Develop Reference

How to use Syslog in Django REST framework?

I’m developing a Python Django REST API. Currently, I need to incorporate a logger to Syslog.
Do I need to just define the logger and Syslog handler in the Settings.py?
I’m relatively new to Django and using the Syslog protocol, so I appreciate any help and what Python modules to use.

Yes, you can for example use the syslog library to log messages.
Using it, is pretty easy.
import syslog
# create syslog handle
syslog.openlog(ident="settings.py", facility=syslog.LOG_LOCAL0)
# log some message
syslog.syslog(syslog.LOG_INFO, "Some log message.")
The log message will not get written to /var/log/local0.log - probably it will also get written to /var/log/rsyslog or /var/log/messages depending on the standard configuration of your /etc/rsyslog.conf file.

Logging on either GCP or local

Suppose there is a system that is run on GCP, but as a backup, can be run locally.
When running on the cloud, stackdriver is pretty straightforward.
However, I need my system to push to stackdriver if on the cloud, and if not on the cloud, use the local python logger.
I also don't want to include any logic to do so, and this should be automatic.
When logging, log straight to Python/local logger.
If on GCP -> push these to stackdriver.
I can write logic that could implement this but that is bad practice. There surely is a direct way of getting this to work.
Example
import google.cloud.logging
client = google.cloud.logging.Client()
client.setup_logging()
import logging
cl = logging.getLogger()
file_handler = logging.FileHandler('file.log')
cl.addHandler(file_handler)
logging.info("INFO!")
This will basically log to python logger, and then 'always' upload to cloud logger. How can I have it so that I don't need to explicitly add import google.cloud.logging and basically if stackdriver is installed, it directly gets the logs? Is that even possible? If not can someone explain how this would be handled from a best practices perspective?
Attempt 1 [works]
Created /etc/google-fluentd/config.d/workflow_log.conf
<source>
#type tail
format none
path /home/daudn/this_log.log
pos_file /var/lib/google-fluentd/pos/this_log.pos
read_from_head true
tag workflow-log
</source>
Created /var/log/this_log.log
pos_file /var/lib/google-fluentd/pos/this_log.pos exists
import logging
cl = logging.getLogger()
file_handler = logging.FileHandler('/var/log/this_log.log')
file_handler.setFormatter(logging.Formatter("%(asctime)s;%(levelname)s;%(message)s"))
cl.addHandler(file_handler)
logging.info("info_log")
logging.error("error_log")
This works! Look for your logs for the specific VM and not global>python

Fortunately, this is a story that is handled. Stackdriver Logging is a very versatile framework for logging. However, there are a variety of logging APIs and Google's intent was not that you had to rewrite all your existing applications to leveraging the Stackdriver logging native APIs. Instead, you can use a logging API of your choice (including standard and defacto APIs) and these logging APIs will then map to Stackdriver. If executed outside a GCP environment or you simply wish to switch to an alternate log collector, your applications would not have to be re-coded or recompiled.
A list of the logging APIs available for different languages can be found at Setting Up Language Runtimes and this includes Setting Up Stackdriver Logging for Python.
For Python, at runtime, you have a configuration property (eg an Environment variable) that declares whether or not you wish to use Stackdriver. If set to true, then .. and only then ... would you execute the login that sets up the native Python logging for Stackdriver otherwise that logic would not be called and hence you would have no dependency on Stackdriver.
A possible piece of code might be:
if os.environ.get('USE_STACKDRIVER') == 'true':
import google.cloud.logging
client = google.cloud.logging.Client()
client.setup_logging()

You do not need to specifically enable or use Stackdriver in your program. You can use the Python logger and write to any file you want. However, Stackdriver only logs specific log files. This means that you would need to manually set up Stackdriver to log "your" log files.
In your example, you are writing to file.log. Modify /etc/google-fluentd/config.d/mylogfile.conf to include the following. You will need to specify the full path for file.log and not just the file name. In this example, I named it /var/log/mylogfile.log. This example also assumes that your logs start each line with a date.
<source>
#type tail
# Parse the timestamp, but still collect the entire line as 'message'
format /^(?<message>(?<time>[^ ]*\s*[^ ]* [^ ]*) .*)$/
path /var/log/mylogfile.log
pos_file /var/lib/google-fluentd/pos/mylogfile.log.pos
read_from_head true
tag auth
</source>
For more information read the following document:
Stackdriver - Configuring the Agent
Now your program will run outside GCP and when running on a configured instance, log to Stackdriver.
Note: I would do the opposite of what you have asked. I would always use Stackdriver. When not running in GCP I would manually set up Stackdriver on my desktop, local server, etc and continue to log to Stackdriver.

Google Stackdriver logging in App Engine (Python) using Redis queue

I want to log using Stackdriver Logging to App Engine using Redis queue. So I'm using Redis Server, Redis Queue and Python logging to do this. Here's my code:
import logging
from redis import Redis
from rq import Queue
import time
class SomeClass():
def log_using_redis(self,text):
log_text = logging.warn(text)
f=open("stack_log.txt","a+")
f.write(str(text))
return "logged Successfully using redis"
def get(self):
text = 'Hello, Logged Successfully!'+time.strftime('%a, %d %b %Y %H:%M:%S %Z(%z)')
redis_conn = Redis()
q = Queue(connection=redis_conn)
job = q.enqueue(self.log_using_redis,text)
print job.result
When I run RQ worker I'm getting some output on terminal but couldn't find where the logs are being stored.
If I try to log directly without using Redis, the logs are being stored at Global in the logging section of Google Cloud. The queue is working properly, to check I've been appending the text to a file.
It seems the logging isn't working. If it is being logged, where can I find my logs on Google Cloud?

Taking into account that you are using Python client library, use print() function to obtain the desired results. I don’t know if you are testing the application locally or you have deployed it.
If you are testing the application locally: print() function
output can be found in the cloud shell.
If you have deployed the application: go to the GCP console, App Engine and services. Select the service in which you have deployed
your application. In the right side click on tools and select
"Logs". This will redirect the page to your app logs.
A more precise logging can be defined using the Stackdriver Logging for Python. The warning level can be defined. This can help you manage your application or identify events of interest. Find an example code here.
You might find useful Stackdriver Logging agent, an application based on fluentd that runs on your virtual machine (VM) instances. The Logging agent is pre-configured to send logs from VM instances to Stackdriver Logging. There are source and configuraiton files available for redis.
If you want a more general vision, App Engine flexible environment logs official documentation can help you to understand the different available logs.

Using Flask and native Python logging?

The trouble with Flask logging (i.e., app.logger.info(...), etc.) is that sub modules don't use it, so it seems to me that the only way to globally configure the app's logging is via the underlying python logging mechanism: e.g.,
logging.config.fileConfig('config/logging.conf')
But this doesn't configure Flask's default handlers, so for example, the HTTP logging is not configured. So I get mixed logs:
2015-07-28 14:57:47,320 [main.py][INFO] Starting... # Python log
[2015-07-28 14:58:49] "GET /demo HTTP/1.1" 200 956 0.318825 # Flask log
Can anyone suggest the standard practice for globally configuring logging via a configuration file (i.e., so that I can easily configure individual packages).
ALSO, I cant seem to remove the HTTP logging (GET, etc.) to stderr (which I presume come from werkzeug); setting logging.getLogger('werkzeug').setLevel() only affects the werkzeug logs that are not related to HTTP logging.
Thanks.

I'm pretty sure there is a piece about this in the Flask docs: https://flask.palletsprojects.com/en/1.1.x/logging/#other-libraries
It basically suggests to add the handlers of other libraries to the root of Flask. This is the example they give:
from flask.logging import default_handler
root = logging.getLogger()
root.addHandler(default_handler)
root.addHandler(mail_handler)

On the google app engine, how do I change the default logging level of the dev_appserver.py?

Dev_appserver.py (the local development server for Python google app engine) spews tons of useless INFO messages. I would like to up this to WARN or ERROR. How can I do that?
I've tried the following, but it has no effect...
logger = logging.getLogger()
logger.setLevel(logging.WARN)
Any ideas?

Currently, from the command line, you can only lower the logging level to DEBUG by the '-d' command line option.
If you're not afraid of editing the scripts, look for
DEFAULT_ARGS = {
...
ARG_LOG_LEVEL: logging.INFO,
in C:\Program Files\Google\google_appengine\google\appengine\tools\dev_appserver_main.py

logging.getLogger().handlers[0].setLevel(logging.DEBUG)
from Google App Engine/Python - Change logging formatting,
This is a bit of a hack because you have to directly access the
handlers list stored in the root logger. The problem is GAE
automatically uses logging before your code is ever run - this creates
a default handler

Check if you have
<!-- Configure java.util.logging -->
<system-properties>
<property name="java.util.logging.config.file" value="WEB-INF/logging.properties"/>
</system-properties>
in your appengine-web.xml file, then go on to change .level = WARNING in your logging.properties file.
That's it!