push_back('.');
+  metric_prefix.append(types[type]);
+
+  if (!tag.empty()) {
+    metric_prefix.push_back('.');
+    metric_prefix.append(tag);
+  } else if (!name.empty()) {
+    metric_prefix.push_back('.');
+    metric_prefix.append(name);
+  }
+
+  for (int i = 0; i < RATE_LIMITER_METRIC_MAX; i++) {
+    size_t const metricsz = metric_prefix.length() + strlen(suffixes[i]) + 2; // padding for dot+terminator
+    char *const  metric   = static_cast<char *>(TSmalloc(metricsz));
+
+    snprintf(metric, metricsz, "%s.%s", metric_prefix.data(), suffixes[i]);
+    metrics[i] = TS_ERROR;
+
+    if (TSStatFindName(metric, &metrics[i]) == TS_ERROR) {
+      metrics[i] = TSStatCreate(metric, TS_RECORDDATATYPE_INT, TS_STAT_NON_PERSISTENT, TS_STAT_SYNC_SUM);
+    }
+
+    if (metrics[i] != TS_ERROR) {
+      Dbg(dbg_ctl, "established metric '%s' as ID %d", metric, metrics[i]);
+    } else {
+      TSError("failed to create metric '%s'", metric);
+    }
+
+    TSfree(metric);
+  }
+}