fix(rest): download unknown cid

Downloading a CID that is unknown to the network would wait for the blockexchange to try to get the data. However, a subsequent API call, eg upload for that CID, or a blockexchange timeout would cause the dagger node to crash, due to an attempt to complete a future that had already been completed.

We were able to narrow this down to an attempt to call  `resp.finish()` when the download block had already returned an `RestApiResponse` (and never sent any chunks to the response from the libp2p stream).

Change the HTTP response code for an unknown cid from 400 to 404.

Fix spelling mistake “cunk”.

Co-authored-by: Michael Bradley <michaelsbradleyjr@gmail.com>

dagger/rest/api.nim

@@ -111,7 +111,7 @@ proc initRestApi*(node: DaggerNodeRef): RestRouter =
         if (
             let retr = await node.retrieve(stream, id.get());
             retr.isErr):
-            return RestApiResponse.error(Http400, retr.error.msg)
+            return RestApiResponse.error(Http404, retr.error.msg)
 
         await resp.prepareChunked()
         while not stream.atEof:
@@ -124,15 +124,15 @@ proc initRestApi*(node: DaggerNodeRef): RestRouter =
             break
 
           bytes += buff.len
-          trace "Sending cunk", size = buff.len
+          trace "Sending chunk", size = buff.len
           await resp.sendChunk(addr buff[0], buff.len)
+        await resp.finish()
       except CatchableError as exc:
         trace "Excepting streaming blocks", exc = exc.msg
         return RestApiResponse.error(Http500)
       finally:
         trace "Sent bytes", cid = id.get(), bytes
         await stream.close()
-        await resp.finish()
 
   router.rawApi(
     MethodPost,