diff options
| -rw-r--r-- | doc/src/sgml/protocol.sgml | 20 | ||||
| -rw-r--r-- | src/backend/replication/logical/logical.c | 6 |
2 files changed, 21 insertions, 5 deletions
diff --git a/doc/src/sgml/protocol.sgml b/doc/src/sgml/protocol.sgml index e8cb78ff1f3..9843953b05f 100644 --- a/doc/src/sgml/protocol.sgml +++ b/doc/src/sgml/protocol.sgml @@ -2410,10 +2410,22 @@ The commands accepted in replication mode are: <term><literal>START_REPLICATION</literal> <literal>SLOT</literal> <replaceable class="parameter">slot_name</replaceable> <literal>LOGICAL</literal> <replaceable class="parameter">XXX/XXX</replaceable> [ ( <replaceable>option_name</replaceable> [ <replaceable>option_value</replaceable> ] [, ...] ) ]</term> <listitem> <para> - Instructs server to start streaming WAL for logical replication, starting - at WAL location <replaceable class="parameter">XXX/XXX</replaceable>. The server can - reply with an error, for example if the requested section of WAL has already - been recycled. On success, server responds with a CopyBothResponse + Instructs server to start streaming WAL for logical replication, + starting at either WAL location <replaceable + class="parameter">XXX/XXX</replaceable> or the slot's + <literal>confirmed_flush_lsn</literal> (see <xref + linkend="view-pg-replication-slots"/>), whichever is greater. This + behavior makes it easier for clients to avoid updating their local LSN + status when there is no data to process. However, starting at a + different LSN than requested might not catch certain kinds of client + errors; so the client may wish to check that + <literal>confirmed_flush_lsn</literal> matches its expectations before + issuing <literal>START_REPLICATION</literal>. + </para> + + <para> + The server can reply with an error, for example if the + slot does not exist. On success, server responds with a CopyBothResponse message, and then starts to stream WAL to the frontend. </para> diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index 8dcb564af8f..64b8280c135 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -520,8 +520,12 @@ CreateDecodingContext(XLogRecPtr start_lsn, * xlog records didn't result in anything relevant for logical * decoding. Clients have to be able to do that to support synchronous * replication. + * + * Starting at a different LSN than requested might not catch certain + * kinds of client errors; so the client may wish to check that + * confirmed_flush_lsn matches its expectations. */ - elog(DEBUG1, "cannot stream from %X/%X, minimum is %X/%X, forwarding", + elog(LOG, "%X/%X has been already streamed, forwarding to %X/%X", LSN_FORMAT_ARGS(start_lsn), LSN_FORMAT_ARGS(slot->data.confirmed_flush)); |