code/flash/server/app.py

"""FastAPI control plane for the managed Flash service.

This is the operator-side component. It holds the
provider credentials (``RUNPOD_API_KEY``, ``HF_TOKEN``, ``PRIME_API_KEY`` —
the worker needs the last to ``prime env install`` the run's Prime Hub env) and
exposes the full run lifecycle to clients that authenticate with their freesolo API
key (verified against the freesolo backend) — clients never see provider credentials.

Run state truth stays in the runner's JSON files; SQLite (server/db.py) holds
keys and run ownership. Runs the server owns are recovered on startup by re-attaching
to their persisted RunPod job handles.
"""

from __future__ import annotations

import contextlib
import os
import threading
import weakref

from flash import __version__
from flash.catalog import public_model_rows
from flash.runner import (
    adapter_prefix,
    cancel_run,
    get_status,
    mark_deployed,
    mark_undeployed,
    new_run_id,
    runs_file_path,
    submit_job,
)
from flash.schema import ConfigError, spec_from_dict
from flash.serve.deploy import chat as serve_chat
from flash.serve.deploy import deploy_adapter, servable_gpu, undeploy_adapter
from flash.spec import JobSpec

from . import auth, db

_RECOVERABLE = {"queued", "provisioning", "running"}
# Run states that have produced a downloadable adapter artifact.
_DEPLOYABLE_STATES = {"done", "deployed"}


class _RunLock:
    """A weak-referenceable mutex usable as a context manager.

    ``threading.Lock()`` returns a ``_thread.lock`` that does NOT support weak references,
    so it can't live in a WeakValueDictionary directly — wrap it in a tiny object that does
    (and acquire/release via ``with``).
    """

    __slots__ = ("__weakref__", "_lock")

    def __init__(self) -> None:
        self._lock = threading.Lock()

    def __enter__(self) -> _RunLock:
        self._lock.acquire()
        return self

    def __exit__(self, *exc: object) -> None:
        self._lock.release()


# Per-run lock serializing deploy vs undeploy: always-on provisioning is slow and runs
# OUTSIDE the status lock, so without this the two could interleave — a racing undeploy
# could leave a billable endpoint unrecorded, or a deploy's rollback could clobber another.
# WeakValueDictionary so an entry is dropped once no request holds the lock — the map
# can't grow unboundedly with one entry per distinct run_id over the server's lifetime.
_DEPLOY_LOCKS: weakref.WeakValueDictionary[str, _RunLock] = weakref.WeakValueDictionary()
_DEPLOY_LOCKS_GUARD = threading.Lock()


def _deploy_lock(run_id: str) -> _RunLock:
    # The returned lock must be held by the caller (a `with` block) to keep it alive; once
    # released and unreferenced, the weak entry is garbage-collected.
    with _DEPLOY_LOCKS_GUARD:
        lk = _DEPLOY_LOCKS.get(run_id)
        if lk is None:
            lk = _RunLock()
            _DEPLOY_LOCKS[run_id] = lk
        return lk


def recover_runs(log=None) -> None:
    """Re-attach to in-flight runs after a server restart (per-run daemon threads)."""
    from flash.runner import _gc_run_endpoints, _update, attach_run, resume_run

    active: set[str] = set()
    for row in db.all_runs():
        try:
            status = get_status(row["run_id"])
        except FileNotFoundError:
            continue
        if status.state not in _RECOVERABLE:
            continue
        if status.remote:
            # Only remote-backed runs are "active" (kept by the orphan sweep). A run
            # with no handle is being failed below; if it had already rented a Vast
            # instance (crash between rent and on_handle), it must NOT shield that
            # instance from the sweep.
            active.add(status.run_id)
            threading.Thread(target=lambda rid=row["run_id"]: attach_run(rid), daemon=True).start()
        elif status.resume_seed_index is not None:
            # Multi-seed run that restarted in the inter-seed gap: the completed seed's
            # handle was deliberately cleared and the next index recorded. There is no
            # live job to reattach to, so resume the remaining seeds rather than failing
            # the run and discarding the already-completed work. Keep it in `active` so
            # the orphan sweep below doesn't reap the label its next seed will reuse.
            active.add(status.run_id)
            threading.Thread(target=lambda rid=row["run_id"]: resume_run(rid), daemon=True).start()
        else:
            # The first attempt may have registered its uniquely-named RunPod
            # endpoint before on_handle() persisted the handle. GC it (by
            # reconstructed name) before failing, so it doesn't hold worker quota
            # until manual cleanup. Best-effort; vast orphans are swept below.
            with contextlib.suppress(Exception):
                _gc_run_endpoints(JobSpec.from_dict(status.spec))
            _update(status.run_id, "failed", error="server restarted before job submission")
    # Standing per-run billing (Vast instances) survives a crash until destroyed:
    # anything labeled ours that no recoverable run owns is an orphan. Each available
    # provider's ``sweep_orphans`` hook reaps its own (RunPod's is a no-op). Dispatched
    # generically through the registry — ``sweep_orphans`` is part of base.Provider, so
    # no provider is special-cased. ``active`` carries raw run ids; each provider applies
    # its own label-prefix transform. Best-effort: never raises.
    from flash.providers import configured_providers

    for prov in configured_providers():
        with contextlib.suppress(Exception):
            prov.sweep_orphans(active_labels=active)


def create_app():
    try:
        from fastapi import Depends, FastAPI, Header, HTTPException
    except ImportError as exc:
        raise RuntimeError(
            "the control plane needs the server extras: pip install 'flash[server]'"
        ) from exc
    from contextlib import asynccontextmanager

    @asynccontextmanager
    async def lifespan(app):
        from flash.providers.preflight import check_run_preflight

        check_run_preflight()  # operator credentials: fail fast, before serving anyone
        recover_runs()
        yield

    app = FastAPI(title="Flash Control Plane", version=__version__, lifespan=lifespan)

    def require_key(authorization: str | None = Header(default=None)) -> dict:
        key = auth.authenticate(authorization)
        if key is None:
            raise HTTPException(
                status_code=401,
                detail="invalid or missing API key; log in with `slm login` using your "
                "freesolo API key",
            )
        return key

    def owned_run(run_id: str, key: dict):
        """Load a run's status iff `key` owns it; 404 otherwise (don't leak existence)."""
        if db.run_owner(run_id) != key["id"]:
            raise HTTPException(status_code=404, detail=f"unknown run_id: {run_id}")
        try:
            return get_status(run_id)
        except FileNotFoundError as exc:
            raise HTTPException(status_code=404, detail=str(exc)) from exc

    @app.get("/v1/health")
    def health():
        return {"ok": True, "service": "flash", "version": __version__}

    @app.get("/v1/me")
    def me(key: dict = Depends(require_key)):
        return {
            "key_prefix": key["key_prefix"],
            "email": key["email"],
            "created_at": key["created_at"],
        }

    @app.get("/v1/models")
    def models(_: dict = Depends(require_key)):
        return {"models": public_model_rows()}

    def _parse_spec(payload: dict, run_id: str) -> JobSpec:
        spec_raw = payload.get("spec") or {}
        env_raw = spec_raw.get("environment") or {}
        if env_raw.get("path"):
            raise HTTPException(
                status_code=400,
                detail="local environment paths are not supported on the managed service; "
                "publish the environment to the Prime Hub (`slm env push`), then reference it "
                'by its Hub id (`[environment] id = "owner/name"`)',
            )
        try:
            return spec_from_dict(spec_raw, run_id=run_id)
        except (ConfigError, ValueError) as exc:
            raise HTTPException(status_code=400, detail=str(exc)) from exc

    @app.post("/v1/runs")
    def create_run(payload: dict, key: dict = Depends(require_key)):
        spec = _parse_spec(payload, run_id=new_run_id())
        dry_run = bool(payload.get("dry_run", False))
        db.record_run(spec.run_id, key["id"], kind="train")
        try:
            status = submit_job(spec, dry_run=dry_run, background=True)
        except Exception as exc:
            db.delete_run(spec.run_id)
            raise HTTPException(status_code=400, detail=str(exc)) from exc
        return status.to_dict()

    @app.get("/v1/runs")
    def list_runs(key: dict = Depends(require_key)):
        out = []
        for row in db.runs_for_key(key["id"]):
            try:
                out.append(get_status(row["run_id"]).to_dict())
            except FileNotFoundError:
                continue
        return {"runs": out}

    @app.get("/v1/runs/{run_id}")
    def run_status(run_id: str, key: dict = Depends(require_key)):
        status = owned_run(run_id, key)
        return status.to_dict()

    @app.get("/v1/runs/{run_id}/logs")
    def run_logs(run_id: str, offset: int = 0, key: dict = Depends(require_key)):
        status = owned_run(run_id, key)
        log_path = runs_file_path(run_id, ".log")
        chunk, end = "", max(0, offset)
        if os.path.exists(log_path):
            with open(log_path) as f:
                f.seek(end)
                chunk = f.read()
                end = f.tell()
        return {"run_id": run_id, "logs": chunk, "offset": end, "state": status.state}

    @app.post("/v1/runs/{run_id}/cancel")
    def cancel(run_id: str, key: dict = Depends(require_key)):
        owned_run(run_id, key)
        return cancel_run(run_id).to_dict()

    @app.post("/v1/runs/{run_id}/deploy")
    def deploy(run_id: str, payload: dict | None = None, key: dict = Depends(require_key)):
        payload = payload or {}
        # Serialize deploy vs undeploy (and a second deploy) for this run: registration
        # with the freesolo serving app runs outside the status lock, so without this they
        # could interleave and leave the serving record and the control plane inconsistent.
        with _deploy_lock(run_id):
            status = owned_run(run_id, key)
            spec = JobSpec.from_dict(status.spec)
            dry_run = bool(payload.get("dry_run", False))
            if not dry_run and status.state not in _DEPLOYABLE_STATES:
                raise HTTPException(
                    status_code=409,
                    detail=(
                        f"run {run_id} is {status.state!r}; only finished runs with "
                        "trained adapter artifacts can be deployed"
                    ),
                )
            # Legacy runs persisted before [train].hf_repo was mandatory rehydrate with an
            # empty hf_repo; without this guard freesolo serving cannot locate the adapter
            # artifacts (the per-run HF dataset repo). Reject early with a clear 409.
            if not dry_run and not spec.train.hf_repo:
                raise HTTPException(
                    status_code=409,
                    detail=(
                        f"run {run_id} has no [train].hf_repo (legacy run); its adapter artifacts "
                        "cannot be located, so it cannot be deployed"
                    ),
                )
            mode = payload.get("mode", "dev")
            # The state the run must still be in for this deploy to finalize — a CAS guard so
            # a /cancel (NOT serialized by the deploy lock) that terminalized the run can't be
            # silently overwritten by the deployment record.
            prev_state = status.state
            try:
                dep = deploy_adapter(
                    run_id=run_id,
                    model=spec.model,
                    hf_repo=spec.train.hf_repo,
                    adapter_prefix=adapter_prefix(spec),
                    gpu_name=spec.gpu.type,
                    mode=mode,
                    idle_timeout_s=int(payload.get("idle_timeout_s", 300)),
                    dry_run=dry_run,
                    lora_rank=spec.train.lora_rank,
                    # a run trained with thinking serves with thinking (per-run parity)
                    thinking=spec.thinking,
                )
            except Exception as exc:
                if isinstance(exc, ValueError):
                    raise HTTPException(status_code=400, detail=str(exc)) from exc
                raise
            if not dry_run:
                # Record the deployment. The CAS no-ops only if a /cancel raced finalization
                # — then the adapter we just registered is orphaned, so deregister it and
                # report the conflict instead of a bogus 200.
                marked = mark_deployed(run_id, dep.to_dict(), expect_state=prev_state)
                if marked.state != "deployed":
                    with contextlib.suppress(Exception):
                        undeploy_adapter(run_id, gpu_name=servable_gpu(spec.gpu.type, spec.model))
                    raise HTTPException(
                        status_code=409,
                        detail=f"run {run_id} became {marked.state!r} during deploy; aborted",
                    )
            return dep.to_dict()

    @app.delete("/v1/runs/{run_id}/deploy")
    def undeploy(run_id: str, key: dict = Depends(require_key)):
        # Same per-run lock as deploy: an undeploy must not interleave with an in-flight
        # deploy's provisioning/finalization.
        with _deploy_lock(run_id):
            status = owned_run(run_id, key)
            spec = JobSpec.from_dict(status.spec)
            # The deployment record carries the class actually served (an unvalidated
            # training class falls back to a RunPod-validated class at deploy time).
            deployed_gpu = (status.deployment or {}).get("gpu") or spec.gpu.type
            deleted = undeploy_adapter(run_id, gpu_name=deployed_gpu)
            # dev mode is scale-to-zero: the serve endpoint is created only on the first
            # chat, so an empty deletion just means it was never warmed — still a clean
            # undeploy. always-on provisions the endpoint at deploy time, so an empty
            # deletion there is a transient RunPod failure that must NOT hide a
            # still-billable endpoint (surface 502 so the user retries).
            dev_mode = (status.deployment or {}).get("mode", "dev") == "dev"
            if status.deployment and (deleted or dev_mode):
                mark_undeployed(run_id)
            elif status.deployment and not deleted:
                raise HTTPException(
                    status_code=502,
                    detail=f"could not delete the serving endpoint for {run_id}; it may still "
                    "be running — retry `slm undeploy`",
                )
            return {"run_id": run_id, "deleted_endpoints": deleted}

    @app.get("/v1/deployments")
    def deployments(key: dict = Depends(require_key)):
        out = []
        for row in db.runs_for_key(key["id"]):
            try:
                status = get_status(row["run_id"])
            except FileNotFoundError:
                continue
            if status.deployment and status.deployment.get("state") not in (
                "undeployed",
                "dry_run",
            ):
                out.append(status.to_dict())
        return {"deployments": out}

    @app.post("/v1/runs/{run_id}/chat")
    def chat(run_id: str, payload: dict, key: dict = Depends(require_key)):
        status = owned_run(run_id, key)
        spec = JobSpec.from_dict(status.spec)
        deployment = status.deployment or {}
        # A cancelled run's serve endpoint was torn down at cancel time; never let a
        # chat recreate it (closes the window before cancel marks the deployment
        # inactive, and covers a teardown that deleted nothing).
        if status.state == "cancelled":
            raise HTTPException(
                status_code=409, detail=f"run {run_id} was cancelled; redeploy is not allowed"
            )
        # Chat must ride an explicit deployment (with its cost controls), not
        # implicitly provision a serving endpoint that /v1/deployments cannot see.
        if deployment.get("state") in (None, "undeployed", "dry_run"):
            raise HTTPException(
                status_code=409,
                detail=f"run {run_id} has no active deployment; `slm deploy {run_id}` first",
            )
        # Legacy run with no artifact repo: reject early with a clear 409 rather than letting
        # serve_chat's adapter download fail deep as an opaque 502 (mirrors /deploy).
        if not spec.train.hf_repo:
            raise HTTPException(
                status_code=409,
                detail=f"run {run_id} has no [train].hf_repo (legacy run); its adapter cannot be served",
            )
        try:
            return serve_chat(
                run_id=run_id,
                messages=payload.get("messages") or [],
                model=spec.model,
                hf_repo=spec.train.hf_repo,
                adapter_prefix=adapter_prefix(spec),
                # Use the class actually deployed (an unvalidated training class falls
                # back to a RunPod-validated class at deploy time). Recomputing from
                # spec.gpu.type could pick a different serve endpoint that undeploy and
                # cancel — which target the recorded deployment GPU — would not delete.
                gpu_name=deployment.get("gpu") or spec.gpu.type,
                temperature=float(payload.get("temperature") or 0.0),
                max_tokens=int(payload.get("max_tokens") or 512),
                mode=deployment.get("mode", "dev"),
                idle_timeout_s=int(deployment.get("idle_timeout_s", 300)),
                lora_rank=spec.train.lora_rank,
                # a run trained with thinking serves with thinking (per-run parity)
                thinking=spec.thinking,
            )
        except Exception as exc:
            raise HTTPException(status_code=502, detail=f"inference failure: {exc}") from exc

    return app


def run_server(host: str = "127.0.0.1", port: int = 8080) -> None:
    try:
        import uvicorn
    except ImportError as exc:
        raise RuntimeError(
            "the control plane needs the server extras: pip install 'flash[server]'"
        ) from exc
    uvicorn.run(create_app(), host=host, port=port)