service: pass service exit status to spawned On{Failure,Success}= dependency

When a service exits and triggers either an OnFailure= or OnSuccess=
dependency we now set a new environment variable for the ExecStart= and
ExecStartPre= process. This variable $MONITOR_METADATA exposes the
metadata relating to the service which triggered the dependency.
MONITOR_METADATA takes the following form:

MONITOR_METADATA="SERVICE_RESULT=<result-string0>,EXIT_CODE=<exit-code0>,EXIT_STATUS=<exit-status0>,INVOCATION_ID=<id>,UNIT=<triggering-unit0.service>;SERVICE_RESULT=<result-stringN>,EXIT_CODE=<exit-codeN>,=EXIT_STATUS=<exit-statusN>,INVOCATION_ID=<id>,UNIT=<triggering-unitN.service>"

MONITOR_METADATA is space separated set of metadata relating to the
service(s) which triggered the dependency. This is a list since if we
have 2 services which trigger the same dependency then the dependency
start job may be merged. In this case we need to pass both service
metadata to the triggered service. If there is no job merging then
MONITOR_METADATA will be a single entry.

For example, in the case we had a service "failer.service" which
triggers "failer-handler.service", the following variable is exported to
the ExecStart= and ExecStartPre= processes in failer-handler.service:

MONITOR_METADATA="SERVICE_RESULT=exit-code,EXIT_CODE=exited,EXIT_STATUS=1,INVOCATION_ID=67c657ed7b34466ea369abdf994c6393,UNIT=failer.service"

In another example where we have failer.service and failer2.service
which both also trigger failer-handler.service then the start job for
failer-handler.service may be merged and we might get the following:

MONITOR_METADATA="SERVICE_RESULT=exit-code,EXIT_CODE=exited,EXIT_STATUS=1,INVOCATION_ID=16a93ad196c94109990fb8b9aa5eef5f,UNIT=failer.service;SERVICE_RESULT=exit-code,EXIT_CODE=exited,EXIT_STATUS=1,INVOCATION_ID=ff70131e4cc145e994fb621de25a3e8f,UNIT=failer2.service"

1 files changed, 16 insertions, 8 deletions

diff --git a/src/core/unit-dependency-atom.c b/src/core/unit-dependency-atom.c
index 761835828a..333eea6c3d 100644
--- a/src/core/unit-dependency-atom.c
+++ b/src/core/unit-dependency-atom.c
@@ -82,11 +82,15 @@ static const UnitDependencyAtom atom_map[_UNIT_DEPENDENCY_MAX] = {
         [UNIT_PROPAGATES_STOP_TO]     = UNIT_ATOM_RETROACTIVE_STOP_ON_STOP |
                                         UNIT_ATOM_PROPAGATE_STOP,
 
+        [UNIT_ON_FAILURE]             = UNIT_ATOM_ON_FAILURE |
+                                        UNIT_ATOM_BACK_REFERENCE_IMPLIED,
+
+        [UNIT_ON_SUCCESS]             = UNIT_ATOM_ON_SUCCESS |
+                                        UNIT_ATOM_BACK_REFERENCE_IMPLIED,
+
         /* These are simple dependency types: they consist of a single atom only */
         [UNIT_BEFORE]                 = UNIT_ATOM_BEFORE,
         [UNIT_AFTER]                  = UNIT_ATOM_AFTER,
-        [UNIT_ON_SUCCESS]             = UNIT_ATOM_ON_SUCCESS,
-        [UNIT_ON_FAILURE]             = UNIT_ATOM_ON_FAILURE,
         [UNIT_TRIGGERS]               = UNIT_ATOM_TRIGGERS,
         [UNIT_TRIGGERED_BY]           = UNIT_ATOM_TRIGGERED_BY,
         [UNIT_PROPAGATES_RELOAD_TO]   = UNIT_ATOM_PROPAGATES_RELOAD_TO,
@@ -196,6 +200,16 @@ UnitDependency unit_dependency_from_unique_atom(UnitDependencyAtom atom) {
         case UNIT_ATOM_PROPAGATE_STOP_FAILURE:
                 return UNIT_CONFLICTED_BY;
 
+        case UNIT_ATOM_ON_FAILURE |
+                UNIT_ATOM_BACK_REFERENCE_IMPLIED:
+        case UNIT_ATOM_ON_FAILURE:
+                return UNIT_ON_FAILURE;
+
+        case UNIT_ATOM_ON_SUCCESS |
+                UNIT_ATOM_BACK_REFERENCE_IMPLIED:
+        case UNIT_ATOM_ON_SUCCESS:
+                return UNIT_ON_SUCCESS;
+
         /* And now, the simple ones */
 
         case UNIT_ATOM_BEFORE:
@@ -204,12 +218,6 @@ UnitDependency unit_dependency_from_unique_atom(UnitDependencyAtom atom) {
         case UNIT_ATOM_AFTER:
                 return UNIT_AFTER;
 
-        case UNIT_ATOM_ON_SUCCESS:
-                return UNIT_ON_SUCCESS;
-
-        case UNIT_ATOM_ON_FAILURE:
-                return UNIT_ON_FAILURE;
-
         case UNIT_ATOM_TRIGGERS:
                 return UNIT_TRIGGERS;