dblink: Replace WAIT_EVENT_EXTENSION with custom wait events

Two custom wait events are added here:
- "DblinkConnect", when waiting to establish a connection to a remote
server.
- "DblinkGetConnect", when waiting to establish a connection to a remote
server but it could not be found in the list of already-opened ones.

Author: Masahiro Ikeda
Discussion: https://postgr.es/m/197bce267fa691a0ac62c86c4ab904c4@oss.nttdata.com

diff --git a/contrib/dblink/dblink.c b/contrib/dblink/dblink.c
index 41e1f6c91d6aebe6f858b4c0045446d81c49cb8f..195b278f55903bf48cd12fe784e2d27beea23036 100644 (file)
--- a/contrib/dblink/dblink.c
+++ b/contrib/dblink/dblink.c
@@ -130,6 +130,10 @@ static void restoreLocalGucs(int nestlevel);
 static remoteConn *pconn = NULL;
 static HTAB *remoteConnHash = NULL;
 
+/* custom wait event values, retrieved from shared memory */
+static uint32 dblink_we_connect = 0;
+static uint32 dblink_we_get_conn = 0;
+
 /*
  * Following is list that holds multiple remote connections.
  * Calling convention of each dblink function changes to accept
@@ -202,8 +206,12 @@ dblink_get_conn(char *conname_or_str,
            connstr = conname_or_str;
        dblink_connstr_check(connstr);
 
+       /* first time, allocate or get the custom wait event */
+       if (dblink_we_get_conn == 0)
+           dblink_we_get_conn = WaitEventExtensionNew("DblinkGetConnect");
+
        /* OK to make connection */
-       conn = libpqsrv_connect(connstr, WAIT_EVENT_EXTENSION);
+       conn = libpqsrv_connect(connstr, dblink_we_get_conn);
 
        if (PQstatus(conn) == CONNECTION_BAD)
        {
@@ -292,8 +300,12 @@ dblink_connect(PG_FUNCTION_ARGS)
    /* check password in connection string if not superuser */
    dblink_connstr_check(connstr);
 
+   /* first time, allocate or get the custom wait event */
+   if (dblink_we_connect == 0)
+       dblink_we_connect = WaitEventExtensionNew("DblinkConnect");
+
    /* OK to make connection */
-   conn = libpqsrv_connect(connstr, WAIT_EVENT_EXTENSION);
+   conn = libpqsrv_connect(connstr, dblink_we_connect);
 
    if (PQstatus(conn) == CONNECTION_BAD)
    {

diff --git a/doc/src/sgml/dblink.sgml b/doc/src/sgml/dblink.sgml
index 7d25f24f490da1f10ee34cc54698ae412d80045f..e8de5a65cb6b67f163b5e0ecd945a245e15da86f 100644 (file)
--- a/doc/src/sgml/dblink.sgml
+++ b/doc/src/sgml/dblink.sgml
@@ -13,6 +13,32 @@
   session.
  </para>
 
+ <para>
+  <filename>dblink</filename> can report the following wait events under the wait
+  event type <literal>Extension</literal>.
+ </para>
+
+ <variablelist>
+  <varlistentry>
+   <term><literal>DblinkConnect</literal></term>
+   <listitem>
+    <para>
+     Waiting to establish a connection to a remote server.
+    </para>
+   </listitem>
+  </varlistentry>
+
+  <varlistentry>
+   <term><literal>DblinkGetConnect</literal></term>
+   <listitem>
+    <para>
+     Waiting to establish a connection to a remote server when it could not
+     be found in the list of already-opened connections.
+    </para>
+   </listitem>
+  </varlistentry>
+ </variablelist>
+
  <para>
   See also <xref linkend="postgres-fdw"/>, which provides roughly the same
   functionality using a more modern and standards-compliant infrastructure.