job-list: rebuild and store eventlog

Problem: In the near future we will need access to the job's
eventlog when a job goes inactive.

Solution: Rebuild the job eventlog from the events journal and
store it internally in struct job.

Author: chu11

src/modules/job-list/job_data.c

@@ -40,6 +40,7 @@ void job_destroy (void *data)
         grudgeset_destroy (job->dependencies);
         json_decref (job->jobspec);
         json_decref (job->R);
+        free (job->eventlog);
         json_decref (job->exception_context);
         free (job);
         errno = save_errno;

src/modules/job-list/job_data.h

@@ -70,6 +70,8 @@ struct job {
     /* cache of job information */
     json_t *jobspec;
     json_t *R;
+    char *eventlog;
+    size_t eventlog_len;
     json_t *exception_context;
 
     /* Track which states we have seen and have completed transition

src/modules/job-list/job_state.c

@@ -409,6 +409,42 @@ void job_state_unpause_cb (flux_t *h, flux_msg_handler_t *mh,
         flux_log_error (h, "error responding to unpause request");
 }
 
+static int store_eventlog_entry (struct job_state_ctx *jsctx,
+                                 struct job *job,
+                                 json_t *entry)
+{
+    char *s = json_dumps (entry, 0);
+    int rv = -1;
+
+    /* entry should have been verified via eventlog_entry_parse()
+     * earlier */
+    assert (s);
+
+    if (!job->eventlog) {
+        job->eventlog_len = strlen (s) + 2; /* +2 for \n and \0 */
+        if (!(job->eventlog = calloc (1, job->eventlog_len))) {
+            flux_log_error (jsctx->h, "calloc");
+            goto error;
+
+        }
+        strcpy (job->eventlog, s);
+        strcat (job->eventlog, "\n");
+    }
+    else {
+        job->eventlog_len += strlen (s) + 1; /* +1 for \n */
+        if (!(job->eventlog = realloc (job->eventlog, job->eventlog_len))) {
+            flux_log_error (jsctx->h, "realloc");
+            goto error;
+        }
+        strcat (job->eventlog, s);
+        strcat (job->eventlog, "\n");
+    }
+    rv = 0;
+error:
+    free (s);
+    return rv;
+}
+
 static int job_transition_state (struct job_state_ctx *jsctx,
                                  struct job *job,
                                  flux_job_state_t newstate,
@@ -487,12 +523,17 @@ static int journal_submit_event (struct job_state_ctx *jsctx,
                                  struct job *job,
                                  flux_jobid_t id,
                                  double timestamp,
+                                 json_t *entry,
                                  json_t *context,
                                  json_t *jobspec)
 {
     if (!job) {
         if (!(job = job_create (jsctx->h, id)))
             return -1;
+        if (store_eventlog_entry (jsctx, job, entry) < 0) {
+            job_destroy (job);
+            return -1;
+        }
         if (jobspec)
             job->jobspec = json_incref (jobspec);
         if (zhashx_insert (jsctx->index, &job->id, job) < 0) {
@@ -895,11 +936,17 @@ static int journal_process_event (struct job_state_ctx *jsctx,
         return 0;
     }
 
+    if (job && job->eventlog) {
+        if (store_eventlog_entry (jsctx, job, event) < 0)
+            return -1;
+    }
+
     if (streq (name, "submit")) {
         if (journal_submit_event (jsctx,
                                   job,
                                   id,
                                   timestamp,
+                                  event,
                                   context,
                                   jobspec) < 0)
             return -1;