This article is shared from Huawei cloud community 《 Teach you how the IOT platform can realize the business configuration center 》, author ： Hua Wei Yun IoT Senior engineer Zhang Jian .

Preface

Last one 《 Huawei cloud Internet of things advanced siege lion 4 Practice sharing of configuration center in 》 The article shares the business configuration center .

This article describes the business configuration center （ The following is a brief description of the configuration center ） The key technology and implementation of . Huawei cloud Internet of things platform implements a business configuration center according to the implementation method in this paper , This configuration center 2020 year 1 Monthly online , Smooth operation up to now .

1      Concept

1.1      Operation and maintenance configuration

It's not about users , It is usually configured at the cluster boundary level , The program will only read , Such as database configuration 、 Mailbox server configuration 、 Network card configuration 、 Subnet address configuration, etc .

1.2      Business configuration

As SaaS  service , Each user has some business configuration on it . Such as the user's certificate configuration 、 Flow control configuration of user server, etc , These business configurations are relatively Operation and maintenance configuration It's more complicated for me , And there may be uniqueness restrictions , By user  id  only . This part of configuration data is usually triggered by user operation , Dynamic code writing , And notify each microservice instance . Usually , We hope that these configurations can be displayed in the interface , And support artificial modification . If the above logic is implemented by each micro service itself , There will be a lot of duplicate code , And there's no guarantee of quality . We want a common component to unify this capability . Open source or smaller projects will not choose to rely on a configuration center , But directly through the connection to the database or etcd To solve the problem

1.3      env

Represents a deployment environment .

1.4      cluster

Represents the cluster in the environment . It is common for blue-green publishing in a single environment , Blue cluster 、 Green clusters 、 Canary clusters, etc .

1.5      To configure

Configuration name , Such as user certificate configuration 、 User flow control configuration, etc .

1.6      Key

Unique key for configuration , Such as user id.

1.7      Value

Configure the value corresponding to the only key .

2      Configuration center design outline

2.1      Business configuration features

• Although there may be concurrency in business configuration writing , But the amount of concurrency is small , The frequency is low .
• Business configuration is often user-oriented id, The number of users in a single cluster is limited , Generally not more than 5 ten thousand .

2.2      Problems to be solved by the configuration center

2.3      Design points

• Single configuration requires configuration id, Every id through version Optimistic concurrency control to solve the problem of multi version conflict
• Notice is not reliable , When the application and configuration center are disconnected and cannot receive notifications , Ensure the reliability of data by regularly synchronizing data
• Support Schema Changes , because Schema Change infrequently , Also used version Optimistic concurrency control to solve the problem of multi version conflict

2.4      Whether the notification contains message content

I think we should only inform Key, The specific values let the application go to the configuration center to query . Just notice Key The implementation is simple and easy to understand . Notice at the same time Key&Value It is necessary to consider the two channels of periodic synchronization and notification concurrency , Possible race conflicts .

3      Configure the business process of the center

This section describes all business processes of the business configuration center , And try to abstract the interface irrelevant to the concrete implementation from the interaction

3.1      Add, delete, modify and check the configuration

3.2      Addition, deletion, modification and query of configuration value

3.3      Synchronize regularly

In the distributed environment , The notice may not be delivered , If the program falls into network interruption （ Or long gc）, Notification message delivery timeout , After the program is restored , The data is no longer accurate . Therefore, the data needs to be synchronized regularly , Improve reliability .

During synchronization , Just request interaction id and version, Avoid transmitting large amounts of data . After the application receives the data that needs to be synchronized ：

• Delete operation , Trigger deletion notification , Remove data from local cache .
• add to 、 Modify the operating , Query the configuration center for the latest data , Trigger notification and write to local cache .

3.4      Service startup

Service startup can also be regarded as a synchronous process , Just need to synchronize a large number of data additions . In order to avoid frequent and large requests to the configuration center , Introduce batch operation to reduce pressure

3.5      Limit

The design idea of the configuration center relies on the client to put all the data into the memory , If the number of users is too large , This model is not suitable .

notes ： One way to save memory is , Only a full amount of... Is placed in memory id and version, Data can only be queried when needed . This idea requires the configuration center to persist some old data for query in the following scenarios

• In the business process , You need to use this configuration value .
• When the callback business program is modified , Need to provide the old value .

There is no other difference .

4      Abstract implementation of business configuration

From the business scenario described above , We abstract the interactive interface and abstract implementation of the business configuration center . Interface Swagger Yaml Uploaded to Github：https://github.com/Shoothzj/config-center/tree/master/swagger

4.1      Configure relevant interfaces

• Provide env、cluster、 Configuration name 、 To configure Schema、 Add configuration version number
• Provide env、cluster、 Configuration name delete configuration
• Provide env、cluster、 Configuration name 、 new Schema、 new Version To modify the configuration
• Provide env、cluster、 The configuration name is used to query the configuration

4.2      Configuration value related interface

• Provide env、cluster、 Configuration name 、Key、Value To add configuration values
• Provide env、cluster、Key、ValueVersion（ Optional ） To delete the configuration value
• Provide env、cluster、Key、Value、ValueVersion（ Optional ） Modify configuration values
• Provide env、cluster、Key Query the configuration value
• according to env、cluster、 The current configuration data of the application is used for periodic synchronization
• according to Key List batch query configuration values

4.3      Notify relevant interfaces

• Notify a env some cluster Next , One of the configuration items Key change , newly added 、 Modify or delete . The options are HTTP Long link （Inspired by Apollo）、Mqtt、WebSocket etc. .

4.4      Configuration center storage layer Abstract implementation

The configuration center storage tier requires storage To configure and Configuration values data , Support UpdateByVersion, And need to capture changes in data , Used to notify the application

4.5      Abstract implementation of service discovery

In order to connect the application to the configuration center , A discovery mechanism is needed to make the application aware of the address of the configuration center . There are many ways of high availability , Such as K8s Find out 、ZooKeeper、Etcd、ServiceComb、 Business environment variable injection ELB Address （ELB The address of the backend mount configuration center ） etc. .

4.6      Abstract summary

According to this abstraction , We can select the key technical points , To implement the business configuration center .

5      Configuration center implementation

5.1      Huawei cloud Internet of things configuration center realizes

• env+cluster+config The name of the data table
• One key、value Corresponding to a row of data

5.2      Another way to do it

As long as the above interfaces and abstraction capabilities are implemented , Business configuration center can be realized , It can also be achieved

• env+cluster+config+key Combine into etcd Of key
• One key、value Corresponding to a key value pair

5.3      Another implementation

Of course

• env+cluster+config+key Combine into RocksDB Of key
• One key、value Corresponding to a key value pair

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