Couchbase服务器管理入门

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"Couchbase Server的管理与入门" Couchbase Server是企业级的分布式内存数据存储系统，尤其适合处理大规模的实时数据。作为NoSQL数据库，它提供了高性能、高可用性和可扩展性，广泛应用于大数据管理和分析。本资料主要针对Couchbase Server的管理进行介绍，旨在帮助用户掌握如何有效地操作和管理Couchbase Server，从而利用数据驱动决策。 Couchbase Server的核心特性包括其分布式架构、内存优先的数据模型以及灵活的数据存储。内存中的数据处理使得Couchbase能提供亚毫秒级的响应时间，这对于需要快速处理大量请求的应用来说至关重要。此外，Couchbase支持自动的故障转移和数据复制，确保了服务的高可用性。在Couchbase Server的管理中，用户需要了解以下几个关键概念和功能： 1. **Bucket**: 是Couchbase中的数据容器，类似于传统数据库的表。每个bucket有自己的配置，包括内存大小、数据持久化策略等。 2. **Document**: 数据以JSON文档的形式存储，这提供了高度结构化的灵活性，允许数据以键值对或文档形式存储。 3. **Indexing and Querying**: Couchbase提供了查询语言N1QL（N1QL是SQL的一个变种，专为NoSQL设计），允许用户创建复杂的查询。同时，可以创建索引来加速查询性能。 4. **Replication and Data Durability**: 数据可以在集群内的节点之间复制，以实现高可用性。还可以设置持久化策略，如写入磁盘或通过XDCR（跨数据中心复制）在多个地理位置保持数据副本。 5. **Cluster Management**: 集群管理涉及节点的添加、删除、监控和故障恢复。管理员需要了解如何平衡负载、调整内存分配以及监控集群的健康状态。 6. **Backup and Recovery**: 定期备份是数据安全的关键。Couchbase提供了多种备份策略，包括在线备份和离线备份，以及如何在灾难发生时恢复数据。 7. **Security**: Couchbase提供了身份验证和授权机制，以保护数据的安全。管理员需要设置访问控制列表（ACLs）来限制对特定bucket或操作的访问。 8. **Cloud Integration**: 云环境下的Couchbase可以通过云服务提供商轻松扩展，例如AWS、Azure或Google Cloud。这使得在云端部署和管理Couchbase成为可能，利用弹性计算和存储资源。 9. **Performance Tuning**: 为了最大化性能，管理员需要了解如何调整配置参数，如内存分配、I/O优化以及网络调优。 10. **Monitoring and Analytics**: Couchbase提供了一套全面的监控工具，可以帮助管理员跟踪性能指标，并做出相应的优化决策。结合日志和分析工具，可以深入理解系统的运行情况。通过学习和实践这些知识，用户可以成为Couchbase Server的有效管理员，从而在大数据时代充分利用Couchbase的能力，实现数据的智能管理和决策支持。访问O'Reilly或其他相关资源，可以获得更深入的教程和指导，进一步提升Couchbase Server的管理技能。

All nodes within Couchbase Server are created equally. There is no

hierarchy or topology, and no single node is a ‘master’ of the rest

of the cluster. Each node is responsible only for the data it stores

and the requests made to it by clients.

Cluster

A cluster is a collection of one or more instances of Couchbase Server that are

configured as a logical cluster. All nodes within the cluster are identical and provide

the same functionality and information. The entire cluster shares data across the

individual nodes, with each node being responsible for only a portion of the entire

data set.

Clusters operate in a completely horizontal fashion. To increase the size of a cluster,

you add another node. There are no parent/child relationships or hierarchical

structures involved. This means that Couchbase Server scales linearly, both in

terms of increasing the storage capacity and the performance and scalability.

Cluster Manager

Every node within a Couchbase Server Cluster includes the Cluster Manager compo-

nent. The Cluster Manager is responsible for the following within a cluster:

• Cluster management

• Node administration

• Node monitoring

• REST API for management

• Statistics gathering and aggregation

• Runtime logging

• Multitenancy

• Security for administrative and client access

Buckets

Couchbase Server provides data management services using named buckets. These are

isolated virtual containers for data. A bucket is a logical grouping of physical resources

within a cluster of Couchbase Servers. They can be used by multiple client applications

across a cluster. Buckets provide a secure mechanism for organizing, managing, and

analyzing data storage resources.

Couchbase Server provides the two core types of buckets that can be created and man-

aged, summarized in Table 1-1. Couchbase Server collects and reports on runtime sta-

tistics by bucket type.

Architecture and Concepts | 3

Table 1-1. Bucket types

Bucket type Description

Couchbase Provides highly available and dynamically reconfigurable distributed data storage, providing persistence to disk

and replication services. Couchbase buckets are 100% protocol compatible with Memcached.

Memcached Provides a directly addressed, distributed (scale-out), in-memory, document cache. Memcached buckets are

designed to be used alongside relational database technology—caching frequently used data, thereby reducing

the number of queries a database server must perform for web servers delivering a web application.

The different bucket types support different core capabilities (as shown in Table 1-2).

Couchbase-type buckets provide a highly available and dynamically reconfigurable

distributed data store. Couchbase-type buckets survive node failures and allow cluster

reconfiguration while continuing to service requests.

Table 1-2. Couchbase bucket capabilities

Capability Description

Persistence Data objects are persisted asynchronously to hard disks from memory to provide protection from server restarts

or minor failures. Persistence properties are set at the bucket level.

Replication A configurable number of replicas can receive copies of all data objects in the Couchbase-type bucket. Every

node within a cluster is responsible for both active and replica data. If a node fails, the replica can be promoted

to be the active container, providing continuous (HA) cluster operations via failover. Replication operates at

the bucket level with replicas distributed over multiple servers in the same way as the bucket data.

Rebalancing Rebalancing enables load distribution across resources and dynamic addition or removal of buckets and servers

in the cluster.

Bucket sizing Couchbase buckets can be sized dynamically, allowing you to change and alter the bucket size as your application

needs change.

Buckets can be used to isolate individual applications to provide multitenancy, or to

isolate data types to enhance performance and visibility. Couchbase Server allows you

to configure different ports to access different buckets. Password authentication is also

available on individual buckets.

Smart clients discover changes in the cluster structure automatically by

using the Couchbase Management REST API. This ensures that the cli-

ent application continues to communicate to the appropriate node for

the data being accessed.

Couchbase Server allows you to use and mix different types of buckets (Couchbase and

Memcached) as appropriate in your environment. Quotas for RAM and disk usage are

configurable per bucket so that resource usage can be managed across the cluster.

Quotas can be modified on a running cluster so that administrators can reallocate re-

sources as usage patterns or priorities change over time.

4 | Chapter 1: Introduction to Couchbase Server

vBuckets

A vBucket is defined as the owner of a subset of the key space of a Couchbase cluster.

These vBuckets are used to allow information to be distributed effectively across the

cluster. The vBucket system is used both for distributing data, and for supporting rep-

licas (copies of bucket data) on more than one node.

Clients access the information stored in a bucket by communicating directly with the

node response for the corresponding vBucket. This direct access enables clients to

communicate with the node storing the data, rather than using a proxy or redistribution

architecture. The result is abstracting the physical topology from the logical partition-

ing of data. This architecture is what gives Couchbase Server elasticity.

This architecture differs from the method used by memcached, which uses client-side

key hashes to determine the server from a defined list. This requires active management

of the list of servers, and specific hashing algorithms such as Ketama to cope with

changes to the topology. The structure is also more flexible and able to cope with

changes than the typical sharding arrangement used in an RDBMS environment.

vBuckets are not a user-accessible component, but they are a critical

component of Couchbase Server and are vital to the availability support

and the elastic nature.

Every document ID belongs to a vBucket. A mapping function is used to calculate the

vBucket in which a given document belongs. In Couchbase Server, that mapping func-

tion is a hashing function that takes a document ID as input and outputs a vBucket

identifier. Once the vBucket identifier has been computed, a table is consulted to look

up the server that “hosts” that vBucket. The table contains one row per vBucket, pairing

the vBucket to its hosting server. A server appearing in this table can be (and usually

is) responsible for multiple vBuckets.

Data in RAM

The architecture of Couchbase Server includes a built-in caching layer. This approach

allows for very fast response times, since the data is initially written to RAM by the

client, and can be returned from RAM to the client when the data is requested.

The effect of this design to provide an extensive built-in caching layer that acts as a

central part of the operation of the system. The client interface works through the RAM-

based data store, with information stored by the clients written into RAM and data

retrieved by the clients returned from RAM; or loaded from disk into RAM before being

returned to the client.

Architecture and Concepts | 5

This process of storing and retrieving stored data through the RAM interface ensures

the best performance. For the highest performance, you should allocate the maximum

amount of RAM on each of your nodes. The aggregated RAM is used across the cluster.

This is different in design from other database systems where the information is written

to the database and either a separate caching layer is employed, or the caching provided

by the operating system is used to keep regularly used information in memory and

accessible.

Ejection

Ejection is a mechanism used with Couchbase buckets, and is the process of removing

data from RAM to make room for active and more frequently used information—a key

part of the caching mechanism. Ejection is automatic and operates in conjunction with

the disk persistence system to ensure that data in RAM has been persisted to disk and

can be safely ejected from the system.

The system ensures that the data stored in RAM will already have been written to disk,

so that it can be loaded back into RAM if the data is requested by a client. Ejection is

a key part of keeping frequently used information in RAM and ensuring that there is

space within the Couchbase RAM allocation to load that data back into RAM when

the information is requested by a client.

For Couchbase buckets, data is never deleted from the system unless a

client explicitly deletes the document from the database or the expira-

tion value for the document is reached. Instead, the ejection mechanism

removes it from RAM, keeping a copy of that information on disk.

Expiration

Each document stored in the database has an optional expiration value. The default is

for there to be no expiration (i.e., the information will be stored indefinitely). The

expiration can be used for data with a naturally limited life that you want to be auto-

matically deleted from the entire database.

The expiration value is user-specified on a document basis at the point when the data

is stored. The expiration can also be updated when the data is updated, or explicitly

changed through the Couchbase protocol. The expiration time can either be specified

as a relative time (for example, in 60 seconds), or absolute time (31st December 2012,

12:00 p.m.).

Typical uses for an expiration value include web session data, where you want the

actively stored information to be removed from the system if the user activity has stop-

ped and not been explicitly deleted. The data will time out and be removed from the

system, freeing up RAM and disk for more active data.

6 | Chapter 1: Introduction to Couchbase Server

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Couchbase服务器管理入门

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