[Router] Fleet-wide sampling contract 1/3: the config surface (#39000)

Co-authored-by: Kangyan Zhou <kangyan.zhou@radixark.ai>
Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

experimental/sgl-router/tests/component/discovery/static_urls.rs

@@ -138,6 +138,7 @@ async fn static_urls_pd_role_resolved_end_to_end() {
             affinity: None,
             fused: None,
             eligibility: None,
+            sampling_overrides: Default::default(),
         },
         discovery: DiscoveryBackend::StaticUrls(StaticUrlsDiscoveryConfig {
             urls: vec![url.clone()],

experimental/sgl-router/tests/proxy/bucket_routing.rs

@@ -69,6 +69,7 @@ fn build_app_context(
             affinity,
             fused: None,
             eligibility: None,
+            sampling_overrides: Default::default(),
         },
         discovery: DiscoveryBackend::StaticUrls(StaticUrlsDiscoveryConfig {
             urls: vec!["http://placeholder:0".into()],

experimental/sgl-router/tests/proxy/chat_routing.rs

@@ -42,6 +42,7 @@ fn config_for(_worker_url: &str) -> Config {
             affinity: None,
             fused: None,
             eligibility: None,
+            sampling_overrides: Default::default(),
         },
         discovery: DiscoveryBackend::StaticUrls(StaticUrlsDiscoveryConfig {
             urls: vec!["http://placeholder:0".into()],

experimental/sgl-router/tests/proxy/common/cache_aware_fixture.rs

@@ -34,6 +34,7 @@ pub fn config() -> Config {
             sticky: None,
             fused: None,
             eligibility: None,
+            sampling_overrides: Default::default(),
         },
         discovery: DiscoveryBackend::StaticUrls(StaticUrlsDiscoveryConfig {
             urls: vec!["http://placeholder:0".into()],

experimental/sgl-router/tests/proxy/failover.rs

@@ -46,6 +46,7 @@ async fn failover_when_one_worker_dies() {
             affinity: None,
             fused: None,
             eligibility: None,
+            sampling_overrides: Default::default(),
         },
         discovery: DiscoveryBackend::StaticUrls(StaticUrlsDiscoveryConfig {
             urls: vec![w1.url.clone(), w2.url.clone(), w3.url.clone()],

experimental/sgl-router/tests/proxy/graceful_shutdown.rs

@@ -52,6 +52,7 @@ fn build_ctx_with_worker(worker_url: &str) -> Arc<AppContext> {
             affinity: None,
             fused: None,
             eligibility: None,
+            sampling_overrides: Default::default(),
         },
         discovery: DiscoveryBackend::StaticUrls(StaticUrlsDiscoveryConfig {
             urls: vec!["http://placeholder:0".into()],

experimental/sgl-router/tests/proxy/header_forwarding.rs

@@ -39,6 +39,7 @@ async fn forwards_whitelisted_headers_strips_others() {
             affinity: None,
             fused: None,
             eligibility: None,
+            sampling_overrides: Default::default(),
         },
         discovery: DiscoveryBackend::StaticUrls(StaticUrlsDiscoveryConfig {
             urls: vec!["http://placeholder:0".into()],

experimental/sgl-router/tests/proxy/pd_bootstrap_injection.rs

@@ -54,6 +54,7 @@ fn config() -> Config {
             affinity: None,
             fused: None,
             eligibility: None,
+            sampling_overrides: Default::default(),
         },
         discovery: DiscoveryBackend::StaticUrls(StaticUrlsDiscoveryConfig {
             urls: vec!["http://placeholder:0".into()],

experimental/sgl-router/tests/proxy/pd_pool_isolation.rs

@@ -53,6 +53,7 @@ fn config() -> Config {
             affinity: None,
             fused: None,
             eligibility: None,
+            sampling_overrides: Default::default(),
         },
         discovery: DiscoveryBackend::StaticUrls(StaticUrlsDiscoveryConfig {
             urls: vec!["http://placeholder:0".into()],

experimental/sgl-router/tests/proxy/roundrobin_input_ids.rs

@@ -50,6 +50,7 @@ fn config() -> Config {
             affinity: None,
             fused: None,
             eligibility: None,
+            sampling_overrides: Default::default(),
         },
         discovery: DiscoveryBackend::StaticUrls(StaticUrlsDiscoveryConfig {
             urls: vec!["http://placeholder:0".into()],

experimental/sgl-router/tests/proxy/shared_prefill_admission.rs

@@ -156,6 +156,7 @@ fn config(policy: PolicyKind) -> Config {
             affinity: None,
             fused: None,
             eligibility: None,
+            sampling_overrides: Default::default(),
         },
         discovery: DiscoveryBackend::StaticUrls(StaticUrlsDiscoveryConfig {
             urls: vec!["http://placeholder:0".into()],

experimental/sgl-router/tests/proxy/sticky_input_ids.rs

@@ -69,6 +69,7 @@ fn config() -> Config {
             affinity: None,
             fused: None,
             eligibility: None,
+            sampling_overrides: Default::default(),
         },
         discovery: DiscoveryBackend::StaticUrls(StaticUrlsDiscoveryConfig {
             urls: vec!["http://placeholder:0".into()],

experimental/sgl-router/tests/proxy/sticky_routing.rs

@@ -55,6 +55,7 @@ fn build_sticky_ctx(header_name: &str, worker_urls: &[String]) -> Arc<AppContext
             affinity: None,
             fused: None,
             eligibility: None,
+            sampling_overrides: Default::default(),
         },
         discovery: DiscoveryBackend::StaticUrls(StaticUrlsDiscoveryConfig {
             urls: vec!["http://placeholder:0".into()],

experimental/sgl-router/tests/proxy/timeout.rs

@@ -46,6 +46,7 @@ fn config(_worker_url: &str) -> Config {
             affinity: None,
             fused: None,
             eligibility: None,
+            sampling_overrides: Default::default(),
         },
         discovery: DiscoveryBackend::StaticUrls(StaticUrlsDiscoveryConfig {
             urls: vec!["http://placeholder:0".into()],