feat: add HTTP subscription support via polling

.vscode/settings.json

@@ -1,3 +1,4 @@
 {
-  "rust-analyzer.rustfmt.extraArgs": ["+nightly"]
+  "rust-analyzer.rustfmt.extraArgs": ["+nightly"],
+  "rust-analyzer.cargo.features": ["http-subscription"]
 }

Cargo.toml

@@ -34,12 +34,14 @@ serde_json = "1.0.149"
 [dev-dependencies]
 anyhow = "1.0"
 alloy = { version = "1.1.2", features = ["node-bindings", "provider-ws"] }
+test-log = { version = "0.2.18", features = ["trace"] }
 
 [package.metadata.docs.rs]
 all-features = true
 
 [features]
 tracing = ["dep:tracing"]
+http-subscription = []
 
 [profile.release]
 lto = "thin"

README.md

@@ -163,6 +163,26 @@ while let Some(result) = stream.next().await {
 - When a fallback fails, the primary is tried first before moving to the next fallback.
 - The `Lagged` error indicates the consumer is not keeping pace with incoming blocks.
 
+#### HTTP-based subscriptions (feature flag)
+
+By default, subscriptions use WebSocket/pubsub-capable providers. Normally, HTTP-only providers are skipped during subscription retries. If your environment only exposes HTTP endpoints, you can enable HTTP-based block subscriptions via polling using the `http-subscription` Cargo feature:
+
+```toml
+[dependencies]
+robust-provider = { version = "1.0.0", features = ["http-subscription"] }
+```
+
+With this feature enabled and `allow_http_subscriptions(true)` is set, those HTTP providers can also act as subscription sources via polling, and are treated like regular pubsub-capable providers in the retry/failover logic:
+
+```rust
+let robust = RobustProviderBuilder::new(http_provider)
+    .allow_http_subscriptions(true)
+    // Optional: tune how often to poll for new blocks (defaults to ~12s)
+    .poll_interval(Duration::from_secs(12))
+    .build()
+    .await?;
+```
+
 ---
 
 ## Provider Conversion

src/lib.rs

@@ -68,5 +68,8 @@ pub use robust_provider::{
     CoreError, DEFAULT_CALL_TIMEOUT, DEFAULT_MAX_RETRIES, DEFAULT_MIN_DELAY,
     DEFAULT_RECONNECT_INTERVAL, DEFAULT_SUBSCRIPTION_BUFFER_CAPACITY, DEFAULT_SUBSCRIPTION_TIMEOUT,
     Error, IntoRobustProvider, IntoRootProvider, RobustProvider, RobustProviderBuilder,
-    RobustSubscription, RobustSubscriptionStream, SubscriptionError,
+    RobustSubscription, RobustSubscriptionStream,
 };
+
+#[cfg(feature = "http-subscription")]
+pub use robust_provider::DEFAULT_POLL_INTERVAL;

src/macros/rpc.rs

@@ -129,7 +129,6 @@ macro_rules! robust_rpc {
                         // Call the provider method with turbofish syntax if generics are present
                         provider.$method $(::<$($generic),+>)? ($($($arg),+)?).await
                     },
-                    false, // is_subscription = false
                 )
                 .await;
 
@@ -203,7 +202,6 @@ macro_rules! robust_rpc {
                             provider.$method $(::<$($generic),+>)? ($($arg),+).await
                         }
                     },
-                    false, // is_subscription = false
                 )
                 .await;