Set server name implementation

doc/configuration.txt

@@ -1817,6 +1817,7 @@ The following keywords are supported in the "global" section :
    - presetenv
    - prealloc-fd
    - resetenv
+   - server-rename
    - set-dumpable
    - set-var
    - setenv
@@ -3209,6 +3210,14 @@ server-state-file <file>
   configuration. See also "server-state-base" and "show servers state",
   "load-server-state-from-file" and "server-state-file-name"
 
+server-rename
+  Enable runtime renaming of servers via the CLI for all backends globally.
+  When set, it allows the name of any server to be changed at runtime using
+  the CLI command "set server <backend>/<server> name <newname>" without
+  requiring "option server-rename" in each backend individually. This option
+  supports the "no" prefix to disable it. See also: 'option server-rename'
+  for per-backend control.
+
 set-dumpable [ on | off | libs ]
   This option helps choose the core dump behavior in case of process crash.
   Available options are:
@@ -6187,6 +6196,7 @@ option pgsql-check                        X          -         X         X
 option prefer-last-server            (*)  X          -         X         X
 option redispatch                    (*)  X          -         X         X
 option redis-check                        X          -         X         X
+option server-rename                      -          -         X         X
 option smtpchk                            X          -         X         X
 option socket-stats                  (*)  X          X         X         -
 option splice-auto                   (*)  X          X         X         X
@@ -6274,6 +6284,36 @@ use-server                                -          -         X         X
 
 
 4.2. Alphabetically sorted keywords reference
+
+option server-rename
+  Enable runtime renaming of servers via the CLI.
+
+  May be used in the following contexts: tcp, http
+
+  May be used in sections :   defaults | frontend | listen | backend
+                                 no    |    no    |   no   |   yes
+
+  When this option is enabled in a backend, it allows the name of any server in that backend to be changed at runtime using the CLI command:
+      set server <backend>/<server> name <newname>
+
+  Restrictions:
+    - The new name must be unique among all servers in the backend.
+    - The change is effective immediately for all runtime operations, stats, and logs.
+    - The new name is not persisted to the configuration file and will be lost on reload.
+    - Renaming is only available if 'option server-rename' is set in the backend
+      or 'server-rename' is set in the global section.
+    - Some features that rely on static server names (such as certain stick-tables or external monitoring) may not recognize the new name until restart.
+
+  Example:
+      backend myapp
+        option server-rename
+        server s1 10.0.0.1:80
+        server s2 10.0.0.2:80
+
+  To rename server 's1' to 'blue':
+      echo "set server myapp/s1 name blue" | socat /var/run/haproxy.sock -
+
+  See also: 'server-rename' in the global section, 'set server <b>/<s> name' in the management guide (doc/management.txt).
 ---------------------------------------------
 
 This section provides a description of each keyword and its usage.

doc/management.txt

@@ -2688,6 +2688,36 @@ set server <backend>/<server> ssl [ on | off ]  (deprecated)
   This command is deprecated, create a new server dynamically with or without
   SSL instead, using the "add server" command.
 
+set server <backend>/<server> name <newname>
+  Change the name of a server at runtime (if 'option server-rename'
+  is enabled in the backend or 'server-rename' is set in the global section).
+
+  The new name must be unique among all servers in the backend. The
+  change is effective immediately for all runtime operations, stats,
+  and logs, but is not persisted to the configuration file and will
+  be lost on reload. Some features that rely on static server names
+  (such as stick-tables or external monitoring) may not recognize
+  the new name until restart.
+
+  There is no strict requirement that no sessions are active
+  before renaming. However, if there are active sessions, log entries
+  for those sessions may use either the old or new name, depending on
+  when the rename occurs relative to logging. This may result in split
+  or inconsistent logs for in-flight requests. If strict log consistency
+  is required, it is the user's responsibility to ensure all sessions
+  have finished before renaming (e.g., by draining or maintenance mode
+  and waiting for all connections to close).
+
+  For most use cases, a clear naming scheme (such as srv1 → srv1-old,
+  srv1-new, or srv1*) allows correlating log entries before and after
+  the rename, even if some overlap occurs. Users should choose a naming
+  convention that fits their operational and troubleshooting needs.
+
+  Example:
+      set server myapp/s1 name blue
+
+  See also: 'option server-rename' in doc/configuration.txt.
+
 set severity-output [ none | number | string ]
   Change the severity output format of the stats socket connected to for the
   duration of the current session.

include/haproxy/event_hdl-t.h

@@ -279,6 +279,8 @@ struct event_hdl_sub {
 #define EVENT_HDL_SUB_SERVER_CHECK                      EVENT_HDL_SUB_TYPE(1,7)
 /* server inet addr (addr:svc_port tuple) change event */
 #define EVENT_HDL_SUB_SERVER_INETADDR                   EVENT_HDL_SUB_TYPE(1,8)
+/* server name change event */
+#define EVENT_HDL_SUB_SERVER_NAME                       EVENT_HDL_SUB_TYPE(1,9)
 
 /* PAT_REF family, only published in pat ref subscription list
  * (not published in global subscription list for performance reasons)

include/haproxy/global-t.h

@@ -80,6 +80,7 @@
 #define GTUNE_DISABLE_ACTIVE_CLOSE (1<<22)
 #define GTUNE_QUICK_EXIT         (1<<23)
 #define GTUNE_COLLECT_LIBS       (1<<24)
+#define GTUNE_SRV_RENAME         (1<<25)
 /* (1<<25) unused */
 #define GTUNE_USE_FAST_FWD       (1<<26)
 #define GTUNE_LISTENER_MQ_FAIR   (1<<27)

include/haproxy/proxy-t.h

@@ -188,7 +188,9 @@ enum PR_SRV_STATE_FILE {
 #define PR_O3_HASHAFNTY_MAXQUEUE 0x00000200 /* preserve hash affinity until maxqueue is reached */
 #define PR_O3_HASHAFNTY_MASK     0x00000300 /* mask for hash-preserve-affinity */
 
-/* unused: 0x00000400 to  0x80000000 */
+#define PR_O3_SRV_RENAME         0x00000400 /* allow runtime server renaming */
+
+/* unused: 0x00000800 to  0x80000000 */
 /* end of proxy->options3 */
 
 /* Cookie settings for pr->ck_opts */

include/haproxy/server-t.h

@@ -566,6 +566,7 @@ struct event_hdl_cb_data_server {
 	 *   EVENT_HDL_SUB_SERVER_ADMIN
 	 *   EVENT_HDL_SUB_SERVER_CHECK
 	 *   EVENT_HDL_SUB_SERVER_INETADDR
+	 *   EVENT_HDL_SUB_SERVER_NAME
 	 */
 	struct {
 		/* safe data can be safely used from both
@@ -769,6 +770,24 @@ struct event_hdl_cb_data_server_inetaddr {
 	/* no unsafe data */
 };
 
+/* data provided to EVENT_HDL_SUB_SERVER_NAME handlers through
+ * event_hdl facility
+ *
+ * Note that this may be casted to regular event_hdl_cb_data_server if
+ * you don't care about name related optional info
+ */
+struct event_hdl_cb_data_server_name {
+	/* provided by:
+	 *   EVENT_HDL_SUB_SERVER_NAME
+	 */
+	struct event_hdl_cb_data_server server;                 /* must be at the beginning */
+	struct {
+		char old_name[64];
+		char new_name[64];
+	} safe;
+	/* no unsafe data */
+};
+
 /* Storage structure to load server-state lines from a flat file into
  * an ebtree, for faster processing
  */

reg-tests/server/cli_set_server_name.vtc

@@ -0,0 +1,186 @@
+varnishtest "Set server name via CLI"
+
+feature ignore_unknown_macro
+
+#REGTEST_TYPE=devel
+
+# Do nothing. Is there only to create s1_* macros
+server s1 {
+	rxreq
+	txresp
+} -start
+
+haproxy h1 -conf {
+    global
+    .if feature(THREAD)
+        thread-groups 1
+    .endif
+
+    defaults
+        mode http
+        timeout connect "${HAPROXY_TEST_TIMEOUT-5s}"
+        timeout client  "${HAPROXY_TEST_TIMEOUT-5s}"
+        timeout server  "${HAPROXY_TEST_TIMEOUT-5s}"
+
+    frontend fe
+        bind "fd@${feS}"
+        default_backend test
+
+    backend test
+        option server-rename
+        balance random
+        server s1 ${s1_addr}:${s1_port}
+        server s2 ${s1_addr}:${s1_port}
+
+    backend norename
+        balance random
+        server s1 ${s1_addr}:${s1_port}
+
+    backend useserver
+        option server-rename
+        balance random
+        server s1 ${s1_addr}:${s1_port}
+        server s2 ${s1_addr}:${s1_port}
+        use-server s1 if { always_true }
+
+    backend tracked
+        option server-rename
+        balance random
+        server s1 ${s1_addr}:${s1_port}
+        server s2 ${s1_addr}:${s1_port} track tracked/s1
+} -start
+
+haproxy h1 -cli {
+    # ---- error cases ----
+
+    # missing new name argument
+    send "set server test/s1 name"
+    expect ~ "set server <b>/<s> name requires a new name."
+
+    # backend without 'option server-rename'
+    send "set server norename/s1 name newname"
+    expect ~ "Backend does not allow server renaming"
+
+    # server not in maintenance mode
+    send "set server test/s1 name newname"
+    expect ~ "Server must be in maintenance mode"
+
+    # put s1 in maintenance for subsequent tests
+    send "disable server test/s1"
+    expect ~ ".*"
+
+    # name containing '/' is rejected
+    send "set server test/s1 name bad/name"
+    expect ~ "Server name must not contain spaces, control characters, or '/'."
+
+    # duplicate name — s2 already exists
+    send "set server test/s1 name s2"
+    expect ~ "A server with the same name already exists"
+
+    # server targeted by a static use-server rule
+    send "disable server useserver/s1"
+    expect ~ ".*"
+    send "set server useserver/s1 name newname"
+    expect ~ "referenced by a 'use-server' rule"
+
+    # server tracked by another server
+    send "disable server tracked/s1"
+    expect ~ ".*"
+    send "set server tracked/s1 name newname"
+    expect ~ "tracked by another server"
+
+    # renaming to the same name is a no-op (success)
+    send "set server test/s1 name s1"
+    expect ~ "Server name updated."
+
+    # ---- success case ----
+
+    # rename s1 -> blue
+    send "set server test/s1 name blue"
+    expect ~ "Server name updated."
+
+    # verify the new name appears in show servers state
+    send "show servers state test"
+    expect ~ "test 1 blue"
+
+    # the old name should no longer resolve
+    send "set server test/s1 state ready"
+    expect ~ "No such server."
+
+    # new name is usable via enable
+    send "enable server test/blue"
+    expect ~ ".*"
+
+    # ---- rename back ----
+
+    # must go through maintenance again
+    send "disable server test/blue"
+    expect ~ ".*"
+
+    send "set server test/blue name s1"
+    expect ~ "Server name updated."
+
+    send "show servers state test"
+    expect ~ "test 1 s1"
+
+    # bring back up
+    send "enable server test/s1"
+    expect ~ ".*"
+}
+
+# verify traffic still works after rename round-trip
+client c1 -connect ${h1_feS_sock} {
+    txreq
+    rxresp
+    expect resp.status == 200
+} -run
+
+# ---- test global server-rename ----
+
+server s2 {
+    rxreq
+    txresp
+} -start
+
+haproxy h2 -conf {
+    global
+        server-rename
+    .if feature(THREAD)
+        thread-groups 1
+    .endif
+
+    defaults
+        mode http
+        timeout connect "${HAPROXY_TEST_TIMEOUT-5s}"
+        timeout client  "${HAPROXY_TEST_TIMEOUT-5s}"
+        timeout server  "${HAPROXY_TEST_TIMEOUT-5s}"
+
+    frontend fe
+        bind "fd@${feS}"
+        default_backend test
+
+    backend test
+        balance random
+        server s1 ${s2_addr}:${s2_port}
+} -start
+
+haproxy h2 -cli {
+    # global server-rename allows renaming without per-backend option
+    send "disable server test/s1"
+    expect ~ ".*"
+
+    send "set server test/s1 name green"
+    expect ~ "Server name updated."
+
+    send "show servers state test"
+    expect ~ "test 1 green"
+
+    send "enable server test/green"
+    expect ~ ".*"
+}
+
+client c2 -connect ${h2_feS_sock} {
+    txreq
+    rxresp
+    expect resp.status == 200
+} -run

src/cfgparse-global.c

@@ -36,6 +36,7 @@ int cluster_secret_isset;
 static const char *common_kw_list[] = {
 	"global", "busy-polling", "set-dumpable",
 	"insecure-fork-wanted", "insecure-setuid-wanted", "nosplice",
+	"server-rename",
 	"nogetaddrinfo", "noreuseport", "uid", "gid",
 	"external-check", "user", "group", "maxconn",
 	"ssl-server-verify", "maxconnrate", "maxsessrate", "maxsslrate",
@@ -123,6 +124,14 @@ int cfg_parse_global(const char *file, int linenum, char **args, int kwm)
 		else
 			global.tune.options |=  GTUNE_INSECURE_FORK;
 	}
+	else if (strcmp(args[0], "server-rename") == 0) { /* "no server-rename" or "server-rename" */
+		if (alertif_too_many_args(0, file, linenum, args, &err_code))
+			goto out;
+		if (kwm == KWM_NO)
+			global.tune.options &= ~GTUNE_SRV_RENAME;
+		else
+			global.tune.options |=  GTUNE_SRV_RENAME;
+	}
 	else if (strcmp(args[0], "insecure-setuid-wanted") == 0) { /* "no insecure-setuid-wanted" or "insecure-setuid-wanted" */
 		if (alertif_too_many_args(0, file, linenum, args, &err_code))
 			goto out;

src/proxy.c

@@ -158,6 +158,7 @@ const struct cfg_opt cfg_opts3[] =
 {
 	{"assume-rfc6587-ntf",            PR_O3_ASSUME_RFC6587_NTF, PR_CAP_FE, 0, PR_MODE_SYSLOG },
 	{"dont-parse-log",                PR_O3_DONTPARSELOG, PR_CAP_FE, 0, PR_MODE_SYSLOG },
+	{"server-rename",                 PR_O3_SRV_RENAME, PR_CAP_BE, 0, 0 },
 	{ NULL, 0, 0, 0 }
 };