Reference: JDL (Job Description Language)

Syntax

• The JDL syntax consists on statements ended by a semicolon, like:

  attribute = value;
  

• The JDL is sensitive to blank characters and tabs. No blank characters or tabs should follow the semicolon at the end of a line.

• Literal strings (for values) are enclosed in double quotes.

  If a string itself contains double quotes, they must be escaped with a backslash (e.g.: Arguments = "\"hello\" 10").

  For special characters, such as &, the shell on the WN will itself expect the escaped form: \&, and therefore both the slash and the ampersand will have to be escaped inside the JDL file, resulting in: \\\&.

  In general, special characters such as &, |, >, < are only allowed if specified inside a quoted string or preceded by triple \. The character ' (single quote) cannot be specified in the JDL.

• Comments must be preceded by a sharp character (#) or have to follow the C++ syntax, i.e a double slash (//) at the beginning of each line or statements begun/ended respectively with /* and */ .

Attributes

Additional Notes of Selected Attributes

• InputSandbox
  • Wildcards allowed.
  • Files are relative to current directory.
  • The executable flag is not preserved for the files included in the Input Sandbox when transferred to the WN. Therefore, for any file needing execution permissions a chmod +x operation should be performed by the initial script specified as the Executable in the JDL file (the chmod +x operation is done automatically for this script).
  • The InputSandbox cannot contain two files with the same name (even if in different paths) as when transferred they would overwrite each other.

• OutputSandbox
  • No absolute file names
  • The OutputSandbox cannot contain two files with the same name (even if in different paths) as when transferred they would overwrite each other.

• Requirements The Requirements attribute can be used to express any kind of constraint on the resources where the job can run. Its value is a Boolean expression that must evaluate to true for a job to run on that specific CE.

  • Forming expressions

    To force a job to only run on a particular CE:-

    Requirements = other.GlueCEName == "minosL";
    

    where the other. prefix is used to indicate that the GlueCEName attribute refers to the CE characteristics and not to those of the job. If other. is not specified, then the default self. is assumed, indicating that the attribute refers to the job characteristics description.

    Requirements can be ANDed together:-

    Requirements =  other.GlueCEName == "minosL" && other.GlueCEInfoTotalCPUs > 1;
    

    which ANDs in the requirement that there are at least 2 CPUs on the machine.

    By default the system always ANDs in other requirement:-

    Requirements = other.GlueCEStateStatus == "Production" ;
    

    A requirement can be negated:-

    Requirements =  (!other.GlueCEInfoTotalCPUs < 10);
    

  • Functions

    • Member

      One essential requirement for production work is that the machine has the appropriate software installed. The attribute we need to test in this case is GlueHostApplicationSoftwareRunTimeEnvironment but there is a complication (apart from the length of the name!): it is a list and all we require is that our software is on the list. This is done with

      Requirements = Member("VO-minos-minossoft-R1.21-build_1",other.GlueCEInfoTotalCPUs);
      

      The Member function is satisfied if the first argument(a scalar value) is a member of its second argument (a list).

    • RegExp

      Another function RegExp can be used to see if a supplied matches as as regular expression, for example

      Requirements = RegExp("cern.ch", other.GlueCEUniqueId);
      

      i.e. GlueCEUniqueId contains "cern.ch".

  • Gangmatching

    The previous requirements affected always two entities: the job and the CE. In order to specify requirements involving three entities (i.e., the job, the CE and a SE), the RB uses a special match-making mechanism, called gangmatching. This is supported by some JDL functions: anyMatch, whichMatch, allMatch. For example to ensure that the job runs on a CE with,, at least 200 MB of free disk space on a close SE, the following JDL expression can be used:-

    Requirements = anyMatch(other.storage.CloseSEs,target.GlueSAStateAvailableSpace > 204800);
    

• Rank The choice of the CE where to execute the job, among all the ones satisfying the requirements, is based on the rank of the CE; namely, a quantity expressed as a floating-point number. The CE with the highest rank is the one selected.

  The user can define the rank with the Rank attribute as a function of the CE attributes. The default definition takes into account the number of CPUs in the CPU that are free:

  Rank = other.GlueCEStateFreeCPUs;
  

  But other definitions are possible. The next one is a more complex expression:

  Rank = ( other.GlueCEStateWaitingJobs == 0 ? other.GlueCEStateFreeCPUs :
  -other.GlueCEStateWaitingJobs);
  

  In this case, the number of waiting jobs in a CE is used if this number is not null. The minus sign is used so that the rank decreases as the number of waiting jobs gets higher. If there are not waiting jobs, then the number of free CPUs is used.

This section has been plundered from @ gLite 3 User Guide / 6.2 Job Description Language