[PATCH 2 of 2] HTTP/3: delayed Insert Count Increment instruction

[Roman Arutyunyan]

# HG changeset patch
# User Roman Arutyunyan <arut at nginx.com>
# Date 1634804424 -10800
#      Thu Oct 21 11:20:24 2021 +0300
# Branch quic
# Node ID e2d65b59ccb9035cbd619358a121ba5bcca3404a
# Parent  8b049432ef2dcdb8d1a8ec1a5e41c0a340285b65
HTTP/3: delayed Insert Count Increment instruction.

Sending the instruction is delayed until the end of the current event cycle.
Delaying the instruction is allowed by quic-qpack-21, section 2.2.2.3.
The goal is to reduce the amount of data sent back to client by accumulating
inserts.

diff --git a/src/http/v3/ngx_http_v3.c b/src/http/v3/ngx_http_v3.c
--- a/src/http/v3/ngx_http_v3.c
+++ b/src/http/v3/ngx_http_v3.c
@@ -47,6 +47,10 @@ ngx_http_v3_init_session(ngx_connection_
     h3c->keepalive.handler = ngx_http_v3_keepalive_handler;
     h3c->keepalive.cancelable = 1;
 
+    h3c->table.send_insert_count.log = pc->log;
+    h3c->table.send_insert_count.data = pc;
+    h3c->table.send_insert_count.handler = ngx_http_v3_inc_insert_count_handler;
+
     cln = ngx_pool_cleanup_add(pc->pool, 0);
     if (cln == NULL) {
         return NGX_ERROR;
@@ -85,6 +89,10 @@ ngx_http_v3_cleanup_session(void *data)
     if (h3c->keepalive.timer_set) {
         ngx_del_timer(&h3c->keepalive);
     }
+
+    if (h3c->table.send_insert_count.posted) {
+        ngx_delete_posted_event(&h3c->table.send_insert_count);
+    }
 }
 
 
diff --git a/src/http/v3/ngx_http_v3_parse.c b/src/http/v3/ngx_http_v3_parse.c
--- a/src/http/v3/ngx_http_v3_parse.c
+++ b/src/http/v3/ngx_http_v3_parse.c
@@ -395,6 +395,8 @@ done:
         if (ngx_http_v3_send_ack_section(c, c->quic->id) != NGX_OK) {
             return NGX_ERROR;
         }
+
+        ngx_http_v3_ack_insert_count(c, st->prefix.insert_count);
     }
 
     st->state = sw_start;
diff --git a/src/http/v3/ngx_http_v3_tables.c b/src/http/v3/ngx_http_v3_tables.c
--- a/src/http/v3/ngx_http_v3_tables.c
+++ b/src/http/v3/ngx_http_v3_tables.c
@@ -232,11 +232,9 @@ ngx_http_v3_insert(ngx_connection_t *c, 
     dt->elts[dt->nelts++] = field;
     dt->size += size;
 
-    /* TODO increment can be sent less often */
+    dt->insert_count++;
 
-    if (ngx_http_v3_send_inc_insert_count(c, 1) != NGX_OK) {
-        return NGX_ERROR;
-    }
+    ngx_post_event(&dt->send_insert_count, &ngx_posted_events);
 
     if (ngx_http_v3_new_entry(c) != NGX_OK) {
         return NGX_ERROR;
@@ -246,6 +244,34 @@ ngx_http_v3_insert(ngx_connection_t *c, 
 }
 
 
+void
+ngx_http_v3_inc_insert_count_handler(ngx_event_t *ev)
+{
+    ngx_connection_t             *c;
+    ngx_http_v3_session_t        *h3c;
+    ngx_http_v3_dynamic_table_t  *dt;
+
+    c = ev->data;
+
+    ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0,
+                   "http3 inc insert count handler");
+
+    h3c = ngx_http_v3_get_session(c);
+    dt = &h3c->table;
+
+    if (dt->insert_count > dt->ack_insert_count) {
+        if (ngx_http_v3_send_inc_insert_count(c,
+                                       dt->insert_count - dt->ack_insert_count)
+            != NGX_OK)
+        {
+            return;
+        }
+
+        dt->ack_insert_count = dt->insert_count;
+    }
+}
+
+
 ngx_int_t
 ngx_http_v3_set_capacity(ngx_connection_t *c, ngx_uint_t capacity)
 {
@@ -603,6 +629,21 @@ ngx_http_v3_check_insert_count(ngx_conne
 }
 
 
+void
+ngx_http_v3_ack_insert_count(ngx_connection_t *c, uint64_t insert_count)
+{
+    ngx_http_v3_session_t        *h3c;
+    ngx_http_v3_dynamic_table_t  *dt;
+
+    h3c = ngx_http_v3_get_session(c);
+    dt = &h3c->table;
+
+    if (dt->ack_insert_count < insert_count) {
+        dt->ack_insert_count = insert_count;
+    }
+}
+
+
 static void
 ngx_http_v3_unblock(void *data)
 {
diff --git a/src/http/v3/ngx_http_v3_tables.h b/src/http/v3/ngx_http_v3_tables.h
--- a/src/http/v3/ngx_http_v3_tables.h
+++ b/src/http/v3/ngx_http_v3_tables.h
@@ -26,9 +26,13 @@ typedef struct {
     ngx_uint_t                    base;
     size_t                        size;
     size_t                        capacity;
+    uint64_t                      insert_count;
+    uint64_t                      ack_insert_count;
+    ngx_event_t                   send_insert_count;
 } ngx_http_v3_dynamic_table_t;
 
 
+void ngx_http_v3_inc_insert_count_handler(ngx_event_t *ev);
 void ngx_http_v3_cleanup_table(ngx_http_v3_session_t *h3c);
 ngx_int_t ngx_http_v3_ref_insert(ngx_connection_t *c, ngx_uint_t dynamic,
     ngx_uint_t index, ngx_str_t *value);
@@ -46,6 +50,7 @@ ngx_int_t ngx_http_v3_decode_insert_coun
     ngx_uint_t *insert_count);
 ngx_int_t ngx_http_v3_check_insert_count(ngx_connection_t *c,
     ngx_uint_t insert_count);
+void ngx_http_v3_ack_insert_count(ngx_connection_t *c, uint64_t insert_count);
 ngx_int_t ngx_http_v3_set_param(ngx_connection_t *c, uint64_t id,
     uint64_t value);