Updated Architecture (markdown)

Architecture.md

@@ -77,71 +77,3 @@ their hashes, which is great for local caching without worries about actual
 version number of given file. On the other hand, **Database** stores information 
 about human readable names, so that the files are presented in a friendly way to 
 users (teachers) in **WebApp**.
-
-## Frontend - broker communication
-
-The communication between the frontend and the workers is mediated by a broker 
-that passes jobs to workers capable of processing them. 
-
-### Assignment evaluation request
-
-The frontend must send a multipart message that contains the following frames:
-
-- The `eval` command
-- The job id (in ASCII representation -- we avoid endianness issues and also 
-  support alphabetic ids)
-- A frame for each header (e.g. `hwgroup=group_1`)
-- An URL of the archive that contains the submitted files and isoeval 
-  configuration
-- An URL where the worker should store the result of the evaluation
-
-If the broker is capable of routing the request to a worker, it responds with 
-`accept`. Otherwise (for example when the requirements specified by the headers 
-cannot be met), it responds with `reject`.
-
-Note that we will need to store the job ID and the assignment configuration 
-somewhere close to the submitted files so it's possible to check how a 
-submission was evaluated. The job ID will likely be a part of the submission's 
-path. The configuration could be linked there under some well-known name.
-
-### Notifying the frontend about evaluation progress
-
-The script that requested the evaluation will have exited by the time a worker 
-processes the request. This issue remains to be resolved.
-
-## Broker - worker communication
-
-When a worker is started, it registers itself with the broker by sending the 
-`init` command followed by its hardware group and headers that describe its 
-capabilities (such as the number of threads it can run simultaneously, 
-languages it can work with...). The headers are expected to be in following 
-format: `header_name=value`. Every header shall be in a separate frame.
-
-Whenever the broker receives an assignment suitable for the worker, it just 
-forwards the evaluation request message it originally received from the 
-frontend. The worker has to:
-
-- Download the archive containing the submission and an isoeval configuration 
-  file
-- Download any supplementary files based on the configuration file, such as test 
-  inputs or helper programs (This can be done on demand, using a `fetch` command
-  in the assignment configuration)
-- Download the source codes of the student's submission
-- Evaluate the submission according to the assignment's configuration
-- Upload the results of the evaluation to the file server
-- Notify the broker that the evaluation is finished
-
-Thanks to this message structure, it's possible to cache the configuration file 
-and only download the student's submissions when the same assignment is 
-evaluated repeatedly for different students (a common case for homeworks and 
-classroom assignments).
-
-After finishing the evaluation, worker notifies the broker of this fact by 
-sending:
-
-- The `done` command
-- The job id
-
-This allows the broker to reliably distribute messages - if a worker doesn't 
-succeed in processing a request (it doesn't respond in a time limit), the 
-request can be sent to another worker.