Single-job submission: implementation notes

BOINC's single-job submission system is a streamlined way to run a single job remotely. It's implemented by:

html/ops/single_job_setup, a script which configures a project to handle single-job submission;
tools/boinc_submit, which submits a job.
single_job_assimilator, an assimilator for single jobs.

The mechanism is implemented as follows:

Single jobs for a given platform use the application single_job_PLATFORM.
App versions for this app run the wrapper program.

single_job_setup does the following:

Check that the wrapper has been compiled (i.e. boinc/samples/wrapper/wrapper exists).
Add the application single_job_PLATFORM to the DB if needed.
Create a project/apps/single_job_PLATFORM directory if needed.
Scan through the subdirectories of this, looking for the highest version number.
If there are no subdirectories, or if the application in the highest-version subdirectory isn't current, create a new subdirectory and copy the wrapper app to it.
Print instructions for running update_versions if needed, and/or adding <daemon> entries to config file.

NOTE: single_job_setup is hardwired with the i686-pc-linux-gnu platform (i.e. Linux on Intel32). If you want to use other platforms, edit the script.

boinc_submit does the following:

Check that the project has been configured to do single jobs for the given platform.
Create a WU record for the job.
Make a job.xml file for this job. This has the physical name sj_WUID.xml, where WUID is the ID of the workunit.
Make a "job directory file", sj_WUID, in the upload directory hierarchy. This contains the directory from which boinc_submit was run, so that the assimilator can put output files there.
Create WU and result template files (sj_wu_template_WUID and sj_result_template_WUID). The input files include the job.xml file and the program executable. The executable is declared as sticky. Its name (logical and physical) is program_PLATFORM_CKSUM, where CKSUM is the first 8 characters of the file's MD5.
Copy input files and the executable to the download hierarchy. The physical name of input files is name_WUID.
Invoke create_work to finish creating the job. Pass a --wu_id flag to tell create_work not to create a new workunit.

single_job_assimilator does the following:

Read the job directory file.
For each output file, look up its logical name in the result's xml_doc_in. Then copy the output file to the job directory, using the logical name.

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