Allow overriding the default number of Thrift CPU and IO threads

Summary:
This allows services to have a default value of their choosing that
can still be overriden by a configuration loaded from configerator.

Reviewed By: yfeldblum

Differential Revision: D77241043

fbshipit-source-id: b2ea77c8303a4e47b6e3385694d6b745c0a909a2

Author: lexprfuncall

third-party/thrift/src/thrift/lib/cpp2/server/ThriftServerConfig.cpp

@@ -343,6 +343,11 @@ void ThriftServerConfig::resetNumIOWorkerThreads(AttributeSource source) {
   resetStaticAttribute(nWorkers_, source);
 }
 
+void ThriftServerConfig::setDefaultNumIOWorkerThreads(
+    size_t numIOWorkerThreads) {
+  nWorkers_.setDefault(numIOWorkerThreads);
+}
+
 void ThriftServerConfig::setNumCPUWorkerThreads(
     size_t numCPUWorkerThreads, AttributeSource source) {
   setStaticAttribute(nPoolThreads_, std::move(numCPUWorkerThreads), source);
@@ -352,6 +357,11 @@ void ThriftServerConfig::resetNumCPUWorkerThreads(AttributeSource source) {
   resetStaticAttribute(nPoolThreads_, source);
 }
 
+void ThriftServerConfig::setDefaultNumCPUWorkerThreads(
+    size_t numCPUWorkerThreads) {
+  nPoolThreads_.setDefault(numCPUWorkerThreads);
+}
+
 void ThriftServerConfig::setListenBacklog(
     int listenBacklog, AttributeSource source) {
   setStaticAttribute(listenBacklog_, std::move(listenBacklog), source);

third-party/thrift/src/thrift/lib/cpp2/server/ThriftServerConfig.h

@@ -348,6 +348,8 @@ class ThriftServerConfig {
   void resetNumIOWorkerThreads(
       AttributeSource source = AttributeSource::OVERRIDE);
 
+  void setDefaultNumIOWorkerThreads(size_t numIOWorkerThreads);
+
   /**
    * Set the number of CPU (pool) threads.
    * Won't be effective if using customized ResourcePool.
@@ -363,6 +365,8 @@ class ThriftServerConfig {
   void resetNumCPUWorkerThreads(
       AttributeSource source = AttributeSource::OVERRIDE);
 
+  void setDefaultNumCPUWorkerThreads(size_t numCPUWorkerThreads);
+
   /**
    * Set the maximum memory usage by each debug payload.
    */

third-party/thrift/src/thrift/lib/cpp2/server/test/ThriftServerConfigTest.cpp

@@ -0,0 +1,44 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * Licensed 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 <gtest/gtest.h>
+
+#include <thrift/lib/cpp2/server/ThriftServerConfig.h>
+
+using namespace ::testing;
+using namespace ::apache::thrift;
+
+TEST(ThriftServerConfigTest, UpdateConfigValueHavingDefault) {
+  ThriftServerConfig config;
+
+  // Zero should be an impossible value
+  EXPECT_NE(config.getNumIOWorkerThreads(), 0);
+
+  config.setDefaultNumIOWorkerThreads(0);
+  EXPECT_EQ(config.getNumIOWorkerThreads(), 0);
+
+  // No baseline value should be present
+  EXPECT_FALSE(config.getBaselineNumIOWorkerThreads().has_value());
+
+  // Set a baseline value and ensure its return by the getter
+  config.setNumIOWorkerThreads(1, AttributeSource::BASELINE);
+  ASSERT_TRUE(config.getBaselineNumIOWorkerThreads().has_value());
+  EXPECT_EQ(config.getNumIOWorkerThreads(), 1);
+
+  // Reset the baseline, the getter should return the default
+  config.resetNumIOWorkerThreads(AttributeSource::BASELINE);
+  EXPECT_EQ(config.getNumIOWorkerThreads(), 0);
+}