An article about the configuration of length for TM center | ali middleware team blog

The Configuration (Configuration)

The concept of Configuration is familiar to every technical person. It can be said that a system that does not provide several Configuration parameters is embarrassed to go online and say hello to other systems. So why would be like this, in its essence is that we humans can’t control and predict everything, mapping to the software, we always need some features of system set aside some control thread, so that we need in the future, can be artificially stir the thread to control the behavior characteristics of the system, I call it “Dynamic attitude adjustment during System Runtime”.

To take a simple example,

logLevel = INFO

In a production environment, only WARNING/ERROR logs are generated. If the system is faulty, the output of logs is dynamically adjusted to DEBUG or TRACE, which contains diagnostic information.

Software’s old friend – configuration files

In the stand-alone system era, we used configuration files to store configuration items. A configuration item, such as logLevel above, contains the = expression, as follows:

config_key = config_value          // value1 or value2, you can choose one from the config_value set
Copy the code

In general config_Value should be a finite set of values and should be optional. If config_Value is not optional, THEN I can only assume that this configuration item must be fucking kidding me. A configuration file is generally a set of configuration items or a configuration set. A system can have one to multiple configuration files based on logical modules. The diagram below:

In the era of centralized development, basic enough to use the configuration files, because at that time the configuration management usually will not become a big problem, a little bit more simple, the system on the production, if need to modify a configuration, login to the production machine, vi to modify this configuration file, and then reload it isn’t a great burden.

The diagram below:

So there was no standard for configuration management in J2EE, the standard for enterprise application architecture. Of course, some manufacturers following J2EE standards, such as WebLogic, the middleware of Oracle, have done some work in this area in practice because the environment of many large enterprise customers is also quite complicated. WebLogic supports a feature called Deployment Plan, as shown in the following figure:

The essence behind it is that the configuration files in the application WAR package produced by developer (DEV) are some PlaceHolder, and the depoloy Plan XML file matching the target environment will be provided when the deployer (OPS) deploys the WAR package. The WebLogic Server itself replaces the PLACEHOLDER value of the WAR package configuration item with the value in the plan at the Deploy stage.

Distributed systems pose challenges to system configuration management

Every distributed system should have a dynamic configuration management system

Yes, you must have noticed that the statement here is a little different from the picture. What I want to emphasize here is that not all configuration centers are necessary. In a distributed system with a small scale, for example, one company has two application clusters, so whether you use configuration file +auto-reload, redis, ZooKeeper, whatever can be used. This dynamic configuration management system does not have to be a stand-alone system and can be independent of other systems, such as registries, or even a subsystem of messaging middleware. But it is important to know that there must be something that gives your system the ability to dynamically adjust its behavior, and that the basic inherent features of a CONFIGURATION management system must be implemented.

The difference between dynamic and static configuration

The build - version = 3.4.6-1569965Copy the code

Why Taobao

After I joined Ali to do Diamond, I thought about an interesting thing: why did the independent configuration center first appear on Taobao? If you search “configuration center” on Baidu, a famous search engine for bidding ranking in China, you will find that there is not much information, but the information in the front is XDiamond, a family of Diamond like SuperDiamond. Anyway, we have not paid any money to Baidu for associating configuration center with the name Diamond. So this search result should be a natural result, the side also reflected in the domestic speaking configuration center in the production of large-scale use is the only one, there is no semicolon.

In the industry, as shown below, Spring Boot/Cloud microservices are still in the preaching stage of introducing a registry (Discovery Service) and a configuration Service (Configuration Service).

And given the technical limitations of the way Spring is implemented, it seems that no company’s solution based on this configuration center has actually supported large-scale distributed systems in production. After all, looking through all the blogs and articles, no foreigner has even started to mention that, How this Git-based solution should address multiple data centers and non-functional requirements related to disaster recovery.

Back to the question, why taobao? We all know that Taobao took the lead in the domestic industry in initiating IOE removal and fully adopting MYSQL. In this process, ali and Ali middleware undoubtedly solved the problem of database and table division on a large scale and systematically in China. One of the core issues associated with TDDL is where the configuration information of the data source of multiple libraries is stored after the database is divided into tables, and the application is shielded from the fact of multiple libraries. Well, maybe you know the rest, put it in the configuration center! However, it should be mentioned that Diamond was not in the registry (ConfigServer), and then Diamond was separated from ConfigServer. In this process, many people saw the difference between persistent and non-persistent data and the stability of the product at that time. This is still true today, but over the years of practice and evolution, it has become clear that Service Discovery and Dynamic Configuration Management are fundamentally different things. It may have been a hunch at the time.

Mo Daojun early, more early pedestrian

Configuration and Environment

Another technical concern is the “Context” property of “configuration”. This expression can be a bit abstract and difficult to understand. It’s a bit like the technical term Context, where many components associate a Context, Component+Context is a complete runtime story. Environment is also one of the questions that people might ask in the post. Why does Diamond expose so many environments for the app to choose from? Those who are more familiar with middleware may ask, in a unified scenario, why is the registry a large cluster pattern and the configuration center a small cluster pattern? On the other hand, multiple environments are also one of the factors aggravating the need for distributed systems to rely on an independent configuration management system. It can be said that the more complex the environment of the company, the more distributed applications and services, the more likely the company will have an independent configuration center system.

A few easy-to-understand statements to help you understand the environment properties of the configuration,

“Set logLevel to DEBUG in the development environment, INFO in the pre-release environment, and WARNING in the production environment.”

“The maximum number of threads in the execution thread pool should be set to 15 in everyday environments, and a larger value should be set to 150 by default in production environments.”

“In the online environment, the application data source in the central machine room should be connected to library A, while the application in the S machine room should be connected to library B nearby.”

“Bidirectional synchronization switch should be turned off only in T environment”

“This is a bit of a big change, the new feature will only be available in unit H online, the rest of the unit environment is not available yet.”

Yes, I believe you must have found that the specific value definition of one of our configuration items is often associated with the specific environment. In reality, a considerable part of the configuration must be set to different values in different environments, but a considerable part of the configuration must be set to completely the same value in different environments. So from an application’s point of view, of the 100 configuration items, 50 May have different values for each environment, and 50 May have exactly the same values for all environments. This alienation brought complexity to the design of the configuration management system, and the final semantic interpretation, clearly should not be in the center of the configuration of the system itself, should be given to applications, configuration management system should do is to provide a convenient way of interaction to ensure the consistency of the two different demands well meet at the same time, this kind of appeal is divided into three aspects, the following diagram:

Yes, I believe you must have found that the specific value definition of one of our configuration items is often associated with the specific environment. In reality, a considerable part of the configuration must be set to different values in different environments, but a considerable part of the configuration must be set to completely the same value in different environments. So from an application’s point of view, of the 100 configuration items, 50 May have different values for each environment, and 50 May have exactly the same values for all environments. This alienation brought complexity to the design of the configuration management system, and the final semantic interpretation, clearly should not be in the center of the configuration of the system itself, should be given to applications, configuration management system should do is to provide a convenient way of interaction to ensure the consistency of the two different demands well meet at the same time, this kind of appeal is divided into three aspects, the following diagram:

Diamond provides all three of these capabilities, and 1,2 are typically represented in client libraries and OPS provided by the configuration center. 3 this implementation is more difficult, because in general, between multiple environments are some physical constraints, such as long-distance network or network isolation, to do distributed uniformity and considerations, such as partition tolerate sexual Diamond, currently only support online multi-cell consistency constraint rules, but because people don’t have to use real historical reasons, The rules themselves are not abstract enough or generic enough. Now we are doing renovation, the future will do more general consistency rules, behind will guide you to use, so much for those environment to maintain consistent the configuration items, environmental complexity can block out of the application, if an application configuration items are all consistent to the environment, so it will be good for you, the sky wave to five words, “so many” environment is not a thing.

In addition, A configuration center also should have the ability is to configure the set of export, import function, can make convenient application environment the configuration in A set of export and import to the environmental capacity of B, it has great significance on three scene, A scene is online configuration values is proven by practice, now in daily or pretest new application environment, Hope to online configuration copy to offline use up, the second is that offline application finally transferred to pretest or online, the better configuration want to line up at a draught, this according to our experience, of course, must be careful, the third is a new station or room, application will need in the new room all configuration migration in the past, Diamond will soon open up this ability.

With this in mind, you’ll have a better idea of what’s going on with the Abstract Environment and PropertySource in the Spring Framework. See:

Spring 3.1 M1: Unified Property Management

Spring. IO/blog / 2011/0…

Three configured properties

• Environmental properties
• Sparse change attribute
• Rapid spread

Environmental attributes have been discussed above.

Sparse change means that configuration changes are basically sparse, because the behavior of the system cannot be dynamically adjusted very frequently. If you adjust the behavior of the system every 100 milliseconds, the system will probably be angry with you.

While fast propagation is about configuration unchanged, a change often requires all nodes of the target cluster to almost receive the change at the same time, and then almost uniform uniform adjustment behavior. In the scenario of database cutting, after the active/standby switchover, the application cluster writes a new master database. This behavior switch is sparse and the whole convergence takes a day. The application cannot stand it.

The difference between configuration center (Diamond) and registry (ConfigServer)

About configuration, latest developments in the industry

There are few famous professional configuration center products in the industry (Diamond Ao Qiao ing~), and most of them are based on git, Redis, Zookeeper, Consul, etc., so if you want to know about the configuration center, you can directly learn about Diamond. : -)

However, there are some libraries that are very popular for configuration management client programming libraries. If you are interested, you can check them out:

• Apache Commons Configuration (commons.apache.org/proper/comm…

  This class library is too cumbersome, use the total feeling a bit kill chicken with a knife, force used too big feeling.

• The owner (owner.aeonbits.org/)

  Easy to use, features seem a lot, but in many key common features are missing.

• cfg4j (www.cfg4j.org/)

  It is easy to use. Cfg4j supports integration with a variety of back-end and provides a configuration center solution. The API design is also very good, and we have borrowed many of its ideas when designing the new Diamond Annotation API.

• Spring Framework (docs. Spring. IO/Spring/docs…).

  The Spring stuff is generally pretty good, and if your application uses Spring itself, of course, that’s it. There’s no need to use the above libraries.

• Spring Cloud Config Server

Configuration and Metadata

Many people don’t make this distinction, but there are subtle differences between configuration centers.

Configuration as described above, configuration modification is basically driven by people, and changes are realized in OPS.

The essence of metadata is a small piece of program metadata, which is mostly generated and consumed by the program and changed by the program through calling Diamond’s client API, without OPS or human intervention.

What’s the point of knowing that? There is no doubt that the configuration of such a requirement selection is relatively clear, and metadata, such as metadata, can choose too many Pub-sub systems, such as message queue products, distributed coordinator products such as ZooKeeper, k-V store with pub-sub capabilities such as Redis, and so on. So if it’s metadata, what to choose needs to be careful, which is useful, save, to fully assess and grasp their own needs.

Diamond is not only an application configuration store, but a large part of the data it stores is metadata, so Diamond is actually a metadata storage center.

conclusion