Improve connection denied error message during recovery.

Previously when an archive recovery or a standby was starting and
reached the consistent recovery state but hot_standby was configured
to off, the error message when a client connectted was "the database
system is starting up", which was needless confusing and not really
all that accurate either.

This commit improves the connection denied error message during
recovery, as follows, so that the users immediately know that their
servers are configured to deny those connections.

- If hot_standby is disabled, the error message "the database system
  is not accepting connections" and the detail message "Hot standby
  mode is disabled." are output when clients connect while an archive
  recovery or a standby is running.

- If hot_standby is enabled, the error message "the database system
  is not yet accepting connections" and the detail message
  "Consistent recovery state has not been yet reached." are output
  when clients connect until the consistent recovery state is reached
  and postmaster starts accepting read only connections.

This commit doesn't change the connection denied error message of
"the database system is starting up" during normal server startup and
crash recovery. Because it's still suitable for those situations.

Author: James Coleman
Reviewed-by: Alvaro Herrera, Andres Freund, David Zhang, Tom Lane, Fujii Masao
Discussion: https://postgr.es/m/CAAaqYe8h5ES_B=F_zDT+Nj9XU7YEwNhKhHA2RE4CFhAQ93hfig@mail.gmail.com

diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c
index ef0be4ca381a0561673645aa2ad9020f6c774a67..4a3ca78c1b7063f69eb20e9d936629cd2849049f 100644 (file)
--- a/src/backend/postmaster/postmaster.c
+++ b/src/backend/postmaster/postmaster.c
@@ -2294,6 +2294,18 @@ retry1:
                    (errcode(ERRCODE_CANNOT_CONNECT_NOW),
                     errmsg("the database system is starting up")));
            break;
+       case CAC_NOTCONSISTENT:
+           if (EnableHotStandby)
+               ereport(FATAL,
+                       (errcode(ERRCODE_CANNOT_CONNECT_NOW),
+                        errmsg("the database system is not yet accepting connections"),
+                        errdetail("Consistent recovery state has not been yet reached.")));
+           else
+               ereport(FATAL,
+                       (errcode(ERRCODE_CANNOT_CONNECT_NOW),
+                        errmsg("the database system is not accepting connections"),
+                        errdetail("Hot standby mode is disabled.")));
+           break;
        case CAC_SHUTDOWN:
            ereport(FATAL,
                    (errcode(ERRCODE_CANNOT_CONNECT_NOW),
@@ -2435,10 +2447,11 @@ canAcceptConnections(int backend_type)
    {
        if (Shutdown > NoShutdown)
            return CAC_SHUTDOWN;    /* shutdown is pending */
-       else if (!FatalError &&
-                (pmState == PM_STARTUP ||
-                 pmState == PM_RECOVERY))
+       else if (!FatalError && pmState == PM_STARTUP)
            return CAC_STARTUP; /* normal startup */
+       else if (!FatalError && pmState == PM_RECOVERY)
+           return CAC_NOTCONSISTENT;   /* not yet at consistent recovery
+                                        * state */
        else
            return CAC_RECOVERY;    /* else must be crash recovery */
    }

diff --git a/src/include/libpq/libpq-be.h b/src/include/libpq/libpq-be.h
index 30fb4e613dae874069f16117edc97116fa6f1b14..891394b0c3ef7e377f69541a2b980b35695c9fac 100644 (file)
--- a/src/include/libpq/libpq-be.h
+++ b/src/include/libpq/libpq-be.h
@@ -70,7 +70,12 @@ typedef struct
 
 typedef enum CAC_state
 {
-   CAC_OK, CAC_STARTUP, CAC_SHUTDOWN, CAC_RECOVERY, CAC_TOOMANY,
+   CAC_OK,
+   CAC_STARTUP,
+   CAC_SHUTDOWN,
+   CAC_RECOVERY,
+   CAC_NOTCONSISTENT,
+   CAC_TOOMANY,
    CAC_SUPERUSER
 } CAC_state;