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docs: [DOCS-3549] Rename Change Feeds to Event Feeds #200

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docs: [DOCS-3549] Rename Change Feeds to Event Feeds #200

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280 changes: 140 additions & 140 deletions README.md
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -285,138 +285,14 @@ for products in pages:
print(products)
```

## Event Streaming

The driver supports [Event Streaming](https://docs.fauna.com/fauna/current/learn/streaming).

### Start a stream

To get a stream token, append ``toStream()`` or ``changesOn()`` to a set from a
[supported source](https://docs.fauna.com/fauna/current/reference/streaming_reference/#supported-sources).


To start and subscribe to the stream, pass the stream token to
``stream()``:

```python
from fauna import fql
from fauna.client import Client

client = Client()

response = client.query(fql('''
let set = Product.all()
{
initialPage: set.pageSize(10),
streamToken: set.toStream()
}
'''))

initialPage = response.data['initialPage']
streamToken = response.data['streamToken']

client.stream(streamToken)
```
## Event Feeds (beta)

You can also pass a query that produces a stream token directly to
``stream()``:

```python
query = fql('Product.all().changesOn(.price, .stock)')

client.stream(query)
```

### Iterate on a stream

``stream()`` returns an iterator that emits events as they occur. You can
use a generator expression to iterate through the events:

```python
query = fql('Product.all().changesOn(.price, .stock)')
The driver supports [Event Feeds](https://docs.fauna.com/fauna/current/learn/track-changes/streaming/#event-feeds).

with client.stream(query) as stream:
for event in stream:
eventType = event['type']
if (eventType == 'add'):
print('Add event: ', event)
## ...
elif (eventType == 'update'):
print('Update event: ', event)
## ...
elif (eventType == 'remove'):
print('Remove event: ', event)
## ...
```

### Close a stream
### Request an Event Feed

Use ``close()`` to close a stream:

```python
query = fql('Product.all().changesOn(.price, .stock)')

count = 0
with client.stream(query) as stream:
for event in stream:
print('Stream event', event)
# ...
count+=1

if (count == 2):
stream.close()
```

### Error handling

If a non-retryable error occurs when opening or processing a stream, Fauna
raises a ``FaunaException``:

```python
from fauna import fql
from fauna.client import Client
from fauna.errors import FaunaException

client = Client()

try:
with client.stream(fql(
'Product.all().changesOn(.price, .stock)'
)) as stream:
for event in stream:
print(event)
# ...
except FaunaException as e:
print('error ocurred with stream: ', e)
```

### Stream options

The client configuration sets default options for the ``stream()``
method.

You can pass a ``StreamOptions`` object to override these defaults:

```python
options = StreamOptions(
max_attempts=3,
max_backoff=20,
start_ts=None,
cursor=None,
status_events=False,
)

client.stream(fql('Product.all().toStream()'), options)
```

## Change Feeds (beta)

The driver supports [Change Feeds](https://docs.fauna.com/fauna/current/learn/track-changes/streaming/#change-feeds).

### Request a Change Feed

A Change Feed asynchronously polls an [event stream](https://docs.fauna.com/fauna/current/learn/streaming),
represented by a stream token, for events.
An Event Feed asynchronously polls an [event stream](https://docs.fauna.com/fauna/current/learn/streaming),
represented by a stream token, for events.

To get a stream token, append ``toStream()`` or ``changesOn()`` to a set from a
[supported source](https://docs.fauna.com/fauna/current/reference/streaming_reference/#supported-sources).
Expand Down Expand Up @@ -453,7 +329,7 @@ You can also pass a query that produces a stream token directly to
client.change_feed(query)
```

### Iterate on a Change Feed
### Iterate on an Event Feed

``change_feed()`` returns an iterator that emits pages of events. You can use a
generator expression to iterate through the pages:
Expand All @@ -464,7 +340,7 @@ generator expression to iterate through the pages:

for page in feed:
print('Page stats: ', page.stats)

for event in page:
eventType = event['type']
if (eventType == 'add'):
Expand All @@ -490,20 +366,20 @@ Alternatively, you can iterate through events instead of pages with
## ...
```

The change feed iterator stops when there are no more events to poll.
The Event Feed iterator stops when there are no more events to poll.

### Error handling

If a non-retryable error occurs when opening or processing a change feed, Fauna
If a non-retryable error occurs when opening or processing an Event Feed, Fauna
raises a ``FaunaException``:

```python
from fauna import fql
from fauna.client import Client
from fauna.errors import FaunaException

client = Client()

try:
feed = client.change_feed(fql(
'Product.all().changesOn(.price, .stock)'
Expand All @@ -512,7 +388,7 @@ raises a ``FaunaException``:
print(event)
# ...
except FaunaException as e:
print('error ocurred with change feed: ', e)
print('error ocurred with event feed: ', e)
```

Errors can be raised at two different places:
Expand All @@ -527,15 +403,15 @@ processing. For example:
from fauna import fql
from fauna.client import Client
from fauna.errors import FaunaException

client = Client()

# Imagine if there are some products with details = null.
# The ones without details will fail due to the toUpperCase call.
feed = client.change_feed(fql(
'Product.all().map(.details.toUpperCase()).toStream()'
))

for page in feed:
try:
for event in page:
Expand All @@ -548,7 +424,7 @@ processing. For example:
print('error ocurred with event processing: ', e)
```

### Change Feed options
### Event Feed options

The client configuration sets default options for the ``change_feed()``
method.
Expand All @@ -568,6 +444,130 @@ options = ChangeFeedOptions(
client.change_feed(fql('Product.all().toStream()'), options)
```

## Event Streaming

The driver supports [Event Streaming](https://docs.fauna.com/fauna/current/learn/streaming).

### Start a stream

To get a stream token, append ``toStream()`` or ``changesOn()`` to a set from a
[supported source](https://docs.fauna.com/fauna/current/reference/streaming_reference/#supported-sources).


To start and subscribe to the stream, pass the stream token to
``stream()``:

```python
from fauna import fql
from fauna.client import Client

client = Client()

response = client.query(fql('''
let set = Product.all()
{
initialPage: set.pageSize(10),
streamToken: set.toStream()
}
'''))

initialPage = response.data['initialPage']
streamToken = response.data['streamToken']

client.stream(streamToken)
```

You can also pass a query that produces a stream token directly to
``stream()``:

```python
query = fql('Product.all().changesOn(.price, .stock)')

client.stream(query)
```

### Iterate on a stream

``stream()`` returns an iterator that emits events as they occur. You can
use a generator expression to iterate through the events:

```python
query = fql('Product.all().changesOn(.price, .stock)')

with client.stream(query) as stream:
for event in stream:
eventType = event['type']
if (eventType == 'add'):
print('Add event: ', event)
## ...
elif (eventType == 'update'):
print('Update event: ', event)
## ...
elif (eventType == 'remove'):
print('Remove event: ', event)
## ...
```

### Close a stream

Use ``close()`` to close a stream:

```python
query = fql('Product.all().changesOn(.price, .stock)')

count = 0
with client.stream(query) as stream:
for event in stream:
print('Stream event', event)
# ...
count+=1

if (count == 2):
stream.close()
```

### Error handling

If a non-retryable error occurs when opening or processing a stream, Fauna
raises a ``FaunaException``:

```python
from fauna import fql
from fauna.client import Client
from fauna.errors import FaunaException

client = Client()

try:
with client.stream(fql(
'Product.all().changesOn(.price, .stock)'
)) as stream:
for event in stream:
print(event)
# ...
except FaunaException as e:
print('error ocurred with stream: ', e)
```

### Stream options

The client configuration sets default options for the ``stream()``
method.

You can pass a ``StreamOptions`` object to override these defaults:

```python
options = StreamOptions(
max_attempts=3,
max_backoff=20,
start_ts=None,
cursor=None,
status_events=False,
)

client.stream(fql('Product.all().toStream()'), options)
```

## Setup

```bash
Expand Down
12 changes: 6 additions & 6 deletions fauna/client/client.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -73,12 +73,12 @@ class StreamOptions:
@dataclass
class ChangeFeedOptions:
"""
A dataclass representing options available for a change feed.
A dataclass representing options available for an Event Feed.

* max_attempts - The maximum number of times to attempt a change feed query when a retryable exception is thrown.
* max_attempts - The maximum number of times to attempt an Event Feed query when a retryable exception is thrown.
* max_backoff - The maximum backoff in seconds for an individual retry.
* query_timeout - Controls the maximum amount of time Fauna will execute a query before returning a page of events.
* start_ts - The starting timestamp of the change feed, exclusive. If set, Fauna will return events starting after
* start_ts - The starting timestamp of the Event Feed, exclusive. If set, Fauna will return events starting after
the timestamp.
* cursor - The starting event cursor, exclusive. If set, Fauna will return events starting after the cursor.
* page_size - The desired number of events per page.
Expand Down Expand Up @@ -465,10 +465,10 @@ def change_feed(
opts: ChangeFeedOptions = ChangeFeedOptions()
) -> "ChangeFeedIterator":
"""
Opens a change feed in Fauna and returns an iterator that consume Fauna events.
Opens an Event Feed in Fauna and returns an iterator that consume Fauna events.

:param fql: A Query that returns a StreamToken or a StreamToken.
:param opts: (Optional) Change feed options.
:param opts: (Optional) Event Feed options.

:return: a :class:`ChangeFeedIterator`

Expand Down Expand Up @@ -658,7 +658,7 @@ def __iter__(self) -> Iterator[Any]:


class ChangeFeedIterator:
"""A class to provide an iterator on top of change feed pages."""
"""A class to provide an iterator on top of Event Feed pages."""

def __init__(self, http: HTTPClient, headers: Dict[str, str], endpoint: str,
max_attempts: int, max_backoff: int, opts: ChangeFeedOptions,
Expand Down
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