Otel : Don't read response body size if the content-type is text/event-stream

[Orygin]

The default behavior of the Otel middleware is to read the response size before proceeding with the request response.
This breaks Server Sent Events using Fiber's SetBodyStreamWriter as the body is never properly flushed to the client.

This change is small and explicit for SSE, but there could be a more advanced mechanism to control this behavior per request.

Summary by CodeRabbit

• Bug Fixes
  • Improved response size calculation in middleware to handle "text/event-stream" content types correctly.

[coderabbitai]

Walkthrough

The Middleware function in the fiber.go file has been updated to conditionally calculate the responseSize based on the response body length only when the response header's "Content-Type" is not "text/event-stream". This change ensures that the responseSize calculation is skipped for server-sent events, improving performance and accuracy.

Changes

File Path	Change Summary
otelfiber/fiber.go	Updated the Middleware function to conditionally calculate responseSize based on response body length, excluding "text/event-stream" content type. Added a declaration for responseSize as an int64 variable.

Poem

In Fiber's code, a change was made,
For streaming events, a rule was laid.
Response size now, it skips the stream,
Efficiency gained, like a coder's dream.
🎉📊✨

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[coderabbitai]

Actionable comments posted: 0

Outside diff range and nitpick comments (3)

otelfiber/fiber.go (3)

136-140: Consider implementing a more flexible mechanism.

While the current solution is effective for the specific case of "text/event-stream", consider implementing a more flexible mechanism that allows developers to specify behaviors based on different conditions or content types. This could enhance the middleware's versatility and applicability to various use cases.

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Line range hint 35-35: Resolve undefined types.

The types Option and config are undefined within the scope of this file. Ensure that these types are either defined in this file or properly imported from another package.

Also applies to: 36-36

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Line range hint 94-94: Resolve undefined functions.

The functions httpServerMetricAttributesFromRequest and httpServerTraceAttributesFromRequest are undefined. Ensure that these functions are defined within the scope of this project or imported correctly if they are part of an external library.

Also applies to: 108-108

Review details

Configuration used: CodeRabbit UI
Review profile: CHILL

Commits

Files that changed from the base of the PR and between bb80ed2 and eaae8b4.

Files selected for processing (1)

• otelfiber/fiber.go (1 hunks)

Additional context used

golangci-lint

otelfiber/fiber.go

35-35: undefined: Option (typecheck)

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179-179: undefined: fiber (typecheck)

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36-36: undefined: config (typecheck)

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83-83: undefined: fiber (typecheck)

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94-94: undefined: httpServerMetricAttributesFromRequest (typecheck)

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108-108: undefined: httpServerTraceAttributesFromRequest (typecheck)

Additional comments not posted (1)

otelfiber/fiber.go (1)

136-140: Avoid reading response size for SSE content types.

The conditional check for the "Content-Type" header to avoid reading the response size for "text/event-stream" is a targeted and effective solution for the issue with SSE in Fiber. This ensures that the middleware does not interfere with the streaming of events.