core: add new "scope" unit type for making a unit of pre-existing processes

"Scope" units are very much like service units, however with the
difference that they are created from pre-existing processes, rather
than processes that systemd itself forks off. This means they are
generated programmatically via the bus API as transient units rather
than from static configuration read from disk. Also, they do not provide
execution-time parameters, as at the time systemd adds the processes to
the scope unit they already exist and the parameters cannot be applied
anymore.

The primary benefit of this new unit type is to create arbitrary cgroups
for worker-processes forked off an existing service.

This commit also adds a a new mode to "systemd-run" to run the specified
processes in a scope rather then a transient service.

1 files changed, 466 insertions, 0 deletions

diff --git a/src/core/scope.c b/src/core/scope.c
new file mode 100644
index 0000000000..f88addadf3
--- /dev/null
+++ b/src/core/scope.c
@@ -0,0 +1,466 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright 2013 Lennart Poettering
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <errno.h>
+#include <signal.h>
+#include <unistd.h>
+
+#include "unit.h"
+#include "scope.h"
+#include "load-fragment.h"
+#include "log.h"
+#include "dbus-scope.h"
+#include "special.h"
+#include "unit-name.h"
+#include "load-dropin.h"
+
+static const UnitActiveState state_translation_table[_SCOPE_STATE_MAX] = {
+        [SCOPE_DEAD] = UNIT_INACTIVE,
+        [SCOPE_RUNNING] = UNIT_ACTIVE,
+        [SCOPE_STOP_SIGTERM] = UNIT_DEACTIVATING,
+        [SCOPE_STOP_SIGKILL] = UNIT_DEACTIVATING,
+        [SCOPE_FAILED] = UNIT_FAILED
+};
+
+static void scope_init(Unit *u) {
+        Scope *s = SCOPE(u);
+
+        assert(u);
+        assert(u->load_state == UNIT_STUB);
+
+        s->timeout_stop_usec = DEFAULT_TIMEOUT_USEC;
+
+        watch_init(&s->timer_watch);
+
+        cgroup_context_init(&s->cgroup_context);
+        kill_context_init(&s->kill_context);
+
+        UNIT(s)->ignore_on_isolate = true;
+        UNIT(s)->ignore_on_snapshot = true;
+}
+
+static void scope_done(Unit *u) {
+        Scope *s = SCOPE(u);
+
+        assert(u);
+
+        cgroup_context_done(&s->cgroup_context);
+
+        set_free(s->pids);
+        s->pids = NULL;
+
+        unit_unwatch_timer(u, &s->timer_watch);
+}
+
+static void scope_set_state(Scope *s, ScopeState state) {
+        ScopeState old_state;
+        assert(s);
+
+        old_state = s->state;
+        s->state = state;
+
+        if (state != SCOPE_STOP_SIGTERM &&
+            state != SCOPE_STOP_SIGKILL)
+                unit_unwatch_timer(UNIT(s), &s->timer_watch);
+
+        if (state != old_state)
+                log_debug("%s changed %s -> %s",
+                          UNIT(s)->id,
+                          scope_state_to_string(old_state),
+                          scope_state_to_string(state));
+
+        unit_notify(UNIT(s), state_translation_table[old_state], state_translation_table[state], true);
+}
+
+static int scope_add_default_dependencies(Scope *s) {
+        int r;
+
+        assert(s);
+
+        /* Make sure scopes are unloaded on shutdown */
+        r = unit_add_two_dependencies_by_name(
+                        UNIT(s),
+                        UNIT_BEFORE, UNIT_CONFLICTS,
+                        SPECIAL_SHUTDOWN_TARGET, NULL, true);
+        if (r < 0)
+                return r;
+
+        return 0;
+}
+
+static int scope_verify(Scope *s) {
+        assert(s);
+
+        if (UNIT(s)->load_state != UNIT_LOADED)
+                return 0;
+
+        if (set_size(s->pids) <= 0) {
+                log_error_unit(UNIT(s)->id, "Scope %s has no PIDs. Refusing.", UNIT(s)->id);
+                return -EINVAL;
+        }
+
+        return 0;
+}
+
+static int scope_load(Unit *u) {
+        Scope *s = SCOPE(u);
+        int r;
+
+        assert(s);
+        assert(u->load_state == UNIT_STUB);
+
+        if (!u->transient && UNIT(s)->manager->n_reloading <= 0)
+                return -ENOENT;
+
+        u->load_state = UNIT_LOADED;
+
+        r = unit_load_dropin(u);
+        if (r < 0)
+                return r;
+
+        r = unit_add_default_slice(u);
+        if (r < 0)
+                return r;
+
+        if (u->default_dependencies) {
+                r = scope_add_default_dependencies(s);
+                if (r < 0)
+                        return r;
+        }
+
+        return scope_verify(s);
+}
+
+static int scope_coldplug(Unit *u) {
+        Scope *s = SCOPE(u);
+        int r;
+
+        assert(s);
+        assert(s->state == SCOPE_DEAD);
+
+        if (s->deserialized_state != s->state) {
+
+                if ((s->deserialized_state == SCOPE_STOP_SIGKILL || s->deserialized_state == SCOPE_STOP_SIGTERM)
+                    && s->timeout_stop_usec > 0) {
+                        r = unit_watch_timer(UNIT(s), CLOCK_MONOTONIC, true, s->timeout_stop_usec, &s->timer_watch);
+                        if (r < 0)
+
+                                return r;
+                }
+
+                scope_set_state(s, s->deserialized_state);
+        }
+
+        return 0;
+}
+
+static void scope_dump(Unit *u, FILE *f, const char *prefix) {
+        Scope *s = SCOPE(u);
+
+        assert(s);
+        assert(f);
+
+        fprintf(f,
+                "%sScope State: %s\n"
+                "%sResult: %s\n",
+                prefix, scope_state_to_string(s->state),
+                prefix, scope_result_to_string(s->result));
+
+        cgroup_context_dump(&s->cgroup_context, f, prefix);
+        kill_context_dump(&s->kill_context, f, prefix);
+}
+
+static void scope_enter_dead(Scope *s, ScopeResult f) {
+        assert(s);
+
+        if (f != SCOPE_SUCCESS)
+                s->result = f;
+
+        scope_set_state(s, s->result != SCOPE_SUCCESS ? SCOPE_FAILED : SCOPE_DEAD);
+}
+
+static void scope_enter_signal(Scope *s, ScopeState state, ScopeResult f) {
+        int r;
+
+        assert(s);
+
+        if (f != SCOPE_SUCCESS)
+                s->result = f;
+
+        r = unit_kill_context(
+                        UNIT(s),
+                        &s->kill_context,
+                        state != SCOPE_STOP_SIGTERM,
+                        -1, -1, false);
+        if (r < 0)
+                goto fail;
+
+        if (r > 0) {
+                if (s->timeout_stop_usec > 0) {
+                        r = unit_watch_timer(UNIT(s), CLOCK_MONOTONIC, true, s->timeout_stop_usec, &s->timer_watch);
+                        if (r < 0)
+                                goto fail;
+                }
+
+                scope_set_state(s, state);
+        } else
+                scope_enter_dead(s, SCOPE_SUCCESS);
+
+        return;
+
+fail:
+        log_warning_unit(UNIT(s)->id,
+                         "%s failed to kill processes: %s", UNIT(s)->id, strerror(-r));
+
+        scope_enter_dead(s, SCOPE_FAILURE_RESOURCES);
+}
+
+static int scope_start(Unit *u) {
+        Scope *s = SCOPE(u);
+        int r;
+
+        assert(s);
+
+        if (s->state == SCOPE_STOP_SIGTERM ||
+            s->state == SCOPE_STOP_SIGKILL)
+                return -EAGAIN;
+
+        assert(s->state == SCOPE_DEAD);
+
+        if (!u->transient && UNIT(s)->manager->n_reloading <= 0)
+                return -ENOENT;
+
+        r = unit_realize_cgroup(u);
+        if (r < 0) {
+                log_error("Failed to realize cgroup: %s", strerror(-r));
+                return r;
+        }
+
+        r = cg_attach_many_with_mask(u->cgroup_mask, u->cgroup_path, s->pids);
+        if (r < 0)
+                return r;
+
+        set_free(s->pids);
+        s->pids = NULL;
+
+        s->result = SCOPE_SUCCESS;
+
+        scope_set_state(s, SCOPE_RUNNING);
+        return 0;
+}
+
+static int scope_stop(Unit *u) {
+        Scope *s = SCOPE(u);
+
+        assert(s);
+        assert(s->state == SCOPE_RUNNING);
+
+        if (s->state == SCOPE_STOP_SIGTERM ||
+            s->state == SCOPE_STOP_SIGKILL)
+                return 0;
+
+        assert(s->state == SCOPE_RUNNING);
+
+        scope_enter_signal(s, SCOPE_STOP_SIGTERM, SCOPE_SUCCESS);
+        return 0;
+}
+
+static int scope_kill(Unit *u, KillWho who, int signo, DBusError *error) {
+        return unit_kill_common(u, who, signo, -1, -1, error);
+}
+
+static int scope_serialize(Unit *u, FILE *f, FDSet *fds) {
+        Scope *s = SCOPE(u);
+
+        assert(s);
+        assert(f);
+        assert(fds);
+
+        unit_serialize_item(u, f, "state", scope_state_to_string(s->state));
+        return 0;
+}
+
+static int scope_deserialize_item(Unit *u, const char *key, const char *value, FDSet *fds) {
+        Scope *s = SCOPE(u);
+
+        assert(u);
+        assert(key);
+        assert(value);
+        assert(fds);
+
+        if (streq(key, "state")) {
+                ScopeState state;
+
+                state = scope_state_from_string(value);
+                if (state < 0)
+                        log_debug("Failed to parse state value %s", value);
+                else
+                        s->deserialized_state = state;
+
+        } else
+                log_debug("Unknown serialization key '%s'", key);
+
+        return 0;
+}
+
+static bool scope_check_gc(Unit *u) {
+        Scope *s = SCOPE(u);
+        int r;
+
+        assert(s);
+
+        /* Never clean up scopes that still have a process around,
+         * even if the scope is formally dead. */
+
+        if (UNIT(s)->cgroup_path) {
+                r = cg_is_empty_recursive(SYSTEMD_CGROUP_CONTROLLER, UNIT(s)->cgroup_path, true);
+                if (r <= 0)
+                        return true;
+        }
+
+        return false;
+}
+
+static void scope_timer_event(Unit *u, uint64_t elapsed, Watch*w) {
+        Scope *s = SCOPE(u);
+
+        assert(s);
+        assert(elapsed == 1);
+        assert(w == &s->timer_watch);
+
+        switch (s->state) {
+
+        case SCOPE_STOP_SIGTERM:
+                if (s->kill_context.send_sigkill) {
+                        log_warning_unit(u->id, "%s stopping timed out. Killing.", u->id);
+                        scope_enter_signal(s, SCOPE_STOP_SIGKILL, SCOPE_FAILURE_TIMEOUT);
+                } else {
+                        log_warning_unit(u->id, "%s stopping timed out. Skipping SIGKILL.", u->id);
+                        scope_enter_dead(s, SCOPE_FAILURE_TIMEOUT);
+                }
+
+                break;
+
+        case SCOPE_STOP_SIGKILL:
+                log_warning_unit(u->id, "%s still around after SIGKILL. Ignoring.", u->id);
+                scope_enter_dead(s, SCOPE_FAILURE_TIMEOUT);
+                break;
+
+        default:
+                assert_not_reached("Timeout at wrong time.");
+        }
+}
+
+static void scope_notify_cgroup_empty_event(Unit *u) {
+        Scope *s = SCOPE(u);
+        assert(u);
+
+        log_debug_unit(u->id, "%s: cgroup is empty", u->id);
+
+        switch (s->state) {
+
+        case SCOPE_RUNNING:
+        case SCOPE_STOP_SIGTERM:
+        case SCOPE_STOP_SIGKILL:
+                scope_enter_dead(s, SCOPE_SUCCESS);
+
+                break;
+
+        default:
+                ;
+        }
+}
+
+_pure_ static UnitActiveState scope_active_state(Unit *u) {
+        assert(u);
+
+        return state_translation_table[SCOPE(u)->state];
+}
+
+_pure_ static const char *scope_sub_state_to_string(Unit *u) {
+        assert(u);
+
+        return scope_state_to_string(SCOPE(u)->state);
+}
+
+static const char* const scope_state_table[_SCOPE_STATE_MAX] = {
+        [SCOPE_DEAD] = "dead",
+        [SCOPE_RUNNING] = "active",
+        [SCOPE_STOP_SIGTERM] = "stop-sigterm",
+        [SCOPE_STOP_SIGKILL] = "stop-sigkill",
+        [SCOPE_FAILED] = "failed",
+};
+
+DEFINE_STRING_TABLE_LOOKUP(scope_state, ScopeState);
+
+static const char* const scope_result_table[_SCOPE_RESULT_MAX] = {
+        [SCOPE_SUCCESS] = "success",
+        [SCOPE_FAILURE_RESOURCES] = "resources",
+        [SCOPE_FAILURE_TIMEOUT] = "timeout",
+};
+
+DEFINE_STRING_TABLE_LOOKUP(scope_result, ScopeResult);
+
+const UnitVTable scope_vtable = {
+        .object_size = sizeof(Scope),
+        .sections =
+                "Unit\0"
+                "Scope\0"
+                "Install\0",
+
+        .private_section = "Scope",
+        .cgroup_context_offset = offsetof(Scope, cgroup_context),
+
+        .no_alias = true,
+        .no_instances = true,
+
+        .init = scope_init,
+        .load = scope_load,
+        .done = scope_done,
+
+        .coldplug = scope_coldplug,
+
+        .dump = scope_dump,
+
+        .start = scope_start,
+        .stop = scope_stop,
+
+        .kill = scope_kill,
+
+        .serialize = scope_serialize,
+        .deserialize_item = scope_deserialize_item,
+
+        .active_state = scope_active_state,
+        .sub_state_to_string = scope_sub_state_to_string,
+
+        .check_gc = scope_check_gc,
+
+        .timer_event = scope_timer_event,
+
+        .notify_cgroup_empty = scope_notify_cgroup_empty_event,
+
+        .bus_interface = "org.freedesktop.systemd1.Scope",
+        .bus_message_handler = bus_scope_message_handler,
+        .bus_set_property = bus_scope_set_property,
+        .bus_commit_properties = bus_scope_commit_properties,
+
+        .can_transient = true
+};