rfc21: add reattach job state

Author: chu11

data/spec_21/states.dot

@@ -12,7 +12,7 @@ digraph states {
         DEPEND;
         PRIORITY;
         SCHED;
-        RUN;
+        {rank=same; RUN; REATTACH;}
         CLEANUP;
     }
 
@@ -25,6 +25,9 @@ digraph states {
 
     SCHED -> PRIORITY [label="flux-restart"]
 
+    RUN -> REATTACH [xlabel="reattach"]
+    REATTACH -> RUN [xlabel="attached"]
+
     edge [weight=0 color="red"];
 
     DEPEND -> CLEANUP [label="exception"];

data/spec_21/states.svg

@@ -110,6 +110,14 @@ RUN
    job shells have been started, and a ``finish`` event once all the job shells
    have exited. The state transitions to CLEANUP.
 
+REATTACH
+   The job was started, but the job manager has lost tracking to it
+   due to an error (for example, a system crash).  The job manager is
+   attempting to reattach itself to the running job.  A
+   ``reattach`` event is logged to indicate transition into this
+   state.  ``attached`` will be logged when the tracking has been
+   reestablished and we can re-enter the RUN state.
+
 CLEANUP
    The job has completed or an exception has occurred. Under normal termination,
    the job manager waits for notification from the exec service that job
@@ -133,10 +141,10 @@ PENDING
   The job is in DEPEND, PRIORITY, or SCHED states.
 
 RUNNING
-  The job is in RUN or CLEANUP states.
+  The job is in RUN, REATTACH, or CLEANUP states.
 
 ACTIVE
-  The job is in DEPEND, PRIORITY, SCHED, RUN, or CLEANUP states.
+  The job is in DEPEND, PRIORITY, SCHED, RUN, REATTACH, or CLEANUP states.
 
 
 Exceptions
@@ -391,6 +399,37 @@ status
    {"timestamp":1552594348.0,"name":"epilog-finish","context":{"description":"/usr/sbin/job-epilog.sh", "status":0}}
 
 
+Reattach Event
+^^^^^^^^^^^^^^
+
+The job manager is attempting to reattach to a running job.
+
+The following keys are OPTIONAL in the event context object:
+
+id
+   (long long) job ID to reattach to
+
+Example:
+
+.. code:: json
+
+    {"timestamp":1636747761.5495925,"name":"reattach","context":{"id":341835776000}}
+
+
+Attached Event
+^^^^^^^^^^^^^^
+
+The job manager has re-connected to the job shells.
+
+The context SHALL be empty.
+
+Example:
+
+.. code:: json
+
+    {"timestamp":1636747761.827836,"name":"reattached"}
+
+
 Free Event
 ^^^^^^^^^^