Cassandra 文件结构 - 文件是如何使用的? [英] Cassandra file structure - how are the files used?

问题描述

在使用 Cassandra 进行试验时，我发现 Cassandra 会写入以下文件:

When experimenting with Cassandra I've observed that Cassandra writes to the following files:

/.../cassandra/commitlog/CommitLog-<id>.log
/.../cassandra/data/Keyspace1/Standard1-1-Data.db
/.../cassandra/data/Keyspace1/Standard1-1-Filter.db
/.../cassandra/data/Keyspace1/Standard1-1-Index.db
/.../cassandra/data/system/LocationInfo-1-Data.db
/.../cassandra/data/system/LocationInfo-1-Filter.db
/.../cassandra/data/system/LocationInfo-1-Index.db
/.../cassandra/data/system/LocationInfo-2-Data.db
/.../cassandra/data/system/LocationInfo-2-Filter.db
/.../cassandra/data/system/LocationInfo-2-Index.db
/.../cassandra/data/system/LocationInfo-3-Data.db
/.../cassandra/data/system/LocationInfo-3-Filter.db
/.../cassandra/data/system/LocationInfo-3-Index.db
/.../cassandra/system.log

一般结构似乎是:

/.../cassandra/commitlog/CommitLog-ID.log
/.../cassandra/data/KEYSPACE/COLUMN_FAMILY-N-Data.db
/.../cassandra/data/KEYSPACE/COLUMN_FAMILY-N-Filter.db
/.../cassandra/data/KEYSPACE/COLUMN_FAMILY-N-Index.db
/.../cassandra/system.log

什么是 Cassandra 文件结构?更具体地说，data、commitlog目录是如何使用的，data目录下的文件结构是怎样的(Data/Filter/Index)?

What is the Cassandra file structure? More specifically, how are the data, commitlog directories used, and what is the structure of the files in the data directory (Data/Filter/Index)?

推荐答案

对 Cassandra 节点的写入首先会命中 CommitLog(顺序).(然后，Cassandra 将值存储到称为 Memtables 的列族特定的内存数据结构中.每当超过一个可配置的阈值时，Memtables 就会刷新到磁盘.(1，memtable 中的数据大小.2，对象数量达到一定限制，3、memtable的生命周期到期.))

A write to a Cassandra node first hits the CommitLog (sequential). (Then Cassandra stores values to column-family specific, in-memory data structures called Memtables. The Memtables are flushed to disk whenever one of the configurable thresholds is exceeded. (1, datasize in memtable. 2, # of objects reach certain limit, 3, lifetime of a memtable expires.))

data 文件夹包含每个键空间的子文件夹.每个子文件夹包含三种文件:

The data folder contains a subfolder for each keyspace. Each subfolder contains three kind of files:

• 数据文件:SSTable(命名法从谷歌借来的)代表排序字符串表，是一个文件键值字符串对(按键).
• 索引文件:(键，偏移量)对(指向数据文件)
• 布隆过滤器:数据文件中的所有键

• Data files: An SSTable (nomenclature borrowed from Google) stands for Sorted Strings Table and is a file of key-value string pairs (sorted by keys).
• Index file: (Key, offset) pairs (points into data file)
• Bloom filter: all keys in data file

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