Python logging library to emit JSON log that can be easily indexed and searchable by logging infrastructure such as ELK , EFK , AWS Cloudwatch, GCP Stackdriver, etc.
If you're using Cloud Foundry, it might worth to check out the library SAP/cf-python-logging-support which I'm also original author.
- Features
- Usage
2.1 Non-web application log
2.2 Web application log
2.3 Get current correlation-id
2.4 Log extra properties
2.5 Root logger
2.6 Custom log formatter
2.7 Exclude certain URL from request instrumentation - Configuration
- Python References
- Framework support plugin development
- FAQ & Troubleshooting
- References
- Emit JSON logs (format detail)
- Lightweight, no dependencies, minimal configuration needed (1 LoC to get it working)
- Seamlessly integrate with Python native logging module. Support both Python 2.7.x and 3.x
- Auto extract correlation-id for distributed tracing [1]
- Support HTTP request instrumentation. Built in support for FastAPI , Flask, Sanic , Quart, Connexion. Extensible to support other web frameworks. PR welcome 😃 .
- Highly customizable: support inject arbitrary extra properties to JSON log message, override logging formatter, etc.
- Production ready, has been used in production since 2017 with more than 8 millions downloads
Install by running this command:
pip install json-logging
By default log will be emitted in normal format to ease the local development. To enable it on production set enable_json in json_logging.init_< framework_name >() method call. Once configured library will try to configure all loggers (existing and newly created) to emit log in JSON format. See following use cases for more detail.
This mode don't support correlation-id.
import json_logging, logging, sys
# log is initialized without a web framework name
json_logging.init_non_web(enable_json=True)
logger = logging.getLogger("test-logger")
logger.setLevel(logging.DEBUG)
logger.addHandler(logging.StreamHandler(sys.stdout))
logger.info("test logging statement")import datetime, logging, sys, json_logging, fastapi, uvicorn
app = fastapi.FastAPI()
json_logging.init_fastapi(enable_json=True)
json_logging.init_request_instrument(app)
# init the logger as usual
logger = logging.getLogger("test-logger")
logger.setLevel(logging.DEBUG)
logger.addHandler(logging.StreamHandler(sys.stdout))
@app.get('/')
def home():
logger.info("test log statement")
logger.info("test log statement with extra props", extra={'props': {"extra_property": 'extra_value'}})
correlation_id = json_logging.get_correlation_id()
return "Hello world : " + str(datetime.datetime.now())
if __name__ == "__main__":
uvicorn.run(app, host='0.0.0.0', port=5000)import datetime, logging, sys, json_logging, flask
app = flask.Flask(__name__)
json_logging.init_flask(enable_json=True)
json_logging.init_request_instrument(app)
# init the logger as usual
logger = logging.getLogger("test-logger")
logger.setLevel(logging.DEBUG)
logger.addHandler(logging.StreamHandler(sys.stdout))
@app.route('/')
def home():
logger.info("test log statement")
logger.info("test log statement with extra props", extra={'props': {"extra_property": 'extra_value'}})
correlation_id = json_logging.get_correlation_id()
return "Hello world : " + str(datetime.datetime.now())
if __name__ == "__main__":
app.run(host='0.0.0.0', port=int(5000), use_reloader=False)import logging, sys, json_logging, sanic
app = sanic.Sanic(name="sanic-web-app")
json_logging.init_sanic(enable_json=True)
json_logging.init_request_instrument(app)
# init the logger as usual
logger = logging.getLogger("sanic-integration-test-app")
logger.setLevel(logging.DEBUG)
logger.addHandler(logging.StreamHandler(sys.stdout))
@app.route("/")
async def home(request):
logger.info("test log statement")
logger.info("test log statement with extra props", extra={'props': {"extra_property": 'extra_value'}})
# this will be faster
correlation_id = json_logging.get_correlation_id(request=request)
# this will be slower, but will work in context you cant get a reference of request object
correlation_id_without_request_obj = json_logging.get_correlation_id()
return sanic.response.text("hello world")
if __name__ == "__main__":
app.run(host="0.0.0.0", port=5000)import asyncio, logging, sys, json_logging, quart
app = quart.Quart(__name__)
json_logging.init_quart(enable_json=True)
json_logging.init_request_instrument(app)
# init the logger as usual
logger = logging.getLogger("test logger")
logger.setLevel(logging.DEBUG)
logger.addHandler(logging.StreamHandler(sys.stdout))
@app.route('/')
async def home():
logger.info("test log statement")
logger.info("test log statement with extra props", extra={'props': {"extra_property": 'extra_value'}})
correlation_id = json_logging.get_correlation_id()
return "Hello world"
if __name__ == "__main__":
loop = asyncio.get_event_loop()
app.run(host='0.0.0.0', port=int(5000), use_reloader=False, loop=loop)import logging, sys, json_logging, connexion
app = connexion.FlaskApp(__name__)
json_logging.init_connexion(enable_json=True)
json_logging.init_request_instrument(app)
app.add_api('api.yaml')
# init the logger as usual
logger = logging.getLogger("test-logger")
logger.setLevel(logging.DEBUG)
logger.addHandler(logging.StreamHandler(sys.stdout))
if __name__ == "__main__":
app.run()you need to explicitly set JSONRequestLogFormatter as default formatter for any extra handler that is added to request_logger
import json_logging.formatters
request_logger = json_logging.get_request_logger()
handler = logging.handlers.RotatingFileHandler(filename='log_req.log', maxBytes=5000000, backupCount=10)
handler.setFormatter(json_logging.formatters.JSONRequestLogFormatter())
request_logger.addHandler(handler)Current request correlation-id can be retrieved and pass to downstream services call as follow:
# this will be faster
correlation_id = json_logging.get_correlation_id(request=request)
# this will be slower, but will work in context where you couldn't get a reference of request object
correlation_id_without_request_obj = json_logging.get_correlation_id()
# use correlation id for upstream service calls hereIn request context, if one is not present, a new one might be generated depends on CREATE_CORRELATION_ID_IF_NOT_EXISTS setting value.
Extra property can be added to logging statement as follows:
logger.info("test log statement", extra={'props': {'extra_property': 'extra_value'}, 'tags': ['app:name']})For backwards compatibility, properties added in props are extracted to the root and take precedence over those set directly in the root of extra. This is relevant only for logs formatted by JSONLogFormatter, other formatters never printed the props details.
A custom correlation id can be passed to logging statement as follow:
logger.info("test log statement", extra={'props': {'correlation_id': 'custom_correlation_id'}})
If you want to use root logger as main logger to emit log. Made sure you call config_root_logger() after initialize root logger (by logging.basicConfig() or logging.getLogger()) [2]
logging.basicConfig()
json_logging.init_ < framework_name > ()
json_logging.config_root_logger()Customer JSON log formatter can be passed to init method. see examples for more detail: non web, web
Certain URL can be excluded from request instrumentation by specifying a list of regex into init_request_instrument method like below:
json_logging.init_request_instrument(app, exclude_url_patterns=[r'/exclude_from_request_instrumentation'])logging library can be configured by setting the value in json_logging, all configuration must be placed before json_logging.init method call
| Name | Description | Default value |
|---|---|---|
| ENABLE_JSON_LOGGING | ** | |
| DEPRECATED** Whether to enable JSON logging mode.Can be set as an environment variable, enable when set to to either one in following list (case-insensitive) ['true', '1', 'y', 'yes'] , this have no effect on request logger | false | |
| CORRELATION_ID_HEADERS | List of HTTP headers that will be used to look for correlation-id value. HTTP headers will be searched one by one according to list order | ['X-Correlation-ID','X-Request-ID'] |
| EMPTY_VALUE | Default value when a logging record property is None | '-' |
| CORRELATION_ID_GENERATOR | function to generate unique correlation-id | uuid.uuid1 |
| JSON_SERIALIZER | function to encode object to JSON | json.dumps |
| COMPONENT_ID | Uniquely identifies the software component that has processed the current request | EMPTY_VALUE |
| COMPONENT_NAME | A human-friendly name representing the software component | EMPTY_VALUE |
| COMPONENT_INSTANCE_INDEX | Instance's index of horizontally scaled service | 0 |
| CREATE_CORRELATION_ID_IF_NOT_EXISTS | Whether to generate a new correlation-id in case one is not present | True |
TODO: update Python API docs on Github page
To add support for a new web framework, you need to extend following classes in ** framework_base** and register support using ** json_logging.register_framework_support** method:
| Class | Description | Mandatory |
|---|---|---|
| BaseRequestInfoExtractor | Helper class help to extract logging-relevant information from HTTP request object | yes |
| BaseResponseInfoExtractor | Helper class help to extract logging-relevant information from HTTP response object | yes |
| BaseFrameworkConfigurator | Class to perform logging configuration for given framework as needed | no |
| BaseAppRequestInstrumentationConfigurator | Class to perform request instrumentation logging configuration | no |
Take a look at json_logging/base_framework.py, ** json_logging.flask** and json_logging.sanic packages for reference implementations.
-
I configured everything, but no logs are printed out?
- Forgot to add handlers to your logger?
- Check whether logger is disabled.
-
Same log statement is printed out multiple times.
- Check whether the same handler is added to both parent and child loggers [2]
- If you using flask, by default option use_reloader is set to True which will start 2 instances of web application. change it to False to disable this behaviour [3]
2 types of logging statement will be emitted by this library:
- Application log: normal logging statement e.g.:
{
"type": "log",
"written_at": "2017-12-23T16:55:37.280Z",
"written_ts": 1514048137280721000,
"component_id": "1d930c0xd-19-s3213",
"component_name": "ny-component_name",
"component_instance_idx": 0,
"logger": "test logger",
"thread": "MainThread",
"level": "INFO",
"line_no": 22,
"filename": "/path/to/foo.py"
"exc_info": "Traceback (most recent call last): \n File "<stdin>", line 1, in <module>\n ValueError: There is something wrong with your input",
"correlation_id": "1975a02e-e802-11e7-8971-28b2bd90b19a",
"extra_property": "extra_value",
"msg": "This is a message"
}
- Request log: request instrumentation logging statement which recorded request information such as response time, request size, etc.
{
"type": "request",
"written_at": "2017-12-23T16:55:37.280Z",
"written_ts": 1514048137280721000,
"component_id": "-",
"component_name": "-",
"component_instance_idx": 0,
"correlation_id": "1975a02e-e802-11e7-8971-28b2bd90b19a",
"remote_user": "user_a",
"request": "/index.html",
"referer": "-",
"x_forwarded_for": "-",
"protocol": "HTTP/1.1",
"method": "GET",
"remote_ip": "127.0.0.1",
"request_size_b": 1234,
"remote_host": "127.0.0.1",
"remote_port": 50160,
"request_received_at": "2017-12-23T16:55:37.280Z",
"response_time_ms": 0,
"response_status": 200,
"response_size_b": "122",
"response_content_type": "text/html; charset=utf-8",
"response_sent_at": "2017-12-23T16:55:37.280Z"
}
See following tables for detail format explanation:
- Common field
| Field | Description | Format | Example |
|---|---|---|---|
| written_at | The date when this log message was written. | ISO 8601 YYYY-MM-DDTHH:MM:SS.milliZ | 2017-12-23T15:14:02.208Z |
| written_ts | The timestamp in nano-second precision when this request metric message was written. | long number | 1456820553816849408 |
| correlation_id | The timestamp in nano-second precision when this request metric message was written. | string | db2d002e-2702-41ec-66f5-c002a80a3d3f |
| type | Type of logging. "logs" or "request" | string | |
| component_id | Uniquely identifies the software component that has processed the current request | string | 9e6f3ecf-def0-4baf-8fac-9339e61d5645 |
| component_name | A human-friendly name representing the software component | string | my-fancy-component |
| component_instance_idx | Instance's index of horizontally scaled service | string | 0 |
- application logs
| Field | Description | Format | Example |
|---|---|---|---|
| msg | The actual message string passed to the logger. | string | This is a log message |
| level | The log "level" indicating the severity of the log message. | string | INFO |
| thread | Identifies the execution thread in which this log message has been written. | string | http-nio-4655 |
| logger | The logger name that emits the log message. | string | requests-logger |
| filename | The file name where an exception originated | string | /path/to/foo.py |
| exc_info | Traceback information about an exception | string | "Traceback (most recent call last): \n File "", line 1, in \n ValueError: There is something wrong with your input" |
- request logs:
| Field | Description | Format | Example |
|---|---|---|---|
| request | request path that has been processed. | string | /get/api/v2 |
| request_received_at | The date when an incoming request was received by the producer. | ISO 8601 YYYY-MM-DDTHH:MM:SS.milliZ The precision is in milliseconds. The timezone is UTC. | 2015-01-24 14:06:05.071Z |
| response_sent_at | The date when the response to an incoming request was sent to the consumer. | ditto | 2015-01-24 14:06:05.071Z |
| response_time_ms | How many milliseconds it took the producer to prepare the response. | float | 43.476 |
| protocol | Which protocol was used to issue a request to a producer. In most cases, this will be HTTP (including a version specifier), but for outgoing requests reported by a producer, it may contain other values. E.g. a database call via JDBC may report, e.g. "JDBC/1.2" | string | HTTP/1.1 |
| method | The corresponding protocol method. | string | GET |
| remote_ip | IP address of the consumer (might be a proxy, might be the actual client) | string | 192.168.0.1 |
| remote_host | host name of the consumer (might be a proxy, might be the actual client) | string | my.happy.host |
| remote_port | Which TCP port is used by the consumer to establish a connection to the remote producer. | string | 1234 |
| remote_user | The username associated with the request | string | user_name |
| request_size_b | The size in bytes of the requesting entity or "body" (e.g., in case of POST requests). | long | 1234 |
| response_size_b | The size in bytes of the response entity | long | 1234 |
| response_status | The status code of the response. | long | 200 |
| response_content_type | The MIME type associated with the entity of the response if available/specified | long | application/json |
| referer | For HTTP requests, identifies the address of the webpage (i.e. the URI or IRI) that linked to the resource being requested. | string | /index.html |
| x_forwarded_for | Comma-separated list of IP addresses, the left-most being the original client, followed by proxy server addresses that forwarded the client request. | string | 192.0.2.60,10.12.9.23 |
https://stackoverflow.com/questions/25433258/what-is-the-x-request-id-http-header
https://docs.python.org/3/library/logging.html#logging.Logger.propagate https://docs.python.org/2/library/logging.html#logging.Logger.propagate
http://flask.pocoo.org/docs/0.12/errorhandling/#working-with-debuggers