First draft of multi-task in a single session. (#622)

ui/media/js/engine.js

@@ -383,7 +383,7 @@
                     throw new Error('exception is not an Error or a string.')
                 }
             }
-            const res = await fetch('/image/stop?session_id=' + SD.sessionId)
+            const res = await fetch('/image/stop?task=' + this.id)
             if (!res.ok) {
                 console.log('Stop response:', res)
                 throw new Error(res.statusText)
@@ -556,13 +556,19 @@
                 case TaskStatus.pending:
                 case TaskStatus.waiting:
                     // Wait for server status to include this task.
-                    await waitUntil(async () => ((task.#id && serverState.task === task.#id)
+                    await waitUntil(
-                        || await Promise.resolve(callback?.call(task))
+                        async () => {
-                        || signal?.aborted),
+                            if (task.#id && typeof serverState.tasks === 'object' && Object.keys(serverState.tasks).includes(String(task.#id))) {
+                                return true
+                            }
+                            if (await Promise.resolve(callback?.call(task)) || signal?.aborted) {
+                                return true
+                            }
+                        },
                         TASK_STATE_SERVER_UPDATE_DELAY,
                         timeout,
                     )
-                    if (this.#id && serverState.task === this.#id) {
+                    if (this.#id && typeof serverState.tasks === 'object' && Object.keys(serverState.tasks).includes(String(task.#id))) {
                         this._setStatus(TaskStatus.waiting)
                     }
                     if (await Promise.resolve(callback?.call(this)) || signal?.aborted) {
@@ -572,19 +578,20 @@
                         return true
                     }
                     // Wait for task to start on server.
-                    await waitUntil(async () => (serverState.task !== task.#id || serverState.session !== 'pending'
+                    await waitUntil(
-                        || await Promise.resolve(callback?.call(task))
+                        async () => {
-                        || signal?.aborted),
+                            if (typeof serverState.tasks !== 'object' || serverState.tasks[String(task.#id)] !== 'pending') {
+                                return true
+                            }
+                            if (await Promise.resolve(callback?.call(task)) || signal?.aborted) {
+                                return true
+                            }
+                        },
                         TASK_STATE_SERVER_UPDATE_DELAY,
                         timeout,
                     )
-                    if (serverState.task === this.#id
+                    const state = (typeof serverState.tasks === 'object' ? serverState.tasks[String(task.#id)] : undefined)
-                        && (
+                    if (state === 'running' || state === 'buffer' || state === 'completed') {
-                            serverState.session === 'running'
-                            || serverState.session === 'buffer'
-                            || serverState.session === 'completed'
-                        )
-                    ) {
                         this._setStatus(TaskStatus.processing)
                     }
                     if (await Promise.resolve(callback?.call(task)) || signal?.aborted) {
@@ -594,9 +601,15 @@
                         return true
                     }
                 case TaskStatus.processing:
-                    await waitUntil(async () => (serverState.task !== task.#id || serverState.session !== 'running'
+                    await waitUntil(
-                        || await Promise.resolve(callback?.call(task))
+                        async () => {
-                        || signal?.aborted),
+                            if (typeof serverState.tasks !== 'object' || serverState.tasks[String(task.#id)] !== 'running') {
+                                return true
+                            }
+                            if (await Promise.resolve(callback?.call(task)) || signal?.aborted) {
+                                return true
+                            }
+                        },
                         TASK_STATE_SERVER_UPDATE_DELAY,
                         timeout,
                     )
@@ -882,7 +895,8 @@
                 throw e
             }
             // Update class status and callback.
-            switch(serverState.session) {
+            const taskState = (typeof serverState.tasks === 'object' ? serverState.tasks[String(this.id)] : undefined)
+            switch(taskState) {
                 case 'pending': // Session has pending tasks.
                     console.error('Server %o render request %o is still waiting.', serverState, renderRequest)
                     //Only update status if not already set by waitUntil
@@ -915,7 +929,7 @@
                     return false
                 default:
                     if (!progressCallback) {
-                        const err = new Error('Unexpected server task state: ' + serverState.session || 'Undefined')
+                        const err = new Error('Unexpected server task state: ' + taskState || 'Undefined')
                         this.abort(err)
                         throw err
                     }
@@ -1065,6 +1079,14 @@
         return models
     }
 
+    function getServerCapacity() {
+        let activeDevicesCount = Object.keys(serverState?.devices?.active || {}).length
+        if (window.document.visibilityState === 'hidden') {
+            activeDevicesCount = 1 + activeDevicesCount
+        }
+        return activeDevicesCount
+    }
+
     function continueTasks() {
         if (typeof navigator?.scheduling?.isInputPending === 'function') {
             const inputPendingOptions = {
@@ -1077,13 +1099,17 @@
                 return asyncDelay(CONCURRENT_TASK_INTERVAL)
             }
         }
+        const serverCapacity = getServerCapacity()
         if (task_queue.size <= 0 && concurrent_generators.size <= 0) {
-            eventSource.fireEvent(EVENT_IDLE, {})
+            eventSource.fireEvent(EVENT_IDLE, {capacity: serverCapacity, idle: true})
             // Calling idle could result in task being added to queue.
             if (task_queue.size <= 0 && concurrent_generators.size <= 0) {
                 return asyncDelay(IDLE_COOLDOWN)
             }
         }
+        if (task_queue.size < serverCapacity) {
+            eventSource.fireEvent(EVENT_IDLE, {capacity: serverCapacity - task_queue.size})
+        }
         const completedTasks = []
         for (let [generator, promise] of concurrent_generators.entries()) {
             if (promise.isPending) {
@@ -1122,7 +1148,6 @@
             concurrent_generators.set(generator, promise)
         }
 
-        const serverCapacity = 2
         for (let [task, generator] of task_queue.entries()) {
             const cTsk = completedTasks.find((item) => item.generator === generator)
             if (cTsk?.promise?.rejectReason || task.hasFailed) {
@@ -1211,6 +1236,7 @@
         removeEventListener: (...args) => eventSource.removeEventListener(...args),
 
         isServerAvailable,
+        getServerCapacity,
 
         getSystemInfo,
         getDevices,
@@ -1228,6 +1254,14 @@
             configurable: false,
             get: () => serverState,
         },
+        isAvailable: {
+            configurable: false,
+            get: () => isServerAvailable(),
+        },
+        serverCapacity: {
+            configurable: false,
+            get: () => getServerCapacity(),
+        },
         sessionId: {
             configurable: false,
             get: () => sessionId,

ui/media/js/main.js

@@ -455,9 +455,10 @@ function makeImage() {
 }
 
 function onIdle() {
+    const serverCapacity = SD.serverCapacity
     for (const taskEntry of getUncompletedTaskEntries()) {
-        if (SD.activeTasks.size >= 1) {
+        if (SD.activeTasks.size >= serverCapacity) {
-            continue
+            break
         }
         const task = htmlTaskMap.get(taskEntry)
         if (!task) {

ui/plugins/ui/jasmineSpec.js

@@ -202,12 +202,12 @@ describe('stable-diffusion-ui', function() {
         // Wait for server status to update.
         await SD.waitUntil(() => {
             console.log('Waiting for %s to be received...', renderRequest.task)
-            return (!SD.serverState.task || SD.serverState.task === renderRequest.task)
+            return (!SD.serverState.tasks || SD.serverState.tasks[String(renderRequest.task)])
         }, 250, 10 * 60 * 1000)
         // Wait for task to start on server.
         await SD.waitUntil(() => {
             console.log('Waiting for %s to start...', renderRequest.task)
-            return SD.serverState.task !== renderRequest.task || SD.serverState.session !== 'pending'
+            return !SD.serverState.tasks || SD.serverState.tasks[String(renderRequest.task)] !== 'pending'
         }, 250)
 
         const reader = new SD.ChunkedStreamReader(renderRequest.stream)

ui/sd_internal/__init__.py

@@ -1,6 +1,7 @@
 import json
 
 class Request:
+    request_id: str = None
     session_id: str = "session"
     prompt: str = ""
     negative_prompt: str = ""

ui/sd_internal/runtime.py

@@ -523,15 +523,16 @@ def update_temp_img(req, x_samples, task_temp_images: list):
         del img, x_sample, x_sample_ddim
         # don't delete x_samples, it is used in the code that called this callback
 
-        thread_data.temp_images[str(req.session_id) + '/' + str(i)] = buf
+        thread_data.temp_images[f'{req.request_id}/{i}'] = buf
         task_temp_images[i] = buf
-        partial_images.append({'path': f'/image/tmp/{req.session_id}/{i}'})
+        partial_images.append({'path': f'/image/tmp/{req.request_id}/{i}'})
     return partial_images
 
 # Build and return the apropriate generator for do_mk_img
 def get_image_progress_generator(req, data_queue: queue.Queue, task_temp_images: list, step_callback, extra_props=None):
     if not req.stream_progress_updates:
-        def empty_callback(x_samples, i): return x_samples
+        def empty_callback(x_samples, i):
+            step_callback()
         return empty_callback
 
     thread_data.partial_x_samples = None
@@ -639,11 +640,6 @@ def do_mk_img(req: Request, data_queue: queue.Queue, task_temp_images: list, ste
         t_enc = int(req.prompt_strength * req.num_inference_steps)
         print(f"target t_enc is {t_enc} steps")
 
-    if req.save_to_disk_path is not None:
-        session_out_path = get_session_out_path(req.save_to_disk_path, req.session_id)
-    else:
-        session_out_path = None
-
     with torch.no_grad():
         for n in trange(opt_n_iter, desc="Sampling"):
             for prompts in tqdm(data, desc="data"):

ui/sd_internal/task_manager.py

@@ -37,7 +37,8 @@ class ServerStates:
 
 class RenderTask(): # Task with output queue and completion lock.
     def __init__(self, req: Request):
-        self.request: Request = req # Initial Request
+        req.request_id = id(self)
+        self.request: Request = req  # Initial Request
         self.response: Any = None # Copy of the last reponse
         self.render_device = None # Select the task affinity. (Not used to change active devices).
         self.temp_images:list = [None] * req.num_outputs * (1 if req.show_only_filtered_image else 2)
@@ -51,6 +52,22 @@ class RenderTask(): # Task with output queue and completion lock.
                 self.buffer_queue.task_done()
                 yield res
         except queue.Empty as e: yield
+    @property
+    def status(self):
+        if self.lock.locked():
+            return 'running'
+        if isinstance(self.error, StopAsyncIteration):
+            return 'stopped'
+        if self.error:
+            return 'error'
+        if not self.buffer_queue.empty():
+            return 'buffer'
+        if self.response:
+            return 'completed'
+        return 'pending'
+    @property
+    def is_pending(self):
+        return bool(not self.response and not self.error)
 
 # defaults from https://huggingface.co/blog/stable_diffusion
 class ImageRequest(BaseModel):
@@ -101,7 +118,7 @@ class FilterRequest(BaseModel):
     output_quality: int = 75
 
 # Temporary cache to allow to query tasks results for a short time after they are completed.
-class TaskCache():
+class DataCache():
     def __init__(self):
         self._base = dict()
         self._lock: threading.Lock = threading.Lock()
@@ -110,7 +127,7 @@ class TaskCache():
     def _is_expired(self, timestamp: int) -> bool:
         return int(time.time()) >= timestamp
     def clean(self) -> None:
-        if not self._lock.acquire(blocking=True, timeout=LOCK_TIMEOUT): raise Exception('TaskCache.clean' + ERR_LOCK_FAILED)
+        if not self._lock.acquire(blocking=True, timeout=LOCK_TIMEOUT): raise Exception('DataCache.clean' + ERR_LOCK_FAILED)
         try:
             # Create a list of expired keys to delete
             to_delete = []
@@ -120,16 +137,22 @@ class TaskCache():
                     to_delete.append(key)
             # Remove Items
             for key in to_delete:
+                (_, val) = self._base[key]
+                if isinstance(val, RenderTask):
+                    print(f'RenderTask {key} expired. Data removed.')
+                elif isinstance(val, SessionState):
+                    print(f'Session {key} expired. Data removed.')
+                else:
+                    print(f'Key {key} expired. Data removed.')
                 del self._base[key]
-                print(f'Session {key} expired. Data removed.')
         finally:
             self._lock.release()
     def clear(self) -> None:
-        if not self._lock.acquire(blocking=True, timeout=LOCK_TIMEOUT): raise Exception('TaskCache.clear' + ERR_LOCK_FAILED)
+        if not self._lock.acquire(blocking=True, timeout=LOCK_TIMEOUT): raise Exception('DataCache.clear' + ERR_LOCK_FAILED)
         try: self._base.clear()
         finally: self._lock.release()
     def delete(self, key: Hashable) -> bool:
-        if not self._lock.acquire(blocking=True, timeout=LOCK_TIMEOUT): raise Exception('TaskCache.delete' + ERR_LOCK_FAILED)
+        if not self._lock.acquire(blocking=True, timeout=LOCK_TIMEOUT): raise Exception('DataCache.delete' + ERR_LOCK_FAILED)
         try:
             if key not in self._base:
                 return False
@@ -138,7 +161,7 @@ class TaskCache():
         finally:
             self._lock.release()
     def keep(self, key: Hashable, ttl: int) -> bool:
-        if not self._lock.acquire(blocking=True, timeout=LOCK_TIMEOUT): raise Exception('TaskCache.keep' + ERR_LOCK_FAILED)
+        if not self._lock.acquire(blocking=True, timeout=LOCK_TIMEOUT): raise Exception('DataCache.keep' + ERR_LOCK_FAILED)
         try:
             if key in self._base:
                 _, value = self._base.get(key)
@@ -148,7 +171,7 @@ class TaskCache():
         finally:
             self._lock.release()
     def put(self, key: Hashable, value: Any, ttl: int) -> bool:
-        if not self._lock.acquire(blocking=True, timeout=LOCK_TIMEOUT): raise Exception('TaskCache.put' + ERR_LOCK_FAILED)
+        if not self._lock.acquire(blocking=True, timeout=LOCK_TIMEOUT): raise Exception('DataCache.put' + ERR_LOCK_FAILED)
         try:
             self._base[key] = (
                 self._get_ttl_time(ttl), value
@@ -162,7 +185,7 @@ class TaskCache():
         finally:
             self._lock.release()
     def tryGet(self, key: Hashable) -> Any:
-        if not self._lock.acquire(blocking=True, timeout=LOCK_TIMEOUT): raise Exception('TaskCache.tryGet' + ERR_LOCK_FAILED)
+        if not self._lock.acquire(blocking=True, timeout=LOCK_TIMEOUT): raise Exception('DataCache.tryGet' + ERR_LOCK_FAILED)
         try:
             ttl, value = self._base.get(key, (None, None))
             if ttl is not None and self._is_expired(ttl):
@@ -181,11 +204,37 @@ current_model_path = None
 current_vae_path = None
 current_hypernetwork_path = None
 tasks_queue = []
-task_cache = TaskCache()
+session_cache = DataCache()
+task_cache = DataCache()
 default_model_to_load = None
 default_vae_to_load = None
 default_hypernetwork_to_load = None
 weak_thread_data = weakref.WeakKeyDictionary()
+idle_event: threading.Event = threading.Event()
+
+class SessionState():
+    def __init__(self, id: str):
+        self._id = id
+        self._tasks_ids = []
+    @property
+    def id(self):
+        return self._id
+    @property
+    def tasks(self):
+        tasks = []
+        for task_id in self._tasks_ids:
+            task = task_cache.tryGet(task_id)
+            if task:
+                tasks.append(task)
+        return tasks
+    def put(self, task, ttl=TASK_TTL):
+        task_id = id(task)
+        self._tasks_ids.append(task_id)
+        if not task_cache.put(task_id, task, ttl):
+            return False
+        while len(self._tasks_ids) > len(render_threads) * 2:
+            self._tasks_ids.pop(0)
+        return True
 
 def preload_model(ckpt_file_path=None, vae_file_path=None, hypernetwork_file_path=None):
     global current_state, current_state_error, current_model_path, current_vae_path, current_hypernetwork_path
@@ -268,6 +317,7 @@ def thread_render(device):
         preload_model()
         current_state = ServerStates.Online
     while True:
+        session_cache.clean()
         task_cache.clean()
         if not weak_thread_data[threading.current_thread()]['alive']:
             print(f'Shutting down thread for device {runtime.thread_data.device}')
@@ -279,7 +329,8 @@ def thread_render(device):
             return
         task = thread_get_next_task()
         if task is None:
-            time.sleep(0.05)
+            idle_event.clear()
+            idle_event.wait(timeout=1)
             continue
         if task.error is not None:
             print(task.error)
@@ -314,10 +365,11 @@ def thread_render(device):
                         current_state_error = None
                         print(f'Session {task.request.session_id} sent cancel signal for task {id(task)}')
 
-                    task_cache.keep(task.request.session_id, TASK_TTL)
-
             current_state = ServerStates.Rendering
             task.response = runtime.mk_img(task.request, task.buffer_queue, task.temp_images, step_callback)
+            # Before looping back to the generator, mark cache as still alive.
+            task_cache.keep(id(task), TASK_TTL)
+            session_cache.keep(task.request.session_id, TASK_TTL)
         except Exception as e:
             task.error = e
             print(traceback.format_exc())
@@ -325,7 +377,8 @@ def thread_render(device):
         finally:
             # Task completed
             task.lock.release()
-        task_cache.keep(task.request.session_id, TASK_TTL)
+        task_cache.keep(id(task), TASK_TTL)
+        session_cache.keep(task.request.session_id, TASK_TTL)
         if isinstance(task.error, StopAsyncIteration):
             print(f'Session {task.request.session_id} task {id(task)} cancelled!')
         elif task.error is not None:
@@ -334,12 +387,21 @@ def thread_render(device):
             print(f'Session {task.request.session_id} task {id(task)} completed by {runtime.thread_data.device_name}.')
         current_state = ServerStates.Online
 
-def get_cached_task(session_id:str, update_ttl:bool=False):
+def get_cached_task(task_id:str, update_ttl:bool=False):
     # By calling keep before tryGet, wont discard if was expired.
-    if update_ttl and not task_cache.keep(session_id, TASK_TTL):
+    if update_ttl and not task_cache.keep(task_id, TASK_TTL):
         # Failed to keep task, already gone.
         return None
-    return task_cache.tryGet(session_id)
+    return task_cache.tryGet(task_id)
+
+def get_cached_session(session_id:str, update_ttl:bool=False):
+    if update_ttl:
+        session_cache.keep(session_id, TASK_TTL)
+    session = session_cache.tryGet(session_id)
+    if not session:
+        session = SessionState(session_id)
+        session_cache.put(session_id, session, TASK_TTL)
+    return session
 
 def get_devices():
     devices = {
@@ -486,14 +548,16 @@ def shutdown_event(): # Signal render thread to close on shutdown
     current_state_error = SystemExit('Application shutting down.')
 
 def render(req : ImageRequest):
-    if is_alive() <= 0: # Render thread is dead
+    current_thread_count = is_alive()
+    if current_thread_count <= 0:  # Render thread is dead
         raise ChildProcessError('Rendering thread has died.')
+
     # Alive, check if task in cache
-    task = task_cache.tryGet(req.session_id)
+    session = get_cached_session(req.session_id, update_ttl=True)
-    if task and not task.response and not task.error and not task.lock.locked():
+    pending_tasks = list(filter(lambda t: t.is_pending, session.tasks))
-        # Unstarted task pending, deny queueing more than one.
+    if current_thread_count < len(pending_tasks):
-        raise ConnectionRefusedError(f'Session {req.session_id} has an already pending task.')
+        raise ConnectionRefusedError(f'Session {req.session_id} already has {len(pending_tasks)} pending tasks out of {current_thread_count}.')
-    #
+
     from . import runtime
     r = Request()
     r.session_id = req.session_id
@@ -530,13 +594,13 @@ def render(req : ImageRequest):
         r.stream_image_progress = False
 
     new_task = RenderTask(r)
-
+    if session.put(new_task, TASK_TTL):
-    if task_cache.put(r.session_id, new_task, TASK_TTL):
         # Use twice the normal timeout for adding user requests.
-        # Tries to force task_cache.put to fail before tasks_queue.put would. 
+        # Tries to force session.put to fail before tasks_queue.put would.
         if manager_lock.acquire(blocking=True, timeout=LOCK_TIMEOUT * 2):
             try:
                 tasks_queue.append(new_task)
+                idle_event.set()
                 return new_task
             finally:
                 manager_lock.release()

ui/server.py

@@ -49,14 +49,12 @@ from fastapi.staticfiles import StaticFiles
 from starlette.responses import FileResponse, JSONResponse, StreamingResponse
 from pydantic import BaseModel
 import logging
-#import queue, threading, time
 from typing import Any, Generator, Hashable, List, Optional, Union
 
 from sd_internal import Request, Response, task_manager
 
 app = FastAPI()
 
-modifiers_cache = None
 outpath = os.path.join(os.path.expanduser("~"), OUTPUT_DIRNAME)
 
 os.makedirs(USER_UI_PLUGINS_DIR, exist_ok=True)
@@ -354,21 +352,8 @@ def ping(session_id:str=None):
     # Alive
     response = {'status': str(task_manager.current_state)}
     if session_id:
-        task = task_manager.get_cached_task(session_id, update_ttl=True)
+        session = task_manager.get_cached_session(session_id, update_ttl=True)
-        if task:
+        response['tasks'] = {id(t): t.status for t in session.tasks}
-            response['task'] = id(task)
-            if task.lock.locked():
-                response['session'] = 'running'
-            elif isinstance(task.error, StopAsyncIteration):
-                response['session'] = 'stopped'
-            elif task.error:
-                response['session'] = 'error'
-            elif not task.buffer_queue.empty():
-                response['session'] = 'buffer'
-            elif task.response:
-                response['session'] = 'completed'
-            else:
-                response['session'] = 'pending'
     response['devices'] = task_manager.get_devices()
     return JSONResponse(response, headers=NOCACHE_HEADERS)
 
@@ -408,23 +393,25 @@ def render(req : task_manager.ImageRequest):
         response = {
             'status': str(task_manager.current_state), 
             'queue': len(task_manager.tasks_queue),
-            'stream': f'/image/stream/{req.session_id}/{id(new_task)}',
+            'stream': f'/image/stream/{id(new_task)}',
             'task': id(new_task)
         }
         return JSONResponse(response, headers=NOCACHE_HEADERS)
     except ChildProcessError as e: # Render thread is dead
         raise HTTPException(status_code=500, detail=f'Rendering thread has died.') # HTTP500 Internal Server Error
-    except ConnectionRefusedError as e: # Unstarted task pending, deny queueing more than one.
+    except ConnectionRefusedError as e: # Unstarted task pending limit reached, deny queueing too many.
-        raise HTTPException(status_code=503, detail=f'Session {req.session_id} has an already pending task.') # HTTP503 Service Unavailable
+        raise HTTPException(status_code=503, detail=str(e)) # HTTP503 Service Unavailable
     except Exception as e:
+        print(e)
+        print(traceback.format_exc())
         raise HTTPException(status_code=500, detail=str(e))
 
-@app.get('/image/stream/{session_id:str}/{task_id:int}')
+@app.get('/image/stream/{task_id:int}')
-def stream(session_id:str, task_id:int):
+def stream(task_id:int):
     #TODO Move to WebSockets ??
-    task = task_manager.get_cached_task(session_id, update_ttl=True)
+    task = task_manager.get_cached_task(task_id, update_ttl=True)
-    if not task: raise HTTPException(status_code=410, detail='No request received.') # HTTP410 Gone
+    if not task: raise HTTPException(status_code=404, detail=f'Request {task_id} not found.') # HTTP404 NotFound
-    if (id(task) != task_id): raise HTTPException(status_code=409, detail=f'Wrong task id received. Expected:{id(task)}, Received:{task_id}') # HTTP409 Conflict
+    #if (id(task) != task_id): raise HTTPException(status_code=409, detail=f'Wrong task id received. Expected:{id(task)}, Received:{task_id}') # HTTP409 Conflict
     if task.buffer_queue.empty() and not task.lock.locked():
         if task.response:
             #print(f'Session {session_id} sending cached response')
@@ -434,22 +421,23 @@ def stream(session_id:str, task_id:int):
     return StreamingResponse(task.read_buffer_generator(), media_type='application/json')
 
 @app.get('/image/stop')
-def stop(session_id:str=None):
+def stop(task: int):
-    if not session_id:
+    if not task:
         if task_manager.current_state == task_manager.ServerStates.Online or task_manager.current_state == task_manager.ServerStates.Unavailable:
             raise HTTPException(status_code=409, detail='Not currently running any tasks.') # HTTP409 Conflict
         task_manager.current_state_error = StopAsyncIteration('')
         return {'OK'}
-    task = task_manager.get_cached_task(session_id, update_ttl=False)
+    task_id = task
-    if not task: raise HTTPException(status_code=404, detail=f'Session {session_id} has no active task.') # HTTP404 Not Found
+    task = task_manager.get_cached_task(task_id, update_ttl=False)
-    if isinstance(task.error, StopAsyncIteration): raise HTTPException(status_code=409, detail=f'Session {session_id} task is already stopped.') # HTTP409 Conflict
+    if not task: raise HTTPException(status_code=404, detail=f'Task {task_id} was not found.') # HTTP404 Not Found
-    task.error = StopAsyncIteration('')
+    if isinstance(task.error, StopAsyncIteration): raise HTTPException(status_code=409, detail=f'Task {task_id} is already stopped.') # HTTP409 Conflict
+    task.error = StopAsyncIteration(f'Task {task_id} stop requested.')
     return {'OK'}
 
-@app.get('/image/tmp/{session_id}/{img_id:int}')
+@app.get('/image/tmp/{task_id:int}/{img_id:int}')
-def get_image(session_id, img_id):
+def get_image(task_id: int, img_id: int):
-    task = task_manager.get_cached_task(session_id, update_ttl=True)
+    task = task_manager.get_cached_task(task_id, update_ttl=True)
-    if not task: raise HTTPException(status_code=410, detail=f'Session {session_id} has not submitted a task.') # HTTP410 Gone
+    if not task: raise HTTPException(status_code=410, detail=f'Task {task_id} could not be found.') # HTTP404 NotFound
     if not task.temp_images[img_id]: raise HTTPException(status_code=425, detail='Too Early, task data is not available yet.') # HTTP425 Too Early
     try:
         img_data = task.temp_images[img_id]