In - depth Analysis of HarmonyOS Next Process Model and Inter - Process Communication Mechanism

I. Overview of HarmonyOS Next Process Model

In the HarmonyOS Next operating system, a process is the basic unit for resource allocation by the system and the foundation of the operating system's structure. For developers, understanding the process model of HarmonyOS Next is crucial for building efficient and stable applications.

1.1 Architecture of the System Process Model

HarmonyOS Next employs a hierarchical process model. Different types of components run in different processes to achieve resource isolation and system stability. The system process model is shown in the following figure:
![[In - depth Analysis of HarmonyOS Next Process Model and Inter - Process Communication Mechanism.png]]
As can be seen from the figure:

• Main Process: In an application with the same Bundle name, all UIAbilities default to running in the same independent process.
• ExtensionAbility Process: ExtensionAbilities of the same type run in an independent process.
• WebView Render Process: WebView has an independent render process.

1.2 Detailed Classification of Processes

1.2.1 Main Process

• In an application with the same Bundle name, all UIAbilities default to running in the same independent process.
• This is the core process of the application, responsible for UI display and main business logic processing.
• It is represented by the green part "Main Process" in the process model diagram.

1.2.2 ExtensionAbility Process

• ExtensionAbilities of the same type run in an independent process.
• This includes FormExtensionAbility, InputMethodExtensionAbility, etc.
• Each type of ExtensionAbility has its own independent process space.
• It is represented by the blue part in the process model diagram.

1.2.3 WebView Render Process

• The WebView component has an independent render process.
• It separates UI rendering from business logic.
• It improves the stability and security of WebView.
• It is represented by the yellow part "Render Process" in the process model diagram.

II. Configuration Method of Independent Processes

HarmonyOS Next provides a flexible process configuration mechanism, allowing developers to configure independent processes according to application requirements.
![[In - depth Analysis of HarmonyOS Next Process Model and Inter - Process Communication Mechanism-1.png]]

2.1 Device Types Supporting Independent Processes

Currently, only 2in1 and tablet devices support setting HAP and UIAbility to independent processes.

2.2 Configuration of HAP Independent Process

If you need to specify that a certain HAP runs in an independent process, you can set it through the module.json5 configuration file:

{
  "module": {
    "isolationMode": "isolationOnly" // or "isolationFirst"
  }
}

• isolationOnly: Run only in an independent process.
• isolationFirst: Give priority to running in an independent process.

2.3 Configuration of UIAbility Independent Process

If you need to specify that a certain UIAbility runs in an independent process, you need to perform the following configurations:

1. Configure the isolationProcess field to true in the module.json5 file.
2. Return a unique process identifier in the onNewProcessRequest callback.

2.4 Special Permissions for System Applications

Only system applications support building ServiceExtensionAbility and DataShareExtensionAbility, and can apply for multi - process permissions:

• Configure a custom process name for the specified HAP.
• Different HAPs can run in different processes by configuring the process attribute in module.json5.

IV. Inter - Process Communication Mechanism

Based on the process model of HarmonyOS Next, the system provides a variety of inter - process communication (IPC) mechanisms to meet the communication needs between applications and among multiple processes within an application.

4.1 Common Event Mechanism

The common event mechanism is an important IPC mechanism provided by HarmonyOS Next, with the following characteristics:

• One - to - many communication: A common event publisher may have multiple subscribers receiving the event simultaneously.
• Loosely coupled communication: The publisher and subscribers do not need to directly reference each other.
• Asynchronous communication: Event publishing and receiving are performed asynchronously.

The common event mechanism is particularly suitable for the following scenarios:

• System event broadcasting (such as network status changes, battery level changes, etc.).
• Communication between modules within an application.
• Cross - process event notification.

V. Best Practices for Process Model Design

Based on the process model of HarmonyOS Next, developers can follow the following best practices:

5.1 Process Isolation Design

• Deploy components with different security levels in different processes.
• Use an independent render process for components with high stability requirements (such as WebView).
• Isolate extension capabilities (ExtensionAbility) into independent processes.

5.2 Resource Optimization Configuration

• Reasonably allocate process resources according to the actual needs of components.
• Avoid creating too many processes to prevent system resource waste.
• Consider using independent processes for performance - sensitive components to reduce interference.

5.3 Selection of Communication Mechanisms

• Select an appropriate IPC mechanism according to the communication scenario.
• The common event mechanism is suitable for one - to - many notification scenarios.
• The ability call mechanism is suitable for point - to - point interaction scenarios.
• The data management mechanism is suitable for data sharing scenarios.

VI. Summary

The process model of HarmonyOS Next provides flexible process management and communication mechanisms for applications. Developers can:

1. Reasonably configure independent processes to achieve resource isolation and performance optimization.
2. Select appropriate inter - process communication mechanisms to meet the communication needs of different scenarios.
3. Follow best practices to build an efficient and stable application architecture. With the continuous development of HarmonyOS Next, its process model and IPC mechanism will be further improved, providing developers with more powerful system - level support.