Implement Trace Context standard#660
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… header On incoming requests, we first check for the presence of `traceparent`, and fall back to `elastic-apm-traceparent`. For outgoing requests, `traceparent` is always set. `elastic-apm-traceparent` is set if the config option `use_elastic_traceparent_header` is set to True. For now, this option defaults to True, but will be changed to False after a grace period.
Initially, we only forward the header, and don't try to parse its content. This will only be necessary once we start adding our own data to tracestate
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| @classmethod | ||
| def merge_duplicate_headers(cls, headers, key): | ||
| """ | ||
| HTTP allows multiple values for the same header name. Most WSGI implementations | ||
| merge these values using a comma as separator (this has been confirmed for wsgiref, | ||
| werkzeug, gunicorn and uwsgi). Other implementations may use containers like | ||
| multidict to store headers and have APIs to iterate over all values for a given key. | ||
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| This method is provided as a hook for framework integrations to provide their own | ||
| TraceParent implementation. The implementation should return a single string. Multiple | ||
| values for the same key should be merged using a comma as separator. | ||
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| :param headers: a dict-like header object | ||
| :param key: header name | ||
| :return: a single string value | ||
| """ | ||
| # this works for all known WSGI implementations | ||
| return headers.get(key) |
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Good work being so thorough with your investigation here. And for providing something to override if Murphy's Law gives us a WSGI implementation with different behavior.
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traceparentheadertracestateheader propagationWhat does this pull request do?
On incoming requests, we first check for the presence of
traceparent,and fall back to
elastic-apm-traceparent.For outgoing requests,
traceparentis always set.elastic-apm-traceparentis set if the config option
use_elastic_traceparent_headeris set toTrue. For now, this option defaults to True, but will be changed to False
after a grace period.
Why is it important?
TraceContext is now a recommendation candidate, time to support it
fully.
Related issues
closes #628
refs elastic/apm#71