Logging integration design discussion

@c24t wish to know your thoughts as you’ve done the pilot work in #536.

1. Currently the use_oc_logging works for all loggers created after the call. There is another way to work with loggers created before the call (although it could have wide impact, and only works for Py3.x), should we consider it (which seems to be useful for automatic capturing unhandled exceptions)?

class ContextLogRecord(logging.LogRecord):
    def __init__(self, name, level, pathname, lineno, msg, args, exc_info, func=None, sinfo=None):
        self.trace_id = 'foo'
        self.span_id = 'bar'
        return super(ContextLogRecord, self).__init__(name, level, pathname, lineno, msg, args, exc_info, func, sinfo)

logging.setLogRecordFactory(ContextLogRecord)

1. Do we want to move use_oc_logging to an ext package and use config_integration?

config_integration.trace_integrations(['logging'])

[c24t]

It’s also not clear why BlankSpan has a real span_id in the first place.

[reyang]

This is happening today. When we receive an incoming request, we always store the span id in the context. So even if sampling flag is off, we can get the top level local span.

Run the following command against the following Flask app:

curl --header "traceparent: 00-d4e6f7396f0d0e85b3f9f2fad6b4987c-1234567890123456-00" localhost:8080

from flask import Flask
import logging

from opencensus.ext.azure.log_exporter import AzureLogHandler
from opencensus.ext.flask.flask_middleware import FlaskMiddleware
from opencensus.trace import config_integration
from opencensus.trace import execution_context

app = Flask(__name__)
middleware = FlaskMiddleware(app)

config_integration.trace_integrations(['logging'])

logger = logging.getLogger(__name__)
handler = AzureLogHandler()
handler.setFormatter(logging.Formatter('%(traceId)s %(spanId)s %(message)s'))
logger.addHandler(handler)

@app.route('/')
def hello():
    logger.warning('before entering parent span')
    span = execution_context.get_opencensus_tracer().current_span()
    with span.span(name='parent') as parent:
        logger.warning('before entering child span')
        with parent.span(name='child'):
            logger.warning('inside child span')
        logger.warning('after leaving child span')
    logger.warning('after leaving parent span')
    return 'Hello, World!'

if __name__ == '__main__':
    config_integration.trace_integrations(['requests'])
    app.run(host='localhost', port=8080, threaded=True)

This is what we get:

127.0.0.1 - - [23/May/2019 13:17:43] "GET / HTTP/1.1" 200 -
d4e6f7396f0d0e85b3f9f2fad6b4987c 1234567890123456 before entering parent span
d4e6f7396f0d0e85b3f9f2fad6b4987c 1234567890123456 before entering child span
d4e6f7396f0d0e85b3f9f2fad6b4987c 1234567890123456 inside child span
d4e6f7396f0d0e85b3f9f2fad6b4987c 1234567890123456 after leaving child span
d4e6f7396f0d0e85b3f9f2fad6b4987c 1234567890123456 after leaving parent span