[FIX] Preserve user baggage header when setting Session ID #1016
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sbarrio
previously approved these changes
Oct 22, 2025
| } | ||
| } | ||
| return result; | ||
| } |
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The encoding is custom since baggage headers support characters that would otherwise be escaped by functions like encodeURIComponent.
The logic is:
- Converts the character to an iterable
utf8buffer - Converts each byte value to a hexadecimal string using
toString(16) - Pads it to always have two digits with
padStart(2, '0') - Uppercases it for canonical form.
- Prefixes it with %.
For example, if you encode "é":
Buffer.from('é', 'utf8') -> [195, 169] (0xC3, 0xA9)
result -> %C3%A9
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sbarrio
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Nov 3, 2025
...es/core/src/rum/instrumentation/resourceTracking/requestProxy/XHRProxy/baggageHeaderUtils.ts
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cdn34dd
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Nov 3, 2025
| expect(logSpy).not.toHaveBeenCalled(); | ||
| }); | ||
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| it('should percent-encode spaces and non-ASCII characters in values', () => { |
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probably not super important, but I quickly tried you branch and added a test:
it('test', () => {
const entries = new Set([
'traceId=abc123;sampled=true;debug',
'test1= this is a test'
]);
const result = formatBaggageHeader(entries);
expect(result).toBe(
'traceId=abc123;sampled=true;debug,test1=this%20is%20a%20test'
);
});
however I believe the correct result should be:
'traceId=abc123;sampled=true;debug,test1=%20this%20is%20a%20test'
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Thanks for trying it out 🙏 However, the result is correct, as keys and values are trimmed on purpose.
In the W3 spec:
baggage-string = list-member 0*179( OWS "," OWS list-member )
list-member = key OWS "=" OWS value *( OWS ";" OWS property )
property = key OWS "=" OWS value
Where OWS stands for "optional whitespace".
sbarrio
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What does this PR do?
When a RUM Session ID is available, we set it in the
Baggageheader of intercepted network requests when usingtrackResources=true.We don't account for pre-existing values in the
Baggageheader, so we end up overwriting it.This PR adds support for user-defined
Baggageheaders by using comma-separated list strings, following the W3C Baggage specification.Requirements for W3 compliance
Entry Format
Each entry must contain at least one = separating key and value.
Key Validation
Keys must follow RFC 7230 §3.2.6 token grammar.
Allowed characters:
!#$%&'*+-.^_|~0-9A-Za-zValue Encoding
Values are UTF-8 encoded.
Characters outside the allowed baggage octet range (
!, #–+, -–:, <–[, ]–~) are percent-encoded.Spaces, commas, semicolons, quotes, backslashes, and non-ASCII characters are encoded.
Example:
Properties (Metadata)
Entries may include properties separated by semi-colons:
Property keys must also follow RFC 7230 token grammar.
Property values are percent-encoded using the same rules as the main value.
Whitespace Handling
Leading and trailing whitespace around keys, values, and properties is trimmed.
Internal whitespace (e.g. "foo = bar ; p1 = one") is normalized.
Limits (per W3C Spec §3.3.2)
The resulting header must contain:
≤ 64 list-members, otherwise a warning is logged.
≤ 8192 bytes total size, otherwise a warning is logged.
Entries beyond these limits may be ignored by consumers. We print a warning on our side, without dropping the entry.
Order Preservation
Entries are formatted in the same order they appear in the original Set.
Logging and Error Handling
Invalid entries and properties are not propagated.
Each failure is logged via InternalLog with
SdkVerbosity.WARN.Review checklist (to be filled by reviewers)