Interaction between Golang coroutine and lock

Coroutines are used to create and switch lightweight threads, while locks are used to synchronize access to shared data. The main way that coroutines interact with locks is to use locks to protect critical sections, which are portions of shared data that are accessed by multiple coroutines. You can use a mutex lock to allow only one coroutine to access the critical section at a time, or a read-write lock to allow multiple coroutines to read the critical section at the same time but only allow one coroutine to write. In practice, locks can be used to protect concurrent access to the server state of the Web server and update operations of database row data.

Interaction between Go coroutine and lock

Coroutine

Coroutine is a lightweight thread. The overhead of coroutine creation and switching is very low compared to threads. In Go, coroutines are created using the goroutine keyword.

Lock

Lock is used to synchronize access to shared data and prevent concurrent access from causing data inconsistency. In Go, there are the following built-in locks:

• sync.Mutex: Mutex lock that allows one coroutine to access the critical section at a time.
• sync.RWMutex: Read-write lock, allows multiple coroutines to read the critical section at the same time, but only one coroutine can write to the critical section.
• sync.Once: One-time lock to ensure that the code block is executed only once.

Interaction between coroutines and locks

The most common interaction between coroutines and locks is the use of locks to protect critical sections. Critical section refers to the part of code where shared data is accessed.

To use a lock to protect a critical section, you need to acquire the lock before the critical section and release the lock after the critical section. For mutex locks and read-write locks, you can use the Lock() and Unlock() methods to acquire and release locks.

import (
    "sync"
)

var mu sync.Mutex
var counter int

func incrementCounter() {
    mu.Lock()
    counter++
    mu.Unlock()
}

In the above example, we put the increment operation of the counter variable in the incrementCounter function and use a mutex lockmu to protect it. This ensures that only one coroutine can access and modify the counter variable at a time.

Practical case

Web server

In a Web server, multiple coroutines can process different HTTPs at the same time ask. To prevent multiple coroutines from accessing server state (such as the current number of connections) at the same time, a mutex can be used to protect access to server state.

Database access

In database access, multiple coroutines can query the database at the same time. In order to prevent multiple coroutines from updating the same row of data at the same time, read-write locks can be used to protect update operations on database row data. Read operations can be performed concurrently, while write operations require exclusive access.

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