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-rw-r--r--web/server/web_client_cache.c231
1 files changed, 231 insertions, 0 deletions
diff --git a/web/server/web_client_cache.c b/web/server/web_client_cache.c
new file mode 100644
index 0000000..ab47056
--- /dev/null
+++ b/web/server/web_client_cache.c
@@ -0,0 +1,231 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#define WEB_SERVER_INTERNALS 1
+#include "web_client_cache.h"
+
+// ----------------------------------------------------------------------------
+// allocate and free web_clients
+
+static void web_client_zero(struct web_client *w) {
+ // zero everything about it - but keep the buffers
+
+ // remember the pointers to the buffers
+ BUFFER *b1 = w->response.data;
+ BUFFER *b2 = w->response.header;
+ BUFFER *b3 = w->response.header_output;
+
+ // empty the buffers
+ buffer_flush(b1);
+ buffer_flush(b2);
+ buffer_flush(b3);
+
+ freez(w->user_agent);
+
+ // zero everything
+ memset(w, 0, sizeof(struct web_client));
+
+ // restore the pointers of the buffers
+ w->response.data = b1;
+ w->response.header = b2;
+ w->response.header_output = b3;
+}
+
+static void web_client_free(struct web_client *w) {
+ buffer_free(w->response.header_output);
+ buffer_free(w->response.header);
+ buffer_free(w->response.data);
+ freez(w->user_agent);
+ freez(w);
+}
+
+static struct web_client *web_client_alloc(void) {
+ struct web_client *w = callocz(1, sizeof(struct web_client));
+ w->response.data = buffer_create(NETDATA_WEB_RESPONSE_INITIAL_SIZE);
+ w->response.header = buffer_create(NETDATA_WEB_RESPONSE_HEADER_SIZE);
+ w->response.header_output = buffer_create(NETDATA_WEB_RESPONSE_HEADER_SIZE);
+ return w;
+}
+
+// ----------------------------------------------------------------------------
+// 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.
+
+// Comments per server:
+// SINGLE-THREADED : 1 cache is maintained
+// MULTI-THREADED : 1 cache is maintained
+// STATIC-THREADED : 1 cache for each thred of the web server
+
+__thread struct clients_cache web_clients_cache = {
+ .pid = 0,
+ .used = NULL,
+ .used_count = 0,
+ .avail = NULL,
+ .avail_count = 0,
+ .allocated = 0,
+ .reused = 0
+};
+
+inline void web_client_cache_verify(int force) {
+#ifdef NETDATA_INTERNAL_CHECKS
+ static __thread size_t count = 0;
+ count++;
+
+ if(unlikely(force || count > 1000)) {
+ count = 0;
+
+ struct web_client *w;
+ size_t used = 0, avail = 0;
+ for(w = web_clients_cache.used; w ; w = w->next) used++;
+ for(w = web_clients_cache.avail; w ; w = w->next) avail++;
+
+ info("web_client_cache has %zu (%zu) used and %zu (%zu) available clients, allocated %zu, reused %zu (hit %zu%%)."
+ , used, web_clients_cache.used_count
+ , avail, web_clients_cache.avail_count
+ , web_clients_cache.allocated
+ , web_clients_cache.reused
+ , (web_clients_cache.allocated + web_clients_cache.reused)?(web_clients_cache.reused * 100 / (web_clients_cache.allocated + web_clients_cache.reused)):0
+ );
+ }
+#else
+ if(unlikely(force)) {
+ info("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.allocated
+ , web_clients_cache.reused
+ , (web_clients_cache.allocated + web_clients_cache.reused)?(web_clients_cache.reused * 100 / (web_clients_cache.allocated + web_clients_cache.reused)):0
+ );
+ }
+#endif
+}
+
+// destroy the cache and free all the memory it uses
+void web_client_cache_destroy(void) {
+#ifdef NETDATA_INTERNAL_CHECKS
+ if(unlikely(web_clients_cache.pid != 0 && web_clients_cache.pid != gettid()))
+ error("Oops! wrong thread accessing the cache. Expected %d, found %d", (int)web_clients_cache.pid, (int)gettid());
+
+ web_client_cache_verify(1);
+#endif
+
+ netdata_thread_disable_cancelability();
+
+ struct web_client *w, *t;
+
+ w = web_clients_cache.used;
+ while(w) {
+ t = w;
+ w = w->next;
+ web_client_free(t);
+ }
+ web_clients_cache.used = NULL;
+ web_clients_cache.used_count = 0;
+
+ w = web_clients_cache.avail;
+ while(w) {
+ t = w;
+ w = w->next;
+ web_client_free(t);
+ }
+ web_clients_cache.avail = NULL;
+ web_clients_cache.avail_count = 0;
+
+ netdata_thread_enable_cancelability();
+}
+
+struct web_client *web_client_get_from_cache_or_allocate() {
+
+#ifdef NETDATA_INTERNAL_CHECKS
+ if(unlikely(web_clients_cache.pid == 0))
+ web_clients_cache.pid = gettid();
+
+ if(unlikely(web_clients_cache.pid != 0 && web_clients_cache.pid != gettid()))
+ error("Oops! wrong thread accessing the cache. Expected %d, found %d", (int)web_clients_cache.pid, (int)gettid());
+#endif
+
+ netdata_thread_disable_cancelability();
+
+ struct web_client *w = web_clients_cache.avail;
+
+ if(w) {
+ // get it from avail
+ if (w == web_clients_cache.avail) web_clients_cache.avail = w->next;
+ if(w->prev) w->prev->next = w->next;
+ if(w->next) w->next->prev = w->prev;
+ web_clients_cache.avail_count--;
+ web_client_zero(w);
+ web_clients_cache.reused++;
+ }
+ else {
+ // allocate it
+ w = web_client_alloc();
+ web_clients_cache.allocated++;
+ }
+
+ // link it to used web clients
+ if (web_clients_cache.used) web_clients_cache.used->prev = w;
+ w->next = web_clients_cache.used;
+ w->prev = NULL;
+ web_clients_cache.used = w;
+ web_clients_cache.used_count++;
+
+ // initialize it
+ w->id = web_client_connected();
+ w->mode = WEB_CLIENT_MODE_NORMAL;
+
+ netdata_thread_enable_cancelability();
+
+ return w;
+}
+
+void web_client_release(struct web_client *w) {
+#ifdef NETDATA_INTERNAL_CHECKS
+ if(unlikely(web_clients_cache.pid != 0 && web_clients_cache.pid != gettid()))
+ error("Oops! wrong thread accessing the cache. Expected %d, found %d", (int)web_clients_cache.pid, (int)gettid());
+
+ if(unlikely(w->running))
+ error("%llu: releasing web client from %s port %s, but it still running.", w->id, w->client_ip, w->client_port);
+#endif
+
+ debug(D_WEB_CLIENT_ACCESS, "%llu: Closing web client from %s port %s.", w->id, w->client_ip, w->client_port);
+
+ web_server_log_connection(w, "DISCONNECTED");
+ web_client_request_done(w);
+ web_client_disconnected();
+
+ netdata_thread_disable_cancelability();
+
+ if(web_server_mode != WEB_SERVER_MODE_STATIC_THREADED) {
+ if (w->ifd != -1) close(w->ifd);
+ if (w->ofd != -1 && w->ofd != w->ifd) close(w->ofd);
+ w->ifd = w->ofd = -1;
+ }
+
+ // unlink it from the used
+ if (w == web_clients_cache.used) web_clients_cache.used = w->next;
+ if(w->prev) w->prev->next = w->next;
+ if(w->next) w->next->prev = w->prev;
+ web_clients_cache.used_count--;
+
+ if(web_clients_cache.avail_count >= 2 * web_clients_cache.used_count) {
+ // we have too many of them - free it
+ web_client_free(w);
+ }
+ else {
+ // link it to the avail
+ if (web_clients_cache.avail) web_clients_cache.avail->prev = w;
+ w->next = web_clients_cache.avail;
+ w->prev = NULL;
+ web_clients_cache.avail = w;
+ web_clients_cache.avail_count++;
+ }
+
+ netdata_thread_enable_cancelability();
+}
+
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