feat(mqtt-bridge): add continuous polling mode

[groupsky]

Summary

Adds continuous polling mode that polls devices with minimal delay (1ms) instead of waiting for the configured interval. This enables maximum data throughput for time-sensitive applications where users want to read from devices as fast as possible.

Implementation

• Type Definition: Added optional mode field to PollingConfig type ('interval' | 'continuous')
• Scheduler Logic: Modified scheduleNextPoll() to use 1ms delay for continuous mode
• Validation: Added Zod schema validation for the mode field
• Tests: Comprehensive test coverage including backoff behavior in continuous mode
• Documentation: Updated README with configuration examples and explanations

Configuration Example

{
  "deviceId": "sensor1",
  "driver": "@ya-modbus/driver-ex9em",
  "connection": {
    "type": "rtu",
    "port": "/dev/ttyUSB0",
    "baudRate": 9600,
    "slaveId": 1
  },
  "polling": {
    "interval": 2000,
    "mode": "continuous"
  }
}

Technical Details

Why 1ms instead of 0ms?

• Prevents test infinite loops with Jest fake timers
• Allows other event loop tasks to execute
• Matches real-world setTimeout(..., 0) behavior
• Still provides effectively immediate polling (next event loop tick)

Backoff Logic

• Continuous mode respects maxRetries and retryBackoff settings
• After exceeding maxRetries, uses retryBackoff interval
• On success, returns to continuous mode (1ms delay)

Testing

All 298 tests pass, including new tests for:

• Continuous mode polling with minimal delay
• Default mode when not specified (interval)
• Backoff behavior in continuous mode
• Recovery to continuous mode after backoff

Breaking Changes

None - this is a backward-compatible feature addition.

Checklist

• Tests added and passing
• Documentation updated
• Type definitions updated
• Validation added
• Backward compatible

[pkg-pr-new]

Open in StackBlitz

@ya-modbus/cli

npm i https://pkg.pr.new/@ya-modbus/cli@383

@ya-modbus/device-profiler

npm i https://pkg.pr.new/@ya-modbus/device-profiler@383

@ya-modbus/driver-ex9em

npm i https://pkg.pr.new/@ya-modbus/driver-ex9em@383

@ya-modbus/driver-loader

npm i https://pkg.pr.new/@ya-modbus/driver-loader@383

@ya-modbus/driver-or-we-516

npm i https://pkg.pr.new/@ya-modbus/driver-or-we-516@383

@ya-modbus/driver-sdk

npm i https://pkg.pr.new/@ya-modbus/driver-sdk@383

@ya-modbus/driver-types

npm i https://pkg.pr.new/@ya-modbus/driver-types@383

@ya-modbus/driver-xymd1

npm i https://pkg.pr.new/@ya-modbus/driver-xymd1@383

@ya-modbus/emulator

npm i https://pkg.pr.new/@ya-modbus/emulator@383

@ya-modbus/mqtt-bridge

npm i https://pkg.pr.new/@ya-modbus/mqtt-bridge@383

@ya-modbus/transport

npm i https://pkg.pr.new/@ya-modbus/transport@383

commit: e03914d