[glib/wip/tingping/gresolver-cache] gresolver: Implement a simple and short-lived dns cache
- From: Patrick Griffis <pgriffis src gnome org>
- To: commits-list gnome org
- Cc:
- Subject: [glib/wip/tingping/gresolver-cache] gresolver: Implement a simple and short-lived dns cache
- Date: Tue, 19 Feb 2019 14:55:07 +0000 (UTC)
commit bd6da07f0b47d96ec77219239b1d4a27d3ed5831
Author: Patrick Griffis <pgriffis igalia com>
Date: Tue Feb 19 09:46:29 2019 -0500
gresolver: Implement a simple and short-lived dns cache
Introducing a local cache is an optimization that smooths over
clients making many requests to the same host in a short period
of time unnecessarily resolving it repeatedly.
The difference can vary from dramatic on systems lacking a caching
resolver to minor on fast and cached systems but in some workloads
like a web browser it can be measurable.
It is only short-lived (1 minute currently) as it is not intended
to fully replace caching system resolvers.
gio/gthreadedresolver.c | 226 +++++++++++++++++++++++++++++++++++++-----------
1 file changed, 175 insertions(+), 51 deletions(-)
---
diff --git a/gio/gthreadedresolver.c b/gio/gthreadedresolver.c
index a6dd35c1b..d46f8f324 100644
--- a/gio/gthreadedresolver.c
+++ b/gio/gthreadedresolver.c
@@ -39,6 +39,118 @@
G_DEFINE_TYPE (GThreadedResolver, g_threaded_resolver, G_TYPE_RESOLVER)
+static GHashTable *dns_caches[3];
+G_LOCK_DEFINE_STATIC (dns_caches);
+
+typedef struct {
+ GList *addresses; /* owned */
+ time_t expiration;
+} CachedResponse;
+
+static void
+cached_response_free (CachedResponse *cache)
+{
+ g_resolver_free_addresses (cache->addresses);
+ g_free (cache);
+}
+
+static void
+init_dns_caches (void)
+{
+ guint i;
+ for (i = 0; i < G_N_ELEMENTS (dns_caches); ++i)
+ dns_caches[i] = g_hash_table_new_full (g_str_hash, g_str_equal, g_free, (GDestroyNotify)
cached_response_free);
+}
+
+static GHashTable *
+get_dns_cache_for_flags (GResolverNameLookupFlags flags)
+{
+ GHashTable *cache;
+
+ /* A cache is kept for each type of response to avoid
+ * the over complication of combining or filtering results.
+ */
+ if (flags & G_RESOLVER_NAME_LOOKUP_FLAGS_IPV4_ONLY)
+ cache = dns_caches[0];
+ else if (flags & G_RESOLVER_NAME_LOOKUP_FLAGS_IPV6_ONLY)
+ cache = dns_caches[1];
+ else
+ cache = dns_caches[2];
+
+ if (G_UNLIKELY (cache == NULL))
+ {
+ init_dns_caches ();
+ return get_dns_cache_for_flags (flags);
+ }
+
+ return cache;
+}
+
+static gpointer
+copy_object (gconstpointer obj, gpointer user_data)
+{
+ return g_object_ref (G_OBJECT (obj));
+}
+
+static GList *
+copy_addresses (GList *addresses)
+{
+ return g_list_copy_deep (addresses, copy_object, NULL);
+}
+
+static void
+update_dns_cache (const char *hostname,
+ GList *addresses,
+ GResolverNameLookupFlags flags)
+{
+ CachedResponse *cached;
+ GHashTable *cache;
+
+ G_LOCK (dns_caches);
+
+ cache = get_dns_cache_for_flags (flags);
+ cached = g_new (CachedResponse, 1);
+ cached->addresses = copy_addresses (addresses);
+ cached->expiration = time (NULL) + 60;
+
+ g_hash_table_insert (cache, g_strdup (hostname), cached);
+
+ G_UNLOCK (dns_caches);
+}
+
+/*
+ * Returns: (transfer full): List of addresses
+ */
+static GList *
+query_dns_cache (const char *hostname,
+ GResolverNameLookupFlags flags)
+{
+ CachedResponse *cached;
+ GHashTable *cache;
+ GList *addresses = NULL;
+ GHashTableIter iter;
+ time_t now = time (NULL);
+
+ G_LOCK (dns_caches);
+
+ cache = get_dns_cache_for_flags (flags);
+
+ g_hash_table_iter_init (&iter, cache);
+ while (g_hash_table_iter_next (&iter, NULL, (gpointer*) &cached))
+ {
+ if (cached->expiration <= now)
+ g_hash_table_iter_remove (&iter);
+ }
+
+ cached = g_hash_table_lookup (cache, hostname);
+ if (cached)
+ addresses = copy_addresses (cached->addresses);
+
+ G_UNLOCK (dns_caches);
+
+ return addresses;
+}
+
static void
g_threaded_resolver_init (GThreadedResolver *gtr)
{
@@ -66,16 +178,16 @@ g_resolver_error_from_addrinfo_error (gint err)
typedef struct {
char *hostname;
- int address_family;
+ GResolverNameLookupFlags flags;
} LookupData;
static LookupData *
-lookup_data_new (const char *hostname,
- int address_family)
+lookup_data_new (const char *hostname,
+ GResolverNameLookupFlags flags)
{
LookupData *data = g_new (LookupData, 1);
data->hostname = g_strdup (hostname);
- data->address_family = address_family;
+ data->flags = flags;
return data;
}
@@ -86,6 +198,24 @@ lookup_data_free (LookupData *data)
g_free (data);
}
+static int
+flags_to_family (GResolverNameLookupFlags flags)
+{
+ int address_family = AF_UNSPEC;
+
+ if (flags & G_RESOLVER_NAME_LOOKUP_FLAGS_IPV4_ONLY)
+ address_family = AF_INET;
+
+ if (flags & G_RESOLVER_NAME_LOOKUP_FLAGS_IPV6_ONLY)
+ {
+ address_family = AF_INET6;
+ /* You can only filter by one family at a time */
+ g_return_val_if_fail (!(flags & G_RESOLVER_NAME_LOOKUP_FLAGS_IPV4_ONLY), address_family);
+ }
+
+ return address_family;
+}
+
static void
do_lookup_by_name (GTask *task,
gpointer source_object,
@@ -109,7 +239,7 @@ do_lookup_by_name (GTask *task,
addrinfo_hints.ai_socktype = SOCK_STREAM;
addrinfo_hints.ai_protocol = IPPROTO_TCP;
- addrinfo_hints.ai_family = lookup_data->address_family;
+ addrinfo_hints.ai_family = flags_to_family (lookup_data->flags);
retval = getaddrinfo (hostname, NULL, &addrinfo_hints, &res);
if (retval == 0)
@@ -140,6 +270,7 @@ do_lookup_by_name (GTask *task,
addresses = g_list_reverse (addresses);
g_task_return_pointer (task, addresses,
(GDestroyNotify)g_resolver_free_addresses);
+ update_dns_cache (hostname, addresses, lookup_data->flags);
}
else
{
@@ -165,46 +296,6 @@ do_lookup_by_name (GTask *task,
freeaddrinfo (res);
}
-static GList *
-lookup_by_name (GResolver *resolver,
- const gchar *hostname,
- GCancellable *cancellable,
- GError **error)
-{
- GTask *task;
- GList *addresses;
- LookupData *data;
-
- data = lookup_data_new (hostname, AF_UNSPEC);
- task = g_task_new (resolver, cancellable, NULL, NULL);
- g_task_set_source_tag (task, lookup_by_name);
- g_task_set_task_data (task, data, (GDestroyNotify)lookup_data_free);
- g_task_set_return_on_cancel (task, TRUE);
- g_task_run_in_thread_sync (task, do_lookup_by_name);
- addresses = g_task_propagate_pointer (task, error);
- g_object_unref (task);
-
- return addresses;
-}
-
-static int
-flags_to_family (GResolverNameLookupFlags flags)
-{
- int address_family = AF_UNSPEC;
-
- if (flags & G_RESOLVER_NAME_LOOKUP_FLAGS_IPV4_ONLY)
- address_family = AF_INET;
-
- if (flags & G_RESOLVER_NAME_LOOKUP_FLAGS_IPV6_ONLY)
- {
- address_family = AF_INET6;
- /* You can only filter by one family at a time */
- g_return_val_if_fail (!(flags & G_RESOLVER_NAME_LOOKUP_FLAGS_IPV4_ONLY), address_family);
- }
-
- return address_family;
-}
-
static GList *
lookup_by_name_with_flags (GResolver *resolver,
const gchar *hostname,
@@ -215,19 +306,42 @@ lookup_by_name_with_flags (GResolver *resolver,
GTask *task;
GList *addresses;
LookupData *data;
+ GList *cached;
- data = lookup_data_new (hostname, AF_UNSPEC);
task = g_task_new (resolver, cancellable, NULL, NULL);
g_task_set_source_tag (task, lookup_by_name_with_flags);
- g_task_set_task_data (task, data, (GDestroyNotify)lookup_data_free);
g_task_set_return_on_cancel (task, TRUE);
- g_task_run_in_thread_sync (task, do_lookup_by_name);
+
+ cached = query_dns_cache (hostname, flags);
+ if (cached)
+ g_task_return_pointer (task, cached,
+ (GDestroyNotify)g_resolver_free_addresses);
+ else
+ {
+ data = lookup_data_new (hostname, flags);
+ g_task_set_task_data (task, data, (GDestroyNotify)lookup_data_free);
+ g_task_run_in_thread_sync (task, do_lookup_by_name);
+ }
+
addresses = g_task_propagate_pointer (task, error);
g_object_unref (task);
return addresses;
}
+static GList *
+lookup_by_name (GResolver *resolver,
+ const gchar *hostname,
+ GCancellable *cancellable,
+ GError **error)
+{
+ return lookup_by_name_with_flags (resolver,
+ hostname,
+ G_RESOLVER_NAME_LOOKUP_FLAGS_DEFAULT,
+ cancellable,
+ error);
+}
+
static void
lookup_by_name_with_flags_async (GResolver *resolver,
const gchar *hostname,
@@ -238,13 +352,23 @@ lookup_by_name_with_flags_async (GResolver *resolver,
{
GTask *task;
LookupData *data;
+ GList *cached;
- data = lookup_data_new (hostname, flags_to_family (flags));
task = g_task_new (resolver, cancellable, callback, user_data);
g_task_set_source_tag (task, lookup_by_name_with_flags_async);
- g_task_set_task_data (task, data, (GDestroyNotify)lookup_data_free);
g_task_set_return_on_cancel (task, TRUE);
- g_task_run_in_thread (task, do_lookup_by_name);
+
+ cached = query_dns_cache (hostname, flags);
+ if (cached)
+ g_task_return_pointer (task, cached,
+ (GDestroyNotify)g_resolver_free_addresses);
+ else
+ {
+ data = lookup_data_new (hostname, flags);
+ g_task_set_task_data (task, data, (GDestroyNotify)lookup_data_free);
+ g_task_run_in_thread (task, do_lookup_by_name);
+ }
+
g_object_unref (task);
}
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