Read Preference in MongoDB
来源:互联网 发布:记账软件破解版 编辑:程序博客网 时间:2024/06/08 08:57
basic concepts
(1)read preference describes how MongoDB clients/drivers route read operations to members of a replica set. five modes are primary,secondary,primaryPreferred,secondaryPreferred,nearest
(2)tag sets that is mappings of arbitrary keys and values and can customize read preference and write concern, target read operations to specific members of a replica set, so as to allow configurable awareness.
as for members in replica set or sharding cluster, they could be tagged as {‘dc’: ‘dc_1’},{‘use’: ‘reporting’, ‘disk’: ‘ssd’} or {‘rack’: ‘a’, ‘use’: ‘production’}
core process
(a)assemble a list of suitable members, taking into account member type(i.e. secondary,primary.etc)
(b)excludes members not matching the tag sets, if specified
(c)determine which suitable members is the closest to client in absolute terms.
(d)…
practice
(1)how read preference interacts with tag sets?
(a)in mongo shell, an example looks like db.collection.find().readPref({mode:'nearest',tags:[{'dc': 'dc_1'}]})
in mongodb enterprise 3.2, the test failed: “mode have wrong type, Excepted String, Found object”. when changing to .readPref(‘nearest’,[{‘dc’: ‘dc_1’}])
that direct read operation/cursor to nearby member in data center called dc_1.
(b)likewise, another example db.collection.find().readPref('primary',[{'dc':'dc_1'}])
, this statement outputs an error as shown below
the cause is as described errmsg field in document.
- Read Preference in MongoDB
- Scratchbox preference in Eclipse
- mongo read preference读优先级设置
- [mongoDB]exception in initAndListen: 20 Attempted to create a lock file on a read-only directory:
- Preference
- Preference
- Preference
- Preference
- Preference
- 关于System.in.read()
- read 'Database In Depth'
- 关于System.in.read()
- System.in.read()问题
- words in read book
- System.in.read()方法
- document read in ios
- System.in.read()使用
- System.in.read()用法
- Linux tasklet 分析笔记
- 计算机网络读书笔记——数据链路层(2)
- JQuery
- 线程的状态
- CentOS7持续集成自动化部署
- Read Preference in MongoDB
- JavaScript基础(五)--- 基本数据类型和引用数据类型
- os.getcwd()和os.path.realpath(__file__)的区别
- PAT程序设计考题——甲级1006(Sign In and Sign Out ) C++实现
- 关于input标签带有enctype="multipart/form-data"而导致getParameter获取不到值的解决方法2
- 软中断和TASKLET
- nginx---浏览器设置缓存
- Python使用linecache高效读入大文件内容(M级以上)
- 简单应用最小二乘准则