HarmonyOS Next Distributed Runtime Revealing—Seamless Synergy across Devices

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This article aims to deeply explore the technical details of Huawei HarmonyOS Next system and summarize them based on actual development practices.
Mainly used as a carrier of technology sharing and communication, it is inevitable to miss mistakes. All colleagues are welcome to put forward valuable opinions and questions in order to make common progress.
This article is original content, and any form of reprinting must indicate the source and original author.

In distributed system development, cross-device collaboration is like a symphony orchestra - each instrument must maintain an independent rhythm and achieve perfect harmony.After practical operations at HarmonyOS Next in the first half of the year, our team successfully built a cross-device rendering system with a latency of less than 8ms.The following is a decryption of the core technologies of this distributed runtime.

1. Distributed Object Model

1.1 Transparent citation mechanism


// Device A declares a distributed object
@Distributed(scope: .cluster)
class RenderTask {
func draw(frame: Frame) { ... }
}

// Transparent call of device B
let task = getRemoteTask() // Get remote reference
task.draw(localFrame) // Like a local call

Reference Type Comparison:
| Features | Local References | Distributed References |
|---------------|----------------|-----------------|
| Call Delay | <1μs | 2-8ms |
| Lifecycle Management | GC Automatic Recycling | Reference Count + Lease |
| Serialization Cost | None | Automatic PB encoding |

1.2 Zero Copy Transfer Optimization


sequenceDiagram
Device A->> Device B: Send memory area descriptor
Device B->> Device A: Establish direct memory mapping
Device A->> Device B: RDMA direct reading

In 4K video streaming test:

• Traditional method: CPU occupancy rate is 45%, delay of 16ms
• Zero copy solution: CPU occupancy rate of 12%, delay of 3.2ms

2. Performance optimization technology

2.1 Device capability aware routing


struct DeviceProfile {
@Dynamic var computeScore: Float
@Dynamic var networkQuality: NetworkGrade
}

// Intelligent routing decision-making
func selectExecutor(task: Task) -> Device {
return availableDevices
.filter { $0.computeScore > task.requirements }
.max { $0.networkQuality.rawValue }
}

Equipment Capacity Matrix:
| Equipment Type | Calculation Score | Network Level | Typical Delay |
|---------------|--------|----------|----------|
| Flagship Mobile | 9.8 | A+ | 3ms |
| Smart Watch | 2.1 | B | 15ms |
| Car Machine | 7.5 | A | 5ms |

2.2 Differential Synchronization Protocol


@DistributedState
class Document {
var version: Version
@DiffSync var content: Text
}

// Collaborative editing scenarios
remoteDoc.content.update { text in
text.insert("Hello", at: 0) // Transfer only the difference
}

Test in collaborative office scenarios:

• Full synchronization: bandwidth consumption 2.4MB/min
• Differential synchronization: bandwidth consumption 380KB/min

3. Fault-tolerant design

3.1 Automatic status synchronization


@Replicated(stategy: .eventual)
class SessionState {
var users: [User]
var lastActive: Time
}

// Automatically merge after the network is restored
session.merge(remoteState) // Conflict Resolution Policy

Comparison of merge strategies:
| Strategy | Applicable scenarios | Conflict resolution methods |
|---------------|------------------|-------------------|
| Last-Write-Win | Temporary Status | Timestamp Latest |
| CRDT | Key Data | Automatic Convergence Algorithm |

3.2 Retry the circuit breaker mechanism


@CircuitBreaker(
threshold: 3,
timeout: .seconds(5),
backoff: .exponential(max: .seconds(30))
)
func requestResource() throws -> Resource

Distributed Transaction Metrics:
| Solutions | Success Rate | Average Latency | Throughput |
|-----------------|--------|----------|---------|
| Simply try again | 89% | 320ms | 1200TPS |
| Fuse + Backoff | 99.7% | 185ms | 8500TPS |

Infrastructure Revelation: When developing distributed games, we once caused performance bottlenecks due to strong consistency requirements.Finally, the *** "strong core state consistency + ultimate consistency of peripheral data" is adopted, and the frame rate is increased from 24FPS to 60FPS while maintaining the experience.Remember: Distributed design is not about pursuing theoretical perfection, but about finding the golden intersection between business needs and technological reality.

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