NDB Cluster

NDB Cluster is a relational database with tables of records. Table rows represent tuples of relational data stored as records. When created, the attribute schema of the table is specified, and thus each record of the table has the same schema.

A Cluster NDB database is a collection of 3 types of nodes:

1. One or more management servers (nodes MGM)
2. One or more database / storage nodes (DB nodes)
3. One or more applications (API nodes)

It should be noted that a node is a program running on any computer. The nodes can run on different computers (or the same) and communicate throughsoftware modules called "transporters".

This type of cluster is a memory storage engine offering high availability and data persistence. It is highly configurable offering a number of options for dealing with load balancing andfault tolerance

Node MGM

This kind of node performs the function of managing, controlling and coordinating the other nodes within the cluster. Implements data configuration functions, start or stopother nodes within the cluster, perform backups, or other administrative tasks. Because it controls and shapes the rest of the nodes must be started before any other nodes

DB nodes

This type of node stores the data. The number of nodes in this type within the cluster is equal to a number of replicas by the number of fragments, for example, handled 4 replicas of the data with 2 fragments would require 8 data nodes. No need to handle more than one replica.

API Nodes

This nodes are used to access cluster data.

How it operates?

• Data is synchronously replicated between storage nodes, this minimizes problems of falls by fail-over.
• The nodes are designed using an shared-nothing architecture.
• No failure points (points of failure). Any node can be deleted without loss of data exist and without stopping the applications that use the base.
• The use of SQL is transparent which simplifies the work of developers and DBAs.
• Applications connect to the server regardless of specific details of how information is stored or such as network connections.
• This allows an application to be "portable" between environments where there is or not and where there is replication or clustering.

Shared nothing architecture

Is a distributed computing architecture in which each node is independent and self-sufficient, and there is no single point of contention across the system. More specifically, none of the nodes share memory or disk storage.

A SN system can scale almost infinitely simply by adding nodes in the form of inexpensive computers, since there is no single bottleneck to slow the system down.

Node and System Recovery

• When a node has a fault, to recover all information restores the help of other nodes.
• As in the version without cluster, error logs and it handles that keep the inf complete and consistent
• The cluster uses "based on pessimistic locking concurrency controls."

Concurrency Control

NDB Cluster uses pessimistic concurrency control based on locking. If a requested lock (implicit and depending on database operation) cannot be attained within a specified time, then a timeout error occurs.

Concurrent transactions (for example parallel application programs, thread-based applications, or applications with asynchronous transactions) sometimes deadlock when they try to access the same information. Applications need to be programmed so that timeout errors occurring due to deadlocks are handled. This generally means that the transaction encountering timeout should be rolled back and restarted.

Example:

Sources

Concepts
udlap
Shared nothing architecture