job variables

Rewritten-docs.md

@@ -678,11 +678,11 @@ At this point we have worker with two internal parts listening one and execution
 
 Another division of tasks is by task-type field in configuration. This field can have four values: initiation, execution, evaluation and inner. All was discussed and described above in configuration analysis. What is important to worker is how to behave if execution of task with some particular type fails. There are two possible situations execution fails due to bad user solution or due to some internal error. If execution fails on internal error solution cannot be declared overally as failed. User should not be punished for bad configuration or some network error. This is where task types are usefull. Generally initiation, execution and evaluation are tasks which are somehow executing code which was given by users who submitted solution of exercise. If this kinds of tasks fail it is probably connected with bad user solution and can be evaluated. But if some inner task fails solution should be re-executed, in best case scenario on different worker. That is why if inner task fails it is sent back to broker which will reassign job to another worker. More on this subject should be discussed in broker assigning algorithms section.
 
-There is also question about working directory or directories of job, which directories should be used and what for. There is one simple answer on this every job will have only one specified directory which will contain every file with which worker will work in the scope of whole job execution. This is of course nonsense there has to be some logical division. The least which must be done are two folders one for internal temporary files and second one for evaluation. The directory for temporary files is enough to comprehend all kind of internal work with filesystem but only one directory for whole evaluation is somehow not enough. Users solutions are downloaded in form of zip archives so why these should be present during execution or why the results and files which should be uploaded back to fileserver should be cherry picked from the one big directory? The answer is of course another logical division into subfolders. The solution which was chosen at the end is to have folders for downloaded archive, decompressed solution, evaluation directory in which user solution is executed and then folders for temporary files and for results and generally files which should be uploaded back to fileserver with solution results. This division proved to be flexible and detailed enough, everything is in logical units and where it is supposed to be which means that searching through this system should be easy. In addition solutions of users do not have access to unnecessary files which is better for overall security of whole ReCodEx.
+There is also question about working directory or directories of job, which directories should be used and what for. There is one simple answer on this every job will have only one specified directory which will contain every file with which worker will work in the scope of whole job execution. This is of course nonsense there has to be some logical division. The least which must be done are two folders one for internal temporary files and second one for evaluation. The directory for temporary files is enough to comprehend all kind of internal work with filesystem but only one directory for whole evaluation is somehow not enough. Users solutions are downloaded in form of zip archives so why these should be present during execution or why the results and files which should be uploaded back to fileserver should be cherry picked from the one big directory? The answer is of course another logical division into subfolders. The solution which was chosen at the end is to have folders for downloaded archive, decompressed solution, evaluation directory in which user solution is executed and then folders for temporary files and for results and generally files which should be uploaded back to fileserver with solution results. Of course there has to be hierarchy which separate folders from different workers on the same machines. That is why paths to directories are in format: ${DEFAULT}/${FOLDER}/${WORKER_ID}/${JOB_ID} where default means default working directory of whole worker, folder is particular directory for some purpose (archives, evaluation...). Mentioned division of job directories proved to be flexible and detailed enough, everything is in logical units and where it is supposed to be which means that searching through this system should be easy. In addition if solutions of users have access only to evaluation directory then they do not have access to unnecessary files which is better for overall security of whole ReCodEx.
 
-@todo: maybe describe folders within execution and what they can be used for?
+As we discovered above worker has job directories but users who are writing and managing job configurations do not know where they are (on some particular worker) and how they can be accessed and written into configuration. For this kind of task we have to introduce some kind of marks or signs which will represent particular folders. Marks or signs can have form of some kind of special strings which can be called variables. These variables then can be used everywhere where filesystems paths are used within configuration file. This will solve problem with specific worker environment and specific hierarchy of directories. Final form of variables is ${...} where triple dot is textual description. This format was used because of special dolar sign character which cannot be used within filesystem path, braces are there only to border textual description of variable.
 
-@todo: how to solve problem with specific worker environment, mention internal job variables
+#### Evaluation
 
 After successful arrival of job, worker has to prepare new execution environment, then solution archive has to be downloaded from fileserver and extracted. Job configuration is located within these files and loaded into internal structures and executed. After that results are uploaded back to fileserver. These steps are the basic ones which are really necessary for whole execution and have to be executed in this precise order.