From: Stefan Eissing <icing@apache.org>
Date: Tue, 19 Jan 2016 15:24:41 +0000 (+0000)
Subject: checking for stopping MPM before going into blocking keepalive read
X-Git-Tag: 2.5.0-alpha~2364
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=11e47dd8f02b37a2e4b96eeb045ea0ae6c10e107;p=thirdparty%2Fapache%2Fhttpd.git

checking for stopping MPM before going into blocking keepalive read

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1725543 13f79535-47bb-0310-9956-ffa450edef68
---

diff --git a/modules/http2/h2_push.c b/modules/http2/h2_push.c
index d69c1e718c8..717865c5aca 100644
--- a/modules/http2/h2_push.c
+++ b/modules/http2/h2_push.c
@@ -466,6 +466,28 @@ void h2_push_policy_determine(struct h2_request *req, apr_pool_t *p, int push_en
 
 /*******************************************************************************
  * push diary 
+ *
+ * - The push diary keeps track of resources already PUSHed via HTTP/2 on this
+ *   connection. It records a hash value from the absolute URL of the resource
+ *   pushed.
+ * - Lacking openssl, it uses 'apr_hashfunc_default' for the value
+ * - with openssl, it uses SHA256 to calculate the hash value
+ * - whatever the method to generate the hash, the diary keeps a maximum of 64
+ *   bits per hash, limiting the memory consumption to about 
+ *      H2PushDiarySize * 8 
+ *   bytes. Entries are sorted by most recently used and oldest entries are
+ *   forgotten first.
+ * - Clients can initialize/replace the push diary by sending a 'Cache-Digest'
+ *   header. Currently, this is the base64url encoded value of the cache digest
+ *   as specified in https://datatracker.ietf.org/doc/draft-kazuho-h2-cache-digest/
+ *   This draft can be expected to evolve and the definition of the header
+ *   will be added there and refined.
+ * - The cache digest header is a Golomb Coded Set of hash values, but it may
+ *   limit the amount of bits per hash value even further. For a good description
+ *   of GCS, read here:
+ *      http://giovanni.bajo.it/post/47119962313/golomb-coded-sets-smaller-than-bloom-filters
+ * - The means that the push diary might be initialized with hash values of much
+ *   less than 64 bits, leading to more false positives, but smaller digest size.
  ******************************************************************************/
  
  
diff --git a/modules/http2/h2_session.c b/modules/http2/h2_session.c
index b0100fa70fc..94f637d2c13 100644
--- a/modules/http2/h2_session.c
+++ b/modules/http2/h2_session.c
@@ -18,6 +18,8 @@
 #include <apr_base64.h>
 #include <apr_strings.h>
 
+#include <ap_mpm.h>
+
 #include <httpd.h>
 #include <http_core.h>
 #include <http_config.h>
@@ -1957,7 +1959,7 @@ apr_status_t h2_session_process(h2_session *session, int async)
 {
     apr_status_t status = APR_SUCCESS;
     conn_rec *c = session->c;
-    int rv, have_written, have_read;
+    int rv, have_written, have_read, mpm_state;
 
     ap_log_cerror( APLOG_MARK, APLOG_TRACE1, status, c,
                   "h2_session(%ld): process start, async=%d", session->id, async);
@@ -1986,6 +1988,20 @@ apr_status_t h2_session_process(h2_session *session, int async)
                 break;
                 
             case H2_SESSION_ST_IDLE:
+                if ((status = ap_mpm_query(AP_MPMQ_MPM_STATE, &mpm_state))) {
+                    goto out;
+                }
+                if (mpm_state == AP_MPMQ_STOPPING) {
+                    dispatch_event(session, H2_SESSION_EV_CONN_TIMEOUT, 0, NULL);
+                    break;
+                }
+                /* We'd like to wait in smaller increments, using a 1 second
+                 * timeout maybe, trying n times. That would allow us to exit
+                 * on MPMQ_STOPPING earlier.
+                 * Unfortunately, once a socket timeout happened, SSL reports
+                 * EOF on reads and the connection is gone. Not sure if we can
+                 * avoid that...
+                 */
                 h2_filter_cin_timeout_set(session->cin, session->keepalive_secs);
                 ap_update_child_status(c->sbh, SERVER_BUSY_KEEPALIVE, NULL);
                 status = h2_session_read(session, 1, 10);
@@ -1998,7 +2014,6 @@ apr_status_t h2_session_process(h2_session *session, int async)
                 }
                 else if (APR_STATUS_IS_TIMEUP(status)) {
                     dispatch_event(session, H2_SESSION_EV_CONN_TIMEOUT, 0, NULL);
-                    break;
                 }
                 else {
                     dispatch_event(session, H2_SESSION_EV_CONN_ERROR, 0, NULL);