redis-log-handler 0.0.1.dev32
A log handler for the Python logging module, emitting all logs to specific Redis channels

# redis_log_handler
Handler for the standard `logging` module which puts logs through to Redis.

## Install
This was developed against Python 3.6.7 specifically, but I don't believe it's version breaking.

#### Development
Set the local environment variable `REDIS_HOST` to point to the host where your Redis runs.

        $ export REDIS_HOST=localhost

Install the dev requirements

        $ pip install -r requirements-dev.txt

## How to use
You can either publish your logs to a channel, `rpush` them onto a key with an optional `ttl`
or implement the desired behaviour by deriving from the base class.

To add a handler to the python logger is very simple:

```python
import logging


from redis_log_handler import RedisKeyHandler

example_handler = RedisKeyHandler('example_key')  # Default parameters for Redis connection are used

logger = logging.getLogger()  # No name gives you the root logger
logger.setLevel("WARNING")
logger.addHandler(example_handler)

logger.warning("This will rpush this message to the 'example_key' in Redis.")
```

### Configuring Redis Connection
By default each handler will create a `StrictRedis` instance, passing on each argument from their `__init__(**kwargs)` to the StrictRedis instantiation.
This means you can configure the connection as specific as you'd like, but every argument should be provided with its keyword; `Handler(host=localhost)` instead of `Handler(localhost)`.
All available configuration options are available in te [python-redis documentation](https://redis-py.readthedocs.io/en/latest/).

```python
handler = RedisKeyHandler("key", host="localhost", port=6379, password=None)

connection_pool = redis.ConnectionPool(host="localhost")
handler = RedisKeyHandler("key", connection_pool=connection_pool)
```

### Configure message logging
Every handler has the `raw_logging` option which can be provided optionally.
Omitting it from the initialisation, will default it to `False`, meaning the message being logged will be purely what's sent.
If you set it to `True`, first the content will be logged, then appended to the line number and finally the pathname.

```python
pure_handler = RedisKeyHandler("key_name")
raw_handler = RedisKeyHandler("other_key_name", raw_logging=True)
...
logging.info("Test message")
```
The `pure_handler` would emit a message like so: `Test message.`,
the `raw_handler` would emit a message like so: `Test message. - 2: /.../file.py`.

### 1. RedisChannelHandler
This opens a connection to a redis channel, allowing subscribers to pickup new messages in realtime.
Every message triggered by the logging instance, will get published to the specified channel.

```python
handler = RedisChannelHandler("channelname")
```

### 2. RedisKeyHandler
This creates/pushes onto the provided key, whatever message the logging instance will emit.
By default every message will be sent via `rpush`, so that when the list is retrieved using `lrange $key 0 -1`, all messages are returned in the order they were sent.
Optionally a `ttl` (time to live) can be provided which will be a counter that **will be set each time** a message is sent, essentially **refreshing the duration** of the time to live for this key.
```python
handler = RedisKeyHandler("some_key_name", ttl=60)
```

### 3. Custom Redis Handler
We also provide the ability to write custom emit functions, which get picked up by the logging instance, by inheriting the Base class.
If none of the provided Redis implementations rock you boat, simply inherit the Base class and overwrite the emit() method.

In the following example we will write an example of a CustomRedisHandler which overwrites the value of the key it already exists.
```python
class CustomRedisHandler(RedisBaseHandler):
    def __init__(self, key: str, **kwargs: Any):
        super().__init__(**kwargs)
        self.key = key

    def emit(self, message: logging.LogRecord):
        self.redis_client.set(self.key, str(message))
```