C Application Examples
The following examples illustrate some application interactions that use the C language bindings. You can find additional examples on the “How To” section of the Grid Engine Community Site.
Example 6–2 Starting and Stopping a Session
The following code segment shows the most basic DRMAA C binding program.
Every call to a DRMAA function returns an error code. If everything goes well, that code is DRMAA_ERRNO_SUCCESS. If an error occurs, an appropriate error code is returned. Every DRMAA function also takes at least two parameters. These two parameters are a string to populate with a error message in case of an error and an integer representing the maximum length of the error string.
On line 8, the example calls drmaa_init(). This function sets up the DRMAA session and must be called before most other DRMAA functions. Some functions, like drmaa_get_contact(), can be called before drmaa_init(), but these functions only provide general information. Any function that performs an action, such as drmaa_run_job() or drmaa_wait() must be called after drmaa_init() returns. If such a function is called before drmaa_init() returns, it will return the error code DRMAA_ERRNO_NO_ACTIVE_SESSION.
The dmraa_init() function creates a session and starts an event client listener thread. The session is used for organizing jobs submitted through DRMAA, and the thread is used to receive updates from the queue master about the state of jobs and the system in general. Once drmaa_init() has been called successfully, the calling application must also call drmaa_exit() before terminating. If an application does not call drmaa_exit() before terminating, the queue master might be left with a dead event client handle, which can decrease queue master performance.
At the end of the program, on line 17, drmaa_exit() cleans up the session and stops the event client listener thread. Most other DRMAA functions must be called before drmaa_exit(). Some functions, like drmaa_get_contact(), can be called after drmaa_exit(), but these functions only provide general information. Any function that performs an action, such as drmaa_run_job() or drmaa_wait() must be called before drmaa_exit() is called. If such a function is called after drmaa_exit() is called, it will return the error code DRMAA_ERRNO_NO_ACTIVE_SESSION.
01: #include
02: #include "drmaa.h"
03:
04: int main(int argc, char **argv) {
05: char error[DRMAA_ERROR_STRING_BUFFER];
06: int errnum = 0;
07:
08: errnum = drmaa_init(NULL, error, DRMAA_ERROR_STRING_BUFFER);
09:
10: if (errnum != DRMAA_ERRNO_SUCCESS) {
11: fprintf(stderr, "Could not initialize the DRMAA library: %s\n", error);
12: return 1;
13: }
14:
15: printf("DRMAA library was started successfully\n");
16:
17: errnum = drmaa_exit(error, DRMAA_ERROR_STRING_BUFFER);
18:
19: if (errnum != DRMAA_ERRNO_SUCCESS) {
20: fprintf(stderr, "Could not shut down the DRMAA library: %s\n", error);
21: return 1;
22: }
23:
24: return 0;
25: }
Example 6–3 Running a Job
The following code segment shows how to use the DRMAA C binding to submit a job to N1 Grid Engine. The beginning and end of this program are the same as in Example 6–2. The differences are on lines 16-59. On line 16, DRMAA allocates a job template. A job template is a structure used to store information about a job to be submitted. The same template can be reused for multiple calls to drmaa_run_job() or drmaa_run_bulk_job().
On line 22, the DRMAA_REMOTE_COMMAND attribute is set. This attribute tells DRMAA where to find the program to run. Its value is the path to the executable. The path can be relative or absolute. If relative, the path is relative to the DRMAA_WD attribute, which defaults to the user's home directory. For more information on DRMAA attributes, see the drmaa_attributes man page. For this program to work, the script sleeper.sh must be in your default path.
On line 32, the DRMAA_V_ARGV attribute is set. This attribute tells DRMAA what arguments to pass to the executable. For more information on DRMAA attributes, refer to the drmaa_attributes man page.
On line 43 , drmaa_run_job() submits the job. DRMAA places the id assigned to the job into the character array that is passed to drmaa_run_job(). The job is now running as though submitted by qsub. At this point, calling drmaa_exit() or terminating the program will have no effect on the job.
To clean things up, the job template is deleted on line 54. This frees the memory DRMAA set aside for the job template, but has no effect on submitted jobs.
Finally, on line 61, call drmaa_exit() is called. The call to drmaa_exit() is outside of the if structure started on line 18 because once drmaa_init() is called drmaa_exit() must be called before terminating, regardless of whether the other commands succeed.
01: #include
02: #include "drmaa.h"
03:
04: int main(int argc, char **argv) {
05: char error[DRMAA_ERROR_STRING_BUFFER];
06: int errnum = 0;
07: drmaa_job_template_t *jt = NULL;
08:
09: errnum = drmaa_init(NULL, error, DRMAA_ERROR_STRING_BUFFER);
10:
11: if (errnum != DRMAA_ERRNO_SUCCESS) {
12: fprintf(stderr, "Could not initialize the DRMAA library: %s\n", error);
13: return 1;
14: }
15:
16: errnum = drmaa_allocate_job_template(&jt, error, DRMAA_ERROR_STRING_BUFFER);
17:
18: if (errnum != DRMAA_ERRNO_SUCCESS) {
19: fprintf(stderr, "Could not create job template: %s\n", error);
20: }
21: else {
22: errnum = drmaa_set_attribute(jt, DRMAA_REMOTE_COMMAND, "sleeper.sh",
23: error, DRMAA_ERROR_STRING_BUFFER);
24:
25: if (errnum != DRMAA_ERRNO_SUCCESS) {
26: fprintf(stderr, "Could not set attribute \"%s\": %s\n",
27: DRMAA_REMOTE_COMMAND, error);
28: }
29: else {
30: const char *args[2] = {"5", NULL};
31:
32: errnum = drmaa_set_vector_attribute(jt, DRMAA_V_ARGV, args, error,
33: DRMAA_ERROR_STRING_BUFFER);
34: }
35:
36: if (errnum != DRMAA_ERRNO_SUCCESS) {
37: fprintf(stderr, "Could not set attribute \"%s\": %s\n",
38: DRMAA_REMOTE_COMMAND, error);
39: }
40: else {
41: char jobid[DRMAA_JOBNAME_BUFFER];
42:
43: errnum = drmaa_run_job(jobid, DRMAA_JOBNAME_BUFFER, jt, error,
44: DRMAA_ERROR_STRING_BUFFER);
45:
46: if (errnum != DRMAA_ERRNO_SUCCESS) {
47: fprintf(stderr, "Could not submit job: %s\n", error);
48: }
49: else {
50: printf("Your job has been submitted with id %s\n", jobid);
51: }
52: } /* else */
53:
54: errnum = drmaa_delete_job_template(jt, error, DRMAA_ERROR_STRING_BUFFER);
55:
56: if (errnum != DRMAA_ERRNO_SUCCESS) {
57: fprintf(stderr, "Could not delete job template: %s\n", error);
58: }
59: } /* else */
60:
61: errnum = drmaa_exit(error, DRMAA_ERROR_STRING_BUFFER);
62:
63: if (errnum != DRMAA_ERRNO_SUCCESS) {
64: fprintf(stderr, "Could not shut down the DRMAA library: %s\n", error);
65: return 1;
66: }
67:
68: return 0;
69: }
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