jobtap: add flux_jobtap_jobspec_update_id_pack()

src/modules/job-manager/jobtap.c

@@ -2263,6 +2263,61 @@
     return rc;
 }
 
+int flux_jobtap_jobspec_update_id_pack (flux_plugin_t *p,
+                                        flux_jobid_t id,
+                                        const char *fmt,
+                                        ...)
+{
+    int rc = -1;
+    va_list ap;
+    struct jobtap *jobtap;
+    struct job *job;
+    json_error_t error;
+    json_t *update = NULL;
+
+    if (!p
+        || !(jobtap = flux_plugin_aux_get (p, "flux::jobtap"))
+        || !(job = jobtap_lookup_active_jobid (p, id))
+        || job->state == FLUX_JOB_STATE_RUN
+        || job->state == FLUX_JOB_STATE_CLEANUP
+        || job->eventlog_readonly) {
+        errno = EINVAL;
+        return -1;
+    }
+
+    /* This interface is only appropriate from outside a jobtap callback,
+     * i.e. called asynchronously to update a job. If 'job' is equivalent
+     * to the current job at the top of the jobtap stack, return an error.
+     */
+    if (job == current_job (jobtap)) {
+        errno = EINVAL;
+        return -1;
+    }
+
+    va_start (ap, fmt);
+    update = json_vpack_ex (&error, 0, fmt, ap);
+    va_end (ap);
+    if (!update) {
+        errno = EINVAL;
+        return -1;
+    }
+    if (!validate_jobspec_updates (update)) {
+        errno = EINVAL;
+        goto out;
+    }
+    /* XXX: should job.validate be called on these updates before posting?
+     */
+    rc = event_job_post_pack (jobtap->ctx->event,
+                              job,
+                              "jobspec-update",
+                              0,
+                              "O",
+                              update);
+out:
+    ERRNO_SAFE_WRAP (json_decref, update);
+    return rc;
+}
+
 int flux_jobtap_jobspec_update_pack (flux_plugin_t *p, const char *fmt, ...)
 {
     int rc = -1;

src/modules/job-manager/jobtap.h

@@ -194,6 +194,19 @@ int flux_jobtap_event_post_pack (flux_plugin_t *p,
  */
 int flux_jobtap_jobspec_update_pack (flux_plugin_t *p, const char *fmt, ...);
 
+/*  Similar to flux_jobtap_jobspec_update_pack(), but asynchronously update
+ *  a specific jobid. This version assumes the job is quiescent, so the event
+ *  is applied immediately.
+ *
+ *  Returns -1 with errno set to EINVAL for invalid arguments, if the job
+ *  does not exist, if the target job is in RUN, CLEANUP or INACTIVE states,
+ *  or if the function is called from a jobtap callback for the target job.
+ */
+int flux_jobtap_jobspec_update_id_pack (flux_plugin_t *p,
+                                        flux_jobid_t id,
+                                        const char *fmt,
+                                        ...);
+
 /*  Return a flux_plugin_arg_t object for a job.
  *
  *  The result can then be unpacked with flux_plugin_arg_unpack(3) to get

t/job-manager/plugins/jobspec-update.c

@@ -25,11 +25,13 @@ static int get_and_update_jobspec_name (flux_error_t *errp,
                                         const char **cur_namep,
                                         char *name)
 {
+    flux_jobid_t id;
     const char *current_name = NULL;
     char *copy = NULL;
     if (flux_plugin_arg_unpack (args,
                                 FLUX_PLUGIN_ARG_IN,
-                                "{s:{s:{s?{s?{s?s}}}}}",
+                                "{s:I s:{s:{s?{s?{s?s}}}}}",
+                                "id", &id,
                                 "jobspec",
                                 "attributes",
                                 "system",
@@ -41,6 +43,20 @@ static int get_and_update_jobspec_name (flux_error_t *errp,
                    flux_plugin_arg_strerror (args));
         return -1;
     }
+
+    /* flux_jobtap_jobspec_update_id_pack() should fail here, since this
+     * function is always called in the context of a jobtap callback:
+     */
+    if (flux_jobtap_jobspec_update_id_pack (p,
+                                            id,
+                                            "{s:s}",
+                                            "attributes.system.foo",
+                                            "bar") == 0) {
+        errprintf (errp,
+                   "flux_jobtap_jobspec_update_id_pack() unexpected success");
+        return -1;
+    }
+
     if (current_name && !(copy = strdup (current_name))) {
         errprintf (errp, "failed to copy job name");
         return -1;
@@ -199,6 +215,20 @@ static int run_cb (flux_plugin_t *p,
     return 0;
 }
 
+static void update_msg_cb (flux_t *h,
+                           flux_msg_handler_t *mh,
+                           const flux_msg_t *msg,
+                           void *arg)
+{
+    flux_plugin_t *p = arg;
+    flux_jobid_t id;
+    json_t *update;
+
+    if (flux_msg_unpack (msg, "{s:I s:o}", "id", &id, "update", &update) < 0
+        || flux_jobtap_jobspec_update_id_pack (p, id, "O", update) < 0)
+        flux_jobtap_raise_exception (p, id, "test", 0, "update failed");
+    flux_respond (h, msg, NULL);
+}
 
 static const struct flux_plugin_handler tab[] = {
     { "job.new", new_cb, NULL },
@@ -214,6 +244,9 @@ int flux_plugin_init (flux_plugin_t *p)
 {
     if (flux_plugin_register (p, "jobspec-update", tab) < 0)
         return -1;
+    if (flux_jobtap_service_register (p, "update", update_msg_cb, p) < 0)
+        flux_log_error (flux_jobtap_get_flux (p),
+                        "flux_jobtap_service_register");
     return 0;
 }
 

t/t2212-job-manager-plugins.t

@@ -529,6 +529,22 @@ test_expect_success 'job-manager: plugins can update jobspec' '
 		--match-context=attributes.system.job.name=new \
 		$jobid jobspec-update
 '
+test_expect_success 'job-manager: plugin can asynchronously update jobspec' '
+	flux dmesg -H | grep jobspec-update &&
+	jobid=$(flux submit -n1 --urgency=hold sleep 0) &&
+	cat <<-EOF >update-test.py &&
+	import flux
+	from flux.job import JobID
+	id=JobID("$jobid")
+	flux.Flux().rpc(
+	    "job-manager.jobspec-update.update",
+	    dict(id=id, update={"attributes.system.job.name": "test"}),
+	).get()
+	EOF
+	flux python update-test.py &&
+	flux job wait-event -Hv -t 30 $jobid jobspec-update &&
+	flux jobs $jobid
+'
 test_expect_success 'job-manager: plugin fails to load on config.update error' '
 	flux jobtap remove all &&
 	test_must_fail flux jobtap load ${PLUGINPATH}/config.so 2>config.err