Support a agent health check performed by opening a TCP socket to a
pre-defined port and reading an ASCII string. The string should have one of
the following forms:

* An ASCII representation of an positive integer percentage.
  e.g. "75%"

  Values in this format will set the weight proportional to the initial
  weight of a server as configured when haproxy starts.

* The string "drain".

  This will cause the weight of a server to be set to 0, and thus it will
  not accept any new connections other than those that are accepted via
  persistence.

* The string "down", optionally followed by a description string.

  Mark the server as down and log the description string as the reason.

* The string "stopped", optionally followed by a description string.

  This currently has the same behaviour as down (iii).

* The string "fail", optionally followed by a description string.

  This currently has the same behaviour as down (iii).

A agent health check may be configured using "option lb-agent-chk".
The use of an alternate check-port, used to obtain agent heath check
information described above as opposed to the port of the service,
may be useful in conjunction with this option.

e.g.

    option  lb-agent-chk
    server  http1_1 10.0.0.10:80 check port 10000 weight 100

Signed-off-by: Simon Horman <ho...@verge.net.au>

---

v2
* Rebase
  - Use server_parse_weight_change_request() instead of
    process_weight_change_request() and description returned
    on error.
* Remove disable as an accepted health string.
* Add down, stopped and fail with optional trailing descriptions
  as accepted health strings.
* Rename dynamic-chk as lb-agent-chk
* Add documentation to doc/configuration.txt
---
 doc/configuration.txt |   53 +++++++++++++++++++++++++++++++++++++++++++------
 include/types/peers.h |    1 +
 include/types/proxy.h |    3 ++-
 src/cfgparse.c        |    7 +++++++
 src/checks.c          |   51 +++++++++++++++++++++++++++++++++++++++++++++++
 5 files changed, 108 insertions(+), 7 deletions(-)

diff --git a/doc/configuration.txt b/doc/configuration.txt
index ad6d0c3..bf1d06b 100644
--- a/doc/configuration.txt
+++ b/doc/configuration.txt
@@ -1141,6 +1141,7 @@ option httpclose                     (*)  X          X    
     X         X
 option httplog                            X          X         X         X
 option http_proxy                    (*)  X          X         X         X
 option independent-streams           (*)  X          X         X         X
+option lb-agent-ch                        X          -         X         X
 option ldap-check                         X          -         X         X
 option log-health-checks             (*)  X          -         X         X
 option log-separate-errors           (*)  X          X         X         -
@@ -3592,9 +3593,9 @@ option httpchk <method> <uri> <version>
           option httpchk OPTIONS * HTTP/1.1\r\nHost:\ www
           server apache1 192.168.1.1:443 check port 80
 
-  See also : "option ssl-hello-chk", "option smtpchk", "option mysql-check",
-             "option pgsql-check", "http-check" and the "check", "port" and
-             "inter" server options.
+  See also : "option lb-agent-chk", "option ssl-hello-chk", "option smtpchk",
+             "option mysql-check", "option pgsql-check", "http-check" and
+             the "check", "port" and "inter" server options.
 
 
 option httpclose
@@ -3731,6 +3732,45 @@ no option independent-streams
   See also : "timeout client", "timeout server" and "timeout tunnel"
 
 
+option lb-agent-chk
+  Use a TCP connection to obtain a metric of server health
+  May be used in sections :   defaults | frontend | listen | backend
+                                 yes   |     no   |   yes  |   yes
+  Arguments : none
+
+  This alters health checking behaviour by connecting making a TCP
+  connection and reading an ASCII string. The string should have one of
+  the following forms:
+
+  * An ASCII representation of an positive integer percentage.
+     e.g. "75%"
+
+     Values in this format will set the weight proportional to the initial
+     weight of a server as configured when haproxy starts.
+
+  * The string "drain".
+
+    This will cause the weight of a server to be set to 0, and thus it will
+    not accept any new connections other than those that are accepted via
+    persistence.
+
+  * The string "down", optionally followed by a description string.
+
+    Mark the server as down and log the description string as the reason.
+
+  * The string "stopped", optionally followed by a description string.
+
+    This currently has the same behaviour as down (iii).
+
+  * The string "fail", optionally followed by a description string.
+
+    This currently has the same behaviour as down (iii).
+
+  The use of an alternate check-port, used to obtain agent heath check
+  information described above as opposed to the port of the service, may be
+  useful in conjunction with this option.
+
+
 option ldap-check
   Use LDAPv3 health checks for server testing
   May be used in sections :   defaults | frontend | listen | backend
@@ -7360,9 +7400,10 @@ check
   backend. It is possible to change the address using the "addr" parameter, the
   port using the "port" parameter, the source address using the "source"
   address, and the interval and timers using the "inter", "rise" and "fall"
-  parameters. The request method is define in the backend using the "httpchk",
-  "smtpchk", "mysql-check", "pgsql-check" and "ssl-hello-chk" options. Please
-  refer to those options and parameters for more information.
+  parameters. The request method is define in the backend using the
+  "httpchk", "lb-agent-chk", "smtpchk", "mysql-check", "pgsql-check" and
+  "ssl-hello-chk" options. Please refer to those options and parameters for
+  more information.
 
   Supported in default-server: No
 
diff --git a/include/types/peers.h b/include/types/peers.h
index d52dc8c..41a1cce 100644
--- a/include/types/peers.h
+++ b/include/types/peers.h
@@ -72,6 +72,7 @@ struct peer {
                int line;         /* line where the section appears */
        } conf;                   /* config information */
        time_t last_change;
+       time_t last_slowstart_change;
        struct sockaddr_storage addr;  /* peer address */
        struct protocol *proto;        /* peer address protocol */
        struct xprt_ops *xprt;         /* peer socket operations at transport 
layer */
diff --git a/include/types/proxy.h b/include/types/proxy.h
index ceb14d1..87e90ee 100644
--- a/include/types/proxy.h
+++ b/include/types/proxy.h
@@ -151,7 +151,8 @@ enum {
 #define PR_O2_MYSQL_CHK 0x50000000      /* use MYSQL check for server health */
 #define PR_O2_LDAP_CHK  0x60000000      /* use LDAP check for server health */
 #define PR_O2_SSL3_CHK  0x70000000      /* use SSLv3 CLIENT_HELLO packets for 
server health */
-/* unused: 0x80000000 to 0xF000000, reserved for health checks */
+#define PR_O2_LB_AGENT_CHK 0x80000000   /* use a TCP connection to obtain a 
metric of server health */
+/* unused: 0x90000000 to 0xF000000, reserved for health checks */
 #define PR_O2_CHK_ANY   0xF0000000      /* Mask to cover any check */
 /* end of proxy->options2 */
 
diff --git a/src/cfgparse.c b/src/cfgparse.c
index 175e30c..8834c32 100644
--- a/src/cfgparse.c
+++ b/src/cfgparse.c
@@ -3459,6 +3459,13 @@ stats_error_parsing:
                                }
                        }
                }
+               else if (!strcmp(args[1], "lb-agent-chk")) {
+                       /* use dynmaic health check */
+                       free(curproxy->check_req);
+                       curproxy->check_req = NULL;
+                       curproxy->options2 &= ~PR_O2_CHK_ANY;
+                       curproxy->options2 |= PR_O2_LB_AGENT_CHK;
+               }
                else if (!strcmp(args[1], "pgsql-check")) {
                        /* use PostgreSQL request to check servers' health */
                        if (warnifnotcap(curproxy, PR_CAP_BE, file, linenum, 
args[1], NULL))
diff --git a/src/checks.c b/src/checks.c
index ca5a7ec..84c6955 100644
--- a/src/checks.c
+++ b/src/checks.c
@@ -25,6 +25,7 @@
 #include <netinet/in.h>
 #include <netinet/tcp.h>
 #include <arpa/inet.h>
+#include <stdbool.h>
 
 #include <common/chunk.h>
 #include <common/compat.h>
@@ -37,6 +38,7 @@
 
 #include <proto/backend.h>
 #include <proto/checks.h>
+#include <proto/dumpstats.h>
 #include <proto/fd.h>
 #include <proto/log.h>
 #include <proto/queue.h>
@@ -966,6 +968,55 @@ static void event_srv_chk_r(struct connection *conn)
                        set_server_check_status(s, HCHK_STATUS_L7STS, desc);
                break;
 
+       case PR_O2_LB_AGENT_CHK: {
+               short status = HCHK_STATUS_L7RSP;
+               const char *desc = "Unknown feedback string";
+               const char *down_cmd = NULL;
+
+               if (!done)
+                       goto wait_more_data;
+
+               cut_crlf(s->check.bi->data);
+
+               if (strchr(s->check.bi->data, '%')) {
+                       desc = server_parse_weight_change_request(s, 
s->check.bi->data);
+                       if (!desc) {
+                               status = HCHK_STATUS_L7OKD;
+                               desc = s->check.bi->data;
+                       }
+               } else if (!strcasecmp(s->check.bi->data, "drain")) {
+                       desc = server_parse_weight_change_request(s, "0%");
+                       if (!desc) {
+                               desc = "drain";
+                               status = HCHK_STATUS_L7OKD;
+                       }
+               } else if (!strncasecmp(s->check.bi->data, "down", 
strlen("down"))) {
+                       down_cmd = "down";
+               } else if (!strncasecmp(s->check.bi->data, "stopped", 
strlen("stopped"))) {
+                       down_cmd = "stopped";
+               } else if (!strncasecmp(s->check.bi->data, "fail", 
strlen("fail"))) {
+                       down_cmd = "fail";
+               }
+
+               if (down_cmd) {
+                       const char *end = s->check.bi->data + strlen(down_cmd);
+                       /*
+                        * The command keyword must terminated the string or
+                        * be followed by a blank.
+                        */
+                       if (end[0] == '\0' || isblank(end[0])) {
+                               status = HCHK_STATUS_L7STS;
+                               /* Skip over leading blanks */
+                               while (end[0] != '\0' && isblank(end[0]))
+                                       end++;
+                               desc = end;
+                       }
+               }
+
+               set_server_check_status(s, status, desc);
+               break;
+       }
+
        case PR_O2_PGSQL_CHK:
                if (!done && s->check.bi->i < 9)
                        goto wait_more_data;
-- 
1.7.10.4


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