Harmony Logger

Introduction

In HarmonyOS application development, an efficient logging system is crucial for debugging and troubleshooting. While the native hilog interface provides comprehensive functionality, it presents several practical limitations:

Complex Data: Requires manual serialization of objects and collection types
Log Filtering: Lacks capability for runtime dynamic log level adjustment
Local Storage: No built-in log file management or rotation mechanism
Cloud Reporting: Missing ready-to-use cloud logging solution

During my experience developing Flutter Apps, I worked with Flutter's logger library whose elegant design left a deep impression. Inspired by this, I developed a similar logging solution for HarmonyOS (logger) featuring:

Support for multiple data types including primitives, objects, Classes, Maps, Sets with JSON serialization
Customizable logging behaviors like dynamic filtering, local file I/O (with automatic periodic cleanup), and cloud reporting
Compatibility with HarmonyOS Next API12+
Stack trace information output

Preparation

Go to [Profile → Security Management] to add your OHPM public key:

 # ssh-keygen creates public/private key pair - NOTE: passphrase MUST NOT be omitted!!!
 # --------------------------------------------------------------
   ssh-keygen -m PEM -t RSA -b 4096 -f ~/.ssh_ohpm/id_rsa_publish
   Generating public/private RSA key pair.
   Enter passphrase (empty for no passphrase):

Go to [Profile] Copy the publish code and configure publish_id on your local device

   # your_publish_id: the publishing code you copied
   # ----------------------------------------------
   ohpm config set publish_id your_publish_id

Development Explanation

API	Purpose	Detailed Description
Filter	Log filtering	Controls which logs should be recorded, supports log level filtering (DEBUG/INFO/WARN/ERROR) etc.
Output	Log output stream management	Defines final log output destinations and behaviors, such as console, local files, network reporting, multiple output source combinations
Printer	Log content formatting	Handles log visual presentation, including text formatting (colors/indentation/borders), structured output, stack tracing
Logger	Log trigger entry point	Provides developer-facing logging interface with multiple level methods (debug, info, warn, error etc.)

API	Inherits From	Purpose	Detailed Description
SafeFilter	`Filter`	Basic log filtering	Fundamental log level filtering (DEBUG, INFO, WARN, ERROR)
SafeWriteFileOutput	`Output`	Filesystem log output	Supports automatic log directory creation (daily), log file rotation, exception recovery mechanism, and uses AsyncMutex to optimize high-frequency write/read operations
SafeConsoleOutput	`Output`	Console log output	Compatible with DevEco Studio console, supports color differentiation and highlighting
SafeMultiOutput	`Output`	Multi-destination output	Supports multiple output sources with configurable output weights
SafeSimplePrinter	`Printer`	Minimalist log format	Single-line text output without decorations (no timestamps/borders), ideal for high-frequency debug logs
SafePrettyPrinter	`Printer`	Beautified formatted output	Multi-line formatted output with borders, auto-aligned key-value pairs, supports stack trace display and complex object tree visualization
SafeHybridPrinter	`Printer`	Hybrid strategy printer	Uses different printing strategies for different log levels with customizable level mapping
SafeLogger	`Logger`	Developer interface	Provides logging API for developers with multiple level methods (debug, info, warn, error, etc.)

Common APIs

Category	Method	Description	Return Type
Custom Options	`reset`	Customize log configuration	`Promise<void>`

Logging	`debug`	Log DEBUG level message	`Promise<void>`
	`info`	Log INFO level message	`Promise<void>`
	`warn`	Log WARN level message	`Promise<void>`
	`error`	Log ERROR level message	`Promise<void>`
	`fatal`	Log FATAL level (highest) message	`Promise<void>`
File Reading	`readAsRequestFile`	Read latest log file (full path)	`Promise<IRequestFile
	`readAsRequestFiles`	Read recent log files (full paths)	`Promise<IRequestFile[]
	`readAsArrayBuffer`	Read latest log file (binary data)	`Promise<IArrayBuffer
	`readAsArrayBuffers`	Read recent log files (binary data)	`Promise<IArrayBuffer[]
	`readAsString`	Read latest log file (text content)	`Promise<IString
	`readAsStrings`	Read recent log files (text content)	`Promise<IString[]
Event Listeners	`addWriteListener`	Register log write event listener	`void`
	`removeWriteListener`	Remove log write event listener	`void`
Log Cleanup	`clearHistory`	Clear expired log files	`Promise<void>`
	`clearAll`	Clear all log files (including current)	`Promise<void>`
Log Inspection	`isEmpty`	Check if log files are empty (non-existent)	`Promise<boolean>`

Source code / Repository

Github logger
OpenHarmony logger

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ArkTS Logger for HarmonyOS: Inspired by Flutter's Logger Package