Durable.LogCapture (Durable v0.1.0-rc)

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Captures Logger output and IO operations during workflow step execution.

Uses process dictionary key :durable_logs for buffering log entries. Optionally replaces group_leader for IO.puts/IO.inspect capture.

Usage

This module is used internally by Durable.Executor.StepRunner to capture logs during step execution:

Durable.LogCapture.start_capture()

# Step execution happens here - Logger calls are captured
Logger.info("Processing order")
IO.puts("Debug output")

logs = Durable.LogCapture.stop_capture()
# => [%{timestamp: ..., level: "info", message: "Processing order", ...}, ...]

Configuration

config :durable,
  log_capture: [
    enabled: true,
    levels: [:debug, :info, :warning, :error],
    io_capture: true,
    io_passthrough: false,
    max_log_entries: 1000,
    max_message_length: 10_000,
    metadata_filter: [:request_id, :user_id, :module, :function, :line]
  ]

Summary

Functions

add_io_log(output)

Adds an IO output entry to the log buffer.

add_log(level, message, metadata)

Adds a log entry to the buffer.

clear_logs()

Clears the log buffer.

get_logs()

Returns the current log buffer contents.

in_workflow_context?()

Checks if the current process is executing within a workflow context.

start_capture()

Starts log capture for the current process.

stop_capture()

Stops log capture and returns the captured logs.

Functions

add_io_log(output)

@spec add_io_log(String.t()) :: :ok

Adds an IO output entry to the log buffer.

Called when processing IO log messages from the IO server.

add_log(level, message, metadata)

@spec add_log(atom(), String.t(), map()) :: :ok

Adds a log entry to the buffer.

Called by the Logger handler when a log event occurs in workflow context. Respects the max_log_entries configuration limit.

Parameters

  • level - The log level atom (:debug, :info, :warning, :error)
  • message - The log message string
  • metadata - Metadata map from the Logger event

clear_logs()

@spec clear_logs() :: :ok

Clears the log buffer.

get_logs()

@spec get_logs() :: [map()]

Returns the current log buffer contents.

Logs are returned in chronological order (oldest first).

in_workflow_context?()

@spec in_workflow_context?() :: boolean()

Checks if the current process is executing within a workflow context.

Returns true if :durable_workflow_id is set in the process dictionary, indicating that log capture should be active.

start_capture()

@spec start_capture() :: :ok

Starts log capture for the current process.

Initializes the log buffer in the process dictionary and optionally starts IO capture by replacing the group_leader.

This should be called before step execution begins.

stop_capture()

@spec stop_capture() :: [map()]

Stops log capture and returns the captured logs.

Restores the original group_leader if IO capture was active, stops the IO server process, and returns the formatted logs.

Returns an empty list if capture was not started or is disabled.