= Legacy applications = A 'legacy application' is one which doesn't use the BOINC API (for example, because the source code is not available). Such applications can be run under BOINC using a '''wrapper''' program supplied by BOINC. The wrapper runs legacy applications as subprocesses, and handles all communication with the core client (e.g., to report CPU time and fraction done). [[Image(http://boinc.berkeley.edu/wrapper.png)]] The '''wrapper''' program is in [ExampleApps boinc_samples]. It reads a file with [BoincFiles logical name] 'job.xml'. This file has the format: {{{ worker [ stdin_file ] [ stdout_file ] [ stderr_file ] [ --foo bar ] [ X ] [ filename ] [ ... ] }}} The job file describes a sequence of tasks. The descriptor for each task includes: '''application''':: The logical name of the application, or 'worker program'. '''stdin_filename''', '''stdout_filename''', '''stderr_filename''':: The logical names of the files to which stdin, stdout, and stderr are to be connected (if any). '''command_line''':: command-line arguments to be passed to the worker program. '''wrapper''' itself may be passed command-line arguments (specified in the [ WorkGeneration#templates input template); these are passed to each worker program after those specified in the job file. '''weight''':: the contribution of each task to the overall fraction done is proportional to its weight (floating-point, default 1). For example, if your job has tasks A and B, and A uses 100 times more CPU time than B, set A.weight=100 and B.weight=1. '''checkpoint_filename''':: the name of the checkpoint file used by the app, if any. When this is modified, the wrapper assumes that a checkpoint has been completed and notifies the core client. The job file can specify multiple tasks. This is useful for two purposes: * To handle jobs that involve multiple steps (e.g., pre-processing and post-processing). * To break a long job up into smaller pieces. This provides a form of checkpointing: ''wrapper'' does checkpointing at the task level, so that lost CPU time is limited even if the legacy applications themselves are not restartable. Notes: * Normally the job file is part of the application version (it's the same between workunits). Alternatively, it can be part of the workunit (e.g. if its command line elements differ between workunits). This requires that you use the same worker program logical names for all platforms. * Files opened directly by a worker program must have the tag. This requires version 5.5 or higher of the BOINC core client (you can specify this limit at either the [AppVersion application] or [ProjectOptions#Clientcontrol project] level. * Worker programs must exit with zero status; nonzero values are interpreted as errors by the wrapper. * If you run '''wrapper''' in standalone mode (while debugging), you must provide input files with the proper logical, not physical, names. == Physical file management == You can use the wrapper together with [PhysicalFileManagement physical file management], where you directly access files in your project directory. For example, you could create a job whose first task unpacks a zip file into the project directory, and whose subsequent tasks access these files. The support for this is: * If a worker program name begins with "$PROJECT_DIR", that substring is replaced with the project directory, and the name is treated as a physical name. * In task command lines, "$PROJECT_DIR" is replaced with the project directory. == Example == Here's an example that shows how to use the legacy application mechanism. We assume that you have already [MakeProject created a project] with root directory PROJECT/. * Compile the program 'worker' from the [ExampleApps boinc_samples] tree, producing (say) 'worker_5.10_windows_intelx86.exe'. This is the legacy app. It reads from stdin and writes to stdout; it also opens and reads a file 'in', and opens and writes a file 'out'. It takes one command-line argument: the number of CPU seconds to use. * Compile the program 'wrapper' from the [ExampleApps boinc_samples] tree, producing (say) 'wrapper_5.10_windows_intelx86.exe'. * [AppVersion Create an application] named 'worker' and a corresponding directory 'PROJECT/apps/worker'. In this directory, create a directory 'wrapper_5.10_windows_intelx86.exe'. Put the files 'wrapper_5.10_windows_intelx86.exe', and 'worker_5.10_windows_intelx86.exe' there. Rename the latter file to 'worker=worker_5.10_windows_intelx86.exe' (this gives it the logical name 'worker'). * In the same directory, create a file 'job.xml=job_1.12.xml' (1.12 is a version number) containing {{{ worker stdin stdout 10 }}} This file (which has logical name 'job.xml' and physical name 'job_1.12.xml') is read by 'wrapper'; it tells it the name of the worker program, what files to connect to its stdin/stdout, and a command line. * In the 'PROJECT/templates' directory create a workunit template file called 'worker_wu': {{{ 0 1 0 in 1 stdin 1000000000000 1000000000000 }}} and a result template file called 'worker_result' {{{ 5000000 5000000 out stdout }}} * Run [UpdateVersions bin/update_versions] to create an app version and to copy the application files to the 'PROJECT/download' directory. * Run [StartTool 'bin/start'] to start the daemons. * Run a script like {{{ #! /bin/sh cp download/input `bin/dir_hier_path input` cp download/input2 `bin/dir_hier_path input2` bin/create_work -appname worker -wu_name worker_nodelete \ -wu_template templates/worker_wu \ -result_template templates/worker_result \ input input2 }}} to generate a workunit. The input files in the 'create_work' command must be in the same order as in the workunit template file (worker_wu). Otherwise the client will generate errors when processing the workunit. To understand how all this works: at the beginning of execution, the file layout is: ||'''Project directory'''||'''slot directory'''|| ||input||in (copy of project/input)|| ||job_1.12.xml||job.xml (link to project/job_1.12.xml)|| ||input2||stdin (link to project/input2)|| ||worker_nodelete_0||stdout (link to project/worker_nodelete_0)|| ||worker_5.10_windows_intelx86.exe||worker (link to project/worker_5.10_windows_intelx86.exe) ||wrapper_5.10_windows_intelx86.exe||wrapper_5.10_windows_intelx86.exe (link to project/wrapper_5.10_windows_intelx86.exe) || The wrapper program executes the worker, connecting its stdin to project/input2 and its stdout to project/worker_nodelete_0. The worker program opens 'in' for reading and 'out' for writing. When the worker program finishes, the wrapper sees this and exits. Then the BOINC core client copies slot/out to project/worker_nodelete_1.