Elastic Search Quantization not always effective and does not match Datadog agent's

[ZStriker19]

Summary of problem

Quantization of ElasticSearch urls does not match that of the Datadog agent and also does not work well. In some cases leading to un-useful resource names and high cardinality.

https://github.com/DataDog/dd-trace-py/blob/main/ddtrace/contrib/elasticsearch/quantize.py
Turns a url like "/en_search/_doc/fa1117d4-7917-5a2d-b001-76e6e4ca83b2"' into '"/en_search/_doc/fa?d4-?-5a2d-b?-?e6e4ca?b2"' before using it for the resource name. Ending up with resource names like '"GET /en_search/_doc/fa?d4-?-5a2d-b?-?e6e4ca?b2"' where instead we would want something like '/en_search/_doc/?'`

Currently we can work around this with a trace filter, however in the next major release (3.0) we should change the quantization to match the Datadog agent's which changes this into '/en_search/_doc/{guid}'` In the meantime, we could also put the new quantization behind a flag for now.

Trace filter example:

from ddtrace import Span, tracer
from ddtrace.filters import TraceFilter

# chops off after last "/" if there are ints after it and replaces it with "/?"
REMOVE_AFTER_LAST_SLASH = re.compile(r"/[^/]*\d[^/]*$")

class CorrectESResourceNameFilter(TraceFilter):
    """example input: '/en_search/_doc/fa?d4-?-5a2d-b?-?e6e4ca?b2' output: '/en_search/_doc/?'"""
    def process_trace(self, trace):
        # type: (List[Span]) -> Optional[List[Span]]
        for span in trace:
            # if you're changing the service name of elasticsearch, use that instead
            if span.service == "elasticsearch":
                url = span.get_tag("elasticsearch.url")
                method = span.get_tag("elasticsearch.method")
                span.resource = "{method} {url}".format(method=method, url=REMOVE_AFTER_LAST_SLASH.sub(r"/?", url))
        return trace
# And then configure it with
tracer.configure(settings={'FILTERS': [CorrectESResourceNameFilter()]})

Which version of dd-trace-py are you using?

2.8.3

Elastic search

How can we reproduce your problem?

Try the current quantize method on `"/en_search/_doc/fa1117d4-7917-5a2d-b001-76e6e4ca83b2"'

What is the result that you get?

'"/en_search/_doc/fa?d4-?-5a2d-b?-?e6e4ca?b2"'

What is the result that you expected?

'/en_search/_doc/?'