v0.3.2-pre.007

crates/ksp-store-postgres-lib/src/error.rs

@@ -1,5 +1,5 @@
 // file: crates/ksp-store-postgres-lib/src/error.rs
-// version: 2
+// version: 3
 
 /// Safe backend-local classification used by the Store facade for stable error mapping.
 #[derive(Clone, Copy, Debug, Eq, PartialEq)]
@@ -11,6 +11,8 @@ pub enum PostgresBackendErrorKind {
     ConnectFailed,
     /// A bounded pool wait, create or recycle operation reached its deadline.
     PoolTimeout,
+    /// A lightweight PostgreSQL health/readiness probe failed without exposing server text or SQL.
+    HealthFailed,
     /// PostgreSQL migration/bootstrap execution failed without exposing server text or SQL.
     MigrationFailed,
     /// Applied PostgreSQL migration history diverges from the embedded immutable KSP history.

crates/ksp-store-postgres-lib/src/health.rs

@@ -0,0 +1,101 @@
+// file: crates/ksp-store-postgres-lib/src/health.rs
+// version: 1
+
+const DEFAULT_HEALTH_TIMEOUT_MS: u64 = 5_000;
+const MIGRATION_VERSION_SQL: &str = "SELECT COALESCE(MAX(version), -1)::BIGINT FROM ksp_store_schema_migrations";
+const READINESS_SQL: &str = "SELECT 1::BIGINT";
+
+/// Runs one bounded lightweight readiness probe and returns only safe classified diagnostics.
+pub(crate) async fn probe_health(pool: &deadpool_postgres::Pool) -> crate::PostgresBackendHealthSnapshot {
+    let runtime = crate::runtime_snapshot_from_status(pool.status());
+    let timeouts = pool.timeouts();
+    let timeout = match timeouts.wait {
+        std::option::Option::Some(value) => value,
+        std::option::Option::None => std::time::Duration::from_millis(DEFAULT_HEALTH_TIMEOUT_MS),
+    };
+    let bounded = tokio::time::timeout(timeout, probe_health_inner(pool, runtime.clone())).await;
+    return match bounded {
+        std::result::Result::Ok(snapshot) => snapshot,
+        std::result::Result::Err(_) => {
+            crate::PostgresBackendHealthSnapshot::not_ready(runtime, std::option::Option::None, 0, crate::PostgresBackendErrorKind::HealthFailed)
+        },
+    };
+}
+
+async fn probe_health_inner(pool: &deadpool_postgres::Pool, runtime: crate::PostgresBackendRuntimeSnapshot) -> crate::PostgresBackendHealthSnapshot {
+    let client_result = pool.get().await;
+    let client = match client_result {
+        std::result::Result::Ok(value) => value,
+        std::result::Result::Err(error) => {
+            let classified = crate::map_pool_error(error);
+            return crate::PostgresBackendHealthSnapshot::not_ready(runtime, std::option::Option::None, 0, classified.kind());
+        },
+    };
+    let readiness_result = client.query_one(READINESS_SQL, &[]).await;
+    let readiness_row = match readiness_result {
+        std::result::Result::Ok(value) => value,
+        std::result::Result::Err(_) => {
+            return crate::PostgresBackendHealthSnapshot::not_ready(runtime, std::option::Option::None, 0, crate::PostgresBackendErrorKind::HealthFailed);
+        },
+    };
+    let readiness_value = match readiness_row.try_get::<usize, i64>(0) {
+        std::result::Result::Ok(value) => value,
+        std::result::Result::Err(_) => {
+            return crate::PostgresBackendHealthSnapshot::not_ready(runtime, std::option::Option::None, 0, crate::PostgresBackendErrorKind::HealthFailed);
+        },
+    };
+    if readiness_value != 1 {
+        return crate::PostgresBackendHealthSnapshot::not_ready(runtime, std::option::Option::None, 0, crate::PostgresBackendErrorKind::HealthFailed);
+    }
+    let migration_result = client.query_one(MIGRATION_VERSION_SQL, &[]).await;
+    let migration_row = match migration_result {
+        std::result::Result::Ok(value) => value,
+        std::result::Result::Err(_) => {
+            return crate::PostgresBackendHealthSnapshot::not_ready(runtime, std::option::Option::None, 0, crate::PostgresBackendErrorKind::HealthFailed);
+        },
+    };
+    let migration_value = migration_row.try_get::<usize, i64>(0);
+    let migration_version = match migration_value {
+        std::result::Result::Ok(value) => value,
+        std::result::Result::Err(_) => {
+            return crate::PostgresBackendHealthSnapshot::not_ready(runtime, std::option::Option::None, 0, crate::PostgresBackendErrorKind::HealthFailed);
+        },
+    };
+    let expected = crate::current_migration_version();
+    if migration_version < 0 || migration_version < expected {
+        let observed = nonnegative_version(migration_version);
+        let pending = pending_migration_count(migration_version, expected);
+        return crate::PostgresBackendHealthSnapshot::not_ready(runtime, observed, pending, crate::PostgresBackendErrorKind::MigrationMismatch);
+    }
+    if migration_version > expected {
+        return crate::PostgresBackendHealthSnapshot::not_ready(
+            runtime,
+            nonnegative_version(migration_version),
+            0,
+            crate::PostgresBackendErrorKind::SchemaNewer,
+        );
+    }
+    return crate::PostgresBackendHealthSnapshot::ready(runtime, migration_version as u64, 0);
+}
+
+fn nonnegative_version(value: i64) -> std::option::Option<u64> {
+    if value < 0 {
+        return std::option::Option::None;
+    }
+    return std::option::Option::Some(value as u64);
+}
+
+fn pending_migration_count(observed: i64, expected: i64) -> u32 {
+    if observed >= expected {
+        return 0;
+    }
+    let delta = expected.saturating_sub(observed);
+    if delta > i64::from(u32::MAX) {
+        return u32::MAX;
+    }
+    return delta as u32;
+}
+
+#[cfg(test)]
+#[path = "../unit_tests/health.rs"]
+mod tests;

crates/ksp-store-postgres-lib/src/lib.rs

@@ -1,5 +1,5 @@
 // file: crates/ksp-store-postgres-lib/src/lib.rs
-// version: 4
+// version: 5
 
 #![warn(missing_docs)]
 #![deny(unreachable_pub)]
@@ -7,9 +7,10 @@
 
 //! Official PostgreSQL backend implementation for KSP Store.
 //!
-//! `0.3.2-pre.006` owns the physical `tokio-postgres` connection, bounded
-//! Deadpool pool, explicit Rustls TLS policy and private KSP migration/bootstrap
-//! engine. Business persistence remains absent from this foundation release.
+//! `0.3.2-pre.007` owns the physical `tokio-postgres` connection, bounded
+//! Deadpool pool, explicit Rustls TLS policy, private KSP migration/bootstrap
+//! engine and safe lightweight health/readiness probe. Business persistence
+//! remains absent from this foundation release.
 //!
 //! This crate depends on `ksp-store-api` and never on `ksp-store-lib`. The
 //! common facade consumes only this crate's narrow backend bridge and never
@@ -17,6 +18,7 @@
 
 mod constants;
 mod error;
+mod health;
 mod migration;
 mod runtime;
 
@@ -26,6 +28,10 @@ pub use self::error::PostgresBackendError;
 pub use self::error::PostgresBackendErrorKind;
 /// Opaque physical PostgreSQL backend owning its connection pool.
 pub use self::runtime::PostgresBackend;
+/// Safe PostgreSQL readiness projection returned through the backend bridge.
+pub use self::runtime::PostgresBackendHealthSnapshot;
+/// Safe PostgreSQL pool counter projection returned through the backend bridge.
+pub use self::runtime::PostgresBackendRuntimeSnapshot;
 /// Physical PostgreSQL settings bridge consumed only by the backend crate.
 pub use self::runtime::PostgresBackendSettings;
 /// TLS mode accepted by the physical PostgreSQL settings bridge.
@@ -33,7 +39,15 @@ pub use self::runtime::PostgresBackendTlsMode;
 
 /// Crate-owned tracing target for PostgreSQL backend behavior.
 pub(crate) use self::constants::TRACING_TARGET;
+/// Private bounded health probe consumed by the physical backend runtime.
+pub(crate) use self::health::probe_health;
 /// Private migration/bootstrap runner consumed by the physical backend runtime.
 pub(crate) use self::migration::bootstrap;
+/// Current embedded migration version consumed by the private health probe.
+pub(crate) use self::migration::current_migration_version;
+/// Private Deadpool error mapper shared with the health probe.
+pub(crate) use self::runtime::map_pool_error;
+/// Private Deadpool status projector shared with the health probe.
+pub(crate) use self::runtime::runtime_snapshot_from_status;
 
 const _: &str = crate::TRACING_TARGET;

crates/ksp-store-postgres-lib/src/migration.rs

@@ -1,5 +1,5 @@
 // file: crates/ksp-store-postgres-lib/src/migration.rs
-// version: 1
+// version: 2
 
 use sha2::Digest; // rust-rules: trait-import
 
@@ -40,6 +40,12 @@ struct AppliedMigration {
     version: i64,
 }
 
+/// Returns the latest migration version embedded by this backend runtime.
+#[must_use]
+pub(crate) const fn current_migration_version() -> i64 {
+    return BOOTSTRAP_MIGRATION_VERSION;
+}
+
 /// Runs the private bounded PostgreSQL schema bootstrap on one dedicated pooled client.
 pub(crate) async fn bootstrap(
     client: &mut deadpool_postgres::Client,

crates/ksp-store-postgres-lib/src/runtime.rs

@@ -1,10 +1,122 @@
 // file: crates/ksp-store-postgres-lib/src/runtime.rs
-// version: 2
+// version: 3
 
 const APPLICATION_NAME: &str = "ksp-store";
 const MAX_CONNECTION_URI_BYTES: usize = 4_096;
 const SHUTDOWN_POLL_INTERVAL_MS: u64 = 10;
 
+/// Safe PostgreSQL runtime counters exported only through the narrow backend bridge.
+#[derive(Clone, Debug, Eq, PartialEq)]
+pub struct PostgresBackendRuntimeSnapshot {
+    pool_available: u32,
+    pool_capacity: u32,
+    pool_size: u32,
+    pool_waiting: u32,
+}
+
+impl PostgresBackendRuntimeSnapshot {
+    /// Creates a safe pool-counter projection from already bounded values.
+    #[must_use]
+    pub(crate) const fn new(pool_capacity: u32, pool_size: u32, pool_available: u32, pool_waiting: u32) -> Self {
+        return Self { pool_available, pool_capacity, pool_size, pool_waiting };
+    }
+
+    /// Returns the number of currently available pooled PostgreSQL clients.
+    #[must_use]
+    pub const fn pool_available(&self) -> u32 {
+        return self.pool_available;
+    }
+
+    /// Returns the configured maximum pooled PostgreSQL client count.
+    #[must_use]
+    pub const fn pool_capacity(&self) -> u32 {
+        return self.pool_capacity;
+    }
+
+    /// Returns the current pooled PostgreSQL client count.
+    #[must_use]
+    pub const fn pool_size(&self) -> u32 {
+        return self.pool_size;
+    }
+
+    /// Returns the number of tasks currently waiting for a pooled PostgreSQL client.
+    #[must_use]
+    pub const fn pool_waiting(&self) -> u32 {
+        return self.pool_waiting;
+    }
+}
+
+/// Safe PostgreSQL readiness projection returned to the common Store facade.
+#[derive(Clone, Debug, Eq, PartialEq)]
+pub struct PostgresBackendHealthSnapshot {
+    error_kind: std::option::Option<crate::PostgresBackendErrorKind>,
+    migration_version: std::option::Option<u64>,
+    pending_migration_count: u32,
+    ready: bool,
+    runtime: PostgresBackendRuntimeSnapshot,
+}
+
+impl PostgresBackendHealthSnapshot {
+    /// Creates one successful safe readiness projection.
+    #[must_use]
+    pub(crate) const fn ready(runtime: PostgresBackendRuntimeSnapshot, migration_version: u64, pending_migration_count: u32) -> Self {
+        return Self {
+            error_kind: std::option::Option::None,
+            migration_version: std::option::Option::Some(migration_version),
+            pending_migration_count,
+            ready: true,
+            runtime,
+        };
+    }
+
+    /// Creates one failed safe readiness projection from a classified backend error.
+    #[must_use]
+    pub(crate) const fn not_ready(
+        runtime: PostgresBackendRuntimeSnapshot,
+        migration_version: std::option::Option<u64>,
+        pending_migration_count: u32,
+        error_kind: crate::PostgresBackendErrorKind,
+    ) -> Self {
+        return Self {
+            error_kind: std::option::Option::Some(error_kind),
+            migration_version,
+            pending_migration_count,
+            ready: false,
+            runtime,
+        };
+    }
+
+    /// Returns the safe backend error classification when readiness could not be proven.
+    #[must_use]
+    pub const fn error_kind(&self) -> std::option::Option<crate::PostgresBackendErrorKind> {
+        return self.error_kind;
+    }
+
+    /// Returns whether the latest bounded PostgreSQL probe proved readiness.
+    #[must_use]
+    pub const fn is_ready(&self) -> bool {
+        return self.ready;
+    }
+
+    /// Returns the migration version observed by the readiness probe when available.
+    #[must_use]
+    pub const fn migration_version(&self) -> std::option::Option<u64> {
+        return self.migration_version;
+    }
+
+    /// Returns the number of embedded migrations newer than the observed applied version.
+    #[must_use]
+    pub const fn pending_migration_count(&self) -> u32 {
+        return self.pending_migration_count;
+    }
+
+    /// Returns the safe PostgreSQL pool counters captured for this probe.
+    #[must_use]
+    pub const fn runtime(&self) -> &PostgresBackendRuntimeSnapshot {
+        return &self.runtime;
+    }
+}
+
 /// TLS mode accepted by the physical PostgreSQL backend bridge.
 #[derive(Clone, Copy, Debug, Eq, PartialEq)]
 #[non_exhaustive]
@@ -165,6 +277,17 @@ impl PostgresBackend {
         return std::result::Result::Ok(Self { network: settings.network, pool });
     }
 
+    /// Returns a safe synchronous snapshot of bounded pool counters without performing PostgreSQL I/O.
+    #[must_use]
+    pub fn runtime_snapshot(&self) -> PostgresBackendRuntimeSnapshot {
+        return runtime_snapshot_from_status(self.pool.status());
+    }
+
+    /// Runs a bounded lightweight PostgreSQL readiness probe and returns only safe classified diagnostics.
+    pub async fn health(&self) -> PostgresBackendHealthSnapshot {
+        return crate::probe_health(&self.pool).await;
+    }
+
     /// Explicitly closes the pool and waits for all owned pooled objects to drain inside the supplied bound.
     pub async fn close(self, timeout: std::time::Duration) -> std::result::Result<(), crate::PostgresBackendError> {
         self.pool.close();
@@ -304,7 +427,8 @@ fn build_verified_tls() -> std::result::Result<tokio_postgres_rustls::MakeRustls
     return std::result::Result::Ok(tokio_postgres_rustls::MakeRustlsConnect::new(client_config));
 }
 
-fn map_pool_error(error: deadpool_postgres::PoolError) -> crate::PostgresBackendError {
+/// Maps one Deadpool acquisition error into a redacted backend classification.
+pub(crate) fn map_pool_error(error: deadpool_postgres::PoolError) -> crate::PostgresBackendError {
     return match error {
         deadpool_postgres::PoolError::Timeout(timeout_type) => crate::PostgresBackendError::new(
             crate::PostgresBackendErrorKind::PoolTimeout,
@@ -321,6 +445,23 @@ fn map_pool_error(error: deadpool_postgres::PoolError) -> crate::PostgresBackend
     };
 }
 
+/// Converts Deadpool status into a bounded safe backend runtime projection.
+pub(crate) fn runtime_snapshot_from_status(status: deadpool_postgres::Status) -> PostgresBackendRuntimeSnapshot {
+    return PostgresBackendRuntimeSnapshot::new(
+        bounded_count(status.max_size),
+        bounded_count(status.size),
+        bounded_count(status.available),
+        bounded_count(status.waiting),
+    );
+}
+
+fn bounded_count(value: usize) -> u32 {
+    if value > u32::MAX as usize {
+        return u32::MAX;
+    }
+    return value as u32;
+}
+
 #[cfg(test)]
 #[path = "../unit_tests/runtime.rs"]
 mod tests;