feat: add prototype for EnvVarsCarrier (env var propagation) by jsurany · Pull Request #3521 · open-telemetry/opentelemetry-rust

jsurany · 2026-05-21T21:53:18Z

Fixes #3285
Design discussion issue (if applicable) N/A?

Changes

Please provide a brief description of the changes here.

Added EnvVarsCarrier type that implements Extractor and Injector traits, with the normalization described in the spec.
EnvVarsCarrier pulls the environment in from_env, with normalization
The Extractor trait seemed straightforward, but Injector felt up to interpretation. In this design, the injection only modifies the internal map on the EnvVarsCarrier type (keys are always normalized).
added environment variable to .cargo/config.toml for testing the carrier's initialization. This seemed better than adding unsafe code to the tests.

Merge requirement checklist

CONTRIBUTING guidelines followed
Unit tests added/updated (if applicable)
Appropriate CHANGELOG.md files updated for non-trivial, user-facing changes
Changes in public API reviewed (if applicable)

Would like some feedback on if this is the correct way to have implemented this feature, and advice on managing the changelog.

linux-foundation-easycla · 2026-05-21T21:53:24Z

The committers listed above are authorized under a signed CLA.

✅ login: chickenbreeder / name: chickenbreeder (f20ef43)
✅ login: cijothomas / name: Cijo Thomas (63b84c7)
✅ login: jsurany / name: jsurany (2fb4648, 8f07458, 983f10c, aa3cf45, d29ab9b, f15c91f, f340a8e, f9a5270)
✅ login: lalitb / name: Lalit Kumar Bhasin (09ae032)
✅ login: scottgerring / name: Scott Gerring (f20ef43)
✅ login: tonghuaroot / name: tonghuaroot (童话) (006e8b0)

codecov · 2026-05-21T22:02:29Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.0%. Comparing base (c14b570) to head (714680e).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@          Coverage Diff           @@
##            main   #3521    +/-   ##
======================================
  Coverage   82.9%   83.0%            
======================================
  Files        130     131     +1     
  Lines      27484   27586   +102     
======================================
+ Hits       22796   22902   +106     
+ Misses      4688    4684     -4

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TommyCpp

Most implementation leave this in API and the carrier is SDK agnostic, so we should move it to api create(opentelemetry/src/propagation)

jsurany · 2026-05-26T15:53:17Z

Most implementation leave this in API and the carrier is SDK agnostic, so we should move it to api create(opentelemetry/src/propagation)

moved the change.

Would it be OK if I rebase? I didn't update my git config for this PR and as a result the EasyCLA thinks that the early commits are coming from a different account (one that I don't use anymore).

pellared · 2026-06-02T08:03:57Z

EasyCLA is failing.

…VarsCarrier

* fix(sdk): enforce W3C Baggage limits in BaggagePropagator extract path BaggagePropagator::extract_with_context parsed each list-member of an inbound `baggage` header in full -- splitting on `;`, decoding the percent-encoded key/value, allocating Vec<String> for property segments, and constructing a KeyValueMetadata -- before passing the result to Baggage::insert_with_metadata. The storage-side limit (MAX_KEY_VALUE_PAIRS=64, MAX_LEN_OF_ALL_PAIRS=8192) silently dropped entries once full, but per-entry allocation work continued for every attacker-supplied member. This change applies the W3C Baggage limits at the propagator boundary: - Reject the header when its byte length exceeds MAX_BAGGAGE_LENGTH (8192). The header is logged at warn level and an empty Context is returned. - Cap the outer comma-split iterator with .take(MAX_BAGGAGE_ITEMS) so parsing stops after 64 list-members regardless of header content. The injection path is unchanged; the existing Baggage storage type already enforces both limits when entries are added. Two unit tests cover the new behavior: - extract_drops_header_exceeding_max_length verifies that an oversized header produces an empty Baggage. - extract_caps_entry_count_at_max_baggage_items verifies that more than 64 syntactically valid entries are truncated to 64. References: - W3C Baggage limits: https://www.w3.org/TR/baggage/#limits Signed-off-by: tonghuaroot <tonghuaroot@gmail.com> * Clarify CHANGELOG: 8192-byte over-limit drops, 64-entry over-limit truncates Address reviewer feedback that 'dropped at the propagator boundary' was ambiguous: the over-length header path drops the whole header, while the over-count path truncates to the first 64 list members. Split the wording into two clauses so the behavior is unambiguous. Signed-off-by: tonghuaroot <tonghuaroot@gmail.com> --------- Signed-off-by: tonghuaroot <tonghuaroot@gmail.com>

…ic (open-telemetry#3514)

Co-authored-by: Scott Gerring <scottgerring@users.noreply.github.com>

jsurany · 2026-06-02T21:22:17Z

Sorry, I had to rebase in order to change the contact info for past commits for EasyCLA to pass

jsurany · 2026-06-04T17:47:09Z

@pellared @TommyCpp I think I've fixed everything. I don't think I'm responsible for the failing integration test, looks like it's from metrics. Let me know what you'd like me to do.

pellared · 2026-06-09T09:09:50Z

It might make sense to keep this as a draft until the following issue is resolved: open-telemetry/opentelemetry-specification#5143. PTAL when you have a chance, and feel free to share your thoughts there. Waiting could help us avoid extra PRs and save reviewers some time.

jsurany · 2026-06-09T15:16:03Z

Converted to draft per above. Waiting for open-telemetry/opentelemetry-specification#5143

pellared · 2026-06-11T09:50:40Z

Converted to draft per above. Waiting for open-telemetry/opentelemetry-specification#5143

open-telemetry/opentelemetry-specification#5144 is going to be merged soon. Feel free to adopt necessary changes in this PR.

jsurany · 2026-06-11T16:06:09Z

open-telemetry/opentelemetry-specification#5144 is going to be merged soon. Feel free to adopt necessary changes in this PR.

@pellared the Set behavior is a bit weird now, isn't it?

when built from the environment, we only include already-normalized strings into the carrier
when Getting a value, we return no value if the request key is not normalized
when Seting a value, we normalize the key before writing the value.

It feels like the overall design would be more consistent if Set only works if the key is already normalized. Otherwise the user can set a value with a key, then try to use that same key to fetch the value later, only for the Get to reject it on the grounds that it's not normalized.

If we make it so Set fails for non-normalized keys, then the Keys API doesn't need to filter out non-normalized keys. It just reports on all keys, with the invariant that all keys in the map are already normalized.

EDIT - correction is that Getting a value still applies normalization, the only is_normalized filter application is when we are building the carrier from the existing environment. All other interactions use normalize on the key.

kamphaus · 2026-06-14T20:39:50Z

@jsurany Get must normalize its argument key before using the normalized key name for lookups.
That way using the same non-normalized key for both Get and Set operations works.

jsurany · 2026-06-15T15:53:17Z

Ok I think I understand now.

pellared · 2026-06-17T07:15:32Z

Is this a draft on purpose?

Copilot

Pull request overview

Adds an environment-variable-backed carrier to the opentelemetry crate’s propagation module to support the OpenTelemetry environment variable context propagation (“env-carriers”) mechanism discussed in #3285.

Changes:

Introduces EnvVarsCarrier implementing Extractor and Injector, including key normalization logic and from_env/empty constructors.
Re-exports EnvVarsCarrier from opentelemetry::propagation.
Adds Cargo [env] config entries used by unit tests that validate from_env() behavior.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
`opentelemetry/src/propagation/mod.rs`	Wires the new carrier module into the propagation API surface via re-export.
`opentelemetry/src/propagation/env_vars_carrier.rs`	Implements the env-var carrier, normalization helpers, and unit tests.
`.cargo/config.toml`	Defines test environment variables used by `EnvVarsCarrier::from_env()` tests.

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+/// Propagates name-value pairs via environment variables.
+///
+/// This propagator provides a mechanism for propagating context information
+/// across process boundaries using environment variables, usually for when
+/// network protocols are not applicable.


+    /// Create a new `EnvVarsCarrier` object, built from environment variables.
+    /// Environment variables are fetched and normalized at construction time.
+    pub fn from_env() -> Self {


 pub use composite::TextMapCompositePropagator;
+pub use env_vars_carrier::EnvVarsCarrier;
 pub use text_map_propagator::TextMapPropagator;


jsurany · 2026-06-18T18:30:13Z

Hey, sorry the effort under which I made this PR has wrapped up and I now need to wait for a different set of approvals to go through to continue work on this PR. It could take up to 6 weeks. I'll finish up the remaining comments when I have approval again.

pellared · 2026-06-29T17:57:25Z

This is only a prototype and at this point of time we rather need an actual experimental implementation. I suggest closing.

kamphaus · 2026-06-29T20:37:42Z

Superseded by #3574

jsurany requested a review from a team as a code owner May 21, 2026 21:53

jsurany changed the title ~~add prototype for EnvVarsCarrier (env var propagation)~~ feat: add prototype for EnvVarsCarrier (env var propagation) May 21, 2026

TommyCpp reviewed May 26, 2026

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Comment thread opentelemetry-sdk/src/propagation/env_vars_carrier.rs Outdated

Comment thread opentelemetry-sdk/src/propagation/env_vars_carrier.rs Outdated

Comment thread opentelemetry/src/propagation/env_vars_carrier.rs

TommyCpp reviewed May 26, 2026

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jsurany requested a review from TommyCpp May 26, 2026 15:53

pellared reviewed Jun 2, 2026

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Comment thread opentelemetry/src/propagation/env_vars_carrier.rs Outdated

Comment thread opentelemetry/src/propagation/env_vars_carrier.rs

Comment thread opentelemetry/src/propagation/env_vars_carrier.rs

jsurany requested a review from pellared June 2, 2026 19:28

jsurany and others added 12 commits June 2, 2026 17:19

add prototype for EnvVarsCarrier

aa3cf45

fix bad docstring in EnvVarsCarrier docs

f15c91f

add environment variable for testing, add new/default testing for Env…

8f07458

…VarsCarrier

add coverage for EnvVarsCarrier::keys() method

d29ab9b

chore: prepare opentelemetry_sdk 0.32.1 release (open-telemetry#3522)

09ae032

pr feedback, rename functions, redefine default, move module

f340a8e

fix lint

f9a5270

fix docs

2fb4648

feat(sdk): add otel.sdk.processor.log.processed self-diagnostics metr…

63b84c7

…ic (open-telemetry#3514)

refactor: parametrize tests (open-telemetry#3256)

f20ef43

Co-authored-by: Scott Gerring <scottgerring@users.noreply.github.com>

add new EnvVarsCarrier test, update docs

983f10c

jsurany force-pushed the env-vars-carrier branch from 317829f to 983f10c Compare June 2, 2026 21:20

jsurany added 2 commits June 2, 2026 17:30

Merge branch 'main' into env-vars-carrier

5483f07

Merge branch 'main' into env-vars-carrier

1755ae5

TommyCpp approved these changes Jun 8, 2026

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jsurany mentioned this pull request Jun 9, 2026

Propagation: avoid env carrier enumeration open-telemetry/opentelemetry-specification#5143

Closed

jsurany marked this pull request as draft June 9, 2026 15:15

kamphaus reviewed Jun 14, 2026

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Comment thread opentelemetry/src/propagation/env_vars_carrier.rs Outdated

jsurany and others added 2 commits June 15, 2026 11:53

Merge branch 'main' into env-vars-carrier

ed459d2

update per specification PR#5144

714680e

kamphaus approved these changes Jun 15, 2026

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cijothomas requested review from Copilot and removed request for pellared June 17, 2026 07:40

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