feat: add an opt-in NATS JetStream publish path for the notify and audit targets (#4634)

feat(targets): add an opt-in NATS JetStream publish path for the notify and audit targets

The NATS notify and audit targets publish through NATS Core, which returns
before the server has durably accepted the message. A broker restart or a
connection drop between the publish and the flush loses the event, even though
the send queue has already cleared it, and no acknowledgement gates that clear.

An opt-in JetStream publish path clears a queued event only after the server
returns a durable PublishAck, so delivery is at-least-once across a broker
restart or a reconnect. It applies to both the notify and audit NATS targets, is
off by default, and is byte-identical to the NATS Core path when disabled.

The path includes durable store-and-forward, a stable dedup id sent as the
Nats-Msg-Id header so a replayed event is collapsed by the stream duplicate
window, pre-flight stream validation, and a bounded failed-events store for
terminally-failed and retry-exhausted events. Three configuration keys per
target select it: JETSTREAM_ENABLE, JETSTREAM_STREAM_NAME, and
JETSTREAM_ACK_TIMEOUT_SECS, under the RUSTFS_NOTIFY_NATS_ and RUSTFS_AUDIT_NATS_
prefixes.

The on-disk batch filename separator changes from colon to underscore so
batch names are valid on Windows filesystems, with transparent read-back
of files written under the previous separator. The migration affects the
shared queue store for every target type and lands with this feature
because the store gains its first Windows-exercised paths here.

Co-authored-by: houseme <housemecn@gmail.com>

crates/audit/src/pipeline.rs

@@ -32,6 +32,7 @@ const EVENT_AUDIT_BATCH_DISPATCH_COMPLETED: &str = "audit_batch_dispatch_complet
 const EVENT_AUDIT_TARGET_STATE_CHANGED: &str = "audit_target_state_changed";
 const EVENT_AUDIT_REPLAY_DELIVERED: &str = "audit_replay_delivered";
 const EVENT_AUDIT_REPLAY_RETRY_SCHEDULED: &str = "audit_replay_retry_scheduled";
+const EVENT_AUDIT_REPLAY_RETRY_EXHAUSTED: &str = "audit_replay_retry_exhausted";
 const EVENT_AUDIT_REPLAY_DROPPED: &str = "audit_replay_dropped";
 const EVENT_AUDIT_REPLAY_STREAM_STATUS: &str = "audit_replay_stream_status";
 
@@ -281,6 +282,7 @@ impl AuditPipeline {
                 let delivery = target.delivery_snapshot();
                 AuditTargetMetricSnapshot {
                     failed_messages: delivery.failed_messages,
+                    failed_store_length: delivery.failed_store_length,
                     queue_length: delivery.queue_length,
                     target_id: target.id().to_string(),
                     total_messages: delivery.total_messages,
@@ -463,18 +465,16 @@ impl AuditRuntimeFacade {
                             target.record_final_failure();
                             observability::record_target_failure();
                         }
-                        ReplayEvent::RetryExhausted { key, target } => {
+                        ReplayEvent::RetryExhausted { detail, key, target } => {
                             warn!(
-                                event = EVENT_AUDIT_REPLAY_DROPPED,
+                                event = EVENT_AUDIT_REPLAY_RETRY_EXHAUSTED,
                                 component = LOG_COMPONENT_AUDIT,
                                 subsystem = LOG_SUBSYSTEM_PIPELINE,
                                 target_id = %target.id(),
                                 replay_key = %key,
-                                reason = "retry_exhausted",
-                                "audit replay delivery"
+                                error = %detail,
+                                "audit replay retry budget exhausted, entry stays queued and retries"
                             );
-                            target.record_final_failure();
-                            observability::record_target_failure();
                         }
                         ReplayEvent::UnreadableEntry { key, error, target } => {
                             warn!(

crates/audit/src/system.rs

@@ -30,6 +30,7 @@ const EVENT_AUDIT_CONFIG_RELOADED: &str = "audit_config_reloaded";
 #[derive(Debug, Clone, Default, PartialEq, Eq)]
 pub struct AuditTargetMetricSnapshot {
     pub failed_messages: u64,
+    pub failed_store_length: u64,
     pub queue_length: u64,
     pub target_id: String,
     pub total_messages: u64,