Implementation:Mage ai Mage ai Destination Emit State
| Knowledge Sources | |
|---|---|
| Domains | Data_Integration, ETL, State_Management |
| Last Updated | 2026-02-09 00:00 GMT |
Overview
Concrete tool for processing and emitting Singer STATE messages on the destination side provided by the Mage integrations Destination base class.
Description
Destination.process_state extracts the state value from a STATE message and calls _emit_state to persist it. _emit_state serializes the state as JSON and writes it to state_file_path (if configured) or to stdout with a flush. In batch mode, __process_batch_set merges bookmarks from multiple accumulated STATE messages before calling process_state once with the merged result.
Usage
Called automatically by _process when STATE messages arrive. Not called directly by subclasses.
Code Reference
Source Location
- Repository: mage-ai
- File: mage_integrations/mage_integrations/destinations/base.py
- Lines: 323-333 (process_state), 598-607 (_emit_state)
Signature
class Destination(ABC):
def process_state(self, row: Dict, tags: Dict = None) -> None:
"""Process a STATE message.
Args:
row: STATE message dict with 'value' key.
tags: Optional logging tags.
"""
def _emit_state(self, state: dict) -> None:
"""Write state to file or stdout.
Args:
state: State dict to emit.
"""
Import
from mage_integrations.destinations.base import Destination
I/O Contract
Inputs
| Name | Type | Required | Description |
|---|---|---|---|
| row | Dict | Yes | STATE message with 'value' key containing bookmarks |
Outputs
| Name | Type | Description |
|---|---|---|
| state_file_path | file | State JSON written to file (if configured) |
| stdout | JSON line | State JSON written to stdout (if no file path) |
Usage Examples
# State is emitted after successful batch export:
# If state_file_path is set:
# Writes to file: {"bookmarks": {"users": {"updated_at": "2024-01-15"}}}
# Otherwise writes to stdout for capture by orchestrator
# In batch mode, bookmarks from multiple STATE messages are merged:
# STATE 1: {"bookmarks": {"users": {"updated_at": "2024-01-10"}}}
# STATE 2: {"bookmarks": {"users": {"updated_at": "2024-01-15"}}}
# Merged: {"bookmarks": {"users": {"updated_at": "2024-01-15"}}}
Related Pages
Implements Principle
Requires Environment
- Environment:Mage_ai_Mage_ai_Python_3_9_Runtime
- Environment:Mage_ai_Mage_ai_Singer_SDK_And_Joblib_Runtime
Uses Heuristic
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