From 909d27fffffb28f4da7752be25e5c47990eba641 Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Mon, 13 Nov 2017 17:14:07 +0100
Subject: [PATCH] core: add a new unit file setting CollectMode= for tweaking
the GC logic
Right now, the option only takes one of two possible values "inactive"
or "inactive-or-failed", the former being the default, and exposing same
behaviour as the status quo ante. If set to "inactive-or-failed" units
may be collected by the GC logic when in the "failed" state too.
This logic should be a nicer alternative to using the "-" modifier for
ExecStart= and friends, as the exit data is collected and logged about
and only removed when the GC comes along. This should be useful in
particular for per-connection socket-activated services, as well as
"systemd-run" command lines that shall leave no artifacts in the
system.
I was thinking about whether to expose this as a boolean, but opted for
an enum instead, as I have the suspicion other tweaks like this might be
a added later on, in which case we extend this setting instead of having
to add yet another one.
Also, let's add some documentation for the GC logic.
(cherry-picked from commit 5afe510c89f26b0e721b276a0e78af914b47f0b0)
Resolves: #1817576
---
man/systemd.unit.xml | 56 +++++++++++++++++++++++++++
src/core/dbus-unit.c | 20 ++++++++++
src/core/load-fragment-gperf.gperf.m4 | 1 +
src/core/load-fragment.c | 2 +
src/core/load-fragment.h | 1 +
src/core/unit.c | 36 ++++++++++++++---
src/core/unit.h | 13 +++++++
7 files changed, 124 insertions(+), 5 deletions(-)
diff --git a/man/systemd.unit.xml b/man/systemd.unit.xml
index 414749bae9..0c06add166 100644
--- a/man/systemd.unit.xml
+++ b/man/systemd.unit.xml
@@ -303,6 +303,45 @@
</para>
</refsect1>
+ <refsect1>
+ <title>Unit Garbage Collection</title>
+
+ <para>The system and service manager loads a unit's configuration automatically when a unit is referenced for the
+ first time. It will automatically unload the unit configuration and state again when the unit is not needed anymore
+ ("garbage collection"). A unit may be referenced through a number of different mechanisms:</para>
+
+ <orderedlist>
+ <listitem><para>Another loaded unit references it with a dependency such as <varname>After=</varname>,
+ <varname>Wants=</varname>, …</para></listitem>
+
+ <listitem><para>The unit is currently starting, running, reloading or stopping.</para></listitem>
+
+ <listitem><para>The unit is currently in the <constant>failed</constant> state. (But see below.)</para></listitem>
+
+ <listitem><para>A job for the unit is pending.</para></listitem>
+
+ <listitem><para>The unit is pinned by an active IPC client program.</para></listitem>
+
+ <listitem><para>The unit is a special "perpetual" unit that is always active and loaded. Examples for perpetual
+ units are the root mount unit <filename>-.mount</filename> or the scope unit <filename>init.scope</filename> that
+ the service manager itself lives in.</para></listitem>
+
+ <listitem><para>The unit has running processes associated with it.</para></listitem>
+ </orderedlist>
+
+ <para>The garbage collection logic may be altered with the <varname>CollectMode=</varname> option, which allows
+ configuration whether automatic unloading of units that are in <constant>failed</constant> state is permissible,
+ see below.</para>
+
+ <para>Note that when a unit's configuration and state is unloaded, all execution results, such as exit codes, exit
+ signals, resource consumption and other statistics are lost, except for what is stored in the log subsystem.</para>
+
+ <para>Use <command>systemctl daemon-reload</command> or an equivalent command to reload unit configuration while
+ the unit is already loaded. In this case all configuration settings are flushed out and replaced with the new
+ configuration (which however might not be in effect immediately), however all runtime state is
+ saved/restored.</para>
+ </refsect1>
+
<refsect1>
<title>[Unit] Section Options</title>
@@ -666,6 +705,23 @@
ones.</para></listitem>
</varlistentry>
+ <varlistentry>
+ <term><varname>CollectMode=</varname></term>
+
+ <listitem><para>Tweaks the "garbage collection" algorithm for this unit. Takes one of <option>inactive</option>
+ or <option>inactive-or-failed</option>. If set to <option>inactive</option> the unit will be unloaded if it is
+ in the <constant>inactive</constant> state and is not referenced by clients, jobs or other units — however it
+ is not unloaded if it is in the <constant>failed</constant> state. In <option>failed</option> mode, failed
+ units are not unloaded until the user invoked <command>systemctl reset-failed</command> on them to reset the
+ <constant>failed</constant> state, or an equivalent command. This behaviour is altered if this option is set to
+ <option>inactive-or-failed</option>: in this case the unit is unloaded even if the unit is in a
+ <constant>failed</constant> state, and thus an explicitly resetting of the <constant>failed</constant> state is
+ not necessary. Note that if this mode is used unit results (such as exit codes, exit signals, consumed
+ resources, …) are flushed out immediately after the unit completed, except for what is stored in the logging
+ subsystem. Defaults to <option>inactive</option>.</para>
+ </listitem>
+ </varlistentry>
+
<varlistentry>
<term><varname>JobTimeoutSec=</varname></term>
<term><varname>JobTimeoutAction=</varname></term>
diff --git a/src/core/dbus-unit.c b/src/core/dbus-unit.c
index 77073308c8..ea6ac6767f 100644
--- a/src/core/dbus-unit.c
+++ b/src/core/dbus-unit.c
@@ -34,6 +34,7 @@
static BUS_DEFINE_PROPERTY_GET_ENUM(property_get_load_state, unit_load_state, UnitLoadState);
static BUS_DEFINE_PROPERTY_GET_ENUM(property_get_job_mode, job_mode, JobMode);
static BUS_DEFINE_PROPERTY_GET_ENUM(property_get_emergency_action, emergency_action, EmergencyAction);
+static BUS_DEFINE_PROPERTY_GET_ENUM(property_get_collect_mode, collect_mode, CollectMode);
static int property_get_names(
sd_bus *bus,
@@ -605,6 +606,7 @@ const sd_bus_vtable bus_unit_vtable[] = {
SD_BUS_PROPERTY("Asserts", "a(sbbsi)", property_get_conditions, offsetof(Unit, asserts), 0),
SD_BUS_PROPERTY("LoadError", "(ss)", property_get_load_error, 0, SD_BUS_VTABLE_PROPERTY_CONST),
SD_BUS_PROPERTY("Transient", "b", bus_property_get_bool, offsetof(Unit, transient), SD_BUS_VTABLE_PROPERTY_CONST),
+ SD_BUS_PROPERTY("CollectMode", "s", property_get_collect_mode, offsetof(Unit, collect_mode), 0),
SD_BUS_METHOD("Start", "s", "o", method_start, 0),
SD_BUS_METHOD("Stop", "s", "o", method_stop, 0),
@@ -937,6 +939,24 @@ static int bus_unit_set_transient_property(
return 1;
+ } else if (streq(name, "CollectMode")) {
+ const char *s;
+ CollectMode m;
+
+ r = sd_bus_message_read(message, "s", &s);
+ if (r < 0)
+ return r;
+
+ m = collect_mode_from_string(s);
+ if (m < 0)
+ return sd_bus_error_setf(error, SD_BUS_ERROR_INVALID_ARGS, "Unknown garbage collection mode: %s", s);
+
+ if (mode != UNIT_CHECK) {
+ u->collect_mode = m;
+ unit_write_drop_in_format(u, mode, name, "[Unit]\nCollectMode=%s", collect_mode_to_string(m));
+ }
+
+ return 1;
} else if (streq(name, "Slice") && unit_get_cgroup_context(u)) {
const char *s;
diff --git a/src/core/load-fragment-gperf.gperf.m4 b/src/core/load-fragment-gperf.gperf.m4
index 664bba0ef6..3a8ee96fa3 100644
--- a/src/core/load-fragment-gperf.gperf.m4
+++ b/src/core/load-fragment-gperf.gperf.m4
@@ -200,6 +200,7 @@ Unit.AssertCapability, config_parse_unit_condition_string, CONDITION_C
Unit.AssertHost, config_parse_unit_condition_string, CONDITION_HOST, offsetof(Unit, asserts)
Unit.AssertACPower, config_parse_unit_condition_string, CONDITION_AC_POWER, offsetof(Unit, asserts)
Unit.AssertNull, config_parse_unit_condition_null, 0, offsetof(Unit, asserts)
+Unit.CollectMode, config_parse_collect_mode, 0, offsetof(Unit, collect_mode)
m4_dnl
Service.PIDFile, config_parse_unit_path_printf, 0, offsetof(Service, pid_file)
Service.ExecStartPre, config_parse_exec, SERVICE_EXEC_START_PRE, offsetof(Service, exec_command)
diff --git a/src/core/load-fragment.c b/src/core/load-fragment.c
index 1721fea8f3..8d73d5df41 100644
--- a/src/core/load-fragment.c
+++ b/src/core/load-fragment.c
@@ -98,6 +98,8 @@ int config_parse_warn_compat(
return 0;
}
+DEFINE_CONFIG_PARSE_ENUM(config_parse_collect_mode, collect_mode, CollectMode, "Failed to parse garbage collection mode");
+
int config_parse_unit_deps(const char *unit,
const char *filename,
unsigned line,
diff --git a/src/core/load-fragment.h b/src/core/load-fragment.h
index 4bd286c11b..7b1193ddb2 100644
--- a/src/core/load-fragment.h
+++ b/src/core/load-fragment.h
@@ -110,6 +110,7 @@ int config_parse_cpu_quota(const char *unit, const char *filename, unsigned line
int config_parse_protect_home(const char* unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
int config_parse_protect_system(const char* unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
int config_parse_bus_name(const char* unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
+int config_parse_collect_mode(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
/* gperf prototypes */
const struct ConfigPerfItem* load_fragment_gperf_lookup(const char *key, GPERF_LEN_TYPE length);
diff --git a/src/core/unit.c b/src/core/unit.c
index eff9fdbe70..502830d2cb 100644
--- a/src/core/unit.c
+++ b/src/core/unit.c
@@ -67,7 +67,7 @@ const UnitVTable * const unit_vtable[_UNIT_TYPE_MAX] = {
[UNIT_TIMER] = &timer_vtable,
[UNIT_PATH] = &path_vtable,
[UNIT_SLICE] = &slice_vtable,
- [UNIT_SCOPE] = &scope_vtable
+ [UNIT_SCOPE] = &scope_vtable,
};
static int maybe_warn_about_dependency(const char *id, const char *other, UnitDependency dependency);
@@ -285,6 +285,7 @@ int unit_set_description(Unit *u, const char *description) {
bool unit_may_gc(Unit *u) {
UnitActiveState state;
+
assert(u);
/* Checks whether the unit is ready to be unloaded for garbage collection.
@@ -308,16 +309,31 @@ bool unit_may_gc(Unit *u) {
UNIT_VTABLE(u)->release_resources)
UNIT_VTABLE(u)->release_resources(u);
- /* But we keep the unit object around for longer when it is referenced or configured to not be gc'ed */
- if (state != UNIT_INACTIVE)
- return false;
-
if (UNIT_VTABLE(u)->no_gc)
return false;
if (u->no_gc)
return false;
+ /* But we keep the unit object around for longer when it is referenced or configured to not be gc'ed */
+ switch (u->collect_mode) {
+
+ case COLLECT_INACTIVE:
+ if (state != UNIT_INACTIVE)
+ return false;
+
+ break;
+
+ case COLLECT_INACTIVE_OR_FAILED:
+ if (!IN_SET(state, UNIT_INACTIVE, UNIT_FAILED))
+ return false;
+
+ break;
+
+ default:
+ assert_not_reached("Unknown garbage collection mode");
+ }
+
if (UNIT_VTABLE(u)->may_gc && !UNIT_VTABLE(u)->may_gc(u))
return false;
@@ -896,6 +912,7 @@ void unit_dump(Unit *u, FILE *f, const char *prefix) {
"%s\tMay GC: %s\n"
"%s\tNeed Daemon Reload: %s\n"
"%s\tTransient: %s\n"
+ "%s\tGarbage Collection Mode: %s\n"
"%s\tSlice: %s\n"
"%s\tCGroup: %s\n"
"%s\tCGroup realized: %s\n"
@@ -913,6 +930,7 @@ void unit_dump(Unit *u, FILE *f, const char *prefix) {
prefix, yes_no(unit_may_gc(u)),
prefix, yes_no(unit_need_daemon_reload(u)),
prefix, yes_no(u->transient),
+ prefix, collect_mode_to_string(u->collect_mode),
prefix, strna(unit_slice_name(u)),
prefix, strna(u->cgroup_path),
prefix, yes_no(u->cgroup_realized),
@@ -3732,3 +3750,11 @@ static const char* const unit_active_state_table[_UNIT_ACTIVE_STATE_MAX] = {
};
DEFINE_STRING_TABLE_LOOKUP(unit_active_state, UnitActiveState);
+
+static const char* const collect_mode_table[_COLLECT_MODE_MAX] = {
+ [COLLECT_INACTIVE] = "inactive",
+ [COLLECT_INACTIVE_OR_FAILED] = "inactive-or-failed",
+};
+
+DEFINE_STRING_TABLE_LOOKUP(collect_mode, CollectMode);
+
diff --git a/src/core/unit.h b/src/core/unit.h
index 3b0fd8d9df..8cc7a9e0b2 100644
--- a/src/core/unit.h
+++ b/src/core/unit.h
@@ -60,6 +60,13 @@ typedef enum KillOperation {
KILL_ABORT,
} KillOperation;
+typedef enum CollectMode {
+ COLLECT_INACTIVE,
+ COLLECT_INACTIVE_OR_FAILED,
+ _COLLECT_MODE_MAX,
+ _COLLECT_MODE_INVALID = -1,
+} CollectMode;
+
static inline bool UNIT_IS_ACTIVE_OR_RELOADING(UnitActiveState t) {
return t == UNIT_ACTIVE || t == UNIT_RELOADING;
}
@@ -198,6 +205,9 @@ struct Unit {
/* How to start OnFailure units */
JobMode on_failure_job_mode;
+ /* Tweaking the GC logic */
+ CollectMode collect_mode;
+
/* Garbage collect us we nobody wants or requires us anymore */
bool stop_when_unneeded;
@@ -630,6 +640,9 @@ pid_t unit_main_pid(Unit *u);
const char *unit_active_state_to_string(UnitActiveState i) _const_;
UnitActiveState unit_active_state_from_string(const char *s) _pure_;
+const char* collect_mode_to_string(CollectMode m) _const_;
+CollectMode collect_mode_from_string(const char *s) _pure_;
+
bool unit_needs_console(Unit *u);
/* Macros which append UNIT= or USER_UNIT= to the message */