dify/api/dify_graph/graph_engine/layers

Layers

Pluggable middleware for engine extensions.

Components

Layer (base)

Abstract base class for layers.

• initialize() - Receive runtime context (runtime state is bound here and always available to hooks)
• on_graph_start() - Execution start hook
• on_event() - Process all events
• on_graph_end() - Execution end hook

DebugLoggingLayer

Comprehensive execution logging.

• Configurable detail levels
• Tracks execution statistics
• Truncates long values

Usage

debug_layer = DebugLoggingLayer(
    level="INFO",
    include_outputs=True
)

engine = GraphEngine(graph)
engine.layer(debug_layer)
engine.run()

engine.layer() binds the read-only runtime state before execution, so graph_runtime_state is always available inside layer hooks.

Custom Layers

class MetricsLayer(Layer):
    def on_event(self, event):
        if isinstance(event, NodeRunSucceededEvent):
            self.metrics[event.node_id] = event.elapsed_time

Configuration

DebugLoggingLayer Options:

• level - Log level (INFO, DEBUG, ERROR)
• include_inputs/outputs - Log data values
• max_value_length - Truncate long values