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perf: optimize hot path for http propagation #15065

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perf: optimize hot path for http propagation #15065

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93 changes: 58 additions & 35 deletions ddtrace/propagation/http.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1222,68 +1222,91 @@ def my_controller(url, headers):
:param dict headers: HTTP headers to extract tracing attributes.
:return: New `Context` with propagated attributes.
"""
context = Context()
# Fast path: empty or no extraction config
if not headers or not config._propagation_style_extract:
return context
return Context()

try:
style = ""
# Normalize header keys once
normalized_headers = {name.lower(): v for name, v in headers.items()}
# tracer configured to extract first only
prop_styles = config._propagation_style_extract

# Short-circuit: first-only extraction mode
if config._propagation_extract_first:
# loop through the extract propagation styles specified in order, return whatever context we get first
for prop_style in config._propagation_style_extract:
propagator = _PROP_STYLES[prop_style]
context = propagator._extract(normalized_headers)
style = prop_style
for ps in prop_styles:
# baggage handled later
if ps == _PROPAGATION_STYLE_BAGGAGE:
continue
context = _PROP_STYLES[ps]._extract(normalized_headers)
style = ps
if context:
_record_http_telemetry("context_header_style.extracted", prop_style)
if config._propagation_http_baggage_enabled is True:
_attach_baggage_to_context(normalized_headers, context)
break

# loop through all extract propagation styles
_record_http_telemetry("context_header_style.extracted", ps)
if config._propagation_http_baggage_enabled:
_attach_baggage_to_context(normalized_headers, context)
break
else:
context = Context()
else:
contexts, styles_w_ctx = HTTPPropagator._extract_configured_contexts_avail(normalized_headers)
# check that styles_w_ctx is not empty
# Multi-style extraction: collect all contexts in a single tight loop
contexts = []
styles_w_ctx = []
append = contexts.append
append_style = styles_w_ctx.append
for ps in prop_styles:
if ps == _PROPAGATION_STYLE_BAGGAGE:
continue
c = _PROP_STYLES[ps]._extract(normalized_headers)
if c:
_record_http_telemetry("context_header_style.extracted", ps)
append(c)
append_style(ps)
if styles_w_ctx:
style = styles_w_ctx[0]

# Context resolution: fast-path single, else resolve
if contexts:
context = HTTPPropagator._resolve_contexts(contexts, styles_w_ctx, normalized_headers)
if config._propagation_http_baggage_enabled is True:
if len(contexts) == 1:
context = contexts[0]
else:
context = HTTPPropagator._resolve_contexts(contexts, styles_w_ctx, normalized_headers)
if config._propagation_http_baggage_enabled:
_attach_baggage_to_context(normalized_headers, context)
else:
context = Context()

# baggage headers are handled separately from the other propagation styles
if _PROPAGATION_STYLE_BAGGAGE in config._propagation_style_extract:
# Baggage extraction, always handled last, only once
baggage_context = None
if _PROPAGATION_STYLE_BAGGAGE in prop_styles:
baggage_context = _BaggageHeader._extract(normalized_headers)
if baggage_context._baggage != {}:
# Record telemetry for successful baggage extraction
_record_http_telemetry("context_header_style.extracted", _PROPAGATION_STYLE_BAGGAGE)
if context:
context._baggage = baggage_context.get_all_baggage_items()
else:
context = baggage_context

# Tagging of baggage keys, single pass
if config._baggage_tag_keys:
raw_keys = [k.strip() for k in config._baggage_tag_keys if k.strip()]
# wildcard: tag all baggage keys
if "*" in raw_keys:
keys = [k.strip() for k in config._baggage_tag_keys if k.strip()]
if "*" in keys:
tag_keys = baggage_context.get_all_baggage_items().keys()
else:
tag_keys = raw_keys

for stripped_key in tag_keys:
if (value := baggage_context.get_baggage_item(stripped_key)) is not None:
prefixed_key = BAGGAGE_TAG_PREFIX + stripped_key
if prefixed_key not in context._meta:
context._meta[prefixed_key] = value

tag_keys = keys
meta = context._meta
bag_dict = baggage_context.get_all_baggage_items()
for k in tag_keys:
v = bag_dict.get(k)
if v is not None:
prefixed = BAGGAGE_TAG_PREFIX + k
if prefixed not in meta:
meta[prefixed] = v

# Propagation behavior: restart, done last for correctness
if config._propagation_behavior_extract == _PROPAGATION_BEHAVIOR_RESTART:
link = HTTPPropagator._context_to_span_link(context, style, "propagation_behavior_extract")
context = Context(baggage=context.get_all_baggage_items(), span_links=[link] if link else [])

return context

except Exception:
log.debug("error while extracting context propagation headers", exc_info=True)
return Context()
return Context()
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