fix(tracer): downgrade default trace api from v05 to v04 [backport 1.20] (#6954)

Backport 107ee1f from #6947 to 1.20.

## Description

Encoding traces in the v05 format has known issues for applications
generating spans at a high frequency. Although this issue impacts
1/1000000 spans, these misformated payloads have the potential to
degrade internal servoces.

## Motivation

Resolves an incident.

## Risk 

This change may introduce a small performance regression in some
applications:
1c12c0a#diff-0b32c6cdae8bdd01786317bcabebf73dbb57e535adab74c94858fda05da411ef

## Checklist

- [x] Change(s) are motivated and described in the PR description.
- [x] Testing strategy is described if automated tests are not included
in the PR.
- [x] Risk is outlined (performance impact, potential for breakage,
maintainability, etc).
- [x] Change is maintainable (easy to change, telemetry, documentation).
- [x] [Library release note
guidelines](https://ddtrace.readthedocs.io/en/stable/releasenotes.html)
are followed. If no release note is required, add label
`changelog/no-changelog`.
- [x] Documentation is included (in-code, generated user docs, [public
corp docs](https://github.com/DataDog/documentation/)).
- [x] Backport labels are set (if
[applicable](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting))

## Reviewer Checklist

- [x] Title is accurate.
- [x] No unnecessary changes are introduced.
- [x] Description motivates each change.
- [x] Avoids breaking
[API](https://ddtrace.readthedocs.io/en/stable/versioning.html#interfaces)
changes unless absolutely necessary.
- [x] Testing strategy adequately addresses listed risk(s).
- [x] Change is maintainable (easy to change, telemetry, documentation).
- [x] Release note makes sense to a user of the library.
- [x] Reviewer has explicitly acknowledged and discussed the performance
implications of this PR as reported in the benchmarks PR comment.
- [x] Backport labels are set in a manner that is consistent with the
[release branch maintenance
policy](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting)
- [x] If this PR touches code that signs or publishes builds or
packages, or handles credentials of any kind, I've requested a review
from `@DataDog/security-design-and-guidance`.
- [x] This PR doesn't touch any of that.

Co-authored-by: Munir Abdinur <[email protected]>

Author: github-actions[bot]

ddtrace/internal/writer/writer.py

@@ -35,8 +35,6 @@
 from ..encoding import JSONEncoderV2
 from ..logger import get_logger
 from ..runtime import container
-from ..serverless import in_azure_function_consumption_plan
-from ..serverless import in_gcp_function
 from ..sma import SimpleMovingAverage
 from .writer_client import AgentWriterClientV3
 from .writer_client import AgentWriterClientV4
@@ -500,11 +498,8 @@ def __init__(
         #      as a safety precaution.
         #      https://docs.python.org/3/library/sys.html#sys.platform
         is_windows = sys.platform.startswith("win") or sys.platform.startswith("cygwin")
-        default_api_version = (
-            "v0.4" if (is_windows or in_gcp_function() or in_azure_function_consumption_plan()) else "v0.5"
-        )
 
-        self._api_version = api_version or config._trace_api or (default_api_version if priority_sampling else "v0.3")
+        self._api_version = api_version or config._trace_api or ("v0.4" if priority_sampling else "v0.3")
         if is_windows and self._api_version == "v0.5":
             raise RuntimeError(
                 "There is a known compatibility issue with v0.5 API and Windows, "

docs/spelling_wordlist.txt

@@ -135,6 +135,7 @@ metadata
 microservices
 middleware
 middlewares
+misencoded
 moderations
 mongoengine
 multiline

releasenotes/notes/downgrade-encoding-to-v05-96458e1942295721.yaml

@@ -0,0 +1,7 @@
+---
+fixes:
+  - |
+    tracing: Encoding traces in the v05 format has a known issue for
+    applications generating spans at a high frequency, causing approximately
+    1/10000000 spans to be misencoded.
+    This change sets ``DD_TRACE_API_VERSION`` to ``v04`` by default. 

tests/integration/test_integration.py

@@ -124,7 +124,7 @@ def test_uds_wrong_socket_path():
         mock.call(
             "failed to send, dropping %d traces to intake at %s after %d retries",
             1,
-            "unix:///tmp/ddagent/nosockethere/{}/traces".format(encoding if encoding else "v0.5"),
+            "unix:///tmp/ddagent/nosockethere/{}/traces".format(encoding if encoding else "v0.4"),
             3,
         )
     ]
@@ -382,7 +382,7 @@ def test_trace_generates_error_logs_when_hostname_invalid():
         mock.call(
             "failed to send, dropping %d traces to intake at %s after %d retries",
             1,
-            "http://bad:1111/{}/traces".format(encoding if encoding else "v0.5"),
+            "http://bad:1111/{}/traces".format(encoding if encoding else "v0.4"),
             3,
         )
     ]
@@ -471,7 +471,7 @@ def test_trace_with_invalid_payload_generates_error_log():
         [
             mock.call(
                 "failed to send traces to intake at %s: HTTP error status %s, reason %s",
-                "http://localhost:8126/v0.5/traces",
+                "http://localhost:8126/v0.4/traces",
                 400,
                 "Bad Request",
             )
@@ -550,9 +550,9 @@ def test_api_version_downgrade_generates_no_warning_logs():
 
     from ddtrace import tracer as t
 
-    encoding = os.environ["DD_TRACE_API_VERSION"]
+    encoding = os.environ["DD_TRACE_API_VERSION"] or "v0.4"
     t._writer._downgrade(None, None, t._writer._clients[0])
-    assert t._writer._endpoint == {"v0.5": "v0.4/traces", "v0.4": "v0.3/traces"}[encoding or "v0.5"]
+    assert t._writer._endpoint == {"v0.5": "v0.4/traces", "v0.4": "v0.3/traces"}[encoding]
     with mock.patch("ddtrace.internal.writer.writer.log") as log:
         t.trace("operation", service="my-svc").finish()
         t.shutdown()

tests/snapshots/test_extended_sampling_resource.json

@@ -1,13 +1,11 @@
 [[
   {
     "name": "should_not_send",
-    "service": "",
+    "service": null,
     "resource": "mycoolre$ource",
     "trace_id": 0,
     "span_id": 1,
     "parent_id": 0,
-    "type": "",
-    "error": 0,
     "meta": {
       "_dd.p.dm": "-3",
       "language": "python",
@@ -26,13 +24,11 @@
 [
   {
     "name": "should_send",
-    "service": "",
+    "service": null,
     "resource": "something else",
     "trace_id": 1,
     "span_id": 1,
     "parent_id": 0,
-    "type": "",
-    "error": 0,
     "meta": {
       "_dd.p.dm": "-0",
       "language": "python",

tests/snapshots/test_extended_sampling_tags.json

@@ -1,13 +1,11 @@
 [[
   {
     "name": "should_not_send",
-    "service": "",
+    "service": null,
     "resource": "should_not_send",
     "trace_id": 0,
     "span_id": 1,
     "parent_id": 0,
-    "type": "",
-    "error": 0,
     "meta": {
       "_dd.p.dm": "-3",
       "language": "python",
@@ -27,13 +25,11 @@
 [
   {
     "name": "should_send",
-    "service": "",
+    "service": null,
     "resource": "should_send",
     "trace_id": 1,
     "span_id": 1,
     "parent_id": 0,
-    "type": "",
-    "error": 0,
     "meta": {
       "_dd.p.dm": "-0",
       "banana": "True",

tests/snapshots/test_extended_sampling_tags_and_resource.json

@@ -1,13 +1,11 @@
 [[
   {
     "name": "should_not_send",
-    "service": "",
+    "service": null,
     "resource": "mycoolre$ource",
     "trace_id": 0,
     "span_id": 1,
     "parent_id": 0,
-    "type": "",
-    "error": 0,
     "meta": {
       "_dd.p.dm": "-3",
       "language": "python",
@@ -27,13 +25,11 @@
 [
   {
     "name": "should_send1",
-    "service": "",
+    "service": null,
     "resource": "should_send1",
     "trace_id": 1,
     "span_id": 1,
     "parent_id": 0,
-    "type": "",
-    "error": 0,
     "meta": {
       "_dd.p.dm": "-0",
       "banana": "True",
@@ -52,13 +48,11 @@
 [
   {
     "name": "should_send2",
-    "service": "",
+    "service": null,
     "resource": "banana",
     "trace_id": 2,
     "span_id": 1,
     "parent_id": 0,
-    "type": "",
-    "error": 0,
     "meta": {
       "_dd.p.dm": "-0",
       "language": "python",
@@ -77,13 +71,11 @@
 [
   {
     "name": "should_send3",
-    "service": "",
+    "service": null,
     "resource": "mycoolre$ource",
     "trace_id": 3,
     "span_id": 1,
     "parent_id": 0,
-    "type": "",
-    "error": 0,
     "meta": {
       "_dd.p.dm": "-0",
       "banana": "True",

tests/snapshots/test_extended_sampling_tags_glob.json

@@ -1,13 +1,11 @@
 [[
   {
     "name": "should_not_send",
-    "service": "",
+    "service": null,
     "resource": "should_not_send",
     "trace_id": 0,
     "span_id": 1,
     "parent_id": 0,
-    "type": "",
-    "error": 0,
     "meta": {
       "_dd.p.dm": "-3",
       "language": "python",
@@ -27,13 +25,11 @@
 [
   {
     "name": "should_send",
-    "service": "",
+    "service": null,
     "resource": "should_send",
     "trace_id": 1,
     "span_id": 1,
     "parent_id": 0,
-    "type": "",
-    "error": 0,
     "meta": {
       "_dd.p.dm": "-0",
       "language": "python",

tests/snapshots/test_sampling_with_default_sample_rate_1.json

@@ -1,13 +1,11 @@
 [[
   {
     "name": "trace2",
-    "service": "",
+    "service": null,
     "resource": "trace2",
     "trace_id": 0,
     "span_id": 1,
     "parent_id": 0,
-    "type": "",
-    "error": 0,
     "meta": {
       "_dd.p.dm": "-3",
       "language": "python",
@@ -25,13 +23,11 @@
   },
      {
        "name": "child",
-       "service": "",
+       "service": null,
        "resource": "child",
        "trace_id": 0,
        "span_id": 2,
        "parent_id": 1,
-       "type": "",
-       "error": 0,
        "duration": 11602,
        "start": 1692637140104307759
      }]]

tests/snapshots/test_sampling_with_default_sample_rate_1_and_manual_drop.json

@@ -1,13 +1,11 @@
 [[
   {
     "name": "trace6",
-    "service": "",
+    "service": null,
     "resource": "trace6",
     "trace_id": 0,
     "span_id": 1,
     "parent_id": 0,
-    "type": "",
-    "error": 0,
     "meta": {
       "_dd.p.dm": "-4",
       "language": "python",
@@ -24,13 +22,11 @@
   },
      {
        "name": "child",
-       "service": "",
+       "service": null,
        "resource": "child",
        "trace_id": 0,
        "span_id": 2,
        "parent_id": 1,
-       "type": "",
-       "error": 0,
        "duration": 16195,
        "start": 1691163616781394547
      }]]