feat(git): add Redis-backed hook worker with per-repo distributed locking

- pool/worker.rs: single-threaded consumer that BLMPOPs from Redis queues
  sequentially. K8s replicas provide HA — each pod runs one worker.
- pool/redis.rs: RedisConsumer with BLMOVE atomic dequeue, ACK/NAK, and
  retry-with-json support.
- pool/types.rs: HookTask, TaskType, PoolConfig (minimal — no pool metrics).
- sync/lock.rs: Redis SET NX EX per-repo lock to prevent concurrent workers
  from processing the same repo. Lock conflicts are handled by requeueing
  without incrementing retry count.
- hook/mod.rs: HookService.start_worker() spawns the background worker.
- ssh/mod.rs / http/mod.rs: ReceiveSyncService RPUSHes to Redis queue.
  Both run_http and run_ssh call start_worker() to launch the consumer.
- Lock conflicts (GitError::Locked) in the worker are requeued without
  incrementing retry_count so another worker can pick them up.

libs/git/hook/mod.rs

@@ -2,13 +2,20 @@ use config::AppConfig;
 use db::cache::AppCache;
 use db::database::AppDatabase;
 use deadpool_redis::cluster::Pool as RedisPool;
-use models::EntityTrait;
 use slog::Logger;
 use std::sync::Arc;
+use tokio_util::sync::CancellationToken;
 
-/// Simplified hook service — no queue, no pool.
-/// K8s StatefulSet HA scheduling ensures only one pod touches a repo at a time.
-/// Execution is direct and sequential per invocation.
+pub mod pool;
+pub mod sync;
+pub mod webhook_dispatch;
+
+pub use pool::{HookWorker, PoolConfig, RedisConsumer};
+pub use pool::types::{HookTask, TaskType};
+
+/// Hook service that manages the Redis-backed task queue worker.
+/// Multiple gitserver pods can run concurrently — the worker acquires a
+/// per-repo Redis lock before processing each task.
 #[derive(Clone)]
 pub struct HookService {
     pub(crate) db: AppDatabase,
@@ -38,92 +45,15 @@ impl HookService {
         }
     }
 
-    /// Full sync: refs → commits → tags → LFS → fsck → gc → skills.
-    pub async fn sync_repo(&self, repo_id: &str) -> Result<(), crate::GitError> {
-        let repo_uuid = models::Uuid::parse_str(repo_id)
-            .map_err(|_| crate::GitError::Internal("invalid repo_id uuid".into()))?;
-
-        let repo = models::repos::repo::Entity::find_by_id(repo_uuid)
-            .one(self.db.reader())
-            .await
-            .map_err(crate::GitError::from)?
-            .ok_or_else(|| crate::GitError::NotFound(format!("repo {} not found", repo_id)))?;
-
-        if !std::path::Path::new(&repo.storage_path).exists() {
-            return Err(crate::GitError::NotFound(format!(
-                "storage path does not exist: {}",
-                repo.storage_path
-            )));
-        }
-
-        let sync = crate::hook::sync::HookMetaDataSync::new(
+    /// Start the background worker and return a cancellation token.
+    pub fn start_worker(&self) -> CancellationToken {
+        let pool_config = PoolConfig::from_env(&self.config);
+        pool::start_worker(
             self.db.clone(),
             self.cache.clone(),
-            repo,
+            self.redis_pool.clone(),
             self.logger.clone(),
-        )?;
-
-        // No distributed lock needed — K8s StatefulSet scheduling guarantees
-        // that at most one pod processes a given repo shard at any time.
-        sync.sync().await
-    }
-
-    /// Run fsck only (no full sync).
-    pub async fn fsck_repo(&self, repo_id: &str) -> Result<(), crate::GitError> {
-        let repo_uuid = models::Uuid::parse_str(repo_id)
-            .map_err(|_| crate::GitError::Internal("invalid repo_id uuid".into()))?;
-
-        let repo = models::repos::repo::Entity::find_by_id(repo_uuid)
-            .one(self.db.reader())
-            .await
-            .map_err(crate::GitError::from)?
-            .ok_or_else(|| crate::GitError::NotFound(format!("repo {} not found", repo_id)))?;
-
-        if !std::path::Path::new(&repo.storage_path).exists() {
-            return Err(crate::GitError::NotFound(format!(
-                "storage path does not exist: {}",
-                repo.storage_path
-            )));
-        }
-
-        let sync = crate::hook::sync::HookMetaDataSync::new(
-            self.db.clone(),
-            self.cache.clone(),
-            repo,
-            self.logger.clone(),
-        )?;
-
-        sync.fsck_only().await
-    }
-
-    /// Run gc only (no full sync).
-    pub async fn gc_repo(&self, repo_id: &str) -> Result<(), crate::GitError> {
-        let repo_uuid = models::Uuid::parse_str(repo_id)
-            .map_err(|_| crate::GitError::Internal("invalid repo_id uuid".into()))?;
-
-        let repo = models::repos::repo::Entity::find_by_id(repo_uuid)
-            .one(self.db.reader())
-            .await
-            .map_err(crate::GitError::from)?
-            .ok_or_else(|| crate::GitError::NotFound(format!("repo {} not found", repo_id)))?;
-
-        if !std::path::Path::new(&repo.storage_path).exists() {
-            return Err(crate::GitError::NotFound(format!(
-                "storage path does not exist: {}",
-                repo.storage_path
-            )));
-        }
-
-        let sync = crate::hook::sync::HookMetaDataSync::new(
-            self.db.clone(),
-            self.cache.clone(),
-            repo,
-            self.logger.clone(),
-        )?;
-
-        sync.gc_only().await
+            pool_config,
+        )
     }
 }
-
-pub mod sync;
-pub mod webhook_dispatch;

libs/git/hook/pool/mod.rs

@@ -0,0 +1,41 @@
+pub mod redis;
+pub mod types;
+pub mod worker;
+
+pub use redis::RedisConsumer;
+pub use types::{HookTask, PoolConfig, TaskType};
+pub use worker::HookWorker;
+
+use db::cache::AppCache;
+use db::database::AppDatabase;
+use deadpool_redis::cluster::Pool as RedisPool;
+use slog::Logger;
+use tokio_util::sync::CancellationToken;
+
+/// Start the hook worker background task.
+/// Returns a handle to the cancellation token so the caller can shut it down.
+pub fn start_worker(
+    db: AppDatabase,
+    cache: AppCache,
+    redis_pool: RedisPool,
+    logger: Logger,
+    config: PoolConfig,
+) -> CancellationToken {
+    let consumer = RedisConsumer::new(
+        redis_pool.clone(),
+        config.redis_list_prefix.clone(),
+        config.redis_block_timeout_secs,
+        logger.clone(),
+    );
+
+    let worker = HookWorker::new(db, cache, logger, consumer);
+
+    let cancel = CancellationToken::new();
+    let cancel_clone = cancel.clone();
+
+    tokio::spawn(async move {
+        worker.run(cancel_clone).await;
+    });
+
+    cancel
+}

libs/git/hook/pool/redis.rs

@@ -0,0 +1,167 @@
+use crate::error::GitError;
+use crate::hook::pool::types::HookTask;
+use deadpool_redis::cluster::Connection as RedisConn;
+use slog::Logger;
+
+/// Redis List consumer using BLMOVE for atomic move-from-queue-to-work pattern.
+pub struct RedisConsumer {
+    pool: deadpool_redis::cluster::Pool,
+    /// Hash-tag-prefixed key prefix, e.g. "{hook}".
+    prefix: String,
+    block_timeout_secs: u64,
+    logger: Logger,
+}
+
+impl RedisConsumer {
+    pub fn new(
+        pool: deadpool_redis::cluster::Pool,
+        prefix: String,
+        block_timeout_secs: u64,
+        logger: Logger,
+    ) -> Self {
+        Self {
+            pool,
+            prefix,
+            block_timeout_secs,
+            logger,
+        }
+    }
+
+    /// Atomically moves a task from the main queue to the work queue using BLMOVE.
+    /// Blocks up to `block_timeout_secs` waiting for a task.
+    ///
+    /// Returns `Some((HookTask, task_json))` where `task_json` is the raw JSON string
+    /// needed for LREM on ACK. Returns `None` if the blocking timed out.
+    pub async fn next(&self, task_type: &str) -> Result<Option<(HookTask, String)>, GitError> {
+        let queue_key = format!("{}:{}", self.prefix, task_type);
+        let work_key = format!("{}:{}:work", self.prefix, task_type);
+
+        let redis = self
+            .pool
+            .get()
+            .await
+            .map_err(|e| GitError::Internal(format!("redis pool get failed: {}", e)))?;
+
+        let mut conn: RedisConn = redis;
+
+        // BLMOVE source destination <LEFT|RIGHT> <LEFT|RIGHT> timeout
+        let task_json: Option<String> = redis::cmd("BLMOVE")
+            .arg(&queue_key)
+            .arg(&work_key)
+            .arg("RIGHT")
+            .arg("LEFT")
+            .arg(self.block_timeout_secs)
+            .query_async(&mut conn)
+            .await
+            .map_err(|e| GitError::Internal(format!("BLMOVE failed: {}", e)))?;
+
+        match task_json {
+            Some(json) => {
+                match serde_json::from_str::<HookTask>(&json) {
+                    Ok(task) => {
+                        slog::debug!(self.logger, "task dequeued";
+                            "task_id" => %task.id,
+                            "task_type" => %task.task_type,
+                            "queue" => %queue_key
+                        );
+                        Ok(Some((task, json)))
+                    }
+                    Err(e) => {
+                        // Malformed task — remove from work queue and discard
+                        slog::warn!(self.logger, "malformed task JSON, discarding";
+                            "error" => %e,
+                            "queue" => %work_key
+                        );
+                        let _ = self.ack_raw(&work_key, &json).await;
+                        Ok(None)
+                    }
+                }
+            }
+            None => {
+                // Timed out, no task available
+                Ok(None)
+            }
+        }
+    }
+
+    /// Acknowledge a task: remove it from the work queue (LREM).
+    pub async fn ack(&self, work_key: &str, task_json: &str) -> Result<(), GitError> {
+        self.ack_raw(work_key, task_json).await
+    }
+
+    async fn ack_raw(&self, work_key: &str, task_json: &str) -> Result<(), GitError> {
+        let redis = self
+            .pool
+            .get()
+            .await
+            .map_err(|e| GitError::Internal(format!("redis pool get failed: {}", e)))?;
+
+        let mut conn: RedisConn = redis;
+
+        let _: i64 = redis::cmd("LREM")
+            .arg(work_key)
+            .arg(-1)
+            .arg(task_json)
+            .query_async(&mut conn)
+            .await
+            .map_err(|e| GitError::Internal(format!("LREM failed: {}", e)))?;
+
+        Ok(())
+    }
+
+    /// Negative acknowledge (retry): remove from work queue and push back to main queue.
+    pub async fn nak(
+        &self,
+        work_key: &str,
+        queue_key: &str,
+        task_json: &str,
+    ) -> Result<(), GitError> {
+        self.nak_with_retry(work_key, queue_key, task_json, task_json).await
+    }
+
+    /// Negative acknowledge with a different (updated) task JSON — used to
+    /// requeue with an incremented retry_count.
+    pub async fn nak_with_retry(
+        &self,
+        work_key: &str,
+        queue_key: &str,
+        old_task_json: &str,
+        new_task_json: &str,
+    ) -> Result<(), GitError> {
+        self.ack_raw(work_key, old_task_json).await?;
+
+        let redis = self
+            .pool
+            .get()
+            .await
+            .map_err(|e| GitError::Internal(format!("redis pool get failed: {}", e)))?;
+
+        let mut conn: RedisConn = redis;
+
+        let _: i64 = redis::cmd("LPUSH")
+            .arg(queue_key)
+            .arg(new_task_json)
+            .query_async(&mut conn)
+            .await
+            .map_err(|e| GitError::Internal(format!("LPUSH retry failed: {}", e)))?;
+
+        slog::warn!(self.logger, "task nack'd and requeued queue={}", queue_key);
+
+        Ok(())
+    }
+
+    pub fn prefix(&self) -> &str {
+        &self.prefix
+    }
+}
+
+impl Clone for RedisConsumer {
+    fn clone(&self) -> Self {
+        Self {
+            pool: self.pool.clone(),
+            prefix: self.prefix.clone(),
+            block_timeout_secs: self.block_timeout_secs,
+            logger: self.logger.clone(),
+        }
+    }
+}

libs/git/hook/pool/types.rs

@@ -0,0 +1,32 @@
+use serde::{Deserialize, Serialize};
+
+pub use config::hook::PoolConfig;
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct HookTask {
+    pub id: String,
+    pub repo_id: String,
+    pub task_type: TaskType,
+    pub payload: serde_json::Value,
+    pub created_at: chrono::DateTime<chrono::Utc>,
+    #[serde(default)]
+    pub retry_count: u32,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
+#[serde(rename_all = "snake_case")]
+pub enum TaskType {
+    Sync,
+    Fsck,
+    Gc,
+}
+
+impl std::fmt::Display for TaskType {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            TaskType::Sync => write!(f, "sync"),
+            TaskType::Fsck => write!(f, "fsck"),
+            TaskType::Gc => write!(f, "gc"),
+        }
+    }
+}

libs/git/hook/pool/worker.rs

@@ -0,0 +1,388 @@
+use crate::error::GitError;
+use crate::hook::pool::redis::RedisConsumer;
+use crate::hook::pool::types::{HookTask, TaskType};
+use crate::hook::sync::HookMetaDataSync;
+use db::cache::AppCache;
+use db::database::AppDatabase;
+use models::EntityTrait;
+use slog::Logger;
+use std::time::Duration;
+use tokio_util::sync::CancellationToken;
+
+/// Single-threaded worker that sequentially consumes tasks from Redis queues.
+/// K8s can scale replicas for concurrency — each replica runs one worker.
+/// Per-repo Redis locking prevents concurrent workers from processing the same repo.
+#[derive(Clone)]
+pub struct HookWorker {
+    db: AppDatabase,
+    cache: AppCache,
+    logger: Logger,
+    consumer: RedisConsumer,
+}
+
+impl HookWorker {
+    pub fn new(
+        db: AppDatabase,
+        cache: AppCache,
+        logger: Logger,
+        consumer: RedisConsumer,
+    ) -> Self {
+        Self {
+            db,
+            cache,
+            logger,
+            consumer,
+        }
+    }
+
+    /// Run the worker loop. Blocks until cancelled.
+    pub async fn run(&self, cancel: CancellationToken) {
+        slog::info!(self.logger, "hook worker started");
+
+        let task_types = [TaskType::Sync, TaskType::Fsck, TaskType::Gc];
+        let poll_interval = Duration::from_millis(500);
+
+        loop {
+            tokio::select! {
+                _ = cancel.cancelled() => {
+                    slog::info!(self.logger, "hook worker shutdown signal received");
+                    break;
+                }
+                _ = tokio::time::sleep(poll_interval) => {}
+            }
+
+            for task_type in &task_types {
+                let result = self
+                    .consumer
+                    .next(&task_type.to_string())
+                    .await;
+
+                let (task, task_json) = match result {
+                    Ok(Some(pair)) => pair,
+                    Ok(None) => continue,
+                    Err(e) => {
+                        slog::warn!(self.logger, "failed to dequeue task: {}", e);
+                        tokio::time::sleep(Duration::from_secs(1)).await;
+                        break;
+                    }
+                };
+
+                let queue_key = format!("{}:{}", self.consumer.prefix(), task_type);
+                let work_key = format!("{}:work", queue_key);
+
+                self.process_task(&task, &task_json, &work_key, &queue_key)
+                    .await;
+            }
+        }
+
+        slog::info!(self.logger, "hook worker stopped");
+    }
+
+    async fn process_task(
+        &self,
+        task: &HookTask,
+        task_json: &str,
+        work_key: &str,
+        queue_key: &str,
+    ) {
+        slog::info!(self.logger, "task started task_id={} task_type={} repo_id={}",
+            task.id, task.task_type, task.repo_id);
+
+        let result = match task.task_type {
+            TaskType::Sync => self.run_sync(&task.repo_id).await,
+            TaskType::Fsck => self.run_fsck(&task.repo_id).await,
+            TaskType::Gc => self.run_gc(&task.repo_id).await,
+        };
+
+        match result {
+            Ok(()) => {
+                if let Err(e) = self.consumer.ack(work_key, task_json).await {
+                    slog::warn!(self.logger, "failed to ack task: {}", e);
+                }
+                slog::info!(self.logger, "task completed task_id={}", task.id);
+            }
+            Err(e) => {
+                // GitError::Locked means another worker is processing this repo —
+                // requeue without incrementing retry count so it can be picked up later.
+                let is_locked = matches!(e, crate::GitError::Locked(_));
+
+                if is_locked {
+                    slog::info!(self.logger, "repo locked by another worker, requeueing task_id={}", task.id);
+                    if let Err(nak_err) = self.consumer.nak(work_key, queue_key, task_json).await {
+                        slog::warn!(self.logger, "failed to requeue locked task: {}", nak_err);
+                    }
+                } else {
+                    slog::warn!(self.logger, "task failed task_id={} task_type={} repo_id={} error={}",
+                        task.id, task.task_type, task.repo_id, e);
+
+                    const MAX_RETRIES: u32 = 5;
+                    if task.retry_count >= MAX_RETRIES {
+                        slog::warn!(self.logger, "task exhausted retries, discarding task_id={} retry_count={}",
+                            task.id, task.retry_count);
+                        let _ = self.consumer.ack(work_key, task_json).await;
+                    } else {
+                        let mut task = task.clone();
+                        task.retry_count += 1;
+                        let retry_json =
+                            serde_json::to_string(&task).unwrap_or_else(|_| task_json.to_string());
+                        let _ = self
+                            .consumer
+                            .nak_with_retry(work_key, queue_key, task_json, &retry_json)
+                            .await;
+                    }
+                }
+            }
+        }
+    }
+
+    async fn run_sync(&self, repo_id: &str) -> Result<(), GitError> {
+        let repo_uuid = models::Uuid::parse_str(repo_id)
+            .map_err(|_| GitError::Internal("invalid repo_id uuid".into()))?;
+
+        let repo = models::repos::repo::Entity::find_by_id(repo_uuid)
+            .one(self.db.reader())
+            .await
+            .map_err(GitError::from)?
+            .ok_or_else(|| GitError::NotFound(format!("repo {} not found", repo_id)))?;
+
+        if !std::path::Path::new(&repo.storage_path).exists() {
+            return Err(GitError::NotFound(format!(
+                "storage path does not exist: {}",
+                repo.storage_path
+            )));
+        }
+
+        // Capture before tips
+        let before_tips = tokio::task::spawn_blocking({
+            let db = self.db.clone();
+            let cache = self.cache.clone();
+            let logger = self.logger.clone();
+            let repo = repo.clone();
+            move || {
+                let sync = HookMetaDataSync::new(db, cache, repo, logger)
+                    .map_err(|e| GitError::Internal(e.to_string()))?;
+                Ok::<_, GitError>((sync.list_branch_tips(), sync.list_tag_tips()))
+            }
+        })
+        .await
+        .map_err(|e| GitError::Internal(format!("spawn_blocking join error: {}", e)))?
+        .map_err(GitError::from)?;
+
+        // Run sync
+        tokio::task::spawn_blocking({
+            let db = self.db.clone();
+            let cache = self.cache.clone();
+            let logger = self.logger.clone();
+            let repo = repo.clone();
+            move || {
+                let result = tokio::runtime::Handle::current().block_on(async {
+                    let sync = HookMetaDataSync::new(db, cache, repo, logger)?;
+                    sync.sync().await
+                });
+                match result {
+                    Ok(()) => Ok::<(), GitError>(()),
+                    Err(e) => Err(GitError::Internal(e.to_string())),
+                }
+            }
+        })
+        .await
+        .map_err(|e| GitError::Internal(format!("spawn_blocking join error: {}", e)))?
+        .map_err(GitError::from)?;
+
+        // Capture after tips
+        let after_tips = tokio::task::spawn_blocking({
+            let db = self.db.clone();
+            let cache = self.cache.clone();
+            let logger = self.logger.clone();
+            let repo = repo.clone();
+            move || {
+                let sync = HookMetaDataSync::new(db, cache, repo, logger)
+                    .map_err(|e| GitError::Internal(e.to_string()))?;
+                Ok::<_, GitError>((sync.list_branch_tips(), sync.list_tag_tips()))
+            }
+        })
+        .await
+        .map_err(|e| GitError::Internal(format!("spawn_blocking join error: {}", e)))?
+        .map_err(GitError::from)?;
+
+        let (before_branch_tips, before_tag_tips) = before_tips;
+        let (after_branch_tips, after_tag_tips) = after_tips;
+        let project = repo.project;
+
+        // Dispatch branch push webhooks
+        for (branch, after_oid) in after_branch_tips {
+            let before_oid = before_branch_tips
+                .iter()
+                .find(|(n, _)| n == &branch)
+                .map(|(_, o)| o.as_str());
+            let changed = before_oid.map(|o| o != after_oid.as_str()).unwrap_or(true);
+            if changed {
+                let before_oid = before_oid.map_or("0", |v| v).to_string();
+                let branch_name = branch.clone();
+                let db = self.db.clone();
+                let logger = self.logger.clone();
+                let repo_id_str = repo.id.to_string();
+                let repo_name = repo.repo_name.clone();
+                let default_branch = repo.default_branch.clone();
+                let ns = models::projects::Project::find_by_id(project)
+                    .one(self.db.reader())
+                    .await
+                    .ok()
+                    .flatten()
+                    .map(|p| p.name)
+                    .unwrap_or_default();
+
+                tokio::spawn(async move {
+                    crate::hook::webhook_dispatch::dispatch_repo_webhooks(
+                        &db,
+                        &reqwest::Client::new(),
+                        &logger,
+                        &repo_id_str,
+                        &ns,
+                        &repo_name,
+                        &default_branch,
+                        "",
+                        "",
+                        crate::hook::webhook_dispatch::WebhookEventKind::Push {
+                            r#ref: format!("refs/heads/{}", branch_name),
+                            before: before_oid,
+                            after: after_oid,
+                            commits: vec![],
+                        },
+                    )
+                    .await;
+                });
+            }
+        }
+
+        // Dispatch tag push webhooks
+        for (tag, after_oid) in after_tag_tips {
+            let before_oid = before_tag_tips
+                .iter()
+                .find(|(n, _)| n == &tag)
+                .map(|(_, o)| o.as_str());
+            let is_new = before_oid.is_none();
+            let was_updated = before_oid.map(|o| o != after_oid.as_str()).unwrap_or(false);
+            if is_new || was_updated {
+                let before_oid = before_oid.map_or("0", |v| v).to_string();
+                let tag_name = tag.clone();
+                let db = self.db.clone();
+                let logger = self.logger.clone();
+                let repo_id_str = repo.id.to_string();
+                let repo_name = repo.repo_name.clone();
+                let default_branch = repo.default_branch.clone();
+                let ns = models::projects::Project::find_by_id(project)
+                    .one(self.db.reader())
+                    .await
+                    .ok()
+                    .flatten()
+                    .map(|p| p.name)
+                    .unwrap_or_default();
+
+                tokio::spawn(async move {
+                    crate::hook::webhook_dispatch::dispatch_repo_webhooks(
+                        &db,
+                        &reqwest::Client::new(),
+                        &logger,
+                        &repo_id_str,
+                        &ns,
+                        &repo_name,
+                        &default_branch,
+                        "",
+                        "",
+                        crate::hook::webhook_dispatch::WebhookEventKind::TagPush {
+                            r#ref: format!("refs/tags/{}", tag_name),
+                            before: before_oid,
+                            after: after_oid,
+                        },
+                    )
+                    .await;
+                });
+            }
+        }
+
+        Ok(())
+    }
+
+    async fn run_fsck(&self, repo_id: &str) -> Result<(), GitError> {
+        let repo_uuid = models::Uuid::parse_str(repo_id)
+            .map_err(|_| GitError::Internal("invalid repo_id uuid".into()))?;
+
+        let repo = models::repos::repo::Entity::find_by_id(repo_uuid)
+            .one(self.db.reader())
+            .await
+            .map_err(GitError::from)?
+            .ok_or_else(|| GitError::NotFound(format!("repo {} not found", repo_id)))?;
+
+        if !std::path::Path::new(&repo.storage_path).exists() {
+            return Err(GitError::NotFound(format!(
+                "storage path does not exist: {}",
+                repo.storage_path
+            )));
+        }
+
+        let db = self.db.clone();
+        let cache = self.cache.clone();
+        let logger = self.logger.clone();
+
+        tokio::task::spawn_blocking({
+            let repo = repo.clone();
+            move || {
+                let result = tokio::runtime::Handle::current().block_on(async {
+                    let sync = HookMetaDataSync::new(db, cache, repo, logger)?;
+                    sync.fsck_only().await
+                });
+                match result {
+                    Ok(()) => Ok::<(), GitError>(()),
+                    Err(e) => Err(GitError::Internal(e.to_string())),
+                }
+            }
+        })
+        .await
+        .map_err(|e| GitError::Internal(format!("spawn_blocking join error: {}", e)))?
+        .map_err(GitError::from)?;
+
+        Ok(())
+    }
+
+    async fn run_gc(&self, repo_id: &str) -> Result<(), GitError> {
+        let repo_uuid = models::Uuid::parse_str(repo_id)
+            .map_err(|_| GitError::Internal("invalid repo_id uuid".into()))?;
+
+        let repo = models::repos::repo::Entity::find_by_id(repo_uuid)
+            .one(self.db.reader())
+            .await
+            .map_err(GitError::from)?
+            .ok_or_else(|| GitError::NotFound(format!("repo {} not found", repo_id)))?;
+
+        if !std::path::Path::new(&repo.storage_path).exists() {
+            return Err(GitError::NotFound(format!(
+                "storage path does not exist: {}",
+                repo.storage_path
+            )));
+        }
+
+        let db = self.db.clone();
+        let cache = self.cache.clone();
+        let logger = self.logger.clone();
+
+        tokio::task::spawn_blocking({
+            let repo = repo.clone();
+            move || {
+                let result = tokio::runtime::Handle::current().block_on(async {
+                    let sync = HookMetaDataSync::new(db, cache, repo, logger)?;
+                    sync.gc_only().await
+                });
+                match result {
+                    Ok(()) => Ok::<(), GitError>(()),
+                    Err(e) => Err(GitError::Internal(e.to_string())),
+                }
+            }
+        })
+        .await
+        .map_err(|e| GitError::Internal(format!("spawn_blocking join error: {}", e)))?
+        .map_err(GitError::from)?;
+
+        Ok(())
+    }
+}

libs/git/hook/sync/lock.rs

@@ -0,0 +1,66 @@
+use crate::GitError;
+use crate::hook::sync::HookMetaDataSync;
+
+impl HookMetaDataSync {
+    const LOCK_TTL_SECS: u64 = 60;
+
+    /// Try to acquire an exclusive lock for this repo.
+    /// Returns the lock value if acquired, which must be passed to `release_lock`.
+    pub async fn acquire_lock(&self) -> Result<String, GitError> {
+        let lock_key = format!("git:repo:lock:{}", self.repo.id);
+        let lock_value = format!("{}:{}", uuid::Uuid::new_v4(), std::process::id());
+
+        let mut conn = self
+            .cache
+            .conn()
+            .await
+            .map_err(|e| GitError::IoError(format!("failed to get redis connection: {}", e)))?;
+
+        let result: bool = redis::cmd("SET")
+            .arg(&lock_key)
+            .arg(&lock_value)
+            .arg("NX")
+            .arg("EX")
+            .arg(Self::LOCK_TTL_SECS)
+            .query_async(&mut conn)
+            .await
+            .map_err(|e| GitError::IoError(format!("failed to acquire lock: {}", e)))?;
+
+        if result {
+            Ok(lock_value)
+        } else {
+            Err(GitError::Locked(format!(
+                "repository {} is locked by another process",
+                self.repo.id
+            )))
+        }
+    }
+
+    /// Release the lock, but only if we still own it (value matches).
+    pub async fn release_lock(&self, lock_value: &str) -> Result<(), GitError> {
+        let lock_key = format!("git:repo:lock:{}", self.repo.id);
+
+        let mut conn = self
+            .cache
+            .conn()
+            .await
+            .map_err(|e| GitError::IoError(format!("failed to get redis connection: {}", e)))?;
+
+        let script = r#"
+            if redis.call("get", KEYS[1]) == ARGV[1] then
+                return redis.call("del", KEYS[1])
+            else
+                return 0
+            end
+        "#;
+
+        let _: i32 = redis::Script::new(script)
+            .key(&lock_key)
+            .arg(lock_value)
+            .invoke_async(&mut conn)
+            .await
+            .map_err(|e| GitError::IoError(format!("failed to release lock: {}", e)))?;
+
+        Ok(())
+    }
+}

libs/git/hook/sync/mod.rs

@@ -3,6 +3,7 @@ pub mod commit;
 pub mod fsck;
 pub mod gc;
 pub mod lfs;
+pub mod lock;
 pub mod tag;
 
 use db::cache::AppCache;
@@ -158,73 +159,56 @@ impl HookMetaDataSync {
     }
 
     /// Full sync: refs → commits → tags → LFS → fsck → gc → skills.
-    /// No distributed lock — K8s StatefulSet scheduling guarantees exclusive access.
+    /// Acquires a per-repo Redis distributed lock to prevent concurrent workers
+    /// from processing the same repository simultaneously.
     pub async fn sync(&self) -> Result<(), crate::GitError> {
-        // All git2 operations must run on a blocking thread since git2 types are not Send.
-        let db = self.db.clone();
-        let cache = self.cache.clone();
-        let repo = self.repo.clone();
-        let logger = self.logger.clone();
+        let lock_value = self.acquire_lock().await?;
 
-        let res = tokio::task::spawn_blocking(move || {
-            tokio::runtime::Handle::current().block_on(async move {
-                let sync = Self::new(db, cache, repo, logger)?;
-                let out = sync.sync_full().await;
-                if let Err(ref e) = out {
-                    slog::error!(sync.logger, "sync failed: {}", e);
+        let res = self.sync_full().await;
+
+        if let Err(ref e) = res {
+            slog::error!(self.logger, "sync failed: {}", e);
         }
-                out
-            })
-        })
-        .await
-        .map_err(|e| crate::GitError::Internal(format!("spawn_blocking join error: {}", e)))??;
 
-        Ok(res)
+        if let Err(release_err) = self.release_lock(&lock_value).await {
+            slog::error!(self.logger, "failed to release lock: {}", release_err);
+        }
+
+        res
     }
 
     /// Run fsck only (refs snapshot + git fsck + rollback on corruption).
+    /// Acquires a per-repo Redis lock.
     pub async fn fsck_only(&self) -> Result<(), crate::GitError> {
-        let db = self.db.clone();
-        let cache = self.cache.clone();
-        let repo = self.repo.clone();
-        let logger = self.logger.clone();
+        let lock_value = self.acquire_lock().await?;
 
-        tokio::task::spawn_blocking(move || {
-            tokio::runtime::Handle::current().block_on(async move {
-                let sync = Self::new(db, cache, repo, logger)?;
-                let mut txn = sync.db.begin().await.map_err(|e| {
-                    crate::GitError::IoError(format!("failed to begin transaction: {}", e))
-                })?;
-                sync.run_fsck_and_rollback_if_corrupt(&mut txn).await?;
+        let res = async {
+            let mut txn = self
+                .db
+                .begin()
+                .await
+                .map_err(|e| crate::GitError::IoError(format!("failed to begin transaction: {}", e)))?;
+            self.run_fsck_and_rollback_if_corrupt(&mut txn)
+                .await?;
             txn.commit().await.map_err(|e| {
                 crate::GitError::IoError(format!("failed to commit transaction: {}", e))
             })?;
             Ok::<(), crate::GitError>(())
-            })
-        })
-        .await
-        .map_err(|e| crate::GitError::Internal(format!("spawn_blocking join error: {}", e)))??;
+        }
+        .await;
 
-        Ok(())
+        let _ = self.release_lock(&lock_value).await;
+        res
     }
 
-    /// Run gc only.
+    /// Run gc only. Acquires a per-repo Redis lock.
     pub async fn gc_only(&self) -> Result<(), crate::GitError> {
-        let db = self.db.clone();
-        let cache = self.cache.clone();
-        let repo = self.repo.clone();
-        let logger = self.logger.clone();
+        let lock_value = self.acquire_lock().await?;
 
-        tokio::task::spawn_blocking(move || {
-            tokio::runtime::Handle::current().block_on(async move {
-                let sync = Self::new(db, cache, repo, logger)?;
-                sync.run_gc().await
-            })
-        })
-        .await
-        .map_err(|e| crate::GitError::Internal(format!("spawn_blocking join error: {}", e)))??;
+        let res = self.run_gc().await;
 
-        Ok(())
+        let _ = self.release_lock(&lock_value).await;
+        res
     }
 
     /// Full sync pipeline inside a single DB transaction.

libs/git/http/mod.rs

@@ -72,16 +72,19 @@ pub async fn run_http(config: AppConfig, logger: Logger) -> anyhow::Result<()> {
     let app_cache = app_cache?;
 
     let redis_pool = app_cache.redis_pool().clone();
-    let http = Arc::new(reqwest::Client::new());
+    let http_client = Arc::new(reqwest::Client::new());
     let hook = HookService::new(
         db.clone(),
         app_cache.clone(),
         redis_pool.clone(),
         logger.clone(),
         config.clone(),
-        http,
+        http_client,
     );
-    let sync = crate::ssh::ReceiveSyncService::new(hook);
+    let _worker_cancel = hook.start_worker();
+    slog::info!(logger, "hook worker started");
+
+    let sync = crate::ssh::ReceiveSyncService::new(redis_pool.clone(), logger.clone());
 
     let rate_limiter = Arc::new(rate_limit::RateLimiter::new(
         rate_limit::RateLimitConfig::default(),

libs/git/lib.rs

@@ -36,6 +36,9 @@ pub use diff::types::{
 };
 pub use domain::GitDomain;
 pub use error::{GitError, GitResult};
+pub use hook::pool::types::{HookTask, TaskType};
+pub use hook::pool::PoolConfig;
+pub use hook::pool::HookWorker;
 pub use hook::sync::HookMetaDataSync;
 pub use lfs::types::{LfsConfig, LfsEntry, LfsOid, LfsPointer};
 pub use merge::types::{MergeAnalysisResult, MergeOptions, MergePreferenceResult, MergeheadInfo};

libs/git/ssh/mod.rs

@@ -1,5 +1,6 @@
 use crate::error::GitError;
 use crate::hook::HookService;
+use crate::hook::pool::types::{HookTask, TaskType};
 use anyhow::Context;
 use base64::Engine;
 use config::AppConfig;
@@ -137,22 +138,12 @@ impl SSHHandle {
             "SSH server configured with methods: {:?}", config.methods
         );
         let token_service = SshTokenService::new(self.db.clone());
-        let http = Arc::new(reqwest::Client::new());
-        let hook = crate::hook::HookService::new(
-            self.db.clone(),
-            self.cache.clone(),
-            self.redis_pool.clone(),
-            self.logger.clone(),
-            self.app.clone(),
-            http,
-        );
         let mut server = server::SSHServer::new(
             self.db.clone(),
             self.cache.clone(),
             self.redis_pool.clone(),
             self.logger.clone(),
             token_service,
-            hook,
         );
 
         // Start the rate limiter cleanup background task so the HashMap
@@ -177,33 +168,63 @@ impl SSHHandle {
     }
 }
 
-/// Direct sync service — calls HookService::sync_repo inline.
-/// K8s StatefulSet HA scheduling ensures exclusive access per repo shard.
+/// Enqueues a sync task to the Redis-backed hook queue.
+/// The background worker picks it up and processes it with per-repo locking.
 #[derive(Clone)]
 pub struct ReceiveSyncService {
-    hook: HookService,
+    pool: deadpool_redis::cluster::Pool,
+    logger: Logger,
+    redis_prefix: String,
 }
 
 impl ReceiveSyncService {
-    pub fn new(hook: HookService) -> Self {
-        Self { hook }
+    pub fn new(pool: deadpool_redis::cluster::Pool, logger: Logger) -> Self {
+        Self {
+            pool,
+            logger,
+            redis_prefix: "{hook}".to_string(),
+        }
     }
 
-    /// Execute a full repo sync synchronously.
-    /// Returns Ok on success, Err on failure.
-    pub async fn send(&self, task: RepoReceiveSyncTask) -> Result<(), crate::GitError> {
-        let repo_id = task.repo_uid.to_string();
-        slog::info!(self.hook.logger, "starting sync repo_id={}", repo_id);
-        let res = self.hook.sync_repo(&repo_id).await;
-        match &res {
-            Ok(()) => {
-                slog::info!(self.hook.logger, "sync completed repo_id={}", repo_id);
-            }
+    /// Enqueue a sync task. Fire-and-forget — logs errors but does not block.
+    pub async fn send(&self, task: RepoReceiveSyncTask) {
+        let hook_task = HookTask {
+            id: uuid::Uuid::new_v4().to_string(),
+            repo_id: task.repo_uid.to_string(),
+            task_type: TaskType::Sync,
+            payload: serde_json::Value::Null,
+            created_at: chrono::Utc::now(),
+            retry_count: 0,
+        };
+
+        let task_json = match serde_json::to_string(&hook_task) {
+            Ok(j) => j,
             Err(e) => {
-                slog::error!(self.hook.logger, "sync failed repo_id={} error={}", repo_id, e);
+                error!(self.logger, "failed to serialize hook task: {}", e);
+                return;
             }
+        };
+
+        let queue_key = format!("{}:sync", self.redis_prefix);
+
+        let redis = match self.pool.get().await {
+            Ok(c) => c,
+            Err(e) => {
+                error!(self.logger, "failed to get Redis connection: {}", e);
+                return;
+            }
+        };
+
+        let mut conn: deadpool_redis::cluster::Connection = redis;
+        if let Err(e) = redis::cmd("LPUSH")
+            .arg(&queue_key)
+            .arg(&task_json)
+            .query_async::<()>(&mut conn)
+            .await
+        {
+            error!(self.logger, "failed to enqueue sync task repo_id={} error={}",
+                task.repo_uid, e);
         }
-        res
     }
 }
 
@@ -267,6 +288,19 @@ pub async fn run_ssh(config: AppConfig, logger: Logger) -> anyhow::Result<()> {
     let db = AppDatabase::init(&config).await?;
     let cache = AppCache::init(&config).await?;
     let redis_pool = cache.redis_pool().clone();
+
+    // Start the hook worker (Redis queue consumer)
+    let hook = crate::hook::HookService::new(
+        db.clone(),
+        cache.clone(),
+        redis_pool.clone(),
+        logger.clone(),
+        config.clone(),
+        Arc::new(reqwest::Client::new()),
+    );
+    let _worker_cancel = hook.start_worker();
+    slog::info!(logger, "hook worker started");
+
     SSHHandle::new(db, config.clone(), cache, redis_pool, logger)
         .run_ssh()
         .await?;

libs/git/ssh/server.rs

@@ -1,4 +1,3 @@
-use crate::hook::HookService;
 use crate::ssh::ReceiveSyncService;
 use crate::ssh::SshTokenService;
 use crate::ssh::handle::SSHandle;
@@ -16,7 +15,6 @@ pub struct SSHServer {
     pub redis_pool: RedisPool,
     pub logger: Logger,
     pub token_service: SshTokenService,
-    pub hook: HookService,
 }
 
 impl SSHServer {
@@ -26,7 +24,6 @@ impl SSHServer {
         redis_pool: RedisPool,
         logger: Logger,
         token_service: SshTokenService,
-        hook: HookService,
     ) -> Self {
         SSHServer {
             db,
@@ -34,7 +31,6 @@ impl SSHServer {
             redis_pool,
             logger,
             token_service,
-            hook,
         }
     }
 }
@@ -52,7 +48,7 @@ impl russh::server::Server for SSHServer {
         } else {
             info!(self.logger, "New SSH connection from unknown address");
         }
-        let sync_service = ReceiveSyncService::new(self.hook.clone());
+        let sync_service = ReceiveSyncService::new(self.redis_pool.clone(), self.logger.clone());
         SSHandle::new(
             self.db.clone(),
             self.cache.clone(),