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Updated docs and updated API to fetch signal descriptors in all modes

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API and Protocol docs have been updated (GPT 5.6)

The API methods for fetching a sepcific signal descriptor and fetching
all signal descriptors now work in offline mode, the core_tui.py example
has been updated to fit the new tri mode architecture and loading
recording offload -> processing and then processing -> playback engine
all works
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# DynaLab Core API
`Core` is the Python interface for running a DynaLab Core instance, inspecting
signals and their current values, recording incoming data, playing recordings,
and creating derived signals. Connectors provide realtime data to a running
core using the [DynaLab protocol](Protocol.md).
`Core` runs a DynaLab Core instance: it accepts connector data, retains live
values, records data, prepares DLPak archives, plays recordings, and manages
derive units. Connector authors should also read the [protocol guide](Protocol.md).
> [!IMPORTANT]
> **Packet model change.** The default packet and signal classes are lightweight
> `@dataclass(slots=True)` objects. They intentionally do not validate or coerce
> input at construction time. Pydantic models are retained only at a JSON
> boundary and are named with the `Json` prefix, such as `JsonHeartbeat` and
> `JsonConnectorHello`. Use the `Json*` classes with JSON-over-TCP and convert
> with `to_pure()`; use the unprefixed classes inside Core, connectors, and
> derive code. See [Packet representations](Protocol.md#packet-representations).
> [!WARNING]
> DynaLab Core is in alpha. Its public API may change between releases.
> DynaLab Core is in alpha. Its API and protocol can change between releases.
## Quick Start
Create a configuration, construct the core, then start it. Always stop the core
when the application exits so its server and worker threads are shut down.
## Quick start
```python
from dynalab_core import Core
from dynalab_core.config import CoreConfig
core = Core(CoreConfig(host="127.0.0.1", port=58763))
try:
core.start()
core.wait() # Blocks until stop() is called or a timeout expires.
core.wait()
finally:
core.stop()
```
`Core` does not currently implement the context-manager protocol. Use
`try`/`finally` when the core may be started.
Constructing `Core` starts its internal workers. `start()` starts the TCP
server. Always call `stop()` during shutdown; a stopped core cannot be started
again.
## Configuration
`CoreConfig` is defined in `dynalab_core.config`.
`CoreConfig` is a Pydantic configuration model in `dynalab_core.config`.
```python
from dynalab_core.config import CoreConfig
config = CoreConfig(
host="127.0.0.1", # Default
port=58763, # Default; must be in the range 0 through 65535
)
```
| Field | Type | Default | Description |
| Field | Type | Default | Meaning |
| --- | --- | --- | --- |
| `host` | `str` | `"127.0.0.1"` | Address on which the core server listens. |
| `port` | `int` | `58763` | TCP port on which the core server listens. |
| `host` | `str` | `"127.0.0.1"` | TCP bind address. |
| `port` | `int` | `58763` | TCP bind port; validated from 0 through 65535. |
| `thread_debug` | `bool` | `False` | Enables periodic per-thread CPU debug logging. |
| `playback_mode` | `"reprocess" \| "read"` | `"reprocess"` | Whether playback recalculates bound derived signals or reads their recorded values. |
`CoreConfig.bind_str() -> str` returns the configured address in
`"host:port"` form.
`CoreConfig.bind_str() -> str` returns `"host:port"`.
## Lifecycle
### `Core(config: CoreConfig)`
Creates a core and starts its internal input worker. The network server is not
started until `start()` is called.
Creates a core, its input, playback, and derive workers, plus the JSON/TCP
server object. It does not bind the network port until `start()`.
### `start() -> None`
Starts the configured server and begins accepting connector connections. This
method returns after the server start sequence completes.
Call `start()` once per `Core` instance. Calling it in any state other than the
initial state raises `CoreError` with code `"invalid_state"`. Server startup
failures, such as an address already in use, raise `JsonServerError` while
retaining the underlying exception as their cause.
Starts the configured JSON/TCP server. It may be called only once, while Core
is initialised; otherwise it raises `CoreError(code="invalid_state")`. A start
timeout or bind failure raises `JsonServerError` with code `"start_timeout"` or
`"startup_failed"`.
### `wait(timeout: float | None = None) -> None`
Blocks until `stop()` is called or until `timeout` seconds have elapsed. Omit
`timeout` to wait indefinitely. This is useful for keeping a command-line
application alive without a busy loop.
Blocks until `stop()` is called or the optional timeout elapses.
### `stop() -> bool`
Stops the server, disconnects connectors, signals the input worker to stop, and
stops the playback engine and all bound derive units. It also releases any call
currently blocked in `wait()`.
Stops the server, connector registry, derive registry, input worker, and
playback worker. Returns `True` only when all required components stop within
their time limits; it returns `False` if shutdown is incomplete.
Returns `True` when the server, connector registry, derive registry, and input
worker stop within their allowed timeouts, or `False` when shutdown is
incomplete.
## Modes and buffers
Call this during application shutdown, including when startup or runtime work
raises an exception. A stopped core cannot be started again.
`CoreMode` is `"realtime" | "playback" | "offline"`; new instances start in
`"realtime"`. `set_mode()` clears cached live values and cannot run during an
active recording (`CoreError(code="recording_active")`).
## Modes
Core operates in one of two modes:
| Mode | Signal source | Available operation |
| Mode | Source | Purpose |
| --- | --- | --- |
| `"realtime"` | Connected connectors | Recording |
| `"playback"` | A loaded recording | Playback |
| `"realtime"` | Connected connectors | Live values and recording. |
| `"playback"` | Loaded DLPak | Time-based replay. |
| `"offline"` | Recorded or loaded DLPak | Prepare a processing buffer without replaying it. |
The initial mode is `"realtime"`. Connected endpoints remain connected in
playback mode, but their incoming values are not routed into Core.
Endpoints remain connected in non-realtime modes, but only realtime connector
values are routed into Core.
`CoreMode` is defined in `dynalab_core.types` as the literal union of these two
strings.
### `set_mode(mode: CoreMode) -> None` / `get_mode() -> CoreMode`
### `set_mode(mode: CoreMode) -> None`
Changes the active mode and clears all cached live values. `mode` must be
`"realtime"` or `"playback"`; any other value raises `CoreError` with code
`"invalid_mode"`.
The mode cannot be changed while a recording is active. Attempting to do so
raises `CoreError` with code `"recording_active"`.
> [!IMPORTANT]
> Changing mode does not automatically pause active playback. Call `pause()`
> before switching from playback to realtime mode.
### `get_mode() -> CoreMode`
Returns the active mode as either `"realtime"` or `"playback"`.
## Signals
Signals are registered by connectors during their protocol handshake. A signal
is described by `SignalDescriptor` from
`dynalab_core.protocols.packets.handshake`.
```python
from uuid import UUID
from dynalab_core.protocols.packets.handshake import SignalDescriptor
signal = SignalDescriptor(
id=UUID("2d60a378-f37c-4c37-867b-c68f5116598b"),
name="Engine RPM",
type="number",
min_value=0.0,
max_value=6000.0,
unit="rpm",
timeout_ms=2_000,
)
```
| Field | Type | Default | Description |
| --- | --- | --- | --- |
| `id` | `UUID` | Required | Stable, unique signal identifier. |
| `name` | `str` | Required | Human-readable signal name. |
| `type` | `"number"` or `"binary"` | Required | Signal value category. Values are represented as `float` by the current data API. |
| `min_value` | `float \| None` | `None` | Optional lower bound. |
| `max_value` | `float \| None` | `None` | Optional upper bound. |
| `unit` | `str \| None` | `None` | Optional display unit. |
| `timeout_ms` | `int` | `2000` | How long a received value remains live. |
| `origin` | `"source"` or `"derived"` | `"source"` | Whether a connector or a derive unit produces the signal. |
### `get_signal_descriptor(signal_id: UUID) -> SignalDescriptor | None`
Returns the descriptor for `signal_id`, including a derived-signal output, or
`None` when no matching signal is available. In realtime mode, source
descriptors come from connected connectors. In playback mode, they come from
the loaded recording. Use a UUID, not its string representation.
### `get_all_signal_descriptors() -> list[SignalDescriptor]`
Returns the source descriptors available in the current mode followed by the
descriptors from bound derive units. In realtime mode, source descriptors come
from connected connectors. In playback mode, they come from the loaded
recording; previously recorded derived descriptors are omitted because bound
derive units recalculate those values.
Connector membership is dynamic: a disconnected connector's signals are no
longer returned in realtime mode.
## Live Values
After a connector sends a value, Core retains its latest value until the
signal's `timeout_ms` has elapsed. A stale, unknown, or not-yet-received value
is represented by `None`.
### `get_live_value(signal_id: UUID) -> float | None`
Returns the latest non-stale value for one signal.
```python
rpm = core.get_live_value(signal_id)
if rpm is not None:
print(f"Engine speed: {rpm:.0f} rpm")
```
### `get_all_live_values() -> dict[UUID, float]`
Returns a snapshot mapping signal IDs to their latest non-stale values. Signals
without a current value are omitted.
```python
for signal_id, value in core.get_all_live_values().items():
print(signal_id, value)
```
Incoming data timestamps use the monotonic-nanosecond timebase. See
[Protocol timestamps](Protocol.md#timestamps) when implementing a connector.
## Recording
Recording captures incoming connector and derived values in an in-memory
buffer. Recording is only available in realtime mode.
### `start_recording() -> None`
Clears the current recording buffer, records a new UTC start timestamp, and
begins capturing subsequent values. Calling this method in playback mode raises
`CoreError` with code `"incorrect_mode"`; calling it while already recording
raises `CoreError` with code `"recording_active"`.
> [!IMPORTANT]
> Starting a recording discards any values captured by a previous recording.
### `stop_recording() -> None`
Stops capture, normalizes the recorded data, and creates a processing buffer
containing the completed recording and its signal manifest. Timestamps in the
completed recording are nanoseconds relative to its first sample.
Calling this method in playback mode raises `CoreError` with code
`"incorrect_mode"`; calling it when no recording is active raises `CoreError`
with code `"not_recording"`.
> [!IMPORTANT]
> Stopping a recording replaces the previous processing buffer. Persist or
> process it before stopping another recording.
### `get_recording_state() -> bool`
Returns `True` while a recording is active and `False` otherwise.
### `write(dir: str | Path, filename: str) -> None`
Writes the most recently completed recording to a DLPak archive. The `.dlpak`
extension is added to `filename` when it is not already present.
```python
from pathlib import Path
core.write(Path("recordings"), "dyno-run-001")
```
Complete a recording with `stop_recording()` before calling `write()`. If no
completed recording is available, the method raises `CoreError` with code
`"no_recording"`. Archive write failures raise `DLPakError` with code
`"write_failed"` and retain the underlying exception as their cause.
## Playback
Playback feeds a completed recording through the same live-value and derive
pipeline used for realtime data. Switch Core to playback mode and load data
before starting playback:
```python
from pathlib import Path
core.set_mode("playback")
core.load_playback_engine(Path("recordings/dyno-run-001.dlpak"))
core.play()
```
Sets or returns the current mode. `CoreMode` is a type contract; callers must
pass one of the three values above. Changing mode does not automatically pause
playback, so pause it before leaving playback mode.
### `load_playback_engine(input: Path | None = None) -> None`
Loads playback data. Pass a DLPak archive path to load a saved recording, or
omit `input` to load the recording most recently completed by this `Core`
instance.
Available only in `"playback"` mode (`CoreError(code="invalid_mode")`). Pass a
`.dlpak` path, or omit `input` to load the current processing buffer. With no
processing buffer, omitting it raises `CoreError(code="no_playback_data")`.
Loading does not start playback; use `play()`.
This method is only available in playback mode; otherwise it raises `CoreError`
with code `"invalid_mode"`. Omitting `input` before a recording has been
completed raises `CoreError` with code `"no_playback_data"`. A file that cannot
be read or validated raises `DLPakError` with code `"read_failed"`. Replacing
data while playback is active raises `PlaybackError` with code
`"already_playing"`.
### `load_processing_buffer(input: Path | None = None) -> None`
Loading data does not start playback.
Available only in `"offline"` mode (`CoreError(code="invalid_mode")`). Pass a
`.dlpak` path to load it, or omit `input` to turn the completed recording into
a processing buffer and create its manifest. Omitting `input` before a
recording is available raises `CoreError(code="no_playback_data")`.
### `play() -> None`
## Signals and live values
Starts or resumes playback from the current position. Playback stops
automatically at the end of the recording and resets its position to the
beginning.
`SignalDescriptor` is the lightweight internal signal type in
`dynalab_core.protocols.packets.handshake`. Its fields are `id`, `name`,
`type` (`"number"` or `"binary"`), `min_value`, `max_value`, `unit`,
`timeout_ms` (default `2000`), and `origin` (`"source"` or `"derived"`, default
`"source"`). Use `JsonSignalDescriptor` only when serializing a descriptor.
Calling this method outside playback mode raises `CoreError` with code
`"invalid_mode"`. Starting before data is loaded raises `PlaybackError` with
code `"no_data"`.
### `get_signal_descriptor(signal_id: UUID) -> SignalDescriptor | None`
### `pause() -> None`
Returns a copy of the matching descriptor or `None`. Realtime descriptors come
from connectors and bound derive units. Playback descriptors come from the
loaded archive; derived descriptors are recalculated only when
`playback_mode="reprocess"`.
Pauses playback. A subsequent `play()` resumes from the current position.
Calling this method outside playback mode raises `CoreError` with code
`"invalid_mode"`. Calling it when playback is already paused has no effect.
### `get_all_signal_descriptors() -> list[SignalDescriptor]`
Returns descriptors available in the current mode. In `"read"` playback mode,
recorded derived descriptors are included; in `"reprocess"` mode, bound derive
units supply them instead.
### `get_live_value(signal_id: UUID) -> float | None`
Returns the most recent non-stale value for a signal, or `None` when unknown,
not yet received, or past the signal's `timeout_ms`.
### `get_all_live_values() -> dict[UUID, float]`
Returns a snapshot of current non-stale values. Signals without a live value
are omitted. Ingress timestamps use `time.monotonic_ns()`; see the protocol
guide for details.
## Recording and DLPak archives
### `start_recording() -> None` / `stop_recording() -> None`
Recording is available only in `"realtime"` mode. Starting clears the prior
in-memory buffer; stopping normalizes and sorts samples and creates an
offload buffer with a manifest. Errors use `"incorrect_mode"`,
`"recording_active"`, or `"not_recording"` as appropriate.
### `get_recording_state() -> bool`
Returns whether a recording is active.
### `write(dir: str | Path, filename: str) -> None`
Writes the current **processing** buffer as a `.dlpak` archive; the extension
is appended when absent. After recording, select `"offline"` mode and call
`load_processing_buffer()` before writing. If no processing buffer exists,
this raises `CoreError(code="no_recording")`. Archive failures raise
`DLPakError` with a stable code such as `"write_failed"`.
## Playback
### `play() -> None` / `pause() -> None`
Start or resume, and pause, a loaded playback engine. Both require
`"playback"` mode (`CoreError(code="invalid_mode")`). `play()` before loading
data raises `PlaybackError(code="no_data")`. Playback returns to timestamp zero
after it reaches the end.
### `seek(timestamp_ns: int) -> None`
Sets the playback position to `timestamp_ns`, measured in nanoseconds from the
recording's first sample. Samples after that timestamp are emitted when
playback starts or resumes. A negative timestamp raises `PlaybackError` with
code `"invalid_timestamp"`.
Calling this method outside playback mode raises `CoreError` with code
`"invalid_mode"`.
Sets the playback position relative to the recording's first sample. Requires
`"playback"` mode; a negative timestamp raises
`PlaybackError(code="invalid_timestamp")`.
### `get_playback_state() -> bool`
Returns `True` while the playback engine is actively emitting data and `False`
while it is paused, has not started, or has reached the end of the recording.
Returns `True` while the playback engine is emitting data.
## Derived Signals
A derive unit calculates a new value whenever one of its input signals receives
an update and all inputs have non-stale live values. Package the calculation,
its input descriptors, and its output descriptor in a `DLUnit`, then bind it
with `bind_derive_unit()`.
## Derived signals
### `bind_derive_unit(dlunit: DLUnit | None = None, file: Path | None = None) -> UUID`
Provide exactly one of `dlunit` or `file`:
Binds an in-memory `DLUnit` or loads one from a `.dlunit` path, then returns
its ID. Provide exactly one source. Missing or competing sources raise
`CoreError(code="bind_derive_failed")`; invalid source or function shape raises
`DeriveError` (for example `"invalid_source"` or `"invalid_signature"`).
- `dlunit` binds an in-memory `DLUnit`.
- `file` loads and binds a `.dlunit` archive.
To create and bind an in-memory unit:
```python
from uuid import uuid4
from dynalab_core.dlunit import DLUnit
from dynalab_core.protocols.packets.handshake import SignalDescriptor
processing_function = """
from dynalab_core.protocols.packets.data import ValueDescriptor
from dynalab_core.protocols.packets.handshake import SignalDescriptor
def add(left: ValueDescriptor, right: ValueDescriptor, output: SignalDescriptor) -> ValueDescriptor:
return ValueDescriptor(
signal_id=output.id,
value=left.value + right.value,
timestamp=left.timestamp,
)
"""
return_signal = SignalDescriptor(
id=uuid4(),
name="Total",
type="number",
origin="derived",
)
derive_unit = DLUnit()
derive_unit.set_manifest(
uuid4(),
[left_signal, right_signal],
return_signal,
)
derive_unit.set_data(processing_function)
unit_id = core.bind_derive_unit(dlunit=derive_unit, file=None)
```
To bind a previously saved archive instead, pass `None` for `dlunit` and its
path for `file`:
```python
from pathlib import Path
unit_id = core.bind_derive_unit(
dlunit=None,
file=Path("units/total.dlunit"),
)
```
The unit's Python source must define exactly one function. Its parameters must
be:
1. Zero or more `ValueDescriptor` parameters, in the same order as
the manifest's `input_signals`.
2. One final `SignalDescriptor` parameter for the manifest's `return_signal`.
3. A return annotation of `ValueDescriptor`.
The parameter annotations must use the imported `ValueDescriptor` and
`SignalDescriptor` classes shown above. The source string is executed with
`exec()`, so only bind code from trusted sources.
The returned UUID identifies the bound unit. Invalid source or function shape
raises `DeriveError`. Its code is `"invalid_source"` when the source cannot be
loaded or does not define exactly one function, and `"invalid_signature"` when
the function annotations or parameter order are invalid.
Derive source operates on internal `ValueDescriptor` and `SignalDescriptor`
dataclasses, not their `Json*` equivalents. Source is executed with `exec()`;
only load units from trusted sources.
### `unbind_derive_unit(unit_id: UUID) -> None`
Stops and removes the derive unit identified by `unit_id`. Passing an unknown
or already unbound ID has no effect.
The returned ID is no longer valid after unbinding. Create and bind a new unit
to resume derived-value processing.
Stops and removes a bound derive unit. An unknown ID has no effect.
## Exceptions
All expected library exceptions are defined in `dynalab_core.errors` and derive
from `DynaLabError`. Exceptions are grouped by subsystem rather than by every
individual failure reason:
Expected library errors inherit from `DynaLabError` in `dynalab_core.errors`
and expose a stable `code` attribute. Catch a specific subsystem class for
recovery, or `DynaLabError` at an application boundary. Operating-system and
validation causes are retained through `error.__cause__` where applicable.
| Exception | Area | Codes |
| --- | --- | --- |
| `CoreError` | Core lifecycle, mode, recording, and derive-unit binding operations. | `invalid_state`, `invalid_mode`, `incorrect_mode`, `recording_active`, `not_recording`, `no_recording`, `no_playback_data`, `bind_derive_failed` |
| `DLPakError` | Recording archive preparation, reading, and writing. | `no_data`, `no_manifest`, `read_failed`, `write_failed` |
| `DLUnitError` | Derive-unit archive preparation, reading, and writing. | `no_data`, `no_manifest`, `read_failed`, `write_failed` |
| `DeriveError` | Derive source, signatures, arguments, and registration. | `invalid_source`, `invalid_signature`, `input_signal_mismatch`, `argument_mismatch`, `already_registered` |
| `PlaybackError` | Playback state and data. | `no_data`, `incomplete_data`, `already_playing`, `invalid_timestamp`, `stopped` |
| `ConnectorError` | Connector queues and registration. | `queue_full`, `already_registered` |
| `JsonServerError` | JSON server startup and timeouts. | `start_timeout`, `startup_failed` |
Every exception has a human-readable message and a stable, machine-readable
`code`. Catch a subsystem exception when the application can recover from that
area, or catch `DynaLabError` at the application's outer boundary:
```python
from dynalab_core.errors import CoreError, DynaLabError
try:
core.start_recording()
except CoreError as error:
if error.code == "incorrect_mode":
core.set_mode("realtime")
core.start_recording()
try:
run_application()
except DynaLabError as error:
print(f"DynaLab operation failed ({error.code}): {error}")
```
Wrapped operating-system, validation, and archive errors are available through
the standard `error.__cause__` attribute. Internal transport conditions such as
a peer disconnect or an invalid incoming frame are handled by the server and
logged instead of being raised from a background task to application code.
| Exception | Area |
| --- | --- |
| `CoreError` | Lifecycle, modes, recording, buffer preparation, derive binding. |
| `DLPakError` | DLPak archive read/write and completeness. |
| `DLUnitError` | DLUnit archive read/write and completeness. |
| `DeriveError` | Derive source, signature, arguments, registration. |
| `PlaybackError` | Playback data, state, and timestamps. |
| `ConnectorError` | Connector queues and registration. |
| `JsonServerError` | JSON/TCP server startup and timeouts. |