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In actual project development, we will often encounter high concurrency situations. It may be a network problem. If there is no response when clicking the mouse continuously, we will quickly initiate N multiple calls to the interface.
As a result, the interface is repeatedly called multiple times in a very short period of time to perform add or update operations, which leads to incomplete data
Table of contents
1. What is concurrency?
1.1. Basic concepts of concurrency
Concurrency refers to the ability to process multiple tasks or events at the same time in the fields of computer science and information technology. In concurrent computing, multiple tasks can be performed simultaneously rather than in a strict sequence. Concurrency is often used to improve system performance, responsiveness, and resource utilization.
In concurrent computing, tasks can be performed simultaneously in different ways, such as multi-threading, multi-process, asynchronous programming, etc. Multi-threading refers to running multiple threads at the same time in a program. Each thread independently performs different tasks and shares the resources of the same process. Multi-process refers to running multiple independent processes at the same time in a system. Each process has its own independent memory space and resources. Asynchronous programming is an event-driven programming paradigm that handles concurrent tasks through callback functions or event loops.
Concurrency can improve the throughput and responsiveness of the system, allowing users to quickly switch between multiple tasks. However, it should be noted that concurrent programming may also cause some special problems, such as race conditions, deadlocks, and resource contention. Therefore, when developing concurrent programs, you need to pay attention to issues such as thread safety, synchronization mechanisms, and resource management.
When concurrency exists in the system, multiple tasks or events may occur at the same time or overlap. In this case, a mechanism is needed to manage and control the execution sequence of these tasks, resource access, and data consistency.
In concurrent programming, commonly used methods for handling concurrency include mutex locks, semaphores, condition variables, and atomic operations. Mutex is a mechanism used to protect shared resources. It can ensure that only one task can access shared resources at the same time. Semaphore is a mechanism used to control resource access permissions. It can limit the number of tasks that can access shared resources at the same time. Condition variable (Condition Variable) is a mechanism used to wait and notify between multiple tasks. It can achieve synchronization and collaboration between tasks. Atomic operations are atomic (uninterruptible) operations that ensure that operations on shared resources in a concurrent environment are thread-safe.
In addition, there are some concurrent programming models, such as message passing, shared memory and data flow. The message passing model is a way of communicating by sending messages. Each task has its own message queue, and information is exchanged by sending and receiving messages. The shared memory model is a way of communicating through a shared memory space, and multiple tasks can directly read and write data in the shared memory. The data flow model is a way to achieve communication and processing between tasks through data flow. Data is transferred between tasks through pipes or channels.
Concurrent programming is a complex field that requires careful consideration of factors such as task interaction, resource contention, deadlocks, and performance. Properly designing concurrent programs can improve the efficiency and scalability of the system, but if not handled properly, it may also cause various problems. Therefore, when doing concurrent programming, you need to carefully analyze and plan, and use appropriate concurrency processing mechanisms and programming models.
2. Concurrency scenarios
In C#, you can use features such as multi-threading, asynchronous programming, and parallel computing to achieve high concurrency scenarios.
- The following are some common C# high concurrency scenarios
1.1. Web server
C# can be used to develop high-performance web servers, handle concurrent requests through multi-threading or asynchronous programming, and improve the server's throughput and response speed.
1.2. Concurrent data access
When multiple threads need to access shared data at the same time, a lock mechanism (such as a mutex lock, ReaderWriterLock) can be used to ensure data consistency and thread safety.
1.3. Database access
ADO.NET in C# provides the function of asynchronous database access, which can use asynchronous programming mode to improve performance during high-concurrency database operations.
1.4. Concurrent task processing
Using C#'s parallel computing library, you can easily perform parallel processing on tasks, such as parallel traversal, parallel computing and task division, etc., to improve processing efficiency.
1.5. Concurrent message processing
Using the message queue or event-driven programming model, highly concurrent message processing can be achieved, such as processing real-time events, message push, etc.
1.6. Concurrent network communication
C# provides various network programming APIs, which can develop concurrent network communication applications, such as chat software, real-time communication, etc.
1.7. Large-scale data processing
Through technologies such as parallel computing, data flow, and asynchronous programming, large-scale data can be efficiently processed, such as data analysis, data mining, and batch processing.
It should be noted that when developing high-concurrency applications, factors such as performance, resource utilization, thread safety, and system stability need to be comprehensively considered to avoid problems such as resource competition, deadlock, and excessive use of threads.
At the same time, for specific scenarios, you can also consider using concurrent collections (such as ConcurrentQueue, ConcurrentDictionary) and concurrent design patterns (such as producer-consumer model, read-write lock model) to simplify the complexity of concurrent programming. sex.
3. Concurrent processing of methods
In C#, the following solutions can be used to solve the problem of high concurrent calls to the same method.
3.1. Lock mechanism
Locking mechanism (Locking) uses locking mechanisms such as mutex (Mutex) or critical section (Monitor) to wrap key code blocks within the scope of the lock to ensure that only one thread can access the code block at the same time. This ensures data consistency and thread safety during concurrent access.
- 例如
private static object lockObj = new object();
public void ProcessData()
{ lock (lockObj) { // 临國区代码，确绿线语Safety // … } }
3.2. Spin lock
Spin Locking. Spin lock is a relatively lightweight locking mechanism. When a thread requests a lock, if the lock is already held by another thread, the thread will wait in a loop. , until the lock is released. Spin locks are suitable for situations where the lock is occupied in a short period of time, avoiding the overhead of thread switching. You can use the
SpinLock class in C# to implement spin locks.
3.3. Read-write lock
Reader-Writer Lock. If the method contains read operations and write operations, you can consider using a read-write lock to allow multiple threads to perform read operations at the same time, but only one thread can Perform a write operation. In C#, you can use the
ReaderWriterLockSlim class to implement read-write locks.
3.4. Concurrent collection
Concurrent Collections (Concurrent Collections), C# provides a series of concurrent collection classes, such as ConcurrentQueue, ConcurrentStack, ConcurrentDictionary, etc., which provide thread-safe operations in a multi-threaded environment. You can put the method parameters to be called concurrently into a concurrent collection and then process them inside the method.
3.5. Asynchronous programming
Asynchronous Programming. If the method is not required to be executed synchronously, you can use the asynchronous programming mode and design the method as an asynchronous method (using the
async and await keywords) , this can avoid blocking the current thread. Multiple concurrent calls can be made simultaneously and communicate by processing results asynchronously or by other means.
When choosing a solution, you need to make an appropriate choice based on specific scenarios and needs. The lock mechanism is suitable for situations where data consistency and thread safety need to be ensured. Spin locks are suitable for situations where the lock is occupied for a short period of time. Read-write locks are suitable for situations where read and write operations compete with each other. Concurrent collections and Asynchronous programming is suitable for scenarios that do not require synchronous execution.