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help / color / mirror / Atom feedFrom: Hayato Kuroda (Fujitsu) <[email protected]>
To: 'Katsuragi Yuta' <[email protected]>
Cc: 'Ted Yu' <[email protected]>
Cc: Tom Lane <[email protected]>
Cc: vignesh C <[email protected]>
Cc: [email protected] <[email protected]>
Cc: Önder Kalacı <[email protected]>
Cc: Fujii Masao <[email protected]>
Cc: [email protected] <[email protected]>
Cc: Kyotaro Horiguchi <[email protected]>
Subject: RE: [Proposal] Add foreign-server health checks infrastructure
Date: Mon, 6 Mar 2023 11:56:42 +0000
Message-ID: <TYCPR01MB58700498838127C54BC9BD48F5B69@TYCPR01MB5870.jpnprd01.prod.outlook.com> (raw)
In-Reply-To: <[email protected]>
References: <TYAPR01MB58669EAAC02493BFF9F39B06F5D99@TYAPR01MB5866.jpnprd01.prod.outlook.com>
<[email protected]>
<TYAPR01MB58669C95604A0EB7BCC1B58CF5A49@TYAPR01MB5866.jpnprd01.prod.outlook.com>
<[email protected]>
<TYAPR01MB5866904CE4F2C30E1CEEFC04F5AA9@TYAPR01MB5866.jpnprd01.prod.outlook.com>
<[email protected]>
<TYAPR01MB586674A3C56AECB9B150BC84F5B39@TYAPR01MB5866.jpnprd01.prod.outlook.com>
<[email protected]>
Dear Katsuragi-san,
Thank you for reviewing! PSA new version.
> >> 4. the code of pqSocketPoll
> >> +#if defined(POLLRDHUP)
> >> + if (forConnCheck)
> >> + input_fd.events |= POLLRDHUP;
> >> +#endif
> >>
> >> I think it is better to use PQconnCheckable() to remove the macro.
> >
> > IIUC the macro is needed. In FreeBSD, macOS and other platforms do not
> > have the
> > macro POLLRDHUP so they cannot compile. I checked by my CI and got
> > following error.
> >
> > ```
> > ...
> > FAILED: src/interfaces/libpq/libpq.a.p/fe-misc.c.o
> > ...
> > ../src/interfaces/libpq/fe-misc.c:1149:22: error: use of undeclared
> > identifier 'POLLRDHUP'
> > input_fd.events |= POLLRDHUP;
> > ````
> >
> > It must be invisible from them.
>
> Sorry, my mistake...
No issues :-).
> >> 9. the document of postgres_fdw
> >> The document of postgres_fdw_verify_connection_states_* is a little
> >> bit old. Could you update it?
> >
> > Updated. IIUC postgres_fdw_verify_connection_states returns
> >
> > * true, if the connection is verified.
> > * false, if the connection seems to be disconnected.
> > * NULL, if this is not the supported platform or connection has not
> > been established.
> >
> > And postgres_fdw_verify_connection_states_all returns
> >
> > * true if all the connections are verified.
> > * false, if one of connections seems to be disconnected.
> > * NULL, if this is not the supported platform or this backend has
> > never established connections
>
> I think 'backend has never established connections' is a little bit
> strong.
> I think the following cases also return NULL. The case where a
> connection was established, however the connection is now closed
> by the postgres_fdw_disconnect() or something. NULL is also returned if
> the connection is invalidated. So, I think 'NULL, if no valid
> connection is established or the function is not supported on
> the platform.' is better. What do you think?
Disconnect functions have never been in my mind. Descriptions must be updated.
> Followings are my comments for v34. Please check.
>
> 0001:
> 1. the document of pqConnCheck
> + <literal>0</literal> if the socket is valid, and returns
> <literal>-1</literal>
> + if the connection has already been closed or an error has
> occurred.
>
> 1.1 if the socket is valid -> returns 0 if the 'connection is not
> closed'?
Fixed.
> 1.2 returns -1 if the connection has already been closed <- Let me ask
> a question.
> Isn't this a situation where we would like to check using this
> function? Is 'error has occurred' insufficient?
Seems right, fixed.
> 2. the comment of pqSocketCheck
> + * means that the socket has not matched POLLRDHUP event and the socket
> has
> + * still survived.
>
> socket has still survived -> connection is not closed by the socket
> peer?
Fixed.
> 3. the comment of pqSocketPoll
> + * returned and forConnCheck is requested, it means that the socket has
> not
> + * matched POLLRDHUP event and the socket has still survived.
>
> socket has still survived -> connection is not closed by the socket
> peer?
Fixed.
> 0002:
> 4. the comment of verify_cached_connections
> + * This function emits warnings if a disconnection is found. This
> return true
> + * if disconnections cannot be found, otherwise return false.
>
> return ture -> return's' true
> return false -> return's' false
Fixed.
> 5. the comment of postgres_fdw_verify_connection_states
> + * if the local session seems to be disconnected from other servers.
> NULL is
> + * returned if a connection to the specified foreign server has not
> been
> + * established yet, or this function is not available on this platform.
>
> Considering the above discussion, 'NULL is returned if a valid
> connection to the specified foreign server is not established or
> this function...' seems better. What do you think?
Right, fixed.
> 6. the document of postgres_fdw_verify_connection_states
> <literal>NULL</literal>
> + is returned if a connection to the specified foreign server has
> not been
> + established yet, or this function is not available on this
> platform
>
> The same as comment no.5.
Right, fixed.
> 7. the document of postgres_fdw_verify_connection_states_all
> <literal>NULL</literal>
> + is returned if the local session does not have connection caches,
> or this
> + function is not available on this platform.
>
> I think there is a case where a connection cache exists but valid
> connections do not exist and NULL is returned (disconnection case).
> Almost the same document as the postgres_fdw_verify_connection_states
> case (comment no.5) seems better.
Yes, but completely same statement cannot be used because these is not
specified foreign server. How about:
NULL is returned if there are no established connections or this function ...
> 8. the document of postgres_fdw_can_verify_connection_states
> + This function checks whether
> <function>postgres_fdw_verify_connection_states</function>
> + and <function>postgres_fdw_verify_connection_states</function>
> work well
>
> Should the latter (or former) postgres_fdw_verify_connection_states be
> postgres_fdw_verify_connection_states_all?
That was copy-and-paste error, fixed.
> regards,
>
> --
> Katsuragi Yuta
> Advanced Computing Technology Center
> Research and Development Headquarters
> NTT DATA CORPORATION
Best Regards,
Hayato Kuroda
FUJITSU LIMITED
Attachments:
[application/octet-stream] v35-0001-Add-PQconnCheck-and-PQconnCheckable-to-libpq.patch (8.7K, ../TYCPR01MB58700498838127C54BC9BD48F5B69@TYCPR01MB5870.jpnprd01.prod.outlook.com/2-v35-0001-Add-PQconnCheck-and-PQconnCheckable-to-libpq.patch)
download | inline diff:
From 7183d0caec360464dbc0e5e83c31eef837d77477 Mon Sep 17 00:00:00 2001
From: Hayato Kuroda <[email protected]>
Date: Fri, 27 Jan 2023 03:17:18 +0000
Subject: [PATCH v35 1/3] Add PQconnCheck and PQconnCheckable to libpq
PQconnCheck() function allows to check the status of the connection by
polling the socket. This function is currently available only on systems
that support the non-standard POLLRDHUP extension to the poll system call,
including Linux.
PQconnCheckable() checks whether the above function is available or not.
---
doc/src/sgml/libpq.sgml | 38 +++++++++++++++
src/interfaces/libpq/exports.txt | 2 +
src/interfaces/libpq/fe-misc.c | 79 ++++++++++++++++++++++++++------
src/interfaces/libpq/libpq-fe.h | 4 ++
4 files changed, 108 insertions(+), 15 deletions(-)
diff --git a/doc/src/sgml/libpq.sgml b/doc/src/sgml/libpq.sgml
index 3ccd8ff942..b1a4471403 100644
--- a/doc/src/sgml/libpq.sgml
+++ b/doc/src/sgml/libpq.sgml
@@ -2679,6 +2679,44 @@ void *PQgetssl(const PGconn *conn);
</listitem>
</varlistentry>
+ <varlistentry id="libpq-PQconnCheck">
+ <term><function>PQconnCheck</function><indexterm><primary>PQconnCheck</primary></indexterm></term>
+ <listitem>
+ <para>
+ Returns the health of the connection.
+
+<synopsis>
+int PQconnCheck(PGconn *conn);
+</synopsis>
+ </para>
+
+ <para>
+ This function checks the health of the connection. Unlike <xref linkend="libpq-PQstatus"/>,
+ this check is performed by polling the corresponding socket. This
+ function is currently available only on systems that support the
+ non-standard <symbol>POLLRDHUP</symbol> extension to the <symbol>poll</symbol>
+ system call, including Linux. <xref linkend="libpq-PQconnCheck"/>
+ returns greater than zero if the remote peer seems to be closed, returns
+ <literal>0</literal> if the connection is not closed, and returns
+ <literal>-1</literal> if an error has occurred.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry id="libpq-PQconnCheckable">
+ <term><function>PQconnCheckable</function><indexterm><primary>PQconnCheckable</primary></indexterm></term>
+ <listitem>
+ <para>
+ Returns true (1) or false (0) to indicate if the <xref linkend="libpq-PQconnCheck"/>
+ function is supported on this platform.
+
+<synopsis>
+int PQconnCheckable(void);
+</synopsis>
+ </para>
+ </listitem>
+ </varlistentry>
+
</variablelist>
</para>
diff --git a/src/interfaces/libpq/exports.txt b/src/interfaces/libpq/exports.txt
index e8bcc88370..e7f0d435bd 100644
--- a/src/interfaces/libpq/exports.txt
+++ b/src/interfaces/libpq/exports.txt
@@ -186,3 +186,5 @@ PQpipelineStatus 183
PQsetTraceFlags 184
PQmblenBounded 185
PQsendFlushRequest 186
+PQconnCheck 187
+PQconnCheckable 188
diff --git a/src/interfaces/libpq/fe-misc.c b/src/interfaces/libpq/fe-misc.c
index 3653a1a8a6..897eb413b1 100644
--- a/src/interfaces/libpq/fe-misc.c
+++ b/src/interfaces/libpq/fe-misc.c
@@ -53,9 +53,10 @@
static int pqPutMsgBytes(const void *buf, size_t len, PGconn *conn);
static int pqSendSome(PGconn *conn, int len);
-static int pqSocketCheck(PGconn *conn, int forRead, int forWrite,
- time_t end_time);
-static int pqSocketPoll(int sock, int forRead, int forWrite, time_t end_time);
+static int pqSocketCheck(PGconn *conn, int forRead,
+ int forWrite, int forConnCheck, time_t end_time);
+static int pqSocketPoll(int sock, int forRead,
+ int forWrite, int forConnCheck, time_t end_time);
/*
* PQlibVersion: return the libpq version number
@@ -993,7 +994,7 @@ pqWaitTimed(int forRead, int forWrite, PGconn *conn, time_t finish_time)
{
int result;
- result = pqSocketCheck(conn, forRead, forWrite, finish_time);
+ result = pqSocketCheck(conn, forRead, forWrite, 0, finish_time);
if (result < 0)
return -1; /* errorMessage is already set */
@@ -1014,7 +1015,7 @@ pqWaitTimed(int forRead, int forWrite, PGconn *conn, time_t finish_time)
int
pqReadReady(PGconn *conn)
{
- return pqSocketCheck(conn, 1, 0, (time_t) 0);
+ return pqSocketCheck(conn, 1, 0, 0, (time_t) 0);
}
/*
@@ -1024,19 +1025,52 @@ pqReadReady(PGconn *conn)
int
pqWriteReady(PGconn *conn)
{
- return pqSocketCheck(conn, 0, 1, (time_t) 0);
+ return pqSocketCheck(conn, 0, 1, 0, (time_t) 0);
+}
+
+/*
+ * Check whether the socket peer closed the connection or not.
+ *
+ * Returns >0 if remote peer seems to be closed, 0 if it is valid,
+ * -1 if the input connection is bad or an error occurred.
+ */
+int
+PQconnCheck(PGconn *conn)
+{
+ return pqSocketCheck(conn, 0, 0, 1, (time_t) 0);
+}
+
+/*
+ * Check whether PQconnCheck() can work on this platform.
+ *
+ * Returns true (1) if this can use PQconnCheck(), otherwise false (0).
+ */
+int
+PQconnCheckable(void)
+{
+#if (defined(HAVE_POLL) && defined(POLLRDHUP))
+ return true;
+#else
+ return false;
+#endif
}
/*
* Checks a socket, using poll or select, for data to be read, written,
- * or both. Returns >0 if one or more conditions are met, 0 if it timed
- * out, -1 if an error occurred.
+ * or both. Moreover, this function can check the health of the connetion on
+ * some limited platforms if forConnCehck is specified.
+ *
+ * Returns >0 if one or more conditions are met, 0 if it timed out, -1 if an
+ * error occurred. Note that if 0 is returned and forConnCheck is requested, it
+ * means that the socket has not matched POLLRDHUP event and the connection is
+ * not closed by the socket peer.
*
* If SSL is in use, the SSL buffer is checked prior to checking the socket
* for read data directly.
*/
static int
-pqSocketCheck(PGconn *conn, int forRead, int forWrite, time_t end_time)
+pqSocketCheck(PGconn *conn, int forRead,
+ int forWrite, int forConnCheck, time_t end_time)
{
int result;
@@ -1059,7 +1093,8 @@ pqSocketCheck(PGconn *conn, int forRead, int forWrite, time_t end_time)
/* We will retry as long as we get EINTR */
do
- result = pqSocketPoll(conn->sock, forRead, forWrite, end_time);
+ result = pqSocketPoll(conn->sock, forRead,
+ forWrite, forConnCheck, end_time);
while (result < 0 && SOCK_ERRNO == EINTR);
if (result < 0)
@@ -1076,15 +1111,21 @@ pqSocketCheck(PGconn *conn, int forRead, int forWrite, time_t end_time)
/*
* Check a file descriptor for read and/or write data, possibly waiting.
- * If neither forRead nor forWrite are set, immediately return a timeout
- * condition (without waiting). Return >0 if condition is met, 0
- * if a timeout occurred, -1 if an error or interrupt occurred.
+ * Moreover, this function can check the health of connection on some limited
+ * platform if forConnCehck is specified.
+ *
+ * If neither forRead, forWrite nor forConnCheck are set, immediately return a
+ * timeout condition (without waiting). Return >0 if condition is met, 0 if a
+ * timeout occurred, -1 if an error or interrupt occurred. Note that if 0 is
+ * returned and forConnCheck is requested, it means that the socket has not
+ * matched POLLRDHUP event and the connection is not closed by the socket peer.
*
* Timeout is infinite if end_time is -1. Timeout is immediate (no blocking)
* if end_time is 0 (or indeed, any time before now).
*/
static int
-pqSocketPoll(int sock, int forRead, int forWrite, time_t end_time)
+pqSocketPoll(int sock, int forRead,
+ int forWrite, int forConnCheck, time_t end_time)
{
/* We use poll(2) if available, otherwise select(2) */
#ifdef HAVE_POLL
@@ -1092,7 +1133,11 @@ pqSocketPoll(int sock, int forRead, int forWrite, time_t end_time)
int timeout_ms;
if (!forRead && !forWrite)
- return 0;
+ {
+ /* Connection check can be available on some limted platforms */
+ if (!(forConnCheck && PQconnCheckable()))
+ return 0;
+ }
input_fd.fd = sock;
input_fd.events = POLLERR;
@@ -1102,6 +1147,10 @@ pqSocketPoll(int sock, int forRead, int forWrite, time_t end_time)
input_fd.events |= POLLIN;
if (forWrite)
input_fd.events |= POLLOUT;
+#if defined(POLLRDHUP)
+ if (forConnCheck)
+ input_fd.events |= POLLRDHUP;
+#endif
/* Compute appropriate timeout interval */
if (end_time == ((time_t) -1))
diff --git a/src/interfaces/libpq/libpq-fe.h b/src/interfaces/libpq/libpq-fe.h
index f3d9220496..e1bd0cd7b7 100644
--- a/src/interfaces/libpq/libpq-fe.h
+++ b/src/interfaces/libpq/libpq-fe.h
@@ -648,6 +648,10 @@ extern int PQdsplen(const char *s, int encoding);
/* Get encoding id from environment variable PGCLIENTENCODING */
extern int PQenv2encoding(void);
+/* Check whether the postgres server is still alive or not */
+extern int PQconnCheck(PGconn *conn);
+extern int PQconnCheckable(void);
+
/* === in fe-auth.c === */
extern char *PQencryptPassword(const char *passwd, const char *user);
--
2.27.0
[application/octet-stream] v35-0002-postgres_fdw-add-postgres_fdw_verify_connection_.patch (12.3K, ../TYCPR01MB58700498838127C54BC9BD48F5B69@TYCPR01MB5870.jpnprd01.prod.outlook.com/3-v35-0002-postgres_fdw-add-postgres_fdw_verify_connection_.patch)
download | inline diff:
From d9ef6cf61b767c3d552c3adb0b65f9cef2bbe57a Mon Sep 17 00:00:00 2001
From: Hayato Kuroda <[email protected]>
Date: Fri, 27 Jan 2023 03:17:30 +0000
Subject: [PATCH v35 2/3] postgres_fdw: add
postgres_fdw_verify_connection_states
This function can verify the status of connections that are establieshed by
postgres_fdw. This check wil be done by PQconnCheck(), which means this is
available only on systems that support the non-standard POLLRDHUP extension
to the poll system call, including Linux.
This returns true if existing connection is not closed by the remote peer.
---
contrib/postgres_fdw/Makefile | 2 +-
contrib/postgres_fdw/connection.c | 162 ++++++++++++++++++
contrib/postgres_fdw/meson.build | 1 +
.../postgres_fdw/postgres_fdw--1.1--1.2.sql | 19 ++
contrib/postgres_fdw/postgres_fdw.control | 2 +-
doc/src/sgml/postgres-fdw.sgml | 74 ++++++++
6 files changed, 258 insertions(+), 2 deletions(-)
create mode 100644 contrib/postgres_fdw/postgres_fdw--1.1--1.2.sql
diff --git a/contrib/postgres_fdw/Makefile b/contrib/postgres_fdw/Makefile
index c1b0cad453..6d23768389 100644
--- a/contrib/postgres_fdw/Makefile
+++ b/contrib/postgres_fdw/Makefile
@@ -14,7 +14,7 @@ PG_CPPFLAGS = -I$(libpq_srcdir)
SHLIB_LINK_INTERNAL = $(libpq)
EXTENSION = postgres_fdw
-DATA = postgres_fdw--1.0.sql postgres_fdw--1.0--1.1.sql
+DATA = postgres_fdw--1.0.sql postgres_fdw--1.0--1.1.sql postgres_fdw--1.1--1.2.sql
REGRESS = postgres_fdw
diff --git a/contrib/postgres_fdw/connection.c b/contrib/postgres_fdw/connection.c
index 12b54f15cd..28f0775ffa 100644
--- a/contrib/postgres_fdw/connection.c
+++ b/contrib/postgres_fdw/connection.c
@@ -87,6 +87,9 @@ static bool xact_got_connection = false;
PG_FUNCTION_INFO_V1(postgres_fdw_get_connections);
PG_FUNCTION_INFO_V1(postgres_fdw_disconnect);
PG_FUNCTION_INFO_V1(postgres_fdw_disconnect_all);
+PG_FUNCTION_INFO_V1(postgres_fdw_verify_connection_states);
+PG_FUNCTION_INFO_V1(postgres_fdw_verify_connection_states_all);
+PG_FUNCTION_INFO_V1(postgres_fdw_can_verify_connection_states);
/* prototypes of private functions */
static void make_new_connection(ConnCacheEntry *entry, UserMapping *user);
@@ -117,6 +120,7 @@ static void pgfdw_finish_pre_subcommit_cleanup(List *pending_entries,
int curlevel);
static bool UserMappingPasswordRequired(UserMapping *user);
static bool disconnect_cached_connections(Oid serverid);
+static bool verify_cached_connections(Oid serverid, bool *checked);
/*
* Get a PGconn which can be used to execute queries on the remote PostgreSQL
@@ -1832,3 +1836,161 @@ disconnect_cached_connections(Oid serverid)
return result;
}
+
+/*
+ * Workhorse to verify cached connections.
+ *
+ * This function scans all the connection cache entries and verifies the
+ * connections whose foreign server OID matches with the specified one. If
+ * InvalidOid is specified, it verifies all the cached connections.
+ *
+ * This function emits warnings if a disconnection is found. This returns true
+ * if disconnections cannot be found, otherwise returns false.
+ *
+ * checked will be set to true if PQconnCheck() is called at least once.
+ */
+static bool
+verify_cached_connections(Oid serverid, bool *checked)
+{
+ HASH_SEQ_STATUS scan;
+ ConnCacheEntry *entry;
+ bool all = !OidIsValid(serverid);
+ bool result = true;
+ StringInfoData str;
+
+ *checked = false;
+
+ Assert(ConnectionHash);
+
+ hash_seq_init(&scan, ConnectionHash);
+ while ((entry = (ConnCacheEntry *) hash_seq_search(&scan)))
+ {
+ /* Ignore cache entry if no open connection right now */
+ if (!entry->conn)
+ continue;
+
+ /* Skip if the entry is invalidated */
+ if (entry->invalidated)
+ continue;
+
+ if (all || entry->serverid == serverid)
+ {
+ if (PQconnCheck(entry->conn))
+ {
+ /* A foreign server might be down, so construct a message */
+ ForeignServer *server = GetForeignServer(entry->serverid);
+
+ if (result)
+ {
+ /*
+ * Initialize and add a prefix if this is the first
+ * disconnection we found.
+ */
+ initStringInfo(&str);
+ appendStringInfo(&str, "could not connect to server ");
+
+ result = false;
+ }
+ else
+ appendStringInfo(&str, ", ");
+
+ appendStringInfo(&str, "\"%s\"", server->servername);
+ }
+
+ /* Set a flag to notify the caller */
+ *checked = true;
+ }
+ }
+
+ /* Raise a warning if disconnections are found */
+ if (!result)
+ {
+ Assert(str.len);
+ ereport(WARNING,
+ (errcode(ERRCODE_CONNECTION_FAILURE),
+ errmsg("%s", str.data),
+ errdetail("Connection close is detected."),
+ errhint("Plsease check the health of server.")));
+ pfree(str.data);
+ }
+
+ return result;
+}
+
+/*
+ * Verify the specified cached connections.
+ *
+ * This function verifies the connections that are established by postgres_fdw
+ * from the local session to the foreign server with the given name.
+ *
+ * This function emits a warning if a disconnection is found. This returns true
+ * if existing connection is not closed by the remote peer. false is returned
+ * if the local session seems to be disconnected from other servers. NULL is
+ * returned if a valid connection to the specified foreign server is not
+ * established or this function is not available on this platform.
+ */
+Datum
+postgres_fdw_verify_connection_states(PG_FUNCTION_ARGS)
+{
+ ForeignServer *server;
+ char *servername;
+ bool result,
+ checked = false;
+
+ /* quick exit if the checking does not work well on this platfrom */
+ if (!PQconnCheckable())
+ PG_RETURN_NULL();
+
+ /* quick exit if connection cache has not been initialized yet */
+ if (!ConnectionHash)
+ PG_RETURN_NULL();
+
+ servername = text_to_cstring(PG_GETARG_TEXT_PP(0));
+ server = GetForeignServerByName(servername, false);
+
+ result = verify_cached_connections(server->serverid, &checked);
+
+ /* Return the result if checking function was called, otherwise NULL */
+ if (checked)
+ PG_RETURN_BOOL(result);
+ else
+ PG_RETURN_NULL();
+}
+
+/*
+ * Verify all the cached connections.
+ *
+ * This function verifies all the connections that are established by postgres_fdw
+ * from the local session to the foreign servers.
+ */
+Datum
+postgres_fdw_verify_connection_states_all(PG_FUNCTION_ARGS)
+{
+ bool result,
+ checked = false;
+
+ /* quick exit if the checking does not work well on this platfrom */
+ if (!PQconnCheckable())
+ PG_RETURN_NULL();
+
+ /* quick exit if connection cache has not been initialized yet */
+ if (!ConnectionHash)
+ PG_RETURN_NULL();
+
+ result = verify_cached_connections(InvalidOid, &checked);
+
+ /* Return the result if checking function was called, otherwise NULL */
+ if (checked)
+ PG_RETURN_BOOL(result);
+ else
+ PG_RETURN_NULL();
+}
+
+/*
+ * Check whether functions for verifying cached connections work well or not
+ */
+Datum
+postgres_fdw_can_verify_connection_states(PG_FUNCTION_ARGS)
+{
+ PG_RETURN_BOOL(PQconnCheckable());
+}
diff --git a/contrib/postgres_fdw/meson.build b/contrib/postgres_fdw/meson.build
index 2b451f165e..29118d47bb 100644
--- a/contrib/postgres_fdw/meson.build
+++ b/contrib/postgres_fdw/meson.build
@@ -26,6 +26,7 @@ install_data(
'postgres_fdw.control',
'postgres_fdw--1.0.sql',
'postgres_fdw--1.0--1.1.sql',
+ 'postgres_fdw--1.1--1.2.sql',
kwargs: contrib_data_args,
)
diff --git a/contrib/postgres_fdw/postgres_fdw--1.1--1.2.sql b/contrib/postgres_fdw/postgres_fdw--1.1--1.2.sql
new file mode 100644
index 0000000000..a8556b4c9f
--- /dev/null
+++ b/contrib/postgres_fdw/postgres_fdw--1.1--1.2.sql
@@ -0,0 +1,19 @@
+/* contrib/postgres_fdw/postgres_fdw--1.1--1.2.sql */
+
+-- complain if script is sourced in psql, rather than via ALTER EXTENSION
+\echo Use "ALTER EXTENSION postgres_fdw UPDATE TO '1.2'" to load this file. \quit
+
+CREATE FUNCTION postgres_fdw_verify_connection_states (text)
+RETURNS bool
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT PARALLEL RESTRICTED;
+
+CREATE FUNCTION postgres_fdw_verify_connection_states_all ()
+RETURNS bool
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT PARALLEL RESTRICTED;
+
+CREATE FUNCTION postgres_fdw_can_verify_connection_states ()
+RETURNS bool
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT PARALLEL SAFE;
diff --git a/contrib/postgres_fdw/postgres_fdw.control b/contrib/postgres_fdw/postgres_fdw.control
index d489382064..a4b800be4f 100644
--- a/contrib/postgres_fdw/postgres_fdw.control
+++ b/contrib/postgres_fdw/postgres_fdw.control
@@ -1,5 +1,5 @@
# postgres_fdw extension
comment = 'foreign-data wrapper for remote PostgreSQL servers'
-default_version = '1.1'
+default_version = '1.2'
module_pathname = '$libdir/postgres_fdw'
relocatable = true
diff --git a/doc/src/sgml/postgres-fdw.sgml b/doc/src/sgml/postgres-fdw.sgml
index 644f51835b..8cdb0d0a9d 100644
--- a/doc/src/sgml/postgres-fdw.sgml
+++ b/doc/src/sgml/postgres-fdw.sgml
@@ -826,6 +826,80 @@ postgres=# SELECT postgres_fdw_disconnect_all();
</para>
</listitem>
</varlistentry>
+
+ <varlistentry>
+ <term><function>postgres_fdw_verify_connection_states(server_name text) returns boolean</function></term>
+ <listitem>
+ <para>
+ This function checks the status of remote connections established by
+ <filename>postgres_fdw</filename> from the local session to the foreign
+ server with the given name. This check is performed by polling the socket
+ and allows long-running transactions to be aborted sooner if the kernel
+ reports that the connection is closed. This function is currently
+ available only on systems that support the non-standard <symbol>POLLRDHUP</symbol>
+ extension to the <symbol>poll</symbol> system call, including Linux. This
+ returns <literal>true</literal> if existing connection is not closed by
+ the remote peer. <literal>false</literal> is returned if the local
+ session seems to be disconnected from other servers. <literal>NULL</literal>
+ is returned if a valid connection to the specified foreign server is not
+ established or this function is not available on this platform. If no
+ foreign server with the given name is found, an error is reported.
+ Example usage of the function:
+<screen>
+postgres=# SELECT postgres_fdw_verify_connection_states('loopback1');
+ postgres_fdw_verify_connection_states
+---------------------------------------
+ t
+</screen>
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><function>postgres_fdw_verify_connection_states_all() returns boolean</function></term>
+ <listitem>
+ <para>
+ This function checks the status of all the remote connections established
+ by <filename>postgres_fdw</filename> from the local session to the
+ foreign servers. This check is performed by polling the socket and allows
+ long-running transactions to be aborted sooner if the kernel reports
+ that the connection is closed. This function is currently available only
+ on systems that support the non-standard <symbol>POLLRDHUP</symbol>
+ extension to the <symbol>poll</symbol> system call, including Linux. This
+ returns <literal>true</literal> if all connections are not closed by the
+ remote peer. <literal>false</literal> is returned if the local session
+ seems to be disconnected from at least one remote server. <literal>NULL</literal>
+ is returned if there are no established connections or this function is
+ not available on this platform. Example usage of the function:
+<screen>
+postgres=# SELECT postgres_fdw_verify_connection_states_all();
+ postgres_fdw_verify_connection_states_all
+-------------------------------------------
+ t
+</screen>
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><function>postgres_fdw_can_verify_connection_states() returns boolean</function></term>
+ <listitem>
+ <para>
+ This function checks whether <function>postgres_fdw_verify_connection_states</function>
+ and <function>postgres_fdw_verify_connection_states_all</function> work
+ well or not. This returns <literal>true</literal> if it can be used,
+ otherwise returns <literal>false</literal>. Example usage of the
+ function:
+
+<screen>
+postgres=# SELECT postgres_fdw_can_verify_connection_states();
+ postgres_fdw_can_verify_connection_states
+-------------------------------------------
+ t
+</screen>
+ </para>
+ </listitem>
+ </varlistentry>
+
</variablelist>
</sect2>
--
2.27.0
[application/octet-stream] v35-0003-add-test.patch (5.3K, ../TYCPR01MB58700498838127C54BC9BD48F5B69@TYCPR01MB5870.jpnprd01.prod.outlook.com/4-v35-0003-add-test.patch)
download | inline diff:
From 987d157a13d8f2dc200b99b0a914f105a167e100 Mon Sep 17 00:00:00 2001
From: Hayato Kuroda <[email protected]>
Date: Fri, 27 Jan 2023 03:17:36 +0000
Subject: [PATCH v35 3/3] add test
---
.../postgres_fdw/expected/postgres_fdw.out | 64 +++++++++++++++++++
contrib/postgres_fdw/sql/postgres_fdw.sql | 62 ++++++++++++++++++
2 files changed, 126 insertions(+)
diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index 04a3ef450c..6446f36092 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -11783,3 +11783,67 @@ ANALYZE analyze_table;
-- cleanup
DROP FOREIGN TABLE analyze_ftable;
DROP TABLE analyze_table;
+-- ===================================================================
+-- test for postgres_fdw_verify_foreign_servers function
+-- ===================================================================
+-- Disable debug_discard_caches in order to manage remote connections
+SET debug_discard_caches TO '0';
+-- -- The text of the error might vary across platforms, so only show SQLSTATE.
+\set VERBOSITY sqlstate
+-- Disconnect once and set application_name to an arbitrary value
+SELECT 1 FROM postgres_fdw_disconnect_all();
+ ?column?
+----------
+ 1
+(1 row)
+
+ALTER SERVER loopback OPTIONS (SET application_name 'healthcheck');
+-- Define procedure for testing verify functions
+CREATE PROCEDURE test_verify_function(use_all boolean) AS $$
+DECLARE
+ can_verify boolean;
+ result boolean;
+BEGIN
+ PERFORM 1 FROM ft1 LIMIT 1;
+
+ -- Terminate the remote backend process
+ PERFORM pg_terminate_backend(pid, 180000) FROM pg_stat_activity
+ WHERE application_name = 'healthcheck';
+
+ -- Check whether we can do health check on this platform
+ SELECT INTO can_verify postgres_fdw_can_verify_connection_states();
+
+ -- If the checking can be done on this platform, call it
+ IF can_verify IS TRUE THEN
+ -- Set client_min_messages to ERROR temporary because the following
+ -- function only throws a WARNING on the supported platform.
+ SET LOCAL client_min_messages TO ERROR;
+
+ IF use_all IS TRUE THEN
+ SELECT INTO result postgres_fdw_verify_connection_states_all();
+ ELSE
+ SELECT INTO result postgres_fdw_verify_connection_states('loopback');
+ END IF;
+
+ RESET client_min_messages;
+ ELSE
+ result = false;
+ END IF;
+
+ -- If result is FALSE, we succeeded to detect the disconnection or it could
+ -- not be done on this platform. Raise an message.
+ IF result IS FALSE THEN
+ RAISE INFO 'postgres_fdw_verify_connection_states_all() could detect the disconnection, or health check cannot be used on this platform';
+ END IF;
+END;
+$$ LANGUAGE plpgsql;
+-- ..And call above function
+CALL test_verify_function(false);
+INFO: 00000
+ERROR: 08006
+CALL test_verify_function(true);
+INFO: 00000
+ERROR: 08006
+-- Clean up
+\set VERBOSITY default
+RESET debug_discard_caches;
diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index 4f3088c03e..b413f96e32 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -3979,3 +3979,65 @@ ANALYZE analyze_table;
-- cleanup
DROP FOREIGN TABLE analyze_ftable;
DROP TABLE analyze_table;
+
+-- ===================================================================
+-- test for postgres_fdw_verify_foreign_servers function
+-- ===================================================================
+
+-- Disable debug_discard_caches in order to manage remote connections
+SET debug_discard_caches TO '0';
+
+-- -- The text of the error might vary across platforms, so only show SQLSTATE.
+\set VERBOSITY sqlstate
+
+-- Disconnect once and set application_name to an arbitrary value
+SELECT 1 FROM postgres_fdw_disconnect_all();
+ALTER SERVER loopback OPTIONS (SET application_name 'healthcheck');
+
+-- Define procedure for testing verify functions
+CREATE PROCEDURE test_verify_function(use_all boolean) AS $$
+DECLARE
+ can_verify boolean;
+ result boolean;
+BEGIN
+ PERFORM 1 FROM ft1 LIMIT 1;
+
+ -- Terminate the remote backend process
+ PERFORM pg_terminate_backend(pid, 180000) FROM pg_stat_activity
+ WHERE application_name = 'healthcheck';
+
+ -- Check whether we can do health check on this platform
+ SELECT INTO can_verify postgres_fdw_can_verify_connection_states();
+
+ -- If the checking can be done on this platform, call it
+ IF can_verify IS TRUE THEN
+ -- Set client_min_messages to ERROR temporary because the following
+ -- function only throws a WARNING on the supported platform.
+ SET LOCAL client_min_messages TO ERROR;
+
+ IF use_all IS TRUE THEN
+ SELECT INTO result postgres_fdw_verify_connection_states_all();
+ ELSE
+ SELECT INTO result postgres_fdw_verify_connection_states('loopback');
+ END IF;
+
+ RESET client_min_messages;
+ ELSE
+ result = false;
+ END IF;
+
+ -- If result is FALSE, we succeeded to detect the disconnection or it could
+ -- not be done on this platform. Raise an message.
+ IF result IS FALSE THEN
+ RAISE INFO 'postgres_fdw_verify_connection_states_all() could detect the disconnection, or health check cannot be used on this platform';
+ END IF;
+END;
+$$ LANGUAGE plpgsql;
+
+-- ..And call above function
+CALL test_verify_function(false);
+CALL test_verify_function(true);
+
+-- Clean up
+\set VERBOSITY default
+RESET debug_discard_caches;
--
2.27.0
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