[Draft PR] Support router as replica with pipelines

src/dstack/_internal/core/models/configurations.py

@@ -801,6 +801,12 @@ class ReplicaGroup(CoreModel):
         CommandsList,
         Field(description="The shell commands to run for replicas in this group"),
     ] = []
+    router: Annotated[
+        Optional[AnyServiceRouterConfig],
+        Field(
+            description="When set, replicas in this group run the in-service HTTP router (e.g. SGLang).",
+        ),
+    ] = None
 
     @validator("name")
     def validate_name(cls, v: Optional[str]) -> Optional[str]:
@@ -1032,6 +1038,16 @@ def validate_replica_groups_have_commands_or_image(cls, values):
 
         return values
 
+    @root_validator()
+    def validate_at_most_one_router_replica_group(cls, values):
+        replicas = values.get("replicas")
+        if not isinstance(replicas, list):
+            return values
+        router_groups = [g for g in replicas if g.router is not None]
+        if len(router_groups) > 1:
+            raise ValueError("At most one replica group may specify `router`.")
+        return values
+
 
 class ServiceConfigurationConfig(
     ProfileParamsConfig,

src/dstack/_internal/proxy/gateway/routers/registry.py

@@ -82,6 +82,7 @@ async def register_replica(
         ssh_head_proxy=body.ssh_head_proxy,
         ssh_head_proxy_private_key=body.ssh_head_proxy_private_key,
         internal_ip=body.internal_ip,
+        is_router_replica=body.is_router_replica,
         repo=repo,
         nginx=nginx,
         service_conn_pool=service_conn_pool,

src/dstack/_internal/proxy/gateway/schemas/registry.py

@@ -58,6 +58,7 @@ class RegisterReplicaRequest(BaseModel):
     ssh_head_proxy: Optional[SSHConnectionParams]
     ssh_head_proxy_private_key: Optional[str]
     internal_ip: Optional[str] = None
+    is_router_replica: bool = False
 
 
 class RegisterEntrypointRequest(BaseModel):

src/dstack/_internal/proxy/gateway/services/registry.py

@@ -141,6 +141,7 @@ async def register_replica(
     nginx: Nginx,
     service_conn_pool: ServiceConnectionPool,
     internal_ip: Optional[str] = None,
+    is_router_replica: bool = False,
 ) -> None:
     replica = models.Replica(
         id=replica_id,
@@ -152,6 +153,7 @@ async def register_replica(
         ssh_head_proxy=ssh_head_proxy,
         ssh_head_proxy_private_key=ssh_head_proxy_private_key,
         internal_ip=internal_ip,
+        is_router_replica=is_router_replica,
     )
 
     async with lock:
@@ -291,6 +293,13 @@ async def apply_service(
             )
             for replica, conn in replica_conns.items()
         ]
+    router_replicas = [r for r in service.replicas if r.is_router_replica]
+    if router_replicas:
+        replica_configs_for_nginx = [c for c in replica_configs if c.id == router_replicas[0].id]
+        service_config = await get_nginx_service_config(service, replica_configs_for_nginx)
+        await nginx.register(service_config, (await repo.get_config()).acme_settings)
+        return replica_failures
+
     service_config = await get_nginx_service_config(service, replica_configs)
     await nginx.register(service_config, (await repo.get_config()).acme_settings)
     return replica_failures

src/dstack/_internal/proxy/lib/models.py

@@ -30,6 +30,7 @@ class Replica(ImmutableModel):
     ssh_head_proxy: Optional[SSHConnectionParams] = None
     ssh_head_proxy_private_key: Optional[str] = None
     internal_ip: Optional[str] = None
+    is_router_replica: bool = False
 
 
 class IPAddressPartitioningKey(ImmutableModel):

src/dstack/_internal/proxy/lib/services/service_connection.py

@@ -151,7 +151,9 @@ async def get_service_replica_client(
             timeout=HTTP_TIMEOUT,
         )
     # Nginx not available, forward directly to the tunnel
-    replica = random.choice(service.replicas)
+    router_replicas = [r for r in service.replicas if r.is_router_replica]
+    replicas_to_use = router_replicas if router_replicas else service.replicas
+    replica = random.choice(replicas_to_use)
     connection = await service_conn_pool.get(replica.id)
     if connection is None:
         project = await repo.get_project(service.project_name)

src/dstack/_internal/server/background/pipeline_tasks/__init__.py

@@ -16,6 +16,9 @@
     PlacementGroupPipeline,
 )
 from dstack._internal.server.background.pipeline_tasks.runs import RunPipeline
+from dstack._internal.server.background.pipeline_tasks.service_router_worker_sync import (
+    ServiceRouterWorkerSyncPipeline,
+)
 from dstack._internal.server.background.pipeline_tasks.volumes import VolumePipeline
 from dstack._internal.utils.logging import get_logger
 
@@ -36,6 +39,7 @@ def __init__(self) -> None:
             InstancePipeline(pipeline_hinter=self._hinter),
             PlacementGroupPipeline(pipeline_hinter=self._hinter),
             RunPipeline(pipeline_hinter=self._hinter),
+            ServiceRouterWorkerSyncPipeline(pipeline_hinter=self._hinter),
             VolumePipeline(pipeline_hinter=self._hinter),
         ]:
             self.register_pipeline(builtin_pipeline)

src/dstack/_internal/server/background/pipeline_tasks/service_router_worker_sync.py

@@ -0,0 +1,259 @@
+import asyncio
+import uuid
+from dataclasses import dataclass
+from datetime import timedelta
+from typing import Sequence
+
+from sqlalchemy import delete, or_, select, update
+from sqlalchemy.orm import load_only, selectinload
+
+from dstack._internal.core.models.runs import RunStatus
+from dstack._internal.server.background.pipeline_tasks.base import (
+    Fetcher,
+    Heartbeater,
+    ItemUpdateMap,
+    Pipeline,
+    PipelineItem,
+    Worker,
+    log_lock_token_changed_after_processing,
+    log_lock_token_mismatch,
+    resolve_now_placeholders,
+    set_processed_update_map_fields,
+    set_unlock_update_map_fields,
+)
+from dstack._internal.server.db import get_db, get_session_ctx
+from dstack._internal.server.models import (
+    InstanceModel,
+    JobModel,
+    RunModel,
+    ServiceRouterWorkerSyncModel,
+)
+from dstack._internal.server.services.locking import get_locker
+from dstack._internal.server.services.pipelines import PipelineHinterProtocol
+from dstack._internal.server.services.router_worker_sync import (
+    run_model_has_router_replica_group,
+    sync_router_workers_for_run_model,
+)
+from dstack._internal.server.utils import sentry_utils
+from dstack._internal.utils.common import get_current_datetime
+from dstack._internal.utils.logging import get_logger
+
+logger = get_logger(__name__)
+
+
+@dataclass
+class ServiceRouterWorkerSyncPipelineItem(PipelineItem):
+    run_id: uuid.UUID
+
+
+class ServiceRouterWorkerSyncPipeline(Pipeline[ServiceRouterWorkerSyncPipelineItem]):
+    def __init__(
+        self,
+        workers_num: int = 8,
+        queue_lower_limit_factor: float = 0.5,
+        queue_upper_limit_factor: float = 2.0,
+        min_processing_interval: timedelta = timedelta(seconds=5),
+        lock_timeout: timedelta = timedelta(seconds=25),
+        heartbeat_trigger: timedelta = timedelta(seconds=10),
+        *,
+        pipeline_hinter: PipelineHinterProtocol,
+    ) -> None:
+        super().__init__(
+            workers_num=workers_num,
+            queue_lower_limit_factor=queue_lower_limit_factor,
+            queue_upper_limit_factor=queue_upper_limit_factor,
+            min_processing_interval=min_processing_interval,
+            lock_timeout=lock_timeout,
+            heartbeat_trigger=heartbeat_trigger,
+        )
+        self.__heartbeater = Heartbeater[ServiceRouterWorkerSyncPipelineItem](
+            model_type=ServiceRouterWorkerSyncModel,
+            lock_timeout=self._lock_timeout,
+            heartbeat_trigger=self._heartbeat_trigger,
+        )
+        self.__fetcher = ServiceRouterWorkerSyncFetcher(
+            queue=self._queue,
+            queue_desired_minsize=self._queue_desired_minsize,
+            min_processing_interval=self._min_processing_interval,
+            lock_timeout=self._lock_timeout,
+            heartbeater=self.__heartbeater,
+        )
+        self.__workers = [
+            ServiceRouterWorkerSyncWorker(
+                queue=self._queue,
+                heartbeater=self.__heartbeater,
+                pipeline_hinter=pipeline_hinter,
+            )
+            for _ in range(self._workers_num)
+        ]
+
+    @property
+    def hint_fetch_model_name(self) -> str:
+        return ServiceRouterWorkerSyncModel.__name__
+
+    @property
+    def _heartbeater(self) -> Heartbeater[ServiceRouterWorkerSyncPipelineItem]:
+        return self.__heartbeater
+
+    @property
+    def _fetcher(self) -> Fetcher[ServiceRouterWorkerSyncPipelineItem]:
+        return self.__fetcher
+
+    @property
+    def _workers(self) -> Sequence["ServiceRouterWorkerSyncWorker"]:
+        return self.__workers
+
+
+class ServiceRouterWorkerSyncFetcher(Fetcher[ServiceRouterWorkerSyncPipelineItem]):
+    @sentry_utils.instrument_named_task("pipeline_tasks.ServiceRouterWorkerSyncFetcher.fetch")
+    async def fetch(self, limit: int) -> list[ServiceRouterWorkerSyncPipelineItem]:
+        sync_lock, _ = get_locker(get_db().dialect_name).get_lockset(
+            ServiceRouterWorkerSyncModel.__tablename__
+        )
+        async with sync_lock:
+            async with get_session_ctx() as session:
+                now = get_current_datetime()
+                res = await session.execute(
+                    select(ServiceRouterWorkerSyncModel)
+                    .join(RunModel, RunModel.id == ServiceRouterWorkerSyncModel.run_id)
+                    .where(
+                        RunModel.status == RunStatus.RUNNING,
+                        or_(
+                            ServiceRouterWorkerSyncModel.last_processed_at
+                            <= now - self._min_processing_interval,
+                            ServiceRouterWorkerSyncModel.last_processed_at
+                            == ServiceRouterWorkerSyncModel.created_at,
+                        ),
+                        or_(
+                            ServiceRouterWorkerSyncModel.lock_expires_at.is_(None),
+                            ServiceRouterWorkerSyncModel.lock_expires_at < now,
+                        ),
+                    )
+                    .order_by(ServiceRouterWorkerSyncModel.last_processed_at.asc())
+                    .limit(limit)
+                    .with_for_update(
+                        skip_locked=True, key_share=True, of=ServiceRouterWorkerSyncModel
+                    )
+                    .options(
+                        load_only(
+                            ServiceRouterWorkerSyncModel.id,
+                            ServiceRouterWorkerSyncModel.run_id,
+                            ServiceRouterWorkerSyncModel.lock_token,
+                            ServiceRouterWorkerSyncModel.lock_expires_at,
+                        )
+                    )
+                )
+                rows = list(res.scalars().all())
+                lock_expires_at = get_current_datetime() + self._lock_timeout
+                lock_token = uuid.uuid4()
+                items: list[ServiceRouterWorkerSyncPipelineItem] = []
+                for row in rows:
+                    prev_lock_expired = row.lock_expires_at is not None
+                    row.lock_expires_at = lock_expires_at
+                    row.lock_token = lock_token
+                    row.lock_owner = ServiceRouterWorkerSyncPipeline.__name__
+                    items.append(
+                        ServiceRouterWorkerSyncPipelineItem(
+                            __tablename__=ServiceRouterWorkerSyncModel.__tablename__,
+                            id=row.id,
+                            lock_expires_at=lock_expires_at,
+                            lock_token=lock_token,
+                            prev_lock_expired=prev_lock_expired,
+                            run_id=row.run_id,
+                        )
+                    )
+                await session.commit()
+        return items
+
+
+class _SyncRowUpdateMap(ItemUpdateMap, total=False):
+    pass
+
+
+class ServiceRouterWorkerSyncWorker(Worker[ServiceRouterWorkerSyncPipelineItem]):
+    def __init__(
+        self,
+        queue: asyncio.Queue[ServiceRouterWorkerSyncPipelineItem],
+        heartbeater: Heartbeater[ServiceRouterWorkerSyncPipelineItem],
+        pipeline_hinter: PipelineHinterProtocol,
+    ) -> None:
+        super().__init__(
+            queue=queue,
+            heartbeater=heartbeater,
+            pipeline_hinter=pipeline_hinter,
+        )
+
+    @sentry_utils.instrument_named_task("pipeline_tasks.ServiceRouterWorkerSyncWorker.process")
+    async def process(self, item: ServiceRouterWorkerSyncPipelineItem) -> None:
+        async with get_session_ctx() as session:
+            res = await session.execute(
+                select(ServiceRouterWorkerSyncModel)
+                .where(
+                    ServiceRouterWorkerSyncModel.id == item.id,
+                    ServiceRouterWorkerSyncModel.lock_token == item.lock_token,
+                )
+                .options(selectinload(ServiceRouterWorkerSyncModel.run))
+            )
+            sync_row = res.unique().scalar_one_or_none()
+            if sync_row is None:
+                log_lock_token_mismatch(logger, item)
+                return
+            run_model = sync_row.run
+            if run_model is None:
+                await session.delete(sync_row)
+                await session.commit()
+                return
+            if (
+                run_model.deleted
+                or run_model.status.is_finished()
+                or run_model.status != RunStatus.RUNNING
+                or not run_model_has_router_replica_group(run_model)
+            ):
+                await session.delete(sync_row)
+                await session.commit()
+                return
+
+        async with get_session_ctx() as session:
+            res = await session.execute(
+                select(RunModel)
+                .where(RunModel.id == item.run_id)
+                .options(
+                    selectinload(RunModel.project),
+                    selectinload(RunModel.jobs).selectinload(JobModel.project),
+                    selectinload(RunModel.jobs)
+                    .selectinload(JobModel.instance)
+                    .selectinload(InstanceModel.project),
+                )
+            )
+            run_for_sync = res.unique().scalar_one_or_none()
+
+        if run_for_sync is None:
+            async with get_session_ctx() as session:
+                await session.execute(
+                    delete(ServiceRouterWorkerSyncModel).where(
+                        ServiceRouterWorkerSyncModel.id == item.id,
+                        ServiceRouterWorkerSyncModel.lock_token == item.lock_token,
+                    )
+                )
+                await session.commit()
+            return
+
+        await sync_router_workers_for_run_model(run_for_sync)
+
+        update_map: _SyncRowUpdateMap = {}
+        set_processed_update_map_fields(update_map)
+        set_unlock_update_map_fields(update_map)
+        async with get_session_ctx() as session:
+            now = get_current_datetime()
+            resolve_now_placeholders(update_map, now=now)
+            res2 = await session.execute(
+                update(ServiceRouterWorkerSyncModel)
+                .where(
+                    ServiceRouterWorkerSyncModel.id == item.id,
+                    ServiceRouterWorkerSyncModel.lock_token == item.lock_token,
+                )
+                .values(**update_map)
+                .returning(ServiceRouterWorkerSyncModel.id)
+            )
+            if not list(res2.scalars().all()):
+                log_lock_token_changed_after_processing(logger, item)