liminal_server/

error.rs

use std::net::SocketAddr;

use crate::server::participant::ParticipantServiceFatal;

const RESERVED_NAMESPACE_MESSAGE: &str =
    "SELF_STREAM_NAMESPACE_REFUSED: connection publication to reserved namespace";

/// Error taxonomy for standalone liminal server deployment failures.
#[derive(Debug, thiserror::Error)]
pub enum ServerError {
    /// The configuration file could not be read or parsed.
    #[error("configuration load failed: {message}")]
    ConfigLoad { message: String },

    /// The configuration file was read but failed semantic validation.
    #[error("configuration validation failed: {message}")]
    ConfigValidation { message: String },

    /// A connection tried to publish into the server-owned namespace.
    #[error("{RESERVED_NAMESPACE_MESSAGE}: {channel}")]
    ReservedNamespace {
        /// Reserved channel the connection addressed.
        channel: String,
    },

    /// The server could not bind its configured listener address.
    #[error("listener bind failed for {address}: {source}")]
    ListenerBind {
        /// Address the server attempted to bind.
        address: SocketAddr,
        /// Underlying operating-system bind failure.
        #[source]
        source: std::io::Error,
    },

    /// The server listener failed while accepting an inbound connection.
    #[error("listener accept failed: {message}")]
    ListenerAccept { message: String },

    /// A prior publisher finish consumed the original error.
    #[error("self-stream publisher already finished with an error: {first_error}")]
    SelfStreamPublisherAlreadyFinished {
        /// Full diagnostic returned by the first finish.
        first_error: String,
    },

    /// Durable participant-incarnation startup or allocation failed before its
    /// result could be published.
    #[error("participant incarnation {phase} failed: {message}")]
    ParticipantIncarnation {
        /// Exact server seam that failed.
        phase: &'static str,
        /// Underlying durable or bounded-bridge diagnostic.
        message: String,
    },

    /// A durable connection-fate Open could not be completed in this process.
    ///
    /// The normal runtime shutdown path returns this typed fatal only after it has
    /// stopped both listeners and run the ordinary connection drain/flush sequence.
    #[error("participant service fatal: {fatal}")]
    ParticipantServiceFatal {
        /// First process-wide post-Open failure; later failures cannot replace it.
        fatal: ParticipantServiceFatal,
    },

    /// Startup found durable connection-fate work that the Decision A/C producer must complete
    /// before listener or semantic-service publication.
    #[error(
        "participant startup requires recovery of {open_count} connection-fate Opens beginning at sequence {first_open_sequence}"
    )]
    ConnectionFateRecoveryRequired {
        /// Number of replay-validated unmatched Opens.
        open_count: usize,
        /// Lowest unmatched Open sequence.
        first_open_sequence: u64,
    },

    /// The durable server-incarnation namespace has no successor.
    #[error("participant server-incarnation namespace is exhausted")]
    ServerIncarnationExhausted,

    /// Production participant startup restore failed: the durable
    /// conversation streams could not be scanned or replayed, so the
    /// server-scope capacity ledger cannot be made exact and the server
    /// refuses to start over state it cannot account for.
    #[error("participant startup restore failed: {message}")]
    ParticipantStartupRestore {
        /// Underlying durable, replay, or bridge diagnostic.
        message: String,
    },

    /// The current durable server incarnation has no collision-free connection
    /// ordinal left, so the accepted socket was not admitted.
    #[error(
        "connection incarnation exhausted for server incarnation {attempted_server_incarnation}"
    )]
    ConnectionIncarnationExhausted {
        /// Server incarnation whose complete ordinal suffix was examined.
        attempted_server_incarnation: u64,
    },

    /// A connection registration found a record already present under its pid.
    /// Enforces the pids-fresh-per-spawn supervision invariant loudly: a silent
    /// replace would drop the displaced record's teardown-held fd guard outside
    /// the single record-removal funnel (orphaning a live connection's stream)
    /// and increment the `liminal_connections_active` gauge a second time with
    /// no paired decrement. The whole registration is refused instead, leaving
    /// the prior record — and its teardown route — intact.
    #[error("connection registration refused: pid {pid} already has a live registry record")]
    ConnectionPidCollision {
        /// The connection pid that already owned a registry record.
        pid: u64,
    },

    /// A frame requested an operation the configured services profile does not
    /// serve (e.g. ordinary publish/subscribe/conversation traffic against the
    /// capability-scoped worker front door). Server-internal taxonomy, not wire
    /// vocabulary: the connection process renders it as the operation's existing
    /// typed error frame with this error's text as the message.
    #[error("{operation} is not supported by the {profile} services profile")]
    UnsupportedOperation {
        /// Human-readable description of the refused operation.
        operation: String,
        /// The configured services profile that refused it.
        profile: &'static str,
    },

    /// A server→client push reply slot was dropped before a correlated reply
    /// arrived — the connection closed (the prompt worker-death signal). Distinct
    /// from [`Self::PushReplyTimeout`] so consumers can tell a worker that DIED
    /// (fast failover) from one that is merely SLOW, by type rather than message.
    #[error(
        "push correlation {correlation_id} did not complete: the connection closed before sending a correlated push reply"
    )]
    PushReplyDisconnected {
        /// Correlation id of the push whose reply will never arrive.
        correlation_id: u64,
    },

    /// A server→client push reply did not arrive within the awaiter's timeout —
    /// the worker is still connected but did not reply in this wait quantum. This
    /// is BENIGN: the reply slot survives untouched and the caller may re-arm
    /// [`PushReplyAwaiter::receive`](crate::server::connection::PushReplyAwaiter::receive)
    /// indefinitely. It is not a worker-death signal.
    #[error(
        "push correlation {correlation_id} did not complete: no correlated push reply arrived within the timeout"
    )]
    PushReplyTimeout {
        /// Correlation id of the push whose wait quantum elapsed.
        correlation_id: u64,
    },

    /// A server→client push carrying an explicit reply deadline (via
    /// [`push_to_connection_with_deadline`](crate::server::connection::ConnectionSupervisor::push_to_connection_with_deadline))
    /// reached that deadline before a correlated reply arrived. Unlike
    /// [`Self::PushReplyTimeout`] this is TERMINAL: the reply slot has been
    /// removed and its §5 `max_pending_pushes_per_connection` cap admission
    /// released. Returned PROMPTLY once the deadline is due — a `receive` call
    /// does not hold a due expiry until its caller's quantum ends, so the
    /// terminal outcome is independent of how the caller polls. Distinct
    /// variant so callers classify by type, not message.
    #[error(
        "push correlation {correlation_id} did not complete: its reply deadline passed before a correlated push reply arrived"
    )]
    PushReplyExpired {
        /// Correlation id of the push whose reply deadline passed.
        correlation_id: u64,
    },

    /// A server→client push's correlated reply ARRIVED and was refused by the
    /// access decision on the subject the push was made on (ACCESS-001 R2: a
    /// connection admitted on a Lys pass has its `PushReply` decided as `serve`
    /// on the push's retained subject, the matrix's `push_binding`). TERMINAL:
    /// the slot is removed and its §5 cap admission released, the reply payload
    /// is never delivered. A push made with no subject
    /// ([`push_to_connection`](crate::server::connection::ConnectionSupervisor::push_to_connection))
    /// to such a connection reads here too, with `reason` saying so: the
    /// subject is recorded at push time
    /// ([`push_to_subject`](crate::server::connection::ConnectionSupervisor::push_to_subject))
    /// or not at all. Distinct variant so callers classify by type.
    #[error("push correlation {correlation_id} was refused: {reason}")]
    PushReplyRefused {
        /// Correlation id of the push whose reply was refused.
        correlation_id: u64,
        /// The refusal, rendered as the four-field access refusal.
        reason: String,
    },

    /// A server→client push was never queued for the wire: its encoded frame is
    /// larger than the WHOLE of the connection's bounded outbound buffer, so no
    /// amount of draining could ever make room for it. TERMINAL and CERTAIN — the
    /// reply slot is removed, its §5 `max_pending_pushes_per_connection` admission
    /// released, and the client never saw a `Push` frame for this correlation id.
    ///
    /// Deliberately NARROW. A frame that would fit an empty buffer but not the
    /// current free space is CONGESTION, not a size defect: it keeps the
    /// connection-teardown path and its retryable
    /// [`Self::PushReplyDisconnected`] reading, because waiting is the correct
    /// answer there. Sharing one outcome between the certain case and the
    /// recoverable one would leave the caller unable to tell them apart — which
    /// is the exact fault this variant exists to end. Distinct variant so callers
    /// classify by type, not message.
    ///
    /// The WORDS carry the bound's value and say the bound was chosen, because a
    /// reader who meets this without that context blames the server for a number
    /// an operator set. Since every outbound bound now comes from
    /// [`max_connection_outbound_bytes`](crate::config::types::LimitsConfig::max_connection_outbound_bytes),
    /// that sentence is true on every occurrence rather than usually.
    #[error(
        "push correlation {correlation_id} was never sent: its {needed}-byte frame exceeds this \
         connection's whole outbound buffer of {capacity} bytes, which is operator-set by \
         `limits.max_connection_outbound_bytes`"
    )]
    PushFrameExceedsOutboundCapacity {
        /// Correlation id of the push that could not be queued.
        correlation_id: u64,
        /// Encoded size of the rejected frame. Exceeds `capacity` on its own.
        needed: usize,
        /// The outbound buffer's whole capacity, which `needed` exceeds.
        capacity: usize,
        /// Bytes already queued when the frame was rejected. Context for the log
        /// only: the decision is `needed` against `capacity` alone, so this frame
        /// would not have fitted an empty buffer either.
        queued: usize,
    },

    /// The server could not join the configured beamr distribution cluster.
    #[error("cluster join failed: {message}")]
    ClusterJoin { message: String },

    /// Cluster state propagation through beamr distribution failed.
    #[error("cluster sync failed: {message}")]
    ClusterSync { message: String },

    /// Graceful shutdown did not drain within the configured timeout.
    #[error("shutdown timed out: {message}")]
    ShutdownTimeout { message: String },

    /// Durable state could not be flushed during graceful shutdown.
    #[error("shutdown flush failed: {message}")]
    ShutdownFlush { message: String },

    /// A clean stop could not complete every connection fate parked on
    /// candidate-lane `Precedence`. Each named durable Open is reconciled by
    /// the next boot instead, so the stop was not clean.
    #[error(
        "shutdown left connection fates unsettled for the next boot to reconcile: durable Opens \
         {open_sequences:?}"
    )]
    ShutdownUnsettledConnectionFates {
        /// Durable Open sequences still parked when the stop finished.
        open_sequences: Vec<u64>,
    },

    /// The health endpoint failed to start or serve requests.
    #[error("health endpoint failed: {message}")]
    HealthEndpoint { message: String },

    /// A new connection was refused because the configured `max_connections`
    /// cap (§5) is already reached. The listener drops the freshly accepted
    /// stream, refusing the connection, rather than admitting an unbounded fleet.
    #[error(
        "connection refused: the configured max_connections limit of {limit} live connections is reached"
    )]
    ConnectionLimitReached {
        /// The configured `max_connections` cap that was hit.
        limit: usize,
    },

    /// An admission-time per-connection cap (§5) refused an operation: too many
    /// subscriptions, conversations, in-flight pushes, or pending conversation
    /// replies on one connection. The connection process renders it as the
    /// operation's existing typed error frame with this text as the message.
    #[error("{operation} refused: the per-connection {cap} limit of {limit} is reached")]
    ConnectionCapReached {
        /// Human-readable description of the refused operation.
        operation: String,
        /// The name of the cap that refused it (a `limits.*` config key).
        cap: &'static str,
        /// The configured cap value that was hit.
        limit: usize,
    },

    /// A publish whose append outcome is not known: the server cannot tell
    /// whether the row was stored. Distinct from every definite publish failure
    /// so the connection process answers it with its own reason code
    /// (`PUBLISH_UNRESOLVED_CODE`) and a producer classifies it by type, never
    /// by message; it is never a Reject, a Defer or a backpressure signal.
    #[error(
        "publish to channel {channel} is unresolved{}: {message}",
        UnresolvedPublishDetail(.idempotency_key, .sequence)
    )]
    PublishUnresolved {
        /// Channel the unresolved publish was addressed to.
        channel: String,
        /// Idempotency key the publish carried, when it carried one.
        idempotency_key: Option<String>,
        /// Sequence the append expected, when one was assigned.
        sequence: Option<u64>,
        /// The underlying append diagnostic, kept as evidence.
        message: String,
    },

    /// The offline participant log migration refused.
    #[error(transparent)]
    ParticipantLogMigration(#[from] crate::server::participant::ParticipantLogMigrationError),

    /// An agent seat refused, in the agent's own words.
    #[error(transparent)]
    Agent(#[from] crate::agents::error::AgentError),
}

/// Renders the optional idempotency key and sequence of
/// [`ServerError::PublishUnresolved`], naming each only when it is present.
struct UnresolvedPublishDetail<'a>(&'a Option<String>, &'a Option<u64>);

impl std::fmt::Display for UnresolvedPublishDetail<'_> {
    fn fmt(&self, formatter: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        if let Some(key) = self.0 {
            write!(formatter, " (idempotency key {key})")?;
        }
        if let Some(sequence) = self.1 {
            write!(formatter, " (sequence {sequence})")?;
        }
        Ok(())
    }
}