# Expiration Timers

```{eval-rst}
.. automodule:: torch.distributed.elastic.timer
.. currentmodule:: torch.distributed.elastic.timer
```

## Client Methods

```{eval-rst}
.. autofunction:: torch.distributed.elastic.timer.configure

.. autofunction:: torch.distributed.elastic.timer.expires
```

## Server/Client Implementations

Below are the timer server and client pairs that are provided by torchelastic.

```{note}
Timer server and clients always have to be implemented and used
in pairs since there is a messaging protocol between the server
and client.
```

Below is a pair of timer server and client that is implemented based on
a `multiprocess.Queue`.

```{eval-rst}
.. autoclass:: LocalTimerServer

.. autoclass:: LocalTimerClient
```

Below is another pair of timer server and client that is implemented
based on a named pipe.

```{eval-rst}
.. autoclass:: FileTimerServer

.. autoclass:: FileTimerClient
```


## Writing a custom timer server/client

To write your own timer server and client extend the
`torch.distributed.elastic.timer.TimerServer` for the server and
`torch.distributed.elastic.timer.TimerClient` for the client. The
`TimerRequest` object is used to pass messages between
the server and client.

```{eval-rst}
.. autoclass:: TimerRequest
   :members:

.. autoclass:: TimerServer
   :members:

.. autoclass:: TimerClient
   :members:
```


## Debug info logging

```{eval-rst}
.. automodule:: torch.distributed.elastic.timer.debug_info_logging

.. autofunction:: torch.distributed.elastic.timer.debug_info_logging.log_debug_info_for_expired_timers
```