ledger locks

Reprint: Implementation of distributed lock based on Redis, Source: http://blog.csdn.net/ugg/article/details/41894947BackgroundIn many Internet product applications, some scenarios require lock processing, such as: seconds, global Increment ID, floor generation, and so on. Most of the solutions are based on DB, Redis is a single-process single-threaded mode, with queue mode to turn concurrent access into serial access, and multi-client connections to Redis do not have a competitive relationship.

built-in lock sychronized with volatile;1.volatile essentially tells the JVM that the value of the current variable in the register (working memory) is indeterminate and needs to be read from main memory; Synchronized is locking the current variable, and other threads are blocked if the variable is accessible to the thread .2.volatile can only be used at variable levels; synchronized can be used in variables, methods, and class-level3.volatile can only implement variable visibility and ensure at

From: http://www.sqlite.com.cn/MySqlite/4/539.Html 2. Transaction) 2.1. Transaction lifecycles)ChengThere are two things worth noting between order and transaction:(1) What objects are running in transactions -- this is directly related to the API.(2)The lifecycle of a transaction, that is, when it starts, when it ends, and when it begins to affect other connections (this is important for concurrency)-This involves the specific implementation of SQLite.IConnections can contain multiple statemen

This article Reprinted from: http://blog.csdn.net/wtz1985/article/details/301637 In the previous article, I have already elaborated on the Implementation of simple locks in multiple threads. At the end of the article, I raised the question that when inserting a chain table, the query operation cannot be implemented if it is just a simple lock. So the "recursive lock" emerged in the world. Some people may see the word recursion, which is a bit silly.

Understanding of iOS multi-thread programming locks and ios multi-thread programming 1. Examples of Mutual Exclusion In a multi-threaded environment, no matter which function method can be executed simultaneously in multiple threads. However, when using shared variables, or when the execution file outputs or graphs are drawn, multiple threads can execute at the same time to get strange results.For example, if you use the integer global variable totalN

Transactions and locks in SQL Server Transactions are all about atomicity. The concept of atomicity refers to the ability to treat things as a unit. From the database perspective, it refers to the minimum combination of one or more statements that should be fully executed or not executed. Points that can be marked in the transaction: 1. Begin Tran: Set the start point. 2. Commit Tran: make transactions a permanent and irreversible part of the databas

Mysql master-slave synchronization error solution: This article is fromLinux O M training for Old BoysSummary of internal teaching plan contentFAQ: Question 1: mysqldump: Got error: 1556: You can't use locks with log tables. When the old boy took the students to master the synchronization practice, he found that the following problems could not be solved during the students' practice. Therefore, the old boy summarized the solution process as follows:

Redis builds distributed locks and redis builds 1. Preface Why should we build a lock? Because building a proper lock can maintain data consistency in high concurrency, that is, the data locked when the client executes a coherent command is not changed by other clients and an error occurs. It also ensures the success rate of command execution. Here you can't help wondering if there are transaction operations in redis? Cannot transaction operations imp

In the driver, when multiple threads access the same resource at the same time (the global variable in the driver is a typical shared resource), it may lead to a "race State ", therefore, we must control the concurrency of shared resources. The most common method to solve Concurrency Control in Linux kernel is spin lock and semaphore (usually used as mutex lock ). Spin locks are similar to semaphores, but not similar to semaphores. Similar to semaphor

Lock as a tool for concurrent shared data, ensuring consistency, there are many implementations in the Java platform (such as synchronized and Reentrantlock, etc.).These locks have been written to provide convenience for our development, but the specific nature and type of the lock are rarely mentioned. This series of articles will analyze the common locks in Java and their features to answer questions.1, S

(@ "sold a ticket-%ld-%@", _maxcount,[nsthread CurrentThread]); } else{ NSLog (@ "ticket sold Out"); Break;}}}} Output Result:2. NslockIn the cocoa Framework, Nslock implements a simple mutex, and the interfaces of all locks (including nslock) are actually defined by the Nslocking protocol, which defines the lock (locking) and unlock (unlock) methods.The lock method cannot be called multiple times, causing

Reference:Http://www.360doc.com/content/12/0723/00/9298584_225900606.shtmlHttp://www.cnblogs.com/biyeymyhjob/archive/2012/07/21/2602015.htmlHttp://blog.chinaunix.net/uid-25100840-id-3147086.htmlhttp://blog.csdn.net/u012719256/article/details/52670098-------------------------------------------------------------------------------------------------In drivers, when multiple threads access the same resource at the same time (global variables in the driver are a typical shared resource), "race" may be

An introductionWhen it comes to volatile memory semantics, there is a saying: There is a good way to understand the volatile nature of a volatile variable, which is to use a single read/write for variables that is synchronized with the same lock for these individual read/write operations. So actually the release and acquisition of the lock has the same memory semantics as the volatile write and read.Release of two locks-acquisition of established Happ

the same method, each thread has its own copy of the local variables.2 . Each instance of the class has its own object-level lock. when a thread accesses a synchronized synchronous code block or synchronous method in an instance object, the thread acquires an object-level lock on the instance, and other threads need to block the wait if they want to access the synchronized synchronous code block or synchronous method. The object-level lock is freed until the previous thread exits from a synchro

the READ UNCOMMITTED transaction isolation LEVELPaglock with multiple page locks where a table lock is usedREADPAST let SQL Server skip any locking lines, perform transactions, apply to READ UNCOMMITTED transaction isolation LEVEL only skip RID lock, skip page, zone and table lockRowlock forcing the use of row locksTablockx enforces exclusive table-level locks, which prevent any other transactions from usi

Tags: style blog color os io data div problem spIn Oracle, if the foreign key is not indexed, the modification to the parent table causes the child table to be added to the full table lock. This consists of two cases: 1. Delete rows from the parent table, if there is no index on the foreign key, causes the child table to be added a full table lock 2. Update the primary key of the parent table (according to the principle of the relational database, updating the primary key is a huge "taboo", so t

SQL Server query performance optimization analysis transactions and locks (I) SQL Server query performance optimization analysis transactions and locks (ii) SQL Server query performance optimization analysis transactions and locks (III) SQL Server query performance optimization analysis transactions and locks (4) (4) u

A frequent requirement of thread security is to allow concurrent reading but not concurrent writing. For example, this is true for files. ReaderwriterlockslimIn. NET Framework 3.5It is provided to replace the previous"Fat"Version"Readerwriterlock" These two classes have two basic locks.----One read lock and one write lock. A write lock is a full exclusive lock. Read locks can be compatible with o

A lock is a mechanism that prevents multiple transactions from accessing the same resource from affecting each other. Generally, high-concurrency databases need to use the lock mechanism to solve the problem of Concurrent Data Access, consistency and integrity.The resources mentioned above can be roughly divided into two types:● User objects: such as tables and data rows● Transparent system objects to users, such as shared data structures in memory and information in data dictionaries Oracle im