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hostnamed: minimize caching of /etc/hostname, /etc/os-release and /et…
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…c/machine-info

Instead of reading these files at startup and never again, let's read
them when we need them. As an optimization (in particular as some of
these files contain the data for many fields at once) let's cache the
results as long as the stat data (i.e. mtime) remains stable.

Also, while we are at it, if we can't read any of these props, let's not
fail everything, but continue without the data.
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@poettering
poettering committed Apr 30, 2020
1 parent a916a88 commit 25d7777
Showing 1 changed file with 142 additions and 24 deletions.
166 changes: 142 additions & 24 deletions src/hostname/hostnamed.c
View file
Expand Up @@ -27,6 +27,7 @@
#include "path-util.h"
#include "selinux-util.h"
#include "signal-util.h"
#include "stat-util.h"
#include "strv.h"
#include "user-util.h"
#include "util.h"
Expand All @@ -35,49 +36,89 @@
#define VALID_DEPLOYMENT_CHARS (DIGITS LETTERS "-.:")

enum {
/* Read from /etc/hostname */
PROP_STATIC_HOSTNAME,

/* Read from /etc/machine-info */
PROP_PRETTY_HOSTNAME,
PROP_ICON_NAME,
PROP_CHASSIS,
PROP_DEPLOYMENT,
PROP_LOCATION,

/* Read from /etc/os-release (or /usr/lib/os-release) */
PROP_OS_PRETTY_NAME,
PROP_OS_CPE_NAME,
PROP_HOME_URL,
_PROP_MAX
PROP_OS_HOME_URL,
_PROP_MAX,
_PROP_INVALID = -1,
};

typedef struct Context {
char *data[_PROP_MAX];

struct stat etc_hostname_stat;
struct stat etc_os_release_stat;
struct stat etc_machine_info_stat;

Hashmap *polkit_registry;
} Context;

static void context_reset(Context *c) {
static void context_reset(Context *c, uint64_t mask) {
int p;

assert(c);

for (p = 0; p < _PROP_MAX; p++)
for (p = 0; p < _PROP_MAX; p++) {
if (!FLAGS_SET(mask, UINT64_C(1) << p))
continue;

c->data[p] = mfree(c->data[p]);
}
}

static void context_destroy(Context *c) {
assert(c);

context_reset(c);
context_reset(c, UINT64_MAX);
bus_verify_polkit_async_registry_free(c->polkit_registry);
}

static int context_read_data(Context *c) {
static void context_read_etc_hostname(Context *c) {
struct stat current_stat = {};
int r;

assert(c);

context_reset(c);
if (stat("/etc/hostname", &current_stat) >= 0 &&
stat_inode_unmodified(&c->etc_hostname_stat, &current_stat))
return;

context_reset(c, UINT64_C(1) << PROP_STATIC_HOSTNAME);

r = read_etc_hostname(NULL, &c->data[PROP_STATIC_HOSTNAME]);
if (r < 0 && r != -ENOENT)
return r;
log_warning_errno(r, "Failed to read /etc/hostname, ignoring: %m");

c->etc_hostname_stat = current_stat;
}

static void context_read_machine_info(Context *c) {
struct stat current_stat = {};
int r;

assert(c);

if (stat("/etc/machine-info", &current_stat) >= 0 &&
stat_inode_unmodified(&c->etc_machine_info_stat, &current_stat))
return;

context_reset(c,
(UINT64_C(1) << PROP_PRETTY_HOSTNAME) |
(UINT64_C(1) << PROP_ICON_NAME) |
(UINT64_C(1) << PROP_CHASSIS) |
(UINT64_C(1) << PROP_DEPLOYMENT) |
(UINT64_C(1) << PROP_LOCATION));

r = parse_env_file(NULL, "/etc/machine-info",
"PRETTY_HOSTNAME", &c->data[PROP_PRETTY_HOSTNAME],
Expand All @@ -86,17 +127,36 @@ static int context_read_data(Context *c) {
"DEPLOYMENT", &c->data[PROP_DEPLOYMENT],
"LOCATION", &c->data[PROP_LOCATION]);
if (r < 0 && r != -ENOENT)
return r;
log_warning_errno(r, "Failed to read /etc/machine-info, ignoring: %m");

c->etc_machine_info_stat = current_stat;
}

static void context_read_os_release(Context *c) {
struct stat current_stat = {};
int r;

assert(c);

if ((stat("/etc/os-release", &current_stat) >= 0 ||
stat("/usr/lib/os-release", &current_stat) >= 0) &&
stat_inode_unmodified(&c->etc_os_release_stat, &current_stat))
return;

context_reset(c,
(UINT64_C(1) << PROP_OS_PRETTY_NAME) |
(UINT64_C(1) << PROP_OS_CPE_NAME) |
(UINT64_C(1) << PROP_OS_HOME_URL));

r = parse_os_release(NULL,
"PRETTY_NAME", &c->data[PROP_OS_PRETTY_NAME],
"CPE_NAME", &c->data[PROP_OS_CPE_NAME],
"HOME_URL", &c->data[PROP_HOME_URL],
"HOME_URL", &c->data[PROP_OS_HOME_URL],
NULL);
if (r < 0 && r != -ENOENT)
return r;
log_warning_errno(r, "Failed to read os-release file, ignoring: %m");

return 0;
c->etc_os_release_stat = current_stat;
}

static bool valid_chassis(const char *chassis) {
Expand Down Expand Up @@ -284,7 +344,6 @@ static int context_update_kernel_hostname(
}

static int context_write_data_static_hostname(Context *c) {

assert(c);

if (isempty(c->data[PROP_STATIC_HOSTNAME])) {
Expand Down Expand Up @@ -369,6 +428,65 @@ static int property_get_hostname(
return sd_bus_message_append(reply, "s", current);
}

static int property_get_static_hostname(
sd_bus *bus,
const char *path,
const char *interface,
const char *property,
sd_bus_message *reply,
void *userdata,
sd_bus_error *error) {

Context *c = userdata;
assert(c);

context_read_etc_hostname(c);

return sd_bus_message_append(reply, "s", c->data[PROP_STATIC_HOSTNAME]);
}

static int property_get_machine_info_field(
sd_bus *bus,
const char *path,
const char *interface,
const char *property,
sd_bus_message *reply,
void *userdata,
sd_bus_error *error) {

sd_bus_slot *slot;
Context *c;

/* The the current context without the property userdata offset added */
assert_se(slot = sd_bus_get_current_slot(bus));
assert_se(c = sd_bus_slot_get_userdata(slot));

context_read_machine_info(c);

return sd_bus_message_append(reply, "s", *(char**) userdata);
}

static int property_get_os_release_field(
sd_bus *bus,
const char *path,
const char *interface,
const char *property,
sd_bus_message *reply,
void *userdata,
sd_bus_error *error) {

sd_bus_slot *slot;
Context *c;

/* The the current context without the property userdata offset added */
assert_se(slot = sd_bus_get_current_slot(bus));
assert_se(c = sd_bus_slot_get_userdata(slot));

context_read_os_release(c);

return sd_bus_message_append(reply, "s", *(char**) userdata);
}

static int property_get_icon_name(
sd_bus *bus,
const char *path,
Expand All @@ -382,6 +500,8 @@ static int property_get_icon_name(
Context *c = userdata;
const char *name;

context_read_machine_info(c);

if (isempty(c->data[PROP_ICON_NAME]))
name = n = context_fallback_icon_name(c);
else
Expand All @@ -405,6 +525,8 @@ static int property_get_chassis(
Context *c = userdata;
const char *name;

context_read_machine_info(c);

if (isempty(c->data[PROP_CHASSIS]))
name = fallback_chassis();
else
Expand Down Expand Up @@ -696,18 +818,18 @@ static int method_get_product_uuid(sd_bus_message *m, void *userdata, sd_bus_err
static const sd_bus_vtable hostname_vtable[] = {
SD_BUS_VTABLE_START(0),
SD_BUS_PROPERTY("Hostname", "s", property_get_hostname, 0, SD_BUS_VTABLE_PROPERTY_EMITS_CHANGE),
SD_BUS_PROPERTY("StaticHostname", "s", NULL, offsetof(Context, data) + sizeof(char*) * PROP_STATIC_HOSTNAME, SD_BUS_VTABLE_PROPERTY_EMITS_CHANGE),
SD_BUS_PROPERTY("PrettyHostname", "s", NULL, offsetof(Context, data) + sizeof(char*) * PROP_PRETTY_HOSTNAME, SD_BUS_VTABLE_PROPERTY_EMITS_CHANGE),
SD_BUS_PROPERTY("StaticHostname", "s", property_get_static_hostname, 0, SD_BUS_VTABLE_PROPERTY_EMITS_CHANGE),
SD_BUS_PROPERTY("PrettyHostname", "s", property_get_machine_info_field, offsetof(Context, data) + sizeof(char*) * PROP_PRETTY_HOSTNAME, SD_BUS_VTABLE_PROPERTY_EMITS_CHANGE),
SD_BUS_PROPERTY("IconName", "s", property_get_icon_name, 0, SD_BUS_VTABLE_PROPERTY_EMITS_CHANGE),
SD_BUS_PROPERTY("Chassis", "s", property_get_chassis, 0, SD_BUS_VTABLE_PROPERTY_EMITS_CHANGE),
SD_BUS_PROPERTY("Deployment", "s", NULL, offsetof(Context, data) + sizeof(char*) * PROP_DEPLOYMENT, SD_BUS_VTABLE_PROPERTY_EMITS_CHANGE),
SD_BUS_PROPERTY("Location", "s", NULL, offsetof(Context, data) + sizeof(char*) * PROP_LOCATION, SD_BUS_VTABLE_PROPERTY_EMITS_CHANGE),
SD_BUS_PROPERTY("Deployment", "s", property_get_machine_info_field, offsetof(Context, data) + sizeof(char*) * PROP_DEPLOYMENT, SD_BUS_VTABLE_PROPERTY_EMITS_CHANGE),
SD_BUS_PROPERTY("Location", "s", property_get_machine_info_field, offsetof(Context, data) + sizeof(char*) * PROP_LOCATION, SD_BUS_VTABLE_PROPERTY_EMITS_CHANGE),
SD_BUS_PROPERTY("KernelName", "s", property_get_uname_field, offsetof(struct utsname, sysname), SD_BUS_VTABLE_ABSOLUTE_OFFSET|SD_BUS_VTABLE_PROPERTY_CONST),
SD_BUS_PROPERTY("KernelRelease", "s", property_get_uname_field, offsetof(struct utsname, release), SD_BUS_VTABLE_ABSOLUTE_OFFSET|SD_BUS_VTABLE_PROPERTY_CONST),
SD_BUS_PROPERTY("KernelVersion", "s", property_get_uname_field, offsetof(struct utsname, version), SD_BUS_VTABLE_ABSOLUTE_OFFSET|SD_BUS_VTABLE_PROPERTY_CONST),
SD_BUS_PROPERTY("OperatingSystemPrettyName", "s", NULL, offsetof(Context, data) + sizeof(char*) * PROP_OS_PRETTY_NAME, SD_BUS_VTABLE_PROPERTY_CONST),
SD_BUS_PROPERTY("OperatingSystemCPEName", "s", NULL, offsetof(Context, data) + sizeof(char*) * PROP_OS_CPE_NAME, SD_BUS_VTABLE_PROPERTY_CONST),
SD_BUS_PROPERTY("HomeURL", "s", NULL, offsetof(Context, data) + sizeof(char*) * PROP_HOME_URL, SD_BUS_VTABLE_PROPERTY_CONST),
SD_BUS_PROPERTY("OperatingSystemPrettyName", "s", property_get_os_release_field, offsetof(Context, data) + sizeof(char*) * PROP_OS_PRETTY_NAME, SD_BUS_VTABLE_PROPERTY_CONST),
SD_BUS_PROPERTY("OperatingSystemCPEName", "s", property_get_os_release_field, offsetof(Context, data) + sizeof(char*) * PROP_OS_CPE_NAME, SD_BUS_VTABLE_PROPERTY_CONST),
SD_BUS_PROPERTY("HomeURL", "s", property_get_os_release_field, offsetof(Context, data) + sizeof(char*) * PROP_OS_HOME_URL, SD_BUS_VTABLE_PROPERTY_CONST),

SD_BUS_METHOD_WITH_NAMES("SetHostname",
"sb",
Expand Down Expand Up @@ -838,10 +960,6 @@ static int run(int argc, char *argv[]) {
if (r < 0)
return r;

r = context_read_data(&context);
if (r < 0)
return log_error_errno(r, "Failed to read hostname and machine information: %m");

r = bus_event_loop_with_idle(event, bus, "org.freedesktop.hostname1", DEFAULT_EXIT_USEC, NULL, NULL);
if (r < 0)
return log_error_errno(r, "Failed to run event loop: %m");
Expand Down

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