dragon.ai.agent.observability.tcp_bridge.TraceTcpBridge

class TraceTcpBridge

Bases: Thread

Bridge between intra-runtime DDict trace data and external TCP viewer.

Runs as a daemon thread in the orchestrator process. Lifecycle:

1. Binds a TCP server socket on a free port.

2. Waits for a viewer client to connect.

3. In a loop: a. For each known agent_id, polls its slot key in DDict to discover

   the agent’s trace key (written by the dispatcher).

   2. For each discovered trace key, reads the span list and detects new/updated spans.

   3. Streams newline-delimited JSON to the connected client.

4. On stop(), sends a {"type": "shutdown"} message and closes.

Unlike a shared index list, per-agent slot keys avoid read-modify-write races during fan-out (parallel dispatchers write to their own unique keys).

The external viewer needs no Dragon runtime — it is a plain TCP client that receives JSON.

Parameters

ddict:

Attached DDict instance.

task_id:

Pipeline run task_id (used to format slot keys).

agent_ids:

List of agent_id values from the pipeline (used to poll slot keys).

host:

Interface to bind to (default: all interfaces).

port:

Port to bind to (default: 0 = OS-assigned free port).

poll_interval:

Seconds between DDict polls (default: 0.5).

__init__(ddict: Any , task_id: str , agent_ids: list [str ] | None = None, host: str = '0.0.0.0', port: int = 0, poll_interval: float = 0.5) → None

This constructor should always be called with keyword arguments. Arguments are:

group should be None; reserved for future extension when a ThreadGroup class is implemented.

target is the callable object to be invoked by the run() method. Defaults to None, meaning nothing is called.

name is the thread name. By default, a unique name is constructed of the form “Thread-N” where N is a small decimal number.

args is a list or tuple of arguments for the target invocation. Defaults to ().

kwargs is a dictionary of keyword arguments for the target invocation. Defaults to {}.

If a subclass overrides the constructor, it must make sure to invoke the base class constructor (Thread.__init__()) before doing anything else to the thread.

Methods

__init__(ddict, task_id[, agent_ids, host, ...])	This constructor should always be called with keyword arguments.
getName()	Return a string used for identification purposes only.
isDaemon()	Return whether this thread is a daemon.
is_alive()	Return whether the thread is alive.
join([timeout])	Wait until the thread terminates.
run()	Main loop — accept client, poll DDict, stream spans.
setDaemon(daemonic)	Set whether this thread is a daemon.
setName(name)	Set the name string for this thread.
start()	Start the thread's activity.
stop()	Signal the bridge to shut down and wait for the thread to finish.

Attributes

address	Return (host, port) the TCP server is listening on.
daemon	A boolean value indicating whether this thread is a daemon thread.
ident	Thread identifier of this thread or None if it has not been started.
name	A string used for identification purposes only.
native_id	Native integral thread ID of this thread, or None if it has not been started.

__init__(ddict: Any , task_id: str , agent_ids: list [str ] | None = None, host: str = '0.0.0.0', port: int = 0, poll_interval: float = 0.5) → None

This constructor should always be called with keyword arguments. Arguments are:

group should be None; reserved for future extension when a ThreadGroup class is implemented.

target is the callable object to be invoked by the run() method. Defaults to None, meaning nothing is called.

name is the thread name. By default, a unique name is constructed of the form “Thread-N” where N is a small decimal number.

args is a list or tuple of arguments for the target invocation. Defaults to ().

kwargs is a dictionary of keyword arguments for the target invocation. Defaults to {}.

If a subclass overrides the constructor, it must make sure to invoke the base class constructor (Thread.__init__()) before doing anything else to the thread.

property address: tuple [str , int ]

Return (host, port) the TCP server is listening on.

run() → None

Main loop — accept client, poll DDict, stream spans.

stop() → None

Signal the bridge to shut down and wait for the thread to finish.

property daemon

A boolean value indicating whether this thread is a daemon thread.

This must be set before start() is called, otherwise RuntimeError is raised. Its initial value is inherited from the creating thread; the main thread is not a daemon thread and therefore all threads created in the main thread default to daemon = False.

The entire Python program exits when only daemon threads are left.

getName()

Return a string used for identification purposes only.

This method is deprecated, use the name attribute instead.

property ident

Thread identifier of this thread or None if it has not been started.

This is a nonzero integer. See the get_ident() function. Thread identifiers may be recycled when a thread exits and another thread is created. The identifier is available even after the thread has exited.

isDaemon()

Return whether this thread is a daemon.

This method is deprecated, use the daemon attribute instead.

is_alive()

Return whether the thread is alive.

This method returns True just before the run() method starts until just after the run() method terminates. See also the module function enumerate().

join(timeout=None)

Wait until the thread terminates.

This blocks the calling thread until the thread whose join() method is called terminates – either normally or through an unhandled exception or until the optional timeout occurs.

When the timeout argument is present and not None, it should be a floating point number specifying a timeout for the operation in seconds (or fractions thereof). As join() always returns None, you must call is_alive() after join() to decide whether a timeout happened – if the thread is still alive, the join() call timed out.

When the timeout argument is not present or None, the operation will block until the thread terminates.

A thread can be join()ed many times.

join() raises a RuntimeError if an attempt is made to join the current thread as that would cause a deadlock. It is also an error to join() a thread before it has been started and attempts to do so raises the same exception.

property name

A string used for identification purposes only.

It has no semantics. Multiple threads may be given the same name. The initial name is set by the constructor.

property native_id

Native integral thread ID of this thread, or None if it has not been started.

This is a non-negative integer. See the get_native_id() function. This represents the Thread ID as reported by the kernel.

setDaemon(daemonic)

Set whether this thread is a daemon.

This method is deprecated, use the .daemon property instead.

setName(name)

Set the name string for this thread.

This method is deprecated, use the name attribute instead.

start()

Start the thread’s activity.

It must be called at most once per thread object. It arranges for the object’s run() method to be invoked in a separate thread of control.

This method will raise a RuntimeError if called more than once on the same thread object.