DOC: load-server-state-from-file

doc/configuration.txt

@@ -763,7 +763,8 @@ stats bind-process [ all | odd | even | <number 1-64>[-<number 1-64>] ] ...
 
 server-state-base <directory>
   Specifies the directory prefix to be prepended in front of all servers state
-  file names which do not start with a '/'. See also "server-state-file".
+  file names which do not start with a '/'. See also "server-state-file",
+  "load-server-state-from-file" and "server-state-file-name".
 
 server-state-file <file>
   Specifies the path to the file containing state of servers. If the path starts
@@ -774,7 +775,8 @@ server-state-file <file>
   output of this command must be written in the file pointed by <file>. When
   starting up, before handling traffic, HAProxy will read, load and apply state
   for each server found in the file and available in its current running
-  configuration. See also "server-state-base" and "show servers state".
+  configuration. See also "server-state-base" and "show servers state",
+  "load-server-state-from-file" and "server-state-file-name"
 
 ssl-default-bind-ciphers <ciphers>
   This setting is only available when support for OpenSSL was built in. It sets
@@ -1642,6 +1644,7 @@ http-reuse                                X          -         X         X
 http-send-name-header                     -          -         X         X
 id                                        -          X         X         X
 ignore-persist                            -          X         X         X
+load-server-state-from-file               X          -         X         X
 log                                  (*)  X          X         X         X
 log-format                                X          X         X         -
 log-tag                                   X          X         X         X
@@ -1732,6 +1735,7 @@ rspideny                                  -          X         X         X
 rspirep                                   -          X         X         X
 rsprep                                    -          X         X         X
 server                                    -          -         X         X
+server-state-file-name                    X          -         X         X
 source                                    X          -         X         X
 srvtimeout                  (deprecated)  X          -         X         X
 stats admin                               -          -         X         X
@@ -4145,6 +4149,97 @@ ignore-persist { if | unless } <condition>
 
   See also : "force-persist", "cookie", and section 7 about ACL usage.
 
+load-server-state-from-file { global | local | none }
+  Allow seamless reload of HAProxy
+  May be used in sections:    defaults | frontend | listen | backend
+                                  yes   |    no   |   yes  |   yes
+
+  This directive points HAProxy to a file where server state from previous
+  running process has been saved. That way, when starting up, before handling
+  traffic, the new process can apply old states to servers exactly has if no
+  reload occured. The purpose of the "load-server-state-from-file" directive is
+  to tell haproxy which file to use. For now, only 2 arguments to either prevent
+  loading state or load states from a file containing all backends and servers.
+  The state file can be generated by running the command "show servers state"
+  over the stats socket and redirect output.
+
+  The format of the file is versionned and is very specific. To understand it,
+  please read the documentation of the "show servers state" command (chapter
+  9.2).
+
+  Arguments:
+    global     load the content of the file pointed by the global directive
+               named "server-state-file".
+
+    local      load the content of the file pointed by the directive
+               "server-state-file-name" if set. If not set, then the backend
+               name is used as a file name.
+
+    none       don't load any stat for this backend
+
+  Notes:
+    - server's IP address is not updated unless DNS resolution is enabled on
+      the server. It means that if a server IP address has been changed using
+      the stat socket, this information won't be re-applied after reloading.
+
+    - server's weight is applied from previous running process unless it has
+      has changed between previous and new configuration files.
+
+  Example 1:
+
+  Minimal configuration:
+
+    global
+     stats socket /tmp/socket
+     server-state-file /tmp/server_state
+
+    defaults
+     load-server-state-from-file global
+
+    backend bk
+     server s1 127.0.0.1:22 check weight 11
+     server s2 127.0.0.1:22 check weight 12
+
+  Then one can run :
+
+    socat /tmp/socket - <<< "show servers state" > /tmp/server_state
+
+  Content of the file /tmp/server_state would be like this:
+
+    1
+    # <field names skipped for the doc example>
+    1 bk 1 s1 127.0.0.1 2 0 11 11 4 6 3 4 6 0 0
+    1 bk 2 s2 127.0.0.1 2 0 12 12 4 6 3 4 6 0 0
+
+  Example 2:
+
+  Minimal configuration:
+
+    global
+     stats socket /tmp/socket
+     server-state-base /etc/haproxy/states
+
+    defaults
+     load-server-state-from-file local
+
+    backend bk
+     server s1 127.0.0.1:22 check weight 11
+     server s2 127.0.0.1:22 check weight 12
+
+  Then one can run :
+
+    socat /tmp/socket - <<< "show servers state bk" > /etc/haproxy/states/bk
+
+  Content of the file /etc/haproxy/states/bk would be like this:
+
+    1
+    # <field names skipped for the doc example>
+    1 bk 1 s1 127.0.0.1 2 0 11 11 4 6 3 4 6 0 0
+    1 bk 2 s2 127.0.0.1 2 0 12 12 4 6 3 4 6 0 0
+
+  See also: "server-state-file", "server-state-file-name", and
+  "show servers state"
+
 
 log global
 log <address> [len <length>] <facility> [<level> [<minlevel>]]
@@ -6896,6 +6991,25 @@ server <name> <address>[:[port]] [param*]
   See also: "default-server", "http-send-name-header" and section 5 about
              server options
 
+server-state-file-name [<file>]
+  Set the server state file to read, load and apply to servers available in
+  this backend. It only applies when the directive "load-server-state-from-file"
+  is set to "local". When <file> is not provided or if this directive is not
+  set, then backend name is used. If <file> starts with a slash '/', then it is
+  considered as an absolute path. Otherwise, <file> is concatenated to the
+  global directive "server-state-file-base".
+
+  Example: the minimal configuration below would make HAProxy look for the
+           state server file '/etc/haproxy/states/bk':
+
+    global
+      server-state-file-base /etc/haproxy/states
+
+   backend bk
+      load-server-state-from-file
+
+  See also: "server-state-file-base", "load-server-state-from-file", and
+  "show servers state"
 
 source <addr>[:<port>] [usesrc { <addr2>[:<port2>] | client | clientip } ]
 source <addr>[:<port>] [usesrc { <addr2>[:<port2>] | hdr_ip(<hdr>[,<occ>]) } ]