diff --git a/docs/manual/mod/mod_session.html.en b/docs/manual/mod/mod_session.html.en

index 96a61e6..4ecc97d 100644

--- a/docs/manual/mod/mod_session.html.en

+++ b/docs/manual/mod/mod_session.html.en

@@ -69,6 +69,7 @@

 
 SessionHeader

 
 SessionInclude

 
 SessionMaxAge

+
 SessionExpiryUpdateInterval

 
Topics

@@ -494,6 +495,37 @@ AuthName realm

     
Setting the maxage to zero disables session expiry.

+

+

+
SessionExpiryUpdateInterval Directive

+

+Description:Define the number of seconds a session's expiry may change without the session being updated

+Syntax:SessionExpiryUpdateInterval interval

+Default:SessionExpiryUpdateInterval 0 (always update)

+Context:server config, virtual host, directory, .htaccess

+Module:mod_session

+

+    
The SessionExpiryUpdateInterval directive allows

+    sessions to avoid the cost associated with writing the session each request

+    when only the expiry time has changed. This can be used to make a website

+    more efficient or reduce load on a database when using

+    <module>mod_session_dbd</module>. The session is always written if the data

+    stored in the session has changed or the expiry has changed by more than the

+    configured interval.

+

+    
Setting the interval to zero disables this directive, and the session

+    expiry is refreshed for each request.

+

+    
This directive only has an effect when combined with SessionMaxAge to enable session

+    expiry. Sessions without an expiry are only written when the data stored in

+    the session has changed.

+

+    
Warning

+    
Because the session expiry may not be refreshed with each request, it's

+    possible for sessions to expire up to interval seconds early.

+    Using a small interval usually provides sufficient savings while having a

+    minimal effect on expiry resolution.

+

diff --git a/modules/session/mod_session.c b/modules/session/mod_session.c

index 3e73c7a..83bf3fc 100644

--- a/modules/session/mod_session.c

+++ b/modules/session/mod_session.c

@@ -177,6 +177,7 @@ static apr_status_t ap_session_save(request_rec * r, session_rec * z)

 {

     if (z) {

         apr_time_t now = apr_time_now();

+        apr_time_t initialExpiry = z->expiry;

         int rv = 0;

         session_dir_conf *dconf = ap_get_module_config(r->per_dir_config,

@@ -202,6 +203,17 @@ static apr_status_t ap_session_save(request_rec * r, session_rec * z)

             z->maxage = dconf->maxage;

         }

+        /* don't save if the only change is the expiry by a small amount */

+        if (!z->dirty && dconf->expiry_update_time

+                && (z->expiry - initialExpiry < dconf->expiry_update_time)) {

+            return APR_SUCCESS;

+        }

+

+        /* also don't save sessions that didn't change at all */

+        if (!z->dirty && !z->maxage) {

+            return APR_SUCCESS;

+        }

+

         /* encode the session */

         rv = ap_run_session_encode(r, z);

         if (OK != rv) {

@@ -544,6 +556,10 @@ static void *merge_session_dir_config(apr_pool_t * p, void *basev, void *addv)

     new->env_set = add->env_set || base->env_set;

     new->includes = apr_array_append(p, base->includes, add->includes);

     new->excludes = apr_array_append(p, base->excludes, add->excludes);

+    new->expiry_update_time = (add->expiry_update_set == 0)

+                                ? base->expiry_update_time

+                                : add->expiry_update_time;

+    new->expiry_update_set = add->expiry_update_set || base->expiry_update_set;

     return new;

 }

@@ -613,6 +629,21 @@ static const char *add_session_exclude(cmd_parms * cmd, void *dconf, const char

     return NULL;

 }

+static const char *

+     set_session_expiry_update(cmd_parms * parms, void *dconf, const char *arg)

+{

+    session_dir_conf *conf = dconf;

+

+    conf->expiry_update_time = atoi(arg);

+    if (conf->expiry_update_time < 0) {

+        return "SessionExpiryUpdateInterval must be positive or nul";

+    }

+    conf->expiry_update_time = apr_time_from_sec(conf->expiry_update_time);

+    conf->expiry_update_set = 1;

+

+    return NULL;

+}

+

 static const command_rec session_cmds[] =

 {

@@ -628,6 +659,9 @@ static const command_rec session_cmds[] =

                   "URL prefixes to include in the session. Defaults to all URLs"),

     AP_INIT_TAKE1("SessionExclude", add_session_exclude, NULL, RSRC_CONF|OR_AUTHCFG,

                   "URL prefixes to exclude from the session. Defaults to no URLs"),

+    AP_INIT_TAKE1("SessionExpiryUpdateInterval", set_session_expiry_update, NULL, RSRC_CONF|OR_AUTHCFG,

+                  "time interval for which a session's expiry time may change "

+                  "without having to be rewritten. Zero to disable"),

     {NULL}

 };

diff --git a/modules/session/mod_session.h b/modules/session/mod_session.h

index a6dd5e9..bdeb532 100644

--- a/modules/session/mod_session.h

+++ b/modules/session/mod_session.h

@@ -115,6 +115,9 @@ typedef struct {

                                    * URLs included if empty */

     apr_array_header_t *excludes; /* URL prefixes to be excluded. No

                                    * URLs excluded if empty */

+    apr_time_t expiry_update_time; /* seconds the session expiry may change and

+                                    * not have to be rewritten */

+    int expiry_update_set;

 } session_dir_conf;

 /**

diff --git a/modules/session/mod_session_cookie.c b/modules/session/mod_session_cookie.c

index 6a02322..4aa75e4 100644

--- a/modules/session/mod_session_cookie.c

+++ b/modules/session/mod_session_cookie.c

@@ -60,9 +60,6 @@ static apr_status_t session_cookie_save(request_rec * r, session_rec * z)

     session_cookie_dir_conf *conf = ap_get_module_config(r->per_dir_config,

                                                     &session_cookie_module);

-    /* don't cache auth protected pages */

-    apr_table_addn(r->headers_out, "Cache-Control", "no-cache");

-

     /* create RFC2109 compliant cookie */

     if (conf->name_set) {

         if (z->encoded && z->encoded[0]) {

@@ -162,6 +159,9 @@ static apr_status_t session_cookie_load(request_rec * r, session_rec ** z)

     /* put the session in the notes so we don't have to parse it again */

     apr_table_setn(m->notes, note, (char *)zz);

+    /* don't cache auth protected pages */

+    apr_table_addn(r->headers_out, "Cache-Control", "no-cache, private");

+

     return OK;

 }

diff --git a/modules/session/mod_session_dbd.c b/modules/session/mod_session_dbd.c

index cf65e5a..20ef72e 100644

--- a/modules/session/mod_session_dbd.c

+++ b/modules/session/mod_session_dbd.c

@@ -243,6 +243,9 @@ static apr_status_t session_dbd_load(request_rec * r, session_rec ** z)

     /* put the session in the notes so we don't have to parse it again */

     apr_table_setn(m->notes, note, (char *)zz);

+    /* don't cache pages with a session */

+    apr_table_addn(r->headers_out, "Cache-Control", "no-cache, private");

+

     return OK;

 }

@@ -407,9 +410,6 @@ static apr_status_t session_dbd_save(request_rec * r, session_rec * z)

     if (conf->name_set || conf->name2_set) {

         char *oldkey = NULL, *newkey = NULL;

-        /* don't cache pages with a session */

-        apr_table_addn(r->headers_out, "Cache-Control", "no-cache");

-

         /* if the session is new or changed, make a new session ID */

         if (z->uuid) {

             oldkey = apr_pcalloc(r->pool, APR_UUID_FORMATTED_LENGTH + 1);

@@ -456,7 +456,7 @@ static apr_status_t session_dbd_save(request_rec * r, session_rec * z)

     else if (conf->peruser) {

         /* don't cache pages with a session */

-        apr_table_addn(r->headers_out, "Cache-Control", "no-cache");

+        apr_table_addn(r->headers_out, "Cache-Control", "no-cache, private");

         if (r->user) {

             ret = dbd_save(r, r->user, r->user, z->encoded, z->expiry);