postfix-2.2-20040801

postfix/HISTORY

@@ -9617,6 +9617,21 @@ Apologies for any names omitted.
 	queue manager is unable to schedule back-to-back deliveries.
 	File: *qmgr/qmgr_entry.c.
 
+20040730
+
+	Hysteresis: turn on "opportunistic session caching" when
+	back-to-back deliveries happen, but don't turn if off
+	until both concurrent and back-to-back delivery ends.
+
+20040801
+
+	Workaround: disable session caching for Linux < 2.2 (does
+	not work) or Glibc < 2 (does not compile).  Files:
+	util/sys_defs.h, util/unix_{recv,send}_fd.c.
+
+	Portability: h_errno is not an lvalue in the UnixWare 7.1
+	multi-threaded environment. Olivier PRENANT.
+
 Open problems:
 
 	Low: update events.c so that 1-second timer requests do

postfix/src/global/mail_params.h

@@ -782,7 +782,9 @@ extern int var_smtp_reuse_limit;
 extern char *var_smtp_cache_dest;
 
 #define VAR_SMTP_CACHE_DEMAND	"smtp_connection_cache_on_demand"
+#ifndef DEF_SMTP_CACHE_DEMAND
 #define DEF_SMTP_CACHE_DEMAND	1
+#endif
 extern bool var_smtp_cache_demand;
 
 #define VAR_SMTP_CONN_TMOUT	"smtp_connect_timeout"

postfix/src/global/mail_version.h

@@ -20,7 +20,7 @@
   * Patches change the patchlevel and the release date. Snapshots change the
   * release date only.
   */
-#define MAIL_RELEASE_DATE	"20040730"
+#define MAIL_RELEASE_DATE	"20040801"
 #define MAIL_VERSION_NUMBER	"2.2"
 
 #define VAR_MAIL_VERSION	"mail_version"

postfix/src/oqmgr/qmgr_entry.c

@@ -108,21 +108,47 @@ QMGR_ENTRY *qmgr_entry_select(QMGR_QUEUE *queue)
 	 * only 1) save a session upon completion, but also 2) reuse a cached
 	 * session upon the next delivery request. In order to not miss out
 	 * on 2), we have to make caching sticky or else we get silly
-	 * behavior when the in-memory queue drains. New connections must not
-	 * be made while cached connections aren't being reused.
+	 * behavior when the in-memory queue drains. Specifically, new
+	 * connections must not be made as long as cached connections exist.
 	 * 
-	 * Safety: don't enable opportunistic session caching until the queue
-	 * manager is able to schedule back-to-back deliveries.
+	 * Safety: don't enable opportunistic session caching unless the queue
+	 * manager is able to schedule concurrent or back-to-back deliveries
+	 * (we need to recognize back-to-back deliveries for transports with
+	 * concurrency 1).
+	 * 
+	 * XXX It would be nice if we could say "try to reuse a cached
+	 * connection, but don't bother saving it when you're done". As long
+	 * as we can't, we must not turn off session caching too early.
+	 */
+#define CONCURRENT_OR_BACK_TO_BACK_DELIVERY() \
+	    (queue->busy_refcount > 1 || BACK_TO_BACK_DELIVERY())
+
+#define BACK_TO_BACK_DELIVERY() \
+		(queue->last_done + 1 >= event_time())
+
+	/*
+	 * Turn on session caching after we get up to speed. Don't enable
+	 * session caching just because we have concurrent deliveries. This
+	 * prevents unnecessary session caching when we have a burst of mail
+	 * <= the initial concurrency limit.
 	 */
 	if ((queue->dflags & DEL_REQ_FLAG_SCACHE) == 0) {
-	    if (queue->last_done + 1 >= event_time()) {
+	    if (BACK_TO_BACK_DELIVERY()) {
 		if (msg_verbose)
 		    msg_info("%s: allowing on-demand session caching for %s",
 			     myname, queue->name);
 		queue->dflags |= DEL_REQ_FLAG_SCACHE;
 	    }
-	} else {
-	    if (queue->last_done + 1 < event_time()) {
+	}
+
+	/*
+	 * Turn off session caching when concurrency drops and we're running
+	 * out of steam. This is what prevents from turning off session
+	 * caching too early, and from making new connections while old ones
+	 * are still cached.
+	 */
+	else {
+	    if (!CONCURRENT_OR_BACK_TO_BACK_DELIVERY()) {
 		if (msg_verbose)
 		    msg_info("%s: disallowing on-demand session caching for %s",
 			     myname, queue->name);

postfix/src/qmgr/qmgr_entry.c

@@ -120,21 +120,47 @@ QMGR_ENTRY *qmgr_entry_select(QMGR_PEER *peer)
 	 * only 1) save a session upon completion, but also 2) reuse a cached
 	 * session upon the next delivery request. In order to not miss out
 	 * on 2), we have to make caching sticky or else we get silly
-	 * behavior when the in-memory queue drains. New connections must not
-	 * be made while cached connections aren't being reused.
+	 * behavior when the in-memory queue drains. Specifically, new
+	 * connections must not be made as long as cached connections exist.
 	 * 
-	 * Safety: don't enable opportunistic session caching until the queue
-	 * manager is able to schedule back-to-back deliveries.
+	 * Safety: don't enable opportunistic session caching unless the queue
+	 * manager is able to schedule concurrent or back-to-back deliveries
+	 * (we need to recognize back-to-back deliveries for transports with
+	 * concurrency 1).
+	 * 
+	 * XXX It would be nice if we could say "try to reuse a cached
+	 * connection, but don't bother saving it when you're done". As long
+	 * as we can't, we must not turn off session caching too early.
+	 */
+#define CONCURRENT_OR_BACK_TO_BACK_DELIVERY() \
+	    (queue->busy_refcount > 1 || BACK_TO_BACK_DELIVERY())
+
+#define BACK_TO_BACK_DELIVERY() \
+		(queue->last_done + 1 >= event_time())
+
+	/*
+	 * Turn on session caching after we get up to speed. Don't enable
+	 * session caching just because we have concurrent deliveries. This
+	 * prevents unnecessary session caching when we have a burst of mail
+	 * <= the initial concurrency limit.
 	 */
 	if ((queue->dflags & DEL_REQ_FLAG_SCACHE) == 0) {
-	    if (queue->last_done + 1 >= event_time()) {
+	    if (BACK_TO_BACK_DELIVERY()) {
 		if (msg_verbose)
 		    msg_info("%s: allowing on-demand session caching for %s",
 			     myname, queue->name);
 		queue->dflags |= DEL_REQ_FLAG_SCACHE;
 	    }
-	} else {
-	    if (queue->last_done + 1 < event_time()) {
+	}
+
+	/*
+	 * Turn off session caching when concurrency drops and we're running
+	 * out of steam. This is what prevents from turning off session
+	 * caching too early, and from making new connections while old ones
+	 * are still cached.
+	 */
+	else {
+	    if (!CONCURRENT_OR_BACK_TO_BACK_DELIVERY()) {
 		if (msg_verbose)
 		    msg_info("%s: disallowing on-demand session caching for %s",
 			     myname, queue->name);

postfix/src/smtpd/smtpd_check.c

@@ -2183,7 +2183,7 @@ static int check_server_access(SMTPD_STATE *state, const char *table,
 				      FULL, &found, reply_name, reply_class,
 					  def_acl)) != 0 || found)
 	    CHECK_SERVER_RETURN(status);
-	h_errno = 0;				/* XXX */
+	SET_H_ERRNO(0);
 	if ((hp = gethostbyname((char *) server->data)) == 0) {
 	    msg_warn("Unable to look up %s host %s for %s %s: %s",
 		     dns_strtype(type), (char *) server->data,

postfix/src/util/sys_defs.h

@@ -341,6 +341,7 @@ extern int opterr;
 #define STATVFS_IN_SYS_STATVFS_H
 #define UNIX_DOMAIN_CONNECT_BLOCKS_FOR_ACCEPT
 #define STRCASECMP_IN_STRINGS_H
+#define SET_H_ERRNO(err) (set_h_errno(err))
 #endif
 
 #ifdef UW21				/* UnixWare 2.1.x */
@@ -560,7 +561,14 @@ extern int initgroups(const char *, int);
 #define SOCKADDR_SIZE	socklen_t
 #define SOCKOPT_SIZE	socklen_t
 #endif
-#define CANT_WRITE_BEFORE_SENDING_FD
+#include <linux/version.h>
+#if !defined(KERNEL_VERSION) || (LINUX_VERSION_CODE < KERNEL_VERSION(2,2,0)) \
+	|| (__GLIBC__ < 2)
+# define CANT_USE_SEND_RECV_MSG
+# define DEF_SMTP_CACHE_DEMAND	0
+#else
+# define CANT_WRITE_BEFORE_SENDING_FD
+#endif
 #endif
 
 #ifdef LINUX1
@@ -589,6 +597,8 @@ extern int initgroups(const char *, int);
 #define NATIVE_NEWALIAS_PATH "/usr/bin/newaliases"
 #define NATIVE_COMMAND_DIR "/usr/sbin"
 #define NATIVE_DAEMON_DIR "/usr/libexec/postfix"
+#define CANT_USE_SEND_RECV_MSG
+#define DEF_SMTP_CACHE_DEMAND	0
 #endif
 
  /*

postfix/src/util/unix_recv_fd.c

@@ -44,6 +44,16 @@
 int     unix_recv_fd(int fd)
 {
     char   *myname = "unix_recv_fd";
+
+    /*
+     * This code does not work with version <2.2 Linux kernels, and it does
+     * not compile with version <2 Linux libraries.
+     */
+#ifdef CANT_USE_SEND_RECV_MSG
+    msg_warn("%s: your system has no support for file descriptor passing",
+	     myname);
+    return (-1);
+#else
     struct msghdr msg;
     int     newfd;
     struct iovec iov[1];
@@ -103,6 +113,7 @@ int     unix_recv_fd(int fd)
     else
 	return (-1);
 #endif
+#endif
 }
 
 #ifdef TEST

postfix/src/util/unix_send_fd.c

@@ -46,6 +46,18 @@
 
 int     unix_send_fd(int fd, int sendfd)
 {
+
+    /*
+     * This code does not work with version <2.2 Linux kernels, and it does
+     * not compile with version <2 Linux libraries.
+     */
+#ifdef CANT_USE_SEND_RECV_MSG
+    char   *myname = "unix_send_fd";
+
+    msg_warn("%s: your system has no support for file descriptor passing",
+	     myname);
+    return (-1);
+#else
     struct msghdr msg;
     struct iovec iov[1];
 
@@ -87,6 +99,7 @@ int     unix_send_fd(int fd, int sendfd)
     msg.msg_iovlen = 1;
 
     return (sendmsg(fd, &msg, 0));
+#endif
 }
 
 #ifdef TEST