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core: add new "PollLimit" settings to .socket units

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This adds a new "PollLimit" pair of settings to .socket units, very
similar to existing "TriggerLimit" logic. The differences are:

* PollLimit focusses on the polling on the sockets, and pauses that
  temporarily if a ratelimit on that is reached. TriggerLimit otoh
  focusses on the triggering effect of socket units, and stops
  triggering once the ratelimit is hit.

* While the trigger limit being hit is an action that causes the socket
  unit to fail the polling limit being reached will just temporarily
  disable polling on the socket fd, and it is resumed once the ratelimit
  interval is over.

* When a socket unit operates on multiple socket fds (e,g, ListenStream=
  on both some ipv6 and an ipv4 address or so). Then the PollLimit will
  be specific to each fd, while the trigger limit is specific to the
  whole unit.

Implementation-wise this is mostly a wrapper around sd-event's
sd_event_source_set_ratelimit(), which exposes the desired behaviour
directly.

Usecase for all of this: socket services which when overloaded with
connections should just slow down reception of it, but not fail
persistently.
This commit is contained in:
Lennart Poettering 2023-09-09 14:46:32 +02:00
parent 8fbf0a214e
commit 2bec84e7a5
6 changed files with 53 additions and 13 deletions
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12
man/org.freedesktop.systemd1.xml
View File

@ -4735,6 +4735,10 @@ node /org/freedesktop/systemd1/unit/avahi_2ddaemon_2esocket {
readonly t TriggerLimitIntervalUSec = ...;
@org.freedesktop.DBus.Property.EmitsChangedSignal("const")
readonly u TriggerLimitBurst = ...;
@org.freedesktop.DBus.Property.EmitsChangedSignal("const")
readonly t PollLimitIntervalUSec = ...;
@org.freedesktop.DBus.Property.EmitsChangedSignal("const")
readonly u PollLimitBurst = ...;
readonly u UID = ...;
readonly u GID = ...;
@org.freedesktop.DBus.Property.EmitsChangedSignal("invalidates")
@ -5969,6 +5973,10 @@ node /org/freedesktop/systemd1/unit/avahi_2ddaemon_2esocket {
<variablelist class="dbus-property" generated="True" extra-ref="TriggerLimitBurst"/>
<variablelist class="dbus-property" generated="True" extra-ref="PollLimitIntervalUSec"/>
<variablelist class="dbus-property" generated="True" extra-ref="PollLimitBurst"/>
<variablelist class="dbus-property" generated="True" extra-ref="UID"/>
<variablelist class="dbus-property" generated="True" extra-ref="GID"/>
@ -6505,6 +6513,10 @@ node /org/freedesktop/systemd1/unit/avahi_2ddaemon_2esocket {
<!--End of Autogenerated section-->
<para><varname>PollLimitIntervalUSec</varname>/<varname>PollLimitBurst</varname> properties configure the
polling limit for the socket unit. Expects a time in µs, resp. an unsigned integer. If either is set to
zero the limiting feature is turned off.</para>
<refsect2>
<title>Properties</title>

8
src/core/dbus-socket.c
View File

@ -129,6 +129,8 @@ const sd_bus_vtable bus_socket_vtable[] = {
SD_BUS_PROPERTY("SocketProtocol", "i", bus_property_get_int, offsetof(Socket, socket_protocol), SD_BUS_VTABLE_PROPERTY_CONST),
SD_BUS_PROPERTY("TriggerLimitIntervalUSec", "t", bus_property_get_usec, offsetof(Socket, trigger_limit.interval), SD_BUS_VTABLE_PROPERTY_CONST),
SD_BUS_PROPERTY("TriggerLimitBurst", "u", bus_property_get_unsigned, offsetof(Socket, trigger_limit.burst), SD_BUS_VTABLE_PROPERTY_CONST),
SD_BUS_PROPERTY("PollLimitIntervalUSec", "t", bus_property_get_usec, offsetof(Socket, poll_limit_interval), SD_BUS_VTABLE_PROPERTY_CONST),
SD_BUS_PROPERTY("PollLimitBurst", "u", bus_property_get_unsigned, offsetof(Socket, poll_limit_burst), SD_BUS_VTABLE_PROPERTY_CONST),
SD_BUS_PROPERTY("UID", "u", bus_property_get_uid, offsetof(Unit, ref_uid), SD_BUS_VTABLE_PROPERTY_EMITS_CHANGE),
SD_BUS_PROPERTY("GID", "u", bus_property_get_gid, offsetof(Unit, ref_gid), SD_BUS_VTABLE_PROPERTY_EMITS_CHANGE),
BUS_EXEC_COMMAND_LIST_VTABLE("ExecStartPre", offsetof(Socket, exec_command[SOCKET_EXEC_START_PRE]), SD_BUS_VTABLE_PROPERTY_EMITS_INVALIDATION),
@ -248,6 +250,9 @@ static int bus_socket_set_transient_property(
if (streq(name, "TriggerLimitBurst"))
return bus_set_transient_unsigned(u, name, &s->trigger_limit.burst, message, flags, error);
if (streq(name, "PollLimitBurst"))
return bus_set_transient_unsigned(u, name, &s->poll_limit_burst, message, flags, error);
if (streq(name, "SocketMode"))
return bus_set_transient_mode_t(u, name, &s->socket_mode, message, flags, error);
@ -275,6 +280,9 @@ static int bus_socket_set_transient_property(
if (streq(name, "TriggerLimitIntervalUSec"))
return bus_set_transient_usec(u, name, &s->trigger_limit.interval, message, flags, error);
if (streq(name, "PollLimitIntervalUSec"))
return bus_set_transient_usec(u, name, &s->poll_limit_interval, message, flags, error);
if (streq(name, "SmackLabel"))
return bus_set_transient_string(u, name, &s->smack, message, flags, error);

2
src/core/load-fragment-gperf.gperf.in
View File

@ -507,6 +507,8 @@ Socket.FileDescriptorName, config_parse_fdname,
Socket.Service, config_parse_socket_service, 0, 0
Socket.TriggerLimitIntervalSec, config_parse_sec, 0, offsetof(Socket, trigger_limit.interval)
Socket.TriggerLimitBurst, config_parse_unsigned, 0, offsetof(Socket, trigger_limit.burst)
Socket.PollLimitIntervalSec, config_parse_sec, 0, offsetof(Socket, poll_limit_interval)
Socket.PollLimitBurst, config_parse_unsigned, 0, offsetof(Socket, poll_limit_burst)
{% if ENABLE_SMACK %}
Socket.SmackLabel, config_parse_unit_string_printf, 0, offsetof(Socket, smack)
Socket.SmackLabelIPIn, config_parse_unit_string_printf, 0, offsetof(Socket, smack_ip_in)

32
src/core/socket.c
View File

@ -102,6 +102,9 @@ static void socket_init(Unit *u) {
s->trigger_limit.interval = USEC_INFINITY;
s->trigger_limit.burst = UINT_MAX;
s->poll_limit_interval = USEC_INFINITY;
s->poll_limit_burst = UINT_MAX;
}
static void socket_unwatch_control_pid(Socket *s) {
@ -307,17 +310,20 @@ static int socket_add_extras(Socket *s) {
* off the queues, which it might not necessarily do. Moreover, while Accept=no services are supposed to
* process whatever is queued in one go, and thus should normally never have to be started frequently. This is
* different for Accept=yes where each connection is processed by a new service instance, and thus frequent
* service starts are typical. */
* service starts are typical.
*
* For the poll limit we follow a similar rule, but use 3/4th of the trigger limit parameters, to
* trigger this earlier. */
if (s->trigger_limit.interval == USEC_INFINITY)
s->trigger_limit.interval = 2 * USEC_PER_SEC;
if (s->trigger_limit.burst == UINT_MAX)
s->trigger_limit.burst = s->accept ? 200 : 20;
if (s->trigger_limit.burst == UINT_MAX) {
if (s->accept)
s->trigger_limit.burst = 200;
else
s->trigger_limit.burst = 20;
}
if (s->poll_limit_interval == USEC_INFINITY)
s->poll_limit_interval = 2 * USEC_PER_SEC;
if (s->poll_limit_burst == UINT_MAX)
s->poll_limit_burst = s->accept ? 150 : 15;
if (have_non_accept_socket(s)) {
@ -767,9 +773,13 @@ static void socket_dump(Unit *u, FILE *f, const char *prefix) {
fprintf(f,
"%sTriggerLimitIntervalSec: %s\n"
"%sTriggerLimitBurst: %u\n",
"%sTriggerLimitBurst: %u\n"
"%sPollLimitIntervalSec: %s\n"
"%sPollLimitBurst: %u\n",
prefix, FORMAT_TIMESPAN(s->trigger_limit.interval, USEC_PER_SEC),
prefix, s->trigger_limit.burst);
prefix, s->trigger_limit.burst,
prefix, FORMAT_TIMESPAN(s->poll_limit_interval, USEC_PER_SEC),
prefix, s->poll_limit_burst);
str = ip_protocol_to_name(s->socket_protocol);
if (str)
@ -1761,6 +1771,10 @@ static int socket_watch_fds(Socket *s) {
(void) sd_event_source_set_description(p->event_source, "socket-port-io");
}
r = sd_event_source_set_ratelimit(p->event_source, s->poll_limit_interval, s->poll_limit_burst);
if (r < 0)
log_unit_debug_errno(UNIT(s), r, "Failed to set poll limit on I/O event source, ignoring: %m");
}
return 0;

2
src/core/socket.h
View File

@ -159,6 +159,8 @@ struct Socket {
char *fdname;
RateLimit trigger_limit;
usec_t poll_limit_interval;
unsigned poll_limit_burst;
};
SocketPeer *socket_peer_ref(SocketPeer *p);

10
src/shared/bus-unit-util.c
View File

@ -2165,10 +2165,10 @@ static int bus_append_path_property(sd_bus_message *m, const char *field, const
return 1;
}
if (streq(field, "TriggerLimitBurst"))
if (STR_IN_SET(field, "TriggerLimitBurst", "PollLimitBurst"))
return bus_append_safe_atou(m, field, eq);
if (streq(field, "TriggerLimitIntervalSec"))
if (STR_IN_SET(field, "TriggerLimitIntervalSec", "PollLimitIntervalSec"))
return bus_append_parse_sec_rename(m, field, eq);
return 0;
@ -2377,7 +2377,8 @@ static int bus_append_socket_property(sd_bus_message *m, const char *field, cons
"MaxConnections",
"MaxConnectionsPerSource",
"KeepAliveProbes",
"TriggerLimitBurst"))
"TriggerLimitBurst",
"PollLimitBurst"))
return bus_append_safe_atou(m, field, eq);
if (STR_IN_SET(field, "SocketMode",
@ -2392,7 +2393,8 @@ static int bus_append_socket_property(sd_bus_message *m, const char *field, cons
"KeepAliveTimeSec",
"KeepAliveIntervalSec",
"DeferAcceptSec",
"TriggerLimitIntervalSec"))
"TriggerLimitIntervalSec",
"PollLimitIntervalSec"))
return bus_append_parse_sec_rename(m, field, eq);
if (STR_IN_SET(field, "ReceiveBuffer",