/*
- * Copyright 2015 Facebook, Inc.
+ * Copyright 2004-present Facebook, Inc.
*
- * 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
+ * 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.
+ * 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.
*/
+
#pragma once
#include <map>
#include <memory>
-#include <glog/logging.h>
-#include <folly/ThreadLocal.h>
-#include <folly/RWSpinLock.h>
-#include <folly/SingletonThreadLocal.h>
+
+#include <folly/SharedMutex.h>
+#include <folly/Synchronized.h>
namespace folly {
class RequestData {
public:
virtual ~RequestData() = default;
+ // Avoid calling RequestContext::setContextData, setContextDataIfAbsent, or
+ // clearContextData from these callbacks. Doing so will cause deadlock. We
+ // could fix these deadlocks, but only at significant performance penalty, so
+ // just don't do it!
+ virtual void onSet() {}
+ virtual void onUnset() {}
};
class RequestContext;
// copied between threads.
class RequestContext {
public:
- // Create a unique requext context for this request.
+ // Create a unique request context for this request.
// It will be passed between queues / threads (where implemented),
// so it should be valid for the lifetime of the request.
static void create() {
- getStaticContext() = std::make_shared<RequestContext>();
+ setContext(std::make_shared<RequestContext>());
}
// Get the current context.
- static RequestContext* get() {
- auto context = getStaticContext();
- if (!context) {
- static RequestContext defaultContext;
- return std::addressof(defaultContext);
- }
- return context.get();
- }
+ static RequestContext* get();
// The following API may be used to set per-request data in a thread-safe way.
// This access is still performance sensitive, so please ask if you need help
// profiling any use of these functions.
void setContextData(
- const std::string& val, std::unique_ptr<RequestData> data) {
- folly::RWSpinLock::WriteHolder guard(lock);
- if (data_.find(val) != data_.end()) {
- LOG_FIRST_N(WARNING, 1) <<
- "Called RequestContext::setContextData with data already set";
-
- data_[val] = nullptr;
- } else {
- data_[val] = std::move(data);
- }
- }
+ const std::string& val,
+ std::unique_ptr<RequestData> data);
// Unlike setContextData, this method does not panic if the key is already
// present. Returns true iff the new value has been inserted.
- bool setContextDataIfAbsent(const std::string& val,
- std::unique_ptr<RequestData> data) {
- folly::RWSpinLock::UpgradedHolder guard(lock);
- if (data_.find(val) != data_.end()) {
- return false;
- }
-
- folly::RWSpinLock::WriteHolder writeGuard(std::move(guard));
- data_[val] = std::move(data);
- return true;
- }
+ bool setContextDataIfAbsent(
+ const std::string& val,
+ std::unique_ptr<RequestData> data);
- bool hasContextData(const std::string& val) {
- folly::RWSpinLock::ReadHolder guard(lock);
- return data_.find(val) != data_.end();
- }
+ bool hasContextData(const std::string& val) const;
- RequestData* getContextData(const std::string& val) {
- folly::RWSpinLock::ReadHolder guard(lock);
- auto r = data_.find(val);
- if (r == data_.end()) {
- return nullptr;
- } else {
- return r->second.get();
- }
- }
+ RequestData* getContextData(const std::string& val);
+ const RequestData* getContextData(const std::string& val) const;
- void clearContextData(const std::string& val) {
- folly::RWSpinLock::WriteHolder guard(lock);
- data_.erase(val);
- }
+ void onSet();
+ void onUnset();
+
+ void clearContextData(const std::string& val);
// The following API is used to pass the context through queues / threads.
- // saveContext is called to geta shared_ptr to the context, and
+ // saveContext is called to get a shared_ptr to the context, and
// setContext is used to reset it on the other side of the queue.
//
+ // Whenever possible, use RequestContextScopeGuard instead of setContext
+ // to make sure that RequestContext is reset to the original value when
+ // we exit the scope.
+ //
// A shared_ptr is used, because many request may fan out across
// multiple threads, or do post-send processing, etc.
-
- static std::shared_ptr<RequestContext>
- setContext(std::shared_ptr<RequestContext> ctx) {
- using std::swap;
- swap(ctx, getStaticContext());
- return ctx;
- }
+ static std::shared_ptr<RequestContext> setContext(
+ std::shared_ptr<RequestContext> ctx);
static std::shared_ptr<RequestContext> saveContext() {
return getStaticContext();
}
private:
- static std::shared_ptr<RequestContext>& getStaticContext() {
- using SingletonT = SingletonThreadLocal<std::shared_ptr<RequestContext>>;
- static SingletonT singleton;
- return singleton.get();
- }
+ static std::shared_ptr<RequestContext>& getStaticContext();
- folly::RWSpinLock lock;
- std::map<std::string, std::unique_ptr<RequestData>> data_;
+ using Data = std::map<std::string, std::unique_ptr<RequestData>>;
+ folly::Synchronized<Data, folly::SharedMutex> data_;
};
+class RequestContextScopeGuard {
+ private:
+ std::shared_ptr<RequestContext> prev_;
+
+ public:
+ RequestContextScopeGuard(const RequestContextScopeGuard&) = delete;
+ RequestContextScopeGuard& operator=(const RequestContextScopeGuard&) = delete;
+ RequestContextScopeGuard(RequestContextScopeGuard&&) = delete;
+ RequestContextScopeGuard& operator=(RequestContextScopeGuard&&) = delete;
+
+ // Create a new RequestContext and reset to the original value when
+ // this goes out of scope.
+ RequestContextScopeGuard() : prev_(RequestContext::saveContext()) {
+ RequestContext::create();
+ }
+
+ // Set a RequestContext that was previously captured by saveContext(). It will
+ // be automatically reset to the original value when this goes out of scope.
+ explicit RequestContextScopeGuard(std::shared_ptr<RequestContext> ctx)
+ : prev_(RequestContext::setContext(std::move(ctx))) {
+ }
+
+ ~RequestContextScopeGuard() {
+ RequestContext::setContext(std::move(prev_));
+ }
+};
}
projects / folly.git / blobdiff