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Version: 0.7.4

Claptrap Lifetime Scope

The claptrap lifetime scope is divided into two major categories according to the writer's view of the, runtime lifetime scope and the design lifetime scope.

The runtime lifetime scope

The runtime lifetime scope is the lifetime scope behavior of each object in memory during the operation of the Claptrap system.For example, In a Web system, each Web request is typically assigned as a lifetime scope, and the Claptrap system has a similar lifetime scope design.These lifetime scopes have an impact on developers' component extensions or business development.The runtime lifetime scope of the Claptrap framework is divided into, Process Level, Claptrap Level, and Event Handler Level.

Process-levelAn object designed as a lifetime scope at the process level is a singleton object in the general sense.Each running Claptrap process has its own singleton object.Typically, for example in the Claptrap framework, in order to improve the speed at which an event is written to a persistent layer, each persistent layer destination corresponds to a batch processor (Batch Event Saver).They have only one instance in the lifetime scope of the entire process, corresponding to the persistent layer, respectively, so that the event can be merged into the persistent layer, thereby boosting the write performance.In general, objects that are designed to be process-level lifecycles have one or more of the following characteristics:

  1. Just have the logic or code that you want to run once in the entire process lifetime scope.It can usually be achieved with the help of Lazy as well as a single case.
  2. Only a single object is required in the entire process lifecycle.For example Claptrap Design Store, Claprap Options and so on.
  3. There can only be a single object in the entire process lifetime scope.For example, Orleans Client.

Claptrap levelObjects in the Claptrap-level lifetime scope are created with the activation of Claptrap and are released with the inactivation of Claptrap.These objects are usually strongly associated with a Claptrap Identity.For example, Claptrap Design, Event Saver, Event Loader, State Saver, State Loader, and so on associated with this Claptrap Identity.

Event Handler LevelEvent Handler level lifetime scope objects are created as the event handler is created and released with the event handler release.This level of lifetime scope is similar to the Web request lifetime scope in Web.Typically, unit of work for a unified database transaction falls to this level.

Design lifetime scope

Design lifetime scope are the lifetime scope of business objects for Claptrap.This has nothing to do with whether the program is running or not, or even whether or not the program is used.To give a specific example, orders in a regular e-commerce system.The activity business time limit for an order will generally not exceed three to six months.When more than this time limit is exceeded, the data of the order cannot already be modified.Here, this "three to six months" time limit is called the design lifetime scope of an order.In a Claptrap system, if an object has exceeded its design lifetime scope, it manifests itself as "there is no longer a need to activate this Claptrap in business."The following inferences can be obtained from this:

  1. The events that the Claptrap has already stored have lost their meaning and deleting them can free up the available space.
  2. The business code corresponding to this Claptrap no longer needs to be maintained, and it is possible to choose to be removed from the reference or to remove the code.

Therefore, the shorter the design lifetime scope of Claptrap, it is more conducive to reducing resource footprint and code maintenance costs, and vice versa, increasing storage costs and maintenance difficulties.Therefore, when designing Claptrap systems, there is a tendency to use a shorter design lifetime scope.And this noun, also directly reflects the actual entirely by "design" to determine. Next, let's list some common design lifetime scope classification.

Business boundary demarcation

This is the most common division.The business objects are divided based on the requirements of domain modeling.And these business objects often have a fixed lifetime scope.As in the previous "order" is a common example of dividing the life cycle by business boundaries.When dividing using this method, you only need to note that Claptrap meets the basic requirement that "the minimum competitive resource range is greater than or equal to".Developers can experience this division with an example of a "train ticketing system".

Conditional boundary demarcation.

In general, the business boundary-based division method has been able to divide a reasonable lifetime scope.However, if you are simply divided along business boundaries, you may have objects with 'permanent' design lifetime scope.If these objects have a very intensive event operation.Then the number of events generated will be unusually large.To do this, we introduce human-controlled ways to shorten the design lifetime scope.This division is based on specific conditions.It is therefore called conditional boundary demarcation.And the most classic of these is the use of "time limit" to divide.

Here we illustrate this division by using the shopping cart object in the Quick Start example.First, a shopping cart is a user-related object, and as long as the user has been in the system, it is possible to be activated, that is, its design lifetime scope is "permanent".Therefore, you cannot delete related events, and they must be permanently saved to ensure that the shopping cart data is correct.But, if we are no longer concerned about the events that the shopping cart has produced over a year ago.We can divide the shopping cart of a single user manually according to the year.At the same time, we can make a "state copy" of the shopping cart in two adjacent years.In this way the state data of the previous year is continued, so that the shopping cart of the user is produced shorter on the design lifetime scope, and this does not affect the business as well.We can use a classic Chinese legend story, "YuGong Move Mountain", to understand this time-based design lifetime scope classification.In the story, YuGong is mortal, although they cannot grow old (shorter design lifetime scope), but the spirit of YuGong (the longer design time lifetime scope) can be renewed with future generations, and thus can complete the great career of moving mountains.When each generation of "YuGong" is replaced, the "state copy" (spiritual continuation) mentioned above occurs.Thus, the requirements of the lifetime scope when a longer or even permanent design is achieved with a shorter design lifetime scope.

"YuGong Move Mountain" Taihang, Wangya two mountains, a square of seven hundred miles, very very high, originally in the southern part of Luzhou, the north of the Yellow River. Under The North Mountain, there is a man named YuGong, who is nearly 90 years old and lives directly opposite the mountain.He suffered from the blockage in the northern part of the mountains and came out to go in and all had to take a detour, so as to convene the whole family to discuss saying:"I will try my best to dig up the steep mountains so that the road has always been to the southern part of Yuzhou (a city), and reach the south coast of the Han water, okay?" everyone expressed their approval.His wife asked, "with your strength, even a littile mountain like KuiFu can not be flattened, what about Taihang, WangWu?"Besides, where do you lay the earth and the stones? "People say: "throw it on the edge of the Bohai Sea, to the north of the YinTu (a place)." So YuGong led the three men who could carry the burden in the children and grandchildren to go up the mountain, chisel stones, dig earth, and transport them to the edge of the Bohai Sea with dustpan.The widow of the neighbor, Jingcheng, had an orphan who was just 7-8 years old and go to help him.They can take a turn only once every half year. ZhiSou (name of a man, wise man) in HeQu (a place) laughed at the fool and stopped him from doing it, saying, "You're so stupid!"Just by virtue of your remaining years, the rest of your strength doesn't even move one of the grass on the mountain, so what about the soil stones? "YuGong sighed and saied: "Your mind is really stubborn and stubborn enough to be unenlightened, even the orphan widow can't compare.Even if I die, there is still a son there; the son has another grandson; the grandson has a son again; and the son has a grandson again; and the children and grandchildren are endless, but the mountains will not increase even more, and are still afraid to dig up? " ZhiSou has no words to answer. The mountain god heard about it, afraid that he had dug down endlessly, and reported it to the Jade Emperor.Jade Emperor was moved by the sincerity of YuGong, and ordered the two sons of ShenKuaE (name of a god) to carry away the two mountains, placed one in the east of ShuFang (a city) and one in the southern part of YongZhou (a city).From then on, there were no more mountains from the south of JiZhou to the southern coast of HanShui River.