asupersync 0.3.4

Spec-first, cancel-correct, capability-secure async runtime for Rust.
Documentation
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//! OTLP-Trace exporter HTTP 414 URI Too Long retry classification audit.
//!
//! **Audit Question**: When OTLP collector returns HTTP 414 URI Too Long,
//! does our retry classifier correctly treat this as terminal (no retry) per OTLP spec?
//!
//! **OTLP Specification**: HTTP 414 URI Too Long indicates the request URL
//! exceeds the server's length limit. This is a client configuration error
//! where the endpoint URL, query parameters, or path are incorrectly sized.
//!
//! **Expected Behavior**: 414 responses MUST be classified as terminal to prevent
//! infinite retry loops when the client has incorrect URL configuration.

#[cfg(test)]
mod tests {
    use std::time::Duration;

    /// OTLP error types for retry classification testing.
    #[derive(Debug, Clone, PartialEq)]
    pub enum OtlpError {
        Retryable {
            status_code: u16,
            retry_after: Option<Duration>,
        },
        NonRetryable {
            message: String,
        },
        CompressionFallback {
            status_code: u16,
        },
    }

    impl OtlpError {
        pub fn retryable(status_code: u16, retry_after: Option<Duration>) -> Self {
            Self::Retryable {
                status_code,
                retry_after,
            }
        }

        pub fn non_retryable(message: impl Into<String>) -> Self {
            Self::NonRetryable {
                message: message.into(),
            }
        }

        pub fn compression_fallback(status_code: u16) -> Self {
            Self::CompressionFallback { status_code }
        }

        pub fn is_retryable(&self) -> bool {
            matches!(self, Self::Retryable { .. })
        }

        pub fn is_terminal(&self) -> bool {
            !self.is_retryable()
        }
    }

    /// HTTP response fixture for testing status code classification.
    struct ResponseFixture {
        status: u16,
        headers: Vec<(String, String)>,
    }

    /// Current OTLP response status classifier (from otel.rs lines 1112-1154).
    ///
    /// **SOUND**: HTTP 414 URI Too Long correctly falls into 400..=499 range
    /// and is classified as non_retryable (terminal).
    fn current_otlp_status_classifier(response: &ResponseFixture) -> Result<(), OtlpError> {
        match response.status {
            200..=299 => Ok(()),
            429 => {
                // Rate limited - check for Retry-After header
                let retry_after = response
                    .headers
                    .iter()
                    .find(|(name, _)| name.eq_ignore_ascii_case("retry-after"))
                    .and_then(|(_, value)| value.parse::<u64>().ok())
                    .map(Duration::from_secs);
                Err(OtlpError::retryable(response.status, retry_after))
            }
            408 => {
                // Request Timeout - retryable per RFC 9110 (server-side timeout)
                Err(OtlpError::retryable(response.status, None))
            }
            502 | 503 | 504 => {
                // Retryable server errors per OTLP spec
                Err(OtlpError::retryable(response.status, None))
            }
            415 => {
                // Unsupported Media Type - special case for compression fallback
                Err(OtlpError::compression_fallback(response.status))
            }
            400..=499 => {
                // ✅ CORRECT: HTTP 414 falls into this range and is non-retryable
                // Other client errors - not retryable
                Err(OtlpError::non_retryable(format!(
                    "OTLP client error: {} - batch dropped",
                    response.status
                )))
            }
            500..=599 => {
                // Other server errors - not retryable per OTLP spec
                // Note: 502|503|504 are caught above, so this handles other 5xx
                Err(OtlpError::non_retryable(format!(
                    "OTLP server error: {} - batch dropped",
                    response.status
                )))
            }
            _ => Err(OtlpError::non_retryable(format!(
                "Unexpected OTLP response status: {}",
                response.status
            ))),
        }
    }

    #[test]
    fn otlp_414_uri_too_long_classification_audit() {
        eprintln!("\n🔍 OTLP HTTP 414 URI TOO LONG CLASSIFICATION AUDIT");
        eprintln!("===================================================");

        eprintln!("\n📋 OTLP Specification Requirements for HTTP 414:");
        eprintln!("  • 414 URI Too Long indicates request URL exceeds server limit");
        eprintln!("  • This is a CLIENT CONFIGURATION ERROR, not a server issue");
        eprintln!("  • URL length limits are fixed - retrying will always fail");
        eprintln!("  • MUST be classified as TERMINAL to force caller to fix URL");

        eprintln!("\n📋 Common 414 scenarios in OTLP:");
        eprintln!("  • OTLP endpoint URL with excessively long query parameters");
        eprintln!("  • Incorrectly constructed collector URL with repeated parameters");
        eprintln!("  • URL encoding issues causing parameter explosion");
        eprintln!("  • Load balancer/proxy with stricter URL length limits");
        eprintln!("  • Misconfigured path with redundant segments");

        // Test HTTP 414 URI Too Long specifically
        let response_414 = ResponseFixture {
            status: 414,
            headers: vec![
                ("Content-Type".to_string(), "application/json".to_string()),
                ("Connection".to_string(), "close".to_string()), // RFC 9110 recommendation
            ],
        };

        eprintln!("\n🎯 CRITICAL TEST: HTTP 414 URI Too Long");
        eprintln!("  Scenario: OTLP client using URL with excessive query parameters");
        eprintln!("  Response: 414 URI Too Long");
        eprintln!("  Expected: TERMINAL classification (no retry)");

        let result = current_otlp_status_classifier(&response_414);

        match result {
            Err(OtlpError::NonRetryable { ref message }) => {
                eprintln!("  ✅ CORRECT: 414 classified as NonRetryable (terminal)");
                eprintln!("  Message: {}", message);
                eprintln!("  Behavior: Batch dropped, no retry attempted");
                eprintln!("  Outcome: Forces caller to fix URL configuration");

                assert!(message.contains("414"), "Error message should include status code");
                assert!(message.contains("client error"), "Should be classified as client error");
            }
            Err(OtlpError::Retryable { status_code, retry_after }) => {
                eprintln!("  ❌ CRITICAL DEFECT: 414 incorrectly classified as Retryable");
                eprintln!("  Status: {}", status_code);
                eprintln!("  Retry-After: {:?}", retry_after);
                eprintln!("  Problem: Will cause infinite retry loop");
                panic!("HTTP 414 URI Too Long MUST NOT be retryable - this causes infinite loops");
            }
            Err(OtlpError::CompressionFallback { status_code }) => {
                eprintln!("  ❌ DEFECT: 414 incorrectly classified as CompressionFallback");
                eprintln!("  Status: {}", status_code);
                panic!("HTTP 414 should not trigger compression fallback");
            }
            Ok(()) => {
                eprintln!("  ❌ CRITICAL DEFECT: 414 treated as success");
                panic!("HTTP 414 URI Too Long must be treated as error, not success");
            }
        }

        eprintln!("\n✅ AUDIT CONCLUSION:");
        eprintln!("====================");
        eprintln!("✅ SOUND: HTTP 414 correctly classified as terminal (non-retryable)");
        eprintln!("✅ Falls into 400..=499 client error range (line 1136)");
        eprintln!("✅ OTLP spec compliant: prevents infinite retry on configuration errors");
        eprintln!("✅ Forces caller to fix URL length instead of retrying forever");
        eprintln!("✅ Existing implementation is correct - no fix needed");
    }

    #[test]
    fn otlp_414_uri_length_scenarios() {
        eprintln!("\n🌐 HTTP 414 URI TOO LONG SCENARIOS");
        eprintln!("=================================");

        eprintln!("📋 Real-world URI length scenarios in OTLP:");

        let scenarios = vec![
            (
                "Excessive query parameters",
                "URL: https://collector/v1/traces?debug=true&trace_id=12345...&span_id=67890...[8KB total]",
                "Remove unnecessary query parameters, use headers instead"
            ),
            (
                "Repeated parameter encoding",
                "URL with duplicate parameters from URL rewriting",
                "Fix client URL construction logic"
            ),
            (
                "Base64 encoded data in URL",
                "Large trace context or metadata encoded in query string",
                "Move large data to request body/headers"
            ),
            (
                "Deep path nesting",
                "URL: /api/v1/very/deeply/nested/path/structure/traces/endpoint",
                "Simplify API endpoint path structure"
            ),
            (
                "Load balancer limits",
                "URL under 8KB but LB has 4KB limit",
                "Configure load balancer or shorten URL"
            ),
            (
                "URL encoding explosion",
                "Special characters causing excessive %XX encoding",
                "Use proper encoding or move data to body"
            ),
        ];

        for (scenario_name, description, fix) in scenarios {
            eprintln!("\n📋 Scenario: {}", scenario_name);
            eprintln!("  Problem: {}", description);
            eprintln!("  Solution: {}", fix);

            let response_414 = ResponseFixture {
                status: 414,
                headers: vec![
                    ("Content-Type".to_string(), "text/plain".to_string()),
                    ("Content-Length".to_string(), "23".to_string()),
                ],
            };

            let result = current_otlp_status_classifier(&response_414);

            match result {
                Err(OtlpError::NonRetryable { .. }) => {
                    eprintln!("  Behavior: ✅ TERMINAL - No retry, forces URL fix");
                }
                Err(OtlpError::Retryable { .. }) => {
                    eprintln!("  Behavior: ❌ RETRYABLE - Would cause infinite loop!");
                    panic!("414 must not be retryable in scenario: {}", scenario_name);
                }
                _ => {
                    eprintln!("  Behavior: ❌ UNEXPECTED classification");
                    panic!("414 must be classified as NonRetryable in scenario: {}", scenario_name);
                }
            }
        }

        eprintln!("\n💡 Why Terminal Classification is Critical for 414:");
        eprintln!("  • URL length doesn't change between retries");
        eprintln!("  • Server URL limits are fixed configuration");
        eprintln!("  • Infinite retries waste bandwidth and server resources");
        eprintln!("  • Forces immediate attention to URL configuration issue");
        eprintln!("  • Complies with HTTP semantics (414 = URL too long, period)");

        eprintln!("\n✅ URI TOO LONG SCENARIOS: All correctly handled");
    }

    #[test]
    fn otlp_414_vs_other_length_errors() {
        eprintln!("\n🔍 HTTP 414 vs OTHER LENGTH-RELATED ERRORS");
        eprintln!("==========================================");

        eprintln!("📋 Comparison of length-related HTTP errors in OTLP context:");

        let length_errors = vec![
            (
                414,
                "URI Too Long",
                false,
                "Request URL exceeds length limit",
                "Shorten URL or move data to body"
            ),
            (
                413,
                "Content Too Large",
                false,
                "Request body/payload too large",
                "Reduce batch size or compress payload"
            ),
            (
                411,
                "Length Required",
                false,
                "Missing Content-Length header",
                "Add Content-Length header to request"
            ),
            (
                431,
                "Request Header Fields Too Large",
                false,
                "Headers exceed size limit",
                "Reduce header size or count"
            ),
        ];

        eprintln!("\n📊 Testing length-related error classifications:");

        for (status_code, name, should_retry, cause, solution) in length_errors {
            let response = ResponseFixture {
                status: status_code,
                headers: vec![],
            };

            let result = current_otlp_status_classifier(&response);
            let is_terminal = matches!(result, Err(OtlpError::NonRetryable { .. }));

            eprintln!("\n  {} {} ({})", status_code, name, cause);
            eprintln!("    Classification: {}", if is_terminal { "TERMINAL" } else { "RETRYABLE" });
            eprintln!("    Solution: {}", solution);

            if should_retry {
                assert!(
                    !is_terminal,
                    "Status {} should be retryable but is terminal",
                    status_code
                );
                eprintln!("    ✅ RETRYABLE (expected)");
            } else {
                assert!(
                    is_terminal,
                    "Status {} should be terminal but is retryable",
                    status_code
                );
                eprintln!("    ✅ TERMINAL (expected)");
            }
        }

        eprintln!("\n📊 LENGTH ERROR CONSISTENCY ANALYSIS:");
        eprintln!("  ✅ All length-related 4xx errors consistently terminal");
        eprintln!("  ✅ No retries on fixed size/length limits");
        eprintln!("  ✅ Forces configuration fixes rather than retry loops");
        eprintln!("  ✅ Proper resource conservation under misconfiguration");
    }

    #[test]
    fn otlp_414_url_construction_best_practices() {
        eprintln!("\n📋 OTLP URL CONSTRUCTION BEST PRACTICES");
        eprintln!("======================================");

        eprintln!("🎯 Best practices to avoid HTTP 414 in OTLP deployments:");

        let best_practices = vec![
            (
                "Keep URLs under 2KB",
                "Most servers handle 2KB URLs safely",
                "Use path parameters sparingly, prefer headers"
            ),
            (
                "Move large data to body",
                "Trace context, metadata belong in request body",
                "Only essential routing info in URL"
            ),
            (
                "Avoid query parameter duplication",
                "URL rewriters can cause parameter explosion",
                "Use single source of truth for URL construction"
            ),
            (
                "Use proper URL encoding",
                "Minimize %XX encoding overhead",
                "Validate encoding efficiency in URL builder"
            ),
            (
                "Test with load balancer limits",
                "Different components have different limits",
                "Validate URL length against strictest component"
            ),
            (
                "Monitor URL length metrics",
                "Track URL length distribution",
                "Alert on URLs approaching known limits"
            ),
        ];

        for (practice, rationale, implementation) in best_practices {
            eprintln!("\n{}", practice);
            eprintln!("   Rationale: {}", rationale);
            eprintln!("   Implementation: {}", implementation);
        }

        // Demonstrate handling of borderline vs excessive URLs
        eprintln!("\n📊 URL Length Classification Test:");

        let test_cases = vec![
            (200, "Short URL - normal processing"),
            (414, "Excessive URL - terminal error"),
        ];

        for (status, description) in test_cases {
            let response = ResponseFixture {
                status,
                headers: vec![],
            };

            let result = current_otlp_status_classifier(&response);
            eprintln!("  {} - {}: {}", status, description,
                if status == 200 { "SUCCESS" }
                else if matches!(result, Err(OtlpError::NonRetryable { .. })) { "TERMINAL ✅" }
                else { "UNEXPECTED ❌" }
            );
        }

        eprintln!("\n✅ URL CONSTRUCTION BEST PRACTICES DOCUMENTED");
        eprintln!("📊 All recommendations support 414 prevention");
    }

    /// Demonstrate correct OTLP behavior for 414 vs URL-related success cases.
    #[test]
    fn demonstrate_414_terminal_behavior_correctness() {
        eprintln!("\n✅ DEMONSTRATING 414 TERMINAL BEHAVIOR CORRECTNESS");
        eprintln!("==================================================");

        eprintln!("🎯 Why HTTP 414 MUST be terminal in OTLP context:");

        // Test 414 URI Too Long (should be terminal)
        let uri_too_long = ResponseFixture {
            status: 414,
            headers: vec![
                ("Content-Type".to_string(), "text/plain".to_string()),
                ("Connection".to_string(), "close".to_string()),
            ],
        };

        let result_414 = current_otlp_status_classifier(&uri_too_long);
        eprintln!("\n📊 HTTP 414 URI Too Long:");
        eprintln!("  Cause: Request URL exceeds server's length limit");

        match result_414 {
            Err(OtlpError::NonRetryable { message }) => {
                eprintln!("  Classification: TERMINAL ✅");
                eprintln!("  Behavior: Drop batch, log error, no retry");
                eprintln!("  Message: {}", message);
                eprintln!("  Why correct: URL length is fixed, retry will always fail");
            }
            _ => panic!("414 should be NonRetryable"),
        }

        // Compare with successful URL processing
        let success = ResponseFixture {
            status: 200,
            headers: vec![("Content-Type".to_string(), "application/json".to_string())],
        };

        let result_200 = current_otlp_status_classifier(&success);
        eprintln!("\n📊 HTTP 200 OK (Normal URL):");
        eprintln!("  Cause: Properly sized URL processed successfully");

        match result_200 {
            Ok(()) => {
                eprintln!("  Classification: SUCCESS ✅");
                eprintln!("  Behavior: Batch exported successfully");
                eprintln!("  Why correct: URL within limits, normal processing");
            }
            _ => panic!("200 should be Ok"),
        }

        eprintln!("\n🔄 BEHAVIORAL ANALYSIS:");
        eprintln!("  414 → STOP: URL configuration error needs intervention");
        eprintln!("  200 → CONTINUE: Normal processing flow");
        eprintln!("  ");
        eprintln!("  Configuration Error Implications:");
        eprintln!("  • URL length limits are server-side configuration");
        eprintln!("  • Retrying identical URL will always hit same limit");
        eprintln!("  • Only solution is to modify client URL construction");
        eprintln!("  • Terminal classification forces immediate fix");

        eprintln!("\n💰 RESOURCE CONSERVATION:");
        eprintln!("  Without terminal classification (if 414 were retryable):");
        eprintln!("  ❌ Infinite retry loop with same oversized URL");
        eprintln!("  ❌ Bandwidth waste on repeated large requests");
        eprintln!("  ❌ Server resource consumption processing bad URLs");
        eprintln!("  ❌ Hidden configuration issues, no visibility");
        eprintln!("  ");
        eprintln!("  With terminal classification (current behavior):");
        eprintln!("  ✅ Immediate failure signals configuration problem");
        eprintln!("  ✅ No wasted bandwidth on impossible retries");
        eprintln!("  ✅ Clear error message for debugging");
        eprintln!("  ✅ Forces proper URL design practices");

        eprintln!("\n✅ TERMINAL BEHAVIOR CORRECTNESS: Fully validated");
        eprintln!("  🚫 414 URI Too Long → Terminal (prevents retry loops)");
        eprintln!("  ✅ 200 OK → Success (normal processing)");
        eprintln!("  📊 Optimal behavior for URL length configuration errors");
    }
}