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// SPDX-License-Identifier: GPL-3.0-or-later
#define WEB_SERVER_INTERNALS 1
#include "web_client_cache.h"
// ----------------------------------------------------------------------------
// allocate and free web_clients
// ----------------------------------------------------------------------------
// web clients caching
// When clients connect and disconnect, avoid allocating and releasing memory.
// Instead, when new clients get connected, reuse any memory previously allocated
// for serving web clients that are now disconnected.
// The size of the cache is adaptive. It caches the structures of 2x
// the number of currently connected clients.
static struct clients_cache {
struct {
SPINLOCK spinlock;
struct web_client *head; // the structures of the currently connected clients
size_t count; // the count the currently connected clients
size_t allocated; // the number of allocations
size_t reused; // the number of re-uses
} used;
struct {
SPINLOCK spinlock;
struct web_client *head; // the cached structures, available for future clients
size_t count; // the number of cached structures
} avail;
} web_clients_cache = {
.used = {
.spinlock = NETDATA_SPINLOCK_INITIALIZER,
.head = NULL,
.count = 0,
.reused = 0,
.allocated = 0,
},
.avail = {
.spinlock = NETDATA_SPINLOCK_INITIALIZER,
.head = NULL,
.count = 0,
},
};
// destroy the cache and free all the memory it uses
void web_client_cache_destroy(void) {
internal_error(true, "web_client_cache has %zu used and %zu available clients, allocated %zu, reused %zu (hit %zu%%)."
, web_clients_cache.used.count
, web_clients_cache.avail.count
, web_clients_cache.used.allocated
, web_clients_cache.used.reused
, (web_clients_cache.used.allocated + web_clients_cache.used.reused)?(web_clients_cache.used.reused * 100 / (web_clients_cache.used.allocated + web_clients_cache.used.reused)):0
);
struct web_client *w, *t;
spinlock_lock(&web_clients_cache.avail.spinlock);
w = web_clients_cache.avail.head;
while(w) {
t = w;
w = w->cache.next;
web_client_free(t);
}
web_clients_cache.avail.head = NULL;
web_clients_cache.avail.count = 0;
spinlock_unlock(&web_clients_cache.avail.spinlock);
// DO NOT FREE THEM IF THEY ARE USED
// spinlock_lock(&web_clients_cache.used.spinlock);
// w = web_clients_cache.used.head;
// while(w) {
// t = w;
// w = w->next;
// web_client_free(t);
// }
// web_clients_cache.used.head = NULL;
// web_clients_cache.used.count = 0;
// web_clients_cache.used.reused = 0;
// web_clients_cache.used.allocated = 0;
// spinlock_unlock(&web_clients_cache.used.spinlock);
}
struct web_client *web_client_get_from_cache(void) {
spinlock_lock(&web_clients_cache.avail.spinlock);
struct web_client *w = web_clients_cache.avail.head;
if(w) {
// get it from avail
DOUBLE_LINKED_LIST_REMOVE_ITEM_UNSAFE(web_clients_cache.avail.head, w, cache.prev, cache.next);
web_clients_cache.avail.count--;
spinlock_unlock(&web_clients_cache.avail.spinlock);
web_client_reuse_from_cache(w);
spinlock_lock(&web_clients_cache.used.spinlock);
web_clients_cache.used.reused++;
}
else {
spinlock_unlock(&web_clients_cache.avail.spinlock);
// allocate it
w = web_client_create(&netdata_buffers_statistics.buffers_web);
spinlock_lock(&web_clients_cache.used.spinlock);
web_clients_cache.used.allocated++;
}
// link it to used web clients
DOUBLE_LINKED_LIST_PREPEND_ITEM_UNSAFE(web_clients_cache.used.head, w, cache.prev, cache.next);
web_clients_cache.used.count++;
spinlock_unlock(&web_clients_cache.used.spinlock);
// initialize it
w->use_count++;
w->id = global_statistics_web_client_connected();
w->mode = WEB_CLIENT_MODE_GET;
return w;
}
void web_client_release_to_cache(struct web_client *w) {
#ifdef ENABLE_HTTPS
netdata_ssl_close(&w->ssl);
#endif
// unlink it from the used
spinlock_lock(&web_clients_cache.used.spinlock);
DOUBLE_LINKED_LIST_REMOVE_ITEM_UNSAFE(web_clients_cache.used.head, w, cache.prev, cache.next);
ssize_t used_count = (ssize_t)--web_clients_cache.used.count;
spinlock_unlock(&web_clients_cache.used.spinlock);
spinlock_lock(&web_clients_cache.avail.spinlock);
if(w->use_count > 100 || (used_count > 0 && web_clients_cache.avail.count >= 2 * (size_t)used_count) || (used_count <= 10 && web_clients_cache.avail.count >= 20)) {
spinlock_unlock(&web_clients_cache.avail.spinlock);
// we have too many of them - free it
web_client_free(w);
}
else {
// link it to the avail
DOUBLE_LINKED_LIST_PREPEND_ITEM_UNSAFE(web_clients_cache.avail.head, w, cache.prev, cache.next);
web_clients_cache.avail.count++;
spinlock_unlock(&web_clients_cache.avail.spinlock);
}
}
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