Added a simple route response and some testing

Draft for #14 (closed) I want to return a link for us to test through the proxy once the proxy CI building and pushing to registry is done. #13 (closed)

Other than please bring whatever design choices you have in mind. I am also using a 503 HTTP response. Will you prefer that or something else if all container 'routes' or lets say instance allocation slots are taken?

north/app/routes/instances.py

@@ -17,14 +17,61 @@
 #
 
 from typing import List
-from fastapi import APIRouter
+from fastapi import APIRouter, HTTPException, Request, Depends
+from collections import deque
+from datetime import datetime, timedelta
+import time
+import docker
+from docker import DockerClient
 
-from north.app.models import InstanceModel
+from north.app.models import InstanceModel, InstanceResponseModel, ChannelUnavailableError
+from north import config
 
 router = APIRouter()
 router_tag = 'instances'
 
 
+def get_http_date_in(minutes=1) -> str:
+    # https://httpwg.org/specs/rfc7231.html#header.date
+    return time.strftime(
+        '%a, %d %b %Y %H:%M:%S GMT',
+        (datetime.utcnow() + timedelta(minutes=minutes))
+        .timetuple())
+
+
+def get_docker_client() -> DockerClient:
+    if config.docker_url:
+        docker_client = DockerClient(base_url=config.docker_url)
+    else:
+        docker_client = docker.from_env()
+
+    return docker_client
+
+
+# Placeholder code for something that retains information of what container channel are available
+# Todo: Add channel number tag to the docker container created and use that as a store
+available_channel = deque(['0', '1', '2', '3'])
+
+
+def get_available_channel() -> str:
+    try:
+        channel = available_channel.popleft()
+        return channel
+    except IndexError as channel_unavailable:
+        raise HTTPException(
+            status_code=503,
+            detail="channel are currently occupied.",
+            headers={"Retry-After": get_http_date_in()}
+        ) from channel_unavailable
+
+
+# temp current_user placeholder. I want to use the user id as
+# a tag to filter out containers. Docker is source of truth.
+# Todo: Implement in the JWT issue and change the return from str to BaseModel
+async def get_current_active_user():
+    return 'test'
+
+
 @router.get(
     '/',
     tags=[router_tag],
@@ -39,9 +86,44 @@ async def get_instances():
 @router.post(
     '/',
     tags=[router_tag],
-    response_model=InstanceModel,
+    response_model=InstanceResponseModel,
     response_model_exclude_unset=True,
-    response_model_exclude_none=True)
-async def post_instances(instance: InstanceModel):
+    response_model_exclude_none=True,
+    responses={
+        200: {
+            "description": "Returns the path to the launched instance",
+            "content": {
+                "application/json": {
+                    "example": {"path": "/container/0/"}
+                }
+            }
+        },
+        503: {"model": ChannelUnavailableError, "description": "Raises a 503 HTTP error when channels are unavailable"}
+    })
+async def post_instances(request: Request, instance: InstanceModel, current_user: str = Depends(get_current_active_user)):
     ''' Create a new tool instance. '''
-    return instance
+    channel = get_available_channel()
+    path = f'{request.scope.get("root_path")}/container/{channel}/'
+    container_name = f'{config.docker_name_prefix}-{current_user}-{instance.name}'
+
+    docker_client = get_docker_client()
+
+    # Does the user have this service running - Todo: Move to a nice class that handles this in simple funcs
+    docker_name_prefix_filter = dict(filters=dict(name=container_name))
+    current_containers = docker_client.containers.list(**docker_name_prefix_filter)
+    if len(current_containers) != 0:
+        path = current_containers[0].labels['path']
+        return InstanceResponseModel(path=path)
+
+    docker_client.containers.run(
+        image="jupyter/datascience-notebook",
+        command=f'start-notebook.sh --NotebookApp.base_url={path}',
+        ports={"8888": int(f'1000{channel}')},
+        detach=True,
+        name=container_name,
+        user="1000:1000",
+        group_add=["1000"],
+        labels={"path": path}
+    )
+
+    return InstanceResponseModel(path=path)