service: set TRIGGER_UNIT= and TRIGGER_TIMER_REALTIME_USEC/MONOTONIC_USEC on activation by timer unit

Same as path unit, best effort.

man/systemd.exec.xml

@@ -3698,8 +3698,10 @@ StandardInputData=V2XigLJyZSBubyBzdHJhbmdlcnMgdG8gbG92ZQpZb3Uga25vdyB0aGUgcnVsZX
         <varlistentry>
           <term><varname>$TRIGGER_UNIT</varname></term>
           <term><varname>$TRIGGER_PATH</varname></term>
+          <term><varname>$TRIGGER_TIMER_REALTIME_USEC</varname></term>
+          <term><varname>$TRIGGER_TIMER_MONOTONIC_USEC</varname></term>
 
-          <listitem><para>If the unit was activated dynamically (e.g.: a corresponding path unit), the
+          <listitem><para>If the unit was activated dynamically (e.g.: a corresponding path unit or timer unit), the
           unit that triggered it and other type-dependent information will be passed via these variables. Note that
           this information is provided in a best-effort way. For example, multiple triggers happening one after
           another will be coalesced and only one will be reported, with no guarantee as to which one it will be.

man/systemd.timer.xml

@@ -366,6 +366,10 @@
 
   <refsect1>
       <title>See Also</title>
+      <para>Environment variables with details on the trigger will be set for triggered units. See the
+      <literal>Environment Variables Set on Triggered Units</literal> section in
+      <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>1</manvolnum></citerefentry>
+      for more details.</para>
       <para>
         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
         <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,

src/core/timer.c

@@ -576,8 +576,10 @@ fail:
 }
 
 static void timer_enter_running(Timer *t) {
+        _cleanup_(activation_details_unrefp) ActivationDetails *details = NULL;
         _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
         Unit *trigger;
+        Job *job;
         int r;
 
         assert(t);
@@ -593,11 +595,20 @@ static void timer_enter_running(Timer *t) {
                 return;
         }
 
-        r = manager_add_job(UNIT(t)->manager, JOB_START, trigger, JOB_REPLACE, NULL, &error, NULL);
+        details = activation_details_new(UNIT(t));
+        if (!details) {
+                r = -ENOMEM;
+                goto fail;
+        }
+
+        r = manager_add_job(UNIT(t)->manager, JOB_START, trigger, JOB_REPLACE, NULL, &error, &job);
         if (r < 0)
                 goto fail;
 
         dual_timestamp_get(&t->last_trigger);
+        ACTIVATION_DETAILS_TIMER(details)->last_trigger = t->last_trigger;
+
+        job_set_activation_details(job, details);
 
         if (t->stamp_path)
                 touch_file(t->stamp_path, true, t->last_trigger.realtime, UID_INVALID, GID_INVALID, MODE_INVALID);
@@ -892,6 +903,91 @@ static int timer_can_start(Unit *u) {
         return 1;
 }
 
+static void activation_details_timer_serialize(ActivationDetails *details, FILE *f) {
+        ActivationDetailsTimer *t = ACTIVATION_DETAILS_TIMER(details);
+
+        assert(details);
+        assert(f);
+        assert(t);
+
+        (void) serialize_dual_timestamp(f, "activation-details-timer-last-trigger", &t->last_trigger);
+}
+
+static int activation_details_timer_deserialize(const char *key, const char *value, ActivationDetails **details) {
+        int r;
+
+        assert(key);
+        assert(value);
+
+        if (!details || !*details)
+                return -EINVAL;
+
+        ActivationDetailsTimer *t = ACTIVATION_DETAILS_TIMER(*details);
+        if (!t)
+                return -EINVAL;
+
+        if (!streq(key, "activation-details-timer-last-trigger"))
+                return -EINVAL;
+
+        r = deserialize_dual_timestamp(value, &t->last_trigger);
+        if (r < 0)
+                return r;
+
+        return 0;
+}
+
+static int activation_details_timer_append_env(ActivationDetails *details, char ***strv) {
+        ActivationDetailsTimer *t = ACTIVATION_DETAILS_TIMER(details);
+        int r;
+
+        assert(details);
+        assert(strv);
+        assert(t);
+
+        if (!dual_timestamp_is_set(&t->last_trigger))
+                return 0;
+
+        r = strv_extendf(strv, "TRIGGER_TIMER_REALTIME_USEC=%" USEC_FMT, t->last_trigger.realtime);
+        if (r < 0)
+                return r;
+
+        r = strv_extendf(strv, "TRIGGER_TIMER_MONOTONIC_USEC=%" USEC_FMT, t->last_trigger.monotonic);
+        if (r < 0)
+                return r;
+
+        return 2; /* Return the number of variables added to the env block */
+}
+
+static int activation_details_timer_append_pair(ActivationDetails *details, char ***strv) {
+        ActivationDetailsTimer *t = ACTIVATION_DETAILS_TIMER(details);
+        int r;
+
+        assert(details);
+        assert(strv);
+        assert(t);
+
+        if (!dual_timestamp_is_set(&t->last_trigger))
+                return 0;
+
+        r = strv_extend(strv, "trigger_timer_realtime_usec");
+        if (r < 0)
+                return r;
+
+        r = strv_extendf(strv, "%" USEC_FMT, t->last_trigger.realtime);
+        if (r < 0)
+                return r;
+
+        r = strv_extend(strv, "trigger_timer_monotonic_usec");
+        if (r < 0)
+                return r;
+
+        r = strv_extendf(strv, "%" USEC_FMT, t->last_trigger.monotonic);
+        if (r < 0)
+                return r;
+
+        return 2; /* Return the number of pairs added to the env block */
+}
+
 static const char* const timer_base_table[_TIMER_BASE_MAX] = {
         [TIMER_ACTIVE]        = "OnActiveSec",
         [TIMER_BOOT]          = "OnBootSec",
@@ -954,3 +1050,12 @@ const UnitVTable timer_vtable = {
 
         .can_start = timer_can_start,
 };
+
+const ActivationDetailsVTable activation_details_timer_vtable = {
+        .object_size = sizeof(ActivationDetailsTimer),
+
+        .serialize = activation_details_timer_serialize,
+        .deserialize = activation_details_timer_deserialize,
+        .append_env = activation_details_timer_append_env,
+        .append_pair = activation_details_timer_append_pair,
+};

src/core/timer.h

@@ -2,6 +2,7 @@
 #pragma once
 
 typedef struct Timer Timer;
+typedef struct ActivationDetailsTimer ActivationDetailsTimer;
 
 #include "calendarspec.h"
 #include "unit.h"
@@ -64,11 +65,17 @@ struct Timer {
         char *stamp_path;
 };
 
+struct ActivationDetailsTimer {
+        ActivationDetails meta;
+        dual_timestamp last_trigger;
+};
+
 #define TIMER_MONOTONIC_CLOCK(t) ((t)->wake_system ? CLOCK_BOOTTIME_ALARM : CLOCK_MONOTONIC)
 
 void timer_free_values(Timer *t);
 
 extern const UnitVTable timer_vtable;
+extern const ActivationDetailsVTable activation_details_timer_vtable;
 
 const char *timer_base_to_string(TimerBase i) _const_;
 TimerBase timer_base_from_string(const char *s) _pure_;
@@ -77,3 +84,4 @@ const char* timer_result_to_string(TimerResult i) _const_;
 TimerResult timer_result_from_string(const char *s) _pure_;
 
 DEFINE_CAST(TIMER, Timer);
+DEFINE_ACTIVATION_DETAILS_CAST(ACTIVATION_DETAILS_TIMER, ActivationDetailsTimer, TIMER);

src/core/unit.c

@@ -5931,6 +5931,7 @@ int unit_get_dependency_array(const Unit *u, UnitDependencyAtom atom, Unit ***re
 
 const ActivationDetailsVTable * const activation_details_vtable[_UNIT_TYPE_MAX] = {
         [UNIT_PATH] = &activation_details_path_vtable,
+        [UNIT_TIMER] = &activation_details_timer_vtable,
 };
 
 ActivationDetails *activation_details_new(Unit *trigger_unit) {

test/units/testsuite-07.sh

@@ -8,6 +8,9 @@ set -o pipefail
 cat >/lib/systemd/system/my.service <<EOF
 [Service]
 Type=oneshot
+ExecStartPre=sh -c 'test "\$TRIGGER_UNIT" = my.timer'
+ExecStartPre=sh -c 'test -n "\$TRIGGER_TIMER_REALTIME_USEC"'
+ExecStartPre=sh -c 'test -n "\$TRIGGER_TIMER_MONOTONIC_USEC"'
 ExecStart=/bin/echo Timer runs me
 EOF