recodex-wiki/Job-configuration.md

Job configuration

Following description will cover configuration as seen from the API point of view, worker may have some optional items mandatory (they are filled by API automatically). Bold items in lists describing the values are mandatory, italic ones are optional.

Variables

Because the frontend does not know which worker gets the job, its necessary to be a little general in a configuration file. This means that some worker specific things has to be transparent. Good example of this is that some (evaluation) directories may be placed differently across all workers. To provide a solution, variables are established. There are some restrictions where variables can be used, basically whenever filesystem paths can be used.

Usage of variables in the configuration is simple and kind of shell-like. Name of a variable is put inside braces which are preceded with dollar sign. Real usage is then something like this: ${VAR}. There should be no quotes or apostrophes around variable name, just simple text in braces. Parsing is simple and whenever there is dollar sign with braces job execution unit automatically assumes that this is a variable, so there is no chance to have this kind of substring anywhere else.

List of usable variables in a job configuration:

• WORKER_ID -- integral identification of worker, unique on a server
• JOB_ID -- identification of this job
• SOURCE_DIR -- directory where source codes of the job are stored
• EVAL_DIR -- evaluation directory which points inside the sandbox and is automatically bound there
• RESULT_DIR -- results from the job can be copied here, but only with internal copy task
• TEMP_DIR -- general temporary directory which is not dependent on operating system
• JUDGES_DIR -- directory in which judges are stored (outside sandbox)

Tasks

Task is an atomic piece of work executed by worker. There are two basic types of tasks:

• Execute external process (optionally inside isolate). External processes are meant for compilation, testing, or execution of judges. Linux default is mandatory usage of isolate sandbox, this option is present because of Windows, where is currently no sandbox available.
• Perform internal operation. Internal operations comprise commands, which are typically related to file/directory maintenance and other evaluation management stuff. Few important examples:
  • Create/delete/move/rename file/directory
  • (un)zip/tar/gzip/bzip file(s)
  • fetch a file from the file repository (either from worker cache or download it by HTTP GET).

Even though the internal operations may be handled by external executables (mv, tar, pkzip, wget, ...), it might be better to keep them inside the worker as it would simplify these operations and their portability among platforms. Furthermore, it is quite easy to implement them using common libraries (e.g., zlib, curl).

A task may be marked as essential; in such case, failure will immediately cause termination of the whole job. Nice example usage is task with program compilation. Without success it is obvious, that the job is broken and every test will fail anyway.

Internal tasks

• Archivate task can be used for packing and compressing a directory. Calling command is archivate. Requires two arguments:
  • path and name of the directory to be archived
  • path and name of the target archive. Only .zip format is supported.
• Extract task is opposite to archivate task. It can extract different types of archives. Supported formats are the same as supports libarchive library (see libarchive wiki), mainly zip, tar, tar.gz, tar.bz2 and 7zip. Please note, that system administrator may not install all needed packages, so some formats may not be accessible. Please, consult your system administrator for more information. Archives could contain only regular files or directories (no symlinks, block and character devices sockets or pipes allowed). Calling command is extract and requires two arguments:
  • path and name of the archive to extract
  • directory, where the archive will be extracted
• Fetch task will get a file. It can be downloaded from remote fileserver or just copied from local cache if available. Calling command is fetch with two arguments:
  • name of the requested file without path (file sources are set up in worker configuration file)
  • path and name on the destination. Providing a different destination name can be used for easy rename.
• Copy task can copy files and directories. Detailed info can be found on reference page of boost::filesystem::copy. Calling command is cp and require two arguments:
  • path and name of source target
  • path and name of destination target
• Make directory task can create arbitrary number of directories. Calling command is mkdir and requires at least one argument. For each provided argument will be called boost::filesystem::create_directories command.
• Rename task will rename files and directories. Detailed bahavior can be found on reference page of boost::filesystem::rename. Calling command is rename and require two arguments:
  • path and name of source target
  • path and name of destination target
• Remove task is for deleting files and directories. Calling command is rm and require at least one argument. For each provided one will be called boost::filesystem::remove_all command.
• Dumpdir task copies a directory (usually a test directory, for debugging purposes) recursively, with a limit on the total size of the destination directory. Files that do not fit into the limit are skipped and placeholders (with names like original_file_name.skipped) are created.
• Truncate task cuts off data from the end of a file so that it fits a limit supplied as an argument. This is done in place, using boost::filesystem::resize_file.
• Exists task is simple task which checks if given paths exists. Arbitrary number of arguments can be given and all of them are going to be checked on existance.

External tasks

External tasks are arbitrary executables, typically ran inside isolate (with given parameters) and the worker waits until they finish. The exit code determines, whether the task succeeded (0) or failed (anything else).

There are several additional options:

• stdin -- task can be configured to read from existing file or from /dev/null.
• stdout and stderr -- task output can be individually redirected to a file or discarded. If this output options are specified, than it is possible to upload output files with results by copying them into result directory.
• limits -- task has time and memory limits; if these limits are exceeded, the task is failed.

The task results (exit code, time, and memory consumption, etc.) are saved into result yaml file and sent back to the frontend application to address which was specified on the initiation of job evaluation.

Judges

Judges are treated as normal external commands, so there is no special task type for them. Binaries are installed alongside with worker executable in standard directories (on both Linux and Windows systems).

All packed judges are adopted from old CodEx with only very small modifications. ReCodEx judges base directory is in ${JUDGES_DIR} variable, which can be used in the job config file.

• recodex-judge-normal is a base judge used by most of the exercises. This judge compares two text files. It compares only text tokens regardless on amount of whitespaces between them.

  Usage: recodex-judge-normal [-r | -n | -rn] <file1> <file2>
  

  • file1 and file2 are paths to files that will be compared
  • switch options -r and -n can be specified as optional arguments.
    • -n judge will treat newlines as ordinary whitespace (it will ignore line breaking)
    • -r judge will treat tokens as real numbers and compares them accordingly (with some amount of error)

• recodex-judge-shuffle is for judging results with semantics of a set, where ordering is not important. Two files are compared with no regards for whitespace (whitespace acts just like token delimiter).

  Usage: recodex-judge-shuffle [-[n][i][r]] <file1> <file2>
  

  • -n ignore newlines (newline is considered only a whitespace)
  • -i ignore items order on the row (tokens on each row may be permuted)
  • -r ignore order of rows (rows may be permuted); this option has no effect when -n is used

Configuration items

• submission -- general information about this particular submission
  • job-id -- textual ID which should be unique in whole recodex
  • file-collector -- URL address from which fetch tasks will download data (API will fill)
  • log -- default is false, can be omitted, determines whether job execution will be logged into one shared log file
  • hw-groups -- a list of hardware groups for which there are limits specified in this configuration
• tasks -- list (not map) of individual tasks
  • task-id -- unique identifier of the task in scope of one submission
  • priority -- higher number, higher priority, defaults to 1
  • fatal-failure -- if true, than execution of whole job will be stopped after failing of this one, defaults to false
  • dependencies -- list of dependencies which have to be fulfilled before this task, can be omitted if there is no dependencies; YAML list of values
  • cmd -- description of command which will be executed
    • bin -- the binary itself (absolute path of external command or name of internal task, job variables can be used)
    • args -- list of arguments which will be sent into execution unit
  • test-id -- ID of the test this task is part of -- must be specified for tasks which the particular test's result depends on
  • type -- type of the task, can be omitted, default value is inner -- possible values are: inner, initiation, execution, evaluation. Each logical test must contain 0 or more initiation tasks, at least one task of type execution (time and memory limits exceeded are presented to user) and exactly one of type evaluation (typicaly judge). Inner task type is mainly for internal tasks, but can be used for external tasks, which are not part of any test.
  • sandbox -- wrapper for external tasks which will run in sandbox, if defined task is automatically external
    • name -- name of used sandbox
    • stdin -- file to which standard input will be redirected, can be omitted; job variables can be used, usually ${EVAL_DIR}, has to be accessible inside sandbox
    • stdout -- file to which standard output will be redirected, can be omitted; job variables can be used, usually ${EVAL_DIR}, has to be accessible inside sandbox
    • stderr -- file to which error output will be redirected, can be omitted; job variables can be used, usually ${EVAL_DIR}, has to be accessible inside sandbox
    • output -- true/false, if true then output from stdout and stderr (in that order) will be written in result.yaml, limitation on length defined in worker configuration
    • chdir -- this will be working directory of executed application
    • working-directory -- directory outside sandbox relative to the sources directory which will be used as the one bound to the default sandbox evaluation directory
    • limits -- list of limits which can be passed to sandbox, can be omitted, in that case defaults will be used
      • hw-group-id -- determines specific limits for specific machines
      • time -- time of execution in second
      • wall-time -- wall time in seconds
      • extra-time -- extra time which will be added to execution
      • stack-size -- size of stack of executed program in kilobytes
      • memory -- overall memory limit for application in kilobytes
      • extra-memory -- memory limit which will be added to overall one, in kilobytes
      • parallel -- integral number of processes which can run simultaneously, time and memory limits are merged from all potential processes/threads, 0 for unlimited
      • disk-size -- size of all IO operations from/to files in kilobytes
      • disk-files -- number of files which can be opened
      • environ-variable -- wrapper for map of environmental variables, union with default worker configuration
      • bound-directories -- list of structures representing directories which will be visible inside sandbox, union with default worker configuration. Contains 3 suboptions: src -- source pointing to actual system directory (absolute path), dst -- destination inside sandbox which can have its own filesystem binding (absolute path inside sandboxed directory structure) and mode -- determines connection mode of specified directory, one of values: RW (allow read-write access), NOEXEC (disallow execution of binaries), FS (mount device-less filesystem like /proc), MAYBE (silently ignore the rule if the bound directory does not exist), DEV (allow access to character and block devices).

Configuration example

This configuration example serves only for demonstration purposes. Some items can be omitted and defaults from worker configuration will be used.

---
submission:  # happy hippoes fence
    job-id: hippoes
    file-collector: http://localhost:9999/exercises
    log: true
    hw-groups:
        - group1
tasks:
    - task-id: "compilation"
      priority: 2
      fatal-failure: true
      cmd:
          bin: "/usr/bin/gcc"
          args:
              - "solution.c"
              - "-o"
              - "a.out"
      sandbox:
          name: "isolate"
          limits:
              - hw-group-id: group1
                parallel: 0
    - task-id: "fetch_test_1"
      priority: 4
      fatal-failure: false
      dependencies:
          - compilation
      cmd:
          bin: "fetch"
          args:
              - "1.in"
              - "${SOURCE_DIR}/kuly.in"
    - task-id: "evaluation_test_1"
      priority: 5
      fatal-failure: false
      dependencies:
          - fetch_test_1
      cmd:
          bin: "a.out"
      sandbox:
          name: "isolate"
          limits:
              - hw-group-id: group1
                time: 0.5
                memory: 8192
    - task-id: "fetch_test_solution_1"
      priority: 6
      fatal-failure: false
      dependencies:
          - evaluation_test_1
      cmd:
          bin: "fetch"
          args:
              - "1.out"
              - "${SOURCE_DIR}/1.out"
    - task-id: "judging_test_1"
      priority: 7
      fatal-failure: false
      dependencies:
          - fetch_test_solution_1
      cmd:
          bin: "${JUDGES_DIR}/recodex-judge-normal"
          args:
              - "1.out"
              - "plot.out"
      sandbox:
          name: "isolate"
          limits:
              - hw-group-id: group1
                parallel: 0
    - task-id: "rm_junk_test_1"
      priority: 8
      fatal-failure: false
      dependencies:
          - judging_test_1
      cmd:
          bin: "rm"
          args:
              - "${SOURCE_DIR}/kuly.in"
              - "${SOURCE_DIR}/plot.out"
              - "${SOURCE_DIR}/1.out"
...

Results

Results of tasks are sent back as YAML file in compressed results archive. This archive can contain additional files, such as job logging information and files which were explicitly copied into results directory. Results file contains job identification and results of individual tasks.

Results items

• job-id -- identification of the job
• hw-group -- hardware group identifier of worker which performed the evaluation
• error_message -- present only if whole execution failed and none of tasks were executed
• results -- list of tasks results
  • task-id -- unique identification of a task in scope of this job
  • status -- three states: OK (execution of task was successful; sandboxed program could be killed, but sandbox exited normally), FAILED (error while executing task), SKIPPED (execution of task was skipped)
  • error_message -- defined only in internal tasks on failure
  • output -- output from stdout and stderr of sandboxed program, limitation on length defined in worker configuration
    • stdout -- Output from standard output
    • stderr -- Output from standard error output
  • sandbox_results -- if defined than this task was external and was run in sandbox
    • exitcode -- exit code integer
    • time -- time in which program exited in seconds
    • wall-time -- wall time in seconds
    • memory -- how much memory program used in kilobytes
    • max-rss -- maximum resident set size used in kilobytes (see manual page of isolate)
    • status -- two letter status code: OK (success), RE (runtime error), SG (program died on signal), TO (timed out), XX (internal error of the sandbox)
    • exitsig -- description of exit signal
    • killed -- boolean determining if program exited correctly or was killed
    • message -- status message on failure

Results example

---
job-id: 5
hw-group: "group1"
results:
	- task-id: compile1
	  status: OK
	  sandbox_results:
		  exitcode: 0
		  time: 5
		  wall-time: 5
		  memory: 50000
		  max-rss: 50000
		  status: RE
		  exitsig: 1
		  killed: true
		  message: "Time limit exceeded"
	- task-id: eval1
	  status: FAILED
	  error_message: "Task failed, something very bad happend!"
	  .
	  .
	  .
...

Writing Job Configuration

To run and evaluate an exercise the backend needs to know the steps how to do that. This is different for each environment (operation system, programming language, etc.), so each of the environments needs to have separate configuration.

Backend works with a powerful, but quite low level description of simple connected tasks written in YAML syntax. More about the syntax and general task overview can be found on separate page. One of the planned features was user friendly configuration editor, but due to tight deadline and team composition it did not make it to the first release. However, writing configuration in the basic format will be always available and allows users to use the full expressive power of the system.

This section walks through creation of job configuration for hello world exercise. The goal is to compile file source.c and check if it prints Hello World! to the standard output. This is the only test case named A.

The problem can be split into several tasks:

• compile source.c into helloworld with /usr/bin/gcc
• run helloworld and save standard output into out.txt
• fetch predefined output (suppose it is already uploaded to fileserver) with hash a0b65939670bc2c010f4d5d6a0b3e4e4590fb92b to reference.txt
• compare out.txt and reference.txt by /usr/bin/diff

The absolute path of tools can be obtained from system administrator. However, /usr/bin/gcc is location, where the GCC binary is available almost everywhere, so location of some tools can be (professionally) guessed.

First, write header of the job to the configuration file.

submission:
    job-id: hello-word-job
    hw-groups:
        - group1

Basically it means, that the job hello-world-job needs to be run on workers that belong to the group_1 hardware group . Reference files are downloaded from the default location configured in API (such as http://localhost:9999/exercises) if not stated explicitly otherwise. Job execution log will not be saved to result archive.

Next the tasks have to be constructed under tasks section. In this demo job, every task depends only on previous one. The first task has input file source.c (if submitted by user) already available in working directory, so just call the GCC. Compilation is run in sandbox as any other external program and should have relaxed time and memory limits. In this scenario, worker defaults are used. If compilation fails, the whole job is immediately terminated (because the fatal-failure bit is set). Because bound-directories option in sandbox limits section is mostly shared between all tasks, it can be set in worker configuration instead of job configuration (suppose this for following tasks). For configuration of workers please contact your administrator.

Please note that working directory inside sandbox is automatically bounded to the directory with fetched user source codes and therefore you do not have to bound it by yourself. Also note that directories inside sandbox can be bound to different paths, so inside sandbox you have to use special paths. For working directory inside sandbox you can use ${EVAL_DIR} variable.

- task-id: "compilation"
  type: "initiation"
  fatal-failure: true
  cmd:
      bin: "/usr/bin/gcc"
      args:
          - "source.c"
          - "-o"
          - "helloworld"
  sandbox:
      name: "isolate"
      limits:
          - hw-group-id: group1

The compiled program is executed with time and memory limit set and the standard output is redirected to a file. This task depends on compilation task, because the program cannot be executed without being compiled first. It is important to mark this task with execution type, so exceeded limits will be reported in frontend.

Time and memory limits set directly for a task have higher priority than worker defaults. One important constraint is, that these limits cannot exceed limits set by workers. Worker defaults are present as a safety measure so that a malformed job configuration cannot block the worker forever. Worker default limits should be reasonably high, like a gigabyte of memory and several hours of execution time. For exact numbers please contact your administrator.

It is important to know that if the output of a program (both standard and error) is redirected to a file, the sandbox disk quotas apply to that file, as well as the files created directly by the program. In case the outputs are ignored, they are redirected to /dev/null, which means there is no limit on the output length (as long as the printing fits in the time limit).

- task-id: "execution_1"
  test-id: "A"
  type: "execution"
  dependencies:
      - compilation
  cmd:
      bin: "helloworld"
  sandbox:
      name: "isolate"
      stdout: ${EVAL_DIR}/out.txt
      limits:
          - hw-group-id: group1
            time: 0.5
            memory: 8192

Fetch sample solution from file server. Base URL of file server is in the header of the job configuration, so only the name of required file (its sha1sum in our case) is necessary.

- task-id: "fetch_solution_1"
  test-id: "A"
  dependencies:
      - execution
  cmd:
      bin: "fetch"
      args:
          - "a0b65939670bc2c010f4d5d6a0b3e4e4590fb92b"
          - "${SOURCE_DIR}/reference.txt"

Comparison of results is quite straightforward. It is important to set the task type to evaluation, so that the return code is set to 0 if the program is correct and 1 otherwise. We do not set our own limits, so the default limits are used.

- task-id: "judge_1"
  test-id: "A"
  type: "evaluation"
  dependencies:
      - fetch_solution_1
  cmd:
      bin: "/usr/bin/diff"
      args:
          - "out.txt"
          - "reference.txt"
  sandbox:
      name: "isolate"
      limits:
          - hw-group-id: group1