siftlog-py 0.9.5
JSON and human-readable logging with context
License: MIT
Requires Python: >=3.8,<4.0
Keywords: logging,logs,structured

Sift Log - JSON logging adapter for Python (now in color)
===============

![](https://raw.githubusercontent.com/papito/siftlog-py/master/assets/screen.png)

## Features
* Tag log statements with arbitrary values for easier grouping and analysis
* Add keyword arguments that are converted to JSON values
* Variable substitution
* Specifies where log calls are made from
* Meant to be used with core Python logging (formatters, handlers, etc)
* Colorized logs on a console (POSIX only)
* `TRACE` log level built-in
 
## Examples
#### A simple log message
```python
log.info('Hello')
```
`{"msg": "Hello", "time": "12-12-14 10:12:01 EST", "level": "INFO", "loc": "test:log_test:20"}`

#### Logging with tags
```python
log.debug('Creating new user', 'MONGO', 'STORAGE')
```
`{"msg": "Creating new user", "time": "12-12-14 10:12:09 EST", "tags": ["MONGO", "STORAGE"], "level": "DEBUG", "loc": "test:log_test:20"}`

#### Appending more data
```python
log.debug('Some key', is_admin=True, username='papito')
```
`{"msg": "Some key", "is_admin": true, "username": "papito", "time": "12-12-14 10:12:04 EST", "level": "DEBUG", "loc": "test:log_test:20"}`

#### String substitution
```python
log.debug('User "$username" admin? $is_admin', is_admin=False, username='fez')
```
`{"msg": "User \"fez\" admin? False",  "username": "fez", "is_admin": false, "time": "12-12-14 10:12:18 EST", "level": "DEBUG", "loc": "test:log_test:20"}`


## Setup
#### Logging to console
```python
import sys
import logging
from siftlog import SiftLog

logger = logging.getLogger()
logger.setLevel(logging.INFO)
handler = logging.StreamHandler(sys.stdout)
logger.addHandler(handler)

log = SiftLog(logger)
```
In this fashion, you can direct the JSON logs to [any logging handler](https://docs.python.org/2/library/logging.handlers.html).

#### Color
For enhanced flamboyancy, attach the `ColorStreamHandler` to your logger. The output will not have color if the logs
are being output to a file, or on systems that are not POSIX (will not work on Windows for now).

```python
from siftlog import SiftLog, ColorStreamHandler

logger = logging.getLogger()
handler = ColorStreamHandler(sys.stdout)
logger.addHandler(handler)

log = SiftLog(logger)
```

For development, you can opt in to use `ColorPlainTextStreamHandler`, for logs that are easier to parse visually.

##### Performance

While the above should play, it's highly recommended that the color handler is only 
attached conditionally for local development.


##### Different colors
You can change font background, text color, and boldness:

```python
from siftlog import ColorStreamHandler

handler = ColorStreamHandler(sys.stdout)
handler.set_color(
    logging.DEBUG, bg=handler.WHITE, fg=handler.BLUE, bold=True
)
```

##### Supported colors
 * ColorStreamHandler.BLACK
 * ColorStreamHandler.RED
 * ColorStreamHandler.GREEN
 * ColorStreamHandler.YELLOW
 * ColorStreamHandler.BLUE
 * ColorStreamHandler.MAGENTA
 * ColorStreamHandler.CYAN
 * ColorStreamHandler.WHITE

#### Constants (re-occurring values)
You can define constants that will appear in every single log message. This is useful, for example, if you'd like to log process PID and hostname with every log message. This is done upon log adapter initialization:

```python
import os
from siftlog import SiftLog
log = SiftLog(logger, pid=os.getpid(), env='INTEGRATION')
```
`{"msg": "And here I am", "time": "12-12-14 11:12:24 EST", "pid": 37463, "env": "INTEGRATION", "level": "INFO"}`

### Dynamic logging context - callbacks
Often you need to add dynamic contextual data to log statements, as opposed to simple constants/literals. You can
pass methods to SiftLog on initialization that will be called on every logging call.

Logging request ids or user ids are very common use cases, so to log a thread-local property with Flask, for example,
we can do the following:

```python
import flask

def get_user_id():
    if flask.has_request_context():
        return flask.g.user_id

user_aware_logger = SiftLog(u_id=get_user_id)
```

#### Custom time format
```python
log = SiftLog(logger)
SiftLog.TIME_FORMAT = '%Y/%m/%d %H:%M:%S.%f'
```
Define the format as accepted by [strftime()](https://strftime.org/)

#### Custom location format
```python
log = SiftLog(logger)
SiftLog.LOCATION_FORMAT = '$module:$method:$line_no'
```
The format should be a string containing any of the following variables:

 * `$file`
 * `$line_no`
 * `$method`
 * `$module`

#### Custom core key names
Core keys, such as `msg` and `level` can be overridden, if they clash with common keys you might be using.

The following can be redefined:

 * SiftLog.MESSAGE (default `msg`)
 * SiftLog.LEVEL (default `level`)
 * SiftLog.LOCATION (default `loc`)
 * SiftLog.TAGS (default `tags`)
 * SiftLog.TIME (default `time`)

As in:

```python
log = SiftLog(logger)
SiftLog.log.MESSAGE = "MESSAGE"
```

## Development flow

`Poetry` is used to manage the dependencies.

Most things can be accessed via the Makefile, if you have Make installed.
Without Make, just inspect the Makefile for the available commands.

    # use the right Python
    poetry use path/to/python/3.8-ish
    
    # make sure correct Python is used
    make info
    
    # install dependencies
    make install
    
    # run tests
    make test
    
    # run visual tests (same as tests but with output)
	make visual
    
    # formatting, linting, and type checking
    make lint

### Running a single test

In the standard Nose tests way:

    poetry run nosetests siftlog/tests/test_log.py:TestLogger.test_tags