# RTDS Python Library

Python library for using the Airship Real-Time Data Streaming API.
## Resources

* [Github Repo](https://github.com/urbanairship/connect-python-library)
* [Python Package Index (PyPI)](https://pypi.python.org/pypi/uaconnect)
* [RTDS API Reference](https://www.airship.com/docs/developer/rest-api/connect/)

## Installation

Install using `pip`:

```bash
pip install uaconnect
```


## Usage

The following sections describe various usage information for the [Real-Time Data Streaming](https://www.airship.com/docs/reference/glossary/#rtds) (RTDS) API.

### RTDS Event Consumer

To consume standard events from the RTDS API, instantiate an ``EventConsumer`` object
with the application key, access token, and an [offset recorder](#offset-recorders). You can then open the
connection and start reading events.

**Create an event consumer**

```python
>>> import uaconnect
>>> consumer = uaconnect.EventConsumer(
...     app_key='application_key',
...     access_token='access_token',
...     recorder=uaconnect.FileRecorder('.offset'))
>>> consumer.connect()
>>> for event in consumer.read():
...     if event is None:
...        continue
>>>     print("Got event: {}".format(event))
>>>     consumer.ack(event)
```


### RTDS Compliance Event Consumer

To consume [compliance events](https://www.airship.com/docs/developer/rest-api/connect/operations/compliance-event-stream/) from the RTDS API, instantiate a ``ComplianceConsumer`` object
with the application key, master secret and an offset recorder. You can then open the
connection and start reading events.

**Create a compliance event consumer**

```python
>>> import uaconnect
 >>> consumer = uaconnect.EventConsumer(
...     app_key='application_key',
...     master_secret='master_secret',
...     recorder=uaconnect.FileRecorder('.offset'))
>>> consumer.connect()
>>> for event in consumer.read():
...     if event is None:
...        continue
>>>     print("Got event: {}".format(event))
 >>>     consumer.ack(event)
```


### Alternate Data Center Support

When instantiating an ``EventConsumer`` or ``ComplianceConsumer``, you can pass the optional
`url` argument to explicitly specify the data center your project is located in. Possible
values are `US`, `EU`, or an arbitrary base URL in the form of `http://domain.xyz/`. The
library will build the URL path properly from there. If no `url` is specified, `US` is used.

**EU example**

```python
>>> import uaconnect
>>> consumer = uaconnect.EventConsumer(
...     app_key='application_key',
...     master_secret='master_secret',
...     url='EU',
...     recorder=uaconnect.FileRecorder('.offset'))
```


### Offset Recorders

Offset recorders inherit from the abstract base class `uaconnect.Recorder`,
implementing `read_offset` and `write_offset` methods. One recorder is
included in the library, `FileRecorder`, which stores the offset on disk. In
the `uaconnect.ext.redisrecorder` package there is an example implementation
of using a Redis instance to store the offset.

`ack` calls should be placed depending on whether in a failure scenario your
app wishes to possibly replay an already handled event or risk dropping one.
For the latter, call ``ack`` as soon as the event is read. For the former, call
`ack` only after the event has been fully handled.

### Advanced Options When Connecting

Airship Real-Time Data Streaming supports a variety of options when connecting
to make sure that you're only consuming the data that you want. `uaconnect`
makes it easy to use these connection parameters and filters.

#### Specifying Offsets

One of the advantages of RTDS is that you can resume from a
specific place in the stream. This is done by specifying the ``offset``
that's associated with the event. While ``uaconnect`` automatically tracks
offsets for you with ``uaconnect.FileRecorder``, you can also explicitly set an
offset.

**Set a particular offset**

```python
>>> import uaconnect
>>> recorder = uaconnect.FileRecorder(".offset") # or wherever you would like the file to exist
>>> recorder.write_offset("8865499359") # a randomly chosen offset
>>> recorder.read_offset()
'8865499359'
```


An alternative here is to just write the offset explicitly into the file or
whatever `Recorder` subclass you're using to track offsets.

**Check the offset**

```bash
cat .offset
886549935
```


Now, the next time you connect, it will pick up from that last offset.

If you'd like to manually set the offset for a connection to a known value
instead of the recorder's offset, set `resume_offset` like so:

**Resume from a particular offset**

```python
>>> consumer.connect(resume_offset='123456789')
```


#### Using filters

Filters are a powerful way of filtering what specific information you'd like to
see from the RTDS stream. You can filter by event type, device type, latency
on an event, or even specific devices or notifications.

Here's a brief example on how to use filters with `uaconnect`:

**Filter example**

```python
>>> import uaconnect
>>> consumer = uaconnect.EventConsumer(
...     app_key='application_key',
...     access_token='access_token',
...     recorder=uaconnect.FileRecorder('.offset')
...     )
>>> f = uaconnect.Filter()
>>> f.types("PUSH_BODY", "SEND") # only receive PUSH_BODY and SEND events.
>>> consumer.add_filter(f)
>>> consumer.connect()
```