Merge pull request #4067 from poettering/invocation-id

Add an "invocation ID" concept to the service manager

3 files changed, 58 insertions, 27 deletions

diff --git a/man/sd-id128.xml b/man/sd-id128.xml
index ea7972055d..5f24feff8e 100644
--- a/man/sd-id128.xml
+++ b/man/sd-id128.xml
@@ -47,10 +47,12 @@
     <refname>sd-id128</refname>
     <refname>sd_id128_t</refname>
     <refname>SD_ID128_MAKE</refname>
+    <refname>SD_ID128_NULL</refname>
     <refname>SD_ID128_CONST_STR</refname>
     <refname>SD_ID128_FORMAT_STR</refname>
     <refname>SD_ID128_FORMAT_VAL</refname>
     <refname>sd_id128_equal</refname>
+    <refname>sd_id128_is_null</refname>
     <refpurpose>APIs for processing 128-bit IDs</refpurpose>
   </refnamediv>
 
@@ -88,8 +90,8 @@
     union type:</para>
 
     <programlisting>typedef union sd_id128 {
-  uint8_t bytes[16];
-  uint64_t qwords[2];
+        uint8_t bytes[16];
+        uint64_t qwords[2];
 } sd_id128_t;</programlisting>
 
     <para>This union type allows accessing the 128-bit ID as 16
@@ -108,37 +110,46 @@
 
     <programlisting>#define SD_MESSAGE_COREDUMP SD_ID128_MAKE(fc,2e,22,bc,6e,e6,47,b6,b9,07,29,ab,34,a2,50,b1)</programlisting>
 
+    <para><function>SD_ID128_NULL</function> may be used to refer to the 128bit ID consisting of only NUL
+    bytes.</para>
+
     <para><function>SD_ID128_CONST_STR()</function> may be used to
     convert constant 128-bit IDs into constant strings for output. The
     following example code will output the string
     "fc2e22bc6ee647b6b90729ab34a250b1":</para>
     <programlisting>int main(int argc, char *argv[]) {
-  puts(SD_ID128_CONST_STR(SD_MESSAGE_COREDUMP));
+        puts(SD_ID128_CONST_STR(SD_MESSAGE_COREDUMP));
 }</programlisting>
 
-    <para><function>SD_ID128_FORMAT_STR</function> and
+    <para><function>SD_ID128_FORMAT_STR()</function> and
     <function>SD_ID128_FORMAT_VAL()</function> may be used to format a
     128-bit ID in a
     <citerefentry project='man-pages'><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry>
     format string, as shown in the following example:</para>
 
     <programlisting>int main(int argc, char *argv[]) {
-  sd_id128_t id;
-  id = SD_ID128_MAKE(ee,89,be,71,bd,6e,43,d6,91,e6,c5,5d,eb,03,02,07);
-  printf("The ID encoded in this C file is " SD_ID128_FORMAT_STR ".\n", SD_ID128_FORMAT_VAL(id));
-  return 0;
+        sd_id128_t id;
+        id = SD_ID128_MAKE(ee,89,be,71,bd,6e,43,d6,91,e6,c5,5d,eb,03,02,07);
+        printf("The ID encoded in this C file is " SD_ID128_FORMAT_STR ".\n", SD_ID128_FORMAT_VAL(id));
+        return 0;
 }</programlisting>
 
     <para>Use <function>sd_id128_equal()</function> to compare two 128-bit IDs:</para>
 
     <programlisting>int main(int argc, char *argv[]) {
-  sd_id128_t a, b, c;
-  a = SD_ID128_MAKE(ee,89,be,71,bd,6e,43,d6,91,e6,c5,5d,eb,03,02,07);
-  b = SD_ID128_MAKE(f2,28,88,9c,5f,09,44,15,9d,d7,04,77,58,cb,e7,3e);
-  c = a;
-  assert(sd_id128_equal(a, c));
-  assert(!sd_id128_equal(a, b));
-  return 0;
+        sd_id128_t a, b, c;
+        a = SD_ID128_MAKE(ee,89,be,71,bd,6e,43,d6,91,e6,c5,5d,eb,03,02,07);
+        b = SD_ID128_MAKE(f2,28,88,9c,5f,09,44,15,9d,d7,04,77,58,cb,e7,3e);
+        c = a;
+        assert(sd_id128_equal(a, c));
+        assert(!sd_id128_equal(a, b));
+        return 0;
+}</programlisting>
+
+    <para>Use <function>sd_id128_is_null()</function> to check if an 128bit ID consists of only NUL bytes:</para>
+
+    <programlisting>int main(int argc, char *argv[]) {
+        assert(sd_id128_is_null(SD_ID128_NULL));
 }</programlisting>
 
     <para>Note that new, randomized IDs may be generated with
diff --git a/man/sd_id128_get_machine.xml b/man/sd_id128_get_machine.xml
index 2ad1f8f728..9a86c24aed 100644
--- a/man/sd_id128_get_machine.xml
+++ b/man/sd_id128_get_machine.xml
@@ -45,6 +45,7 @@
   <refnamediv>
     <refname>sd_id128_get_machine</refname>
     <refname>sd_id128_get_boot</refname>
+    <refname>sd_id128_get_invocation</refname>
     <refpurpose>Retrieve 128-bit IDs</refpurpose>
   </refnamediv>
 
@@ -62,6 +63,11 @@
         <paramdef>sd_id128_t *<parameter>ret</parameter></paramdef>
       </funcprototype>
 
+      <funcprototype>
+        <funcdef>int <function>sd_id128_get_invocation</function></funcdef>
+        <paramdef>sd_id128_t *<parameter>ret</parameter></paramdef>
+      </funcprototype>
+
     </funcsynopsis>
   </refsynopsisdiv>
 
@@ -83,11 +89,15 @@
     for more information. This function also internally caches the
     returned ID to make this call a cheap operation.</para>
 
-    <para>Note that <function>sd_id128_get_boot()</function> always
-    returns a UUID v4 compatible ID.
-    <function>sd_id128_get_machine()</function> will also return a
-    UUID v4-compatible ID on new installations but might not on older.
-    It is possible to convert the machine ID into a UUID v4-compatible
+    <para><function>sd_id128_get_invocation()</function> returns the invocation ID of the currently executed
+    service. In its current implementation, this reads and parses the <varname>$INVOCATION_ID</varname> environment
+    variable that the service manager sets when activating a service, see
+    <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry> for details. The
+    ID is cached internally. In future a different mechanism to determine the invocation ID may be added.</para>
+
+    <para>Note that <function>sd_id128_get_boot()</function> and <function>sd_id128_get_invocation()</function> always
+    return UUID v4 compatible IDs.  <function>sd_id128_get_machine()</function> will also return a UUID v4-compatible
+    ID on new installations but might not on older.  It is possible to convert the machine ID into a UUID v4-compatible
     one. For more information, see
     <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 
@@ -107,11 +117,10 @@
   <refsect1>
     <title>Notes</title>
 
-    <para>The <function>sd_id128_get_machine()</function> and
-    <function>sd_id128_get_boot()</function> interfaces are available
-    as a shared library, which can be compiled and linked to with the
-    <literal>libsystemd</literal> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
-    file.</para>
+    <para>The <function>sd_id128_get_machine()</function>, <function>sd_id128_get_boot()</function> and
+    <function>sd_id128_get_invocation()</function> interfaces are available as a shared library, which can be compiled
+    and linked to with the <literal>libsystemd</literal> <citerefentry
+    project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry> file.</para>
   </refsect1>
 
   <refsect1>
@@ -121,8 +130,9 @@
       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
       <citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
       <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
-      <citerefentry><refentrytitle>random</refentrytitle><manvolnum>4</manvolnum></citerefentry>,
-      <citerefentry><refentrytitle>sd_id128_randomize</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+      <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>sd_id128_randomize</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+      <citerefentry project='man-pages'><refentrytitle>random</refentrytitle><manvolnum>4</manvolnum></citerefentry>
     </para>
   </refsect1>
 
diff --git a/man/systemd.exec.xml b/man/systemd.exec.xml
index 5e6787338d..c73ccaa493 100644
--- a/man/systemd.exec.xml
+++ b/man/systemd.exec.xml
@@ -1514,6 +1514,16 @@
       </varlistentry>
 
       <varlistentry>
+        <term><varname>$INVOCATION_ID</varname></term>
+
+        <listitem><para>Contains a randomized, unique 128bit ID identifying each runtime cycle of the unit, formatted
+        as 32 character hexadecimal string. A new ID is assigned each time the unit changes from an inactive state into
+        an activating or active state, and may be used to identify this specific runtime cycle, in particular in data
+        stored offline, such as the journal. The same ID is passed to all processes run as part of the
+        unit.</para></listitem>
+      </varlistentry>
+
+      <varlistentry>
         <term><varname>$XDG_RUNTIME_DIR</varname></term>
 
         <listitem><para>The directory for volatile state. Set for the