Doc: Update information about manually creating slots.

There are some cases (e.g. when the subscription is created using the
connect = false option) where the remote replication slot was not created
automatically and the user must create it manually before the subscription
can be activated. There was not enough information in the docs for users
to do this easily.

Author: Peter Smith
Reviewd by: Shi yu, Amit Kapila
Discussion: https://postgr.es/m/CAHut+PvqdqOanheWSHDyhQiF+Z-7w=-+k4U+bwbT=b6YQ_hrXQ@mail.gmail.com

diff --git a/doc/src/sgml/logical-replication.sgml b/doc/src/sgml/logical-replication.sgml
index 434bc3118054b828f78ee764d99e78f4f1d6a3fe..f8756389a3bf6121ec86fddd119626faaafd72fa 100644 (file)
--- a/doc/src/sgml/logical-replication.sgml
+++ b/doc/src/sgml/logical-replication.sgml
@@ -320,7 +320,7 @@
   </sect2>
 
   <sect2 id="logical-replication-subscription-examples">
-    <title>Examples</title>
+    <title>Examples - Setup Logical Replication</title>
 
     <para>
      Create some test tables on the publisher.
@@ -512,6 +512,163 @@ test_sub=# SELECT * FROM t3;
 </programlisting></para>
   </sect2>
 
+  <sect2 id="logical-replication-subscription-examples-deferred-slot">
+   <title>Examples - Deferred Replication Slot Creation</title>
+
+   <para>
+    There are some cases (e.g.
+    <xref linkend="logical-replication-subscription-slot"/>) where, if the
+    remote replication slot was not created automatically, the user must create
+    it manually before the subscription can be activated. The steps to create
+    the slot and activate the subscription are shown in the following examples.
+    These examples specify the standard logical decoding plugin
+    (<literal>pgoutput</literal>), which is what the built-in logical
+    replication uses.
+   </para>
+   <para>
+    First, create a publication for the examples to use.
+<programlisting>
+test_pub=# CREATE PUBLICATION pub1 FOR ALL TABLES;
+CREATE PUBLICATION
+</programlisting></para>
+   <para>
+    Example 1: Where the subscription says <literal>connect = false</literal>
+   </para>
+   <para>
+    <itemizedlist>
+     <listitem>
+      <para>
+       Create the subscription.
+<programlisting>
+test_sub=# CREATE SUBSCRIPTION sub1
+test_sub-# CONNECTION 'host=localhost dbname=test_pub'
+test_sub-# PUBLICATION pub1
+test_sub-# WITH (connect=false);
+WARNING:  subscription was created, but is not connected
+HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
+CREATE SUBSCRIPTION
+</programlisting></para>
+     </listitem>
+     <listitem>
+      <para>
+       On the publisher, manually create a slot. Because the name was not
+       specified during <literal>CREATE SUBSCRIPTION</literal>, the name of the
+       slot to create is same as the subscription name, e.g. "sub1".
+<programlisting>
+test_pub=# SELECT * FROM pg_create_logical_replication_slot('sub1', 'pgoutput');
+ slot_name |    lsn
+-----------+-----------
+ sub1      | 0/19404D0
+(1 row)
+</programlisting></para>
+     </listitem>
+     <listitem>
+      <para>
+       On the subscriber, complete the activation of the subscription. After
+       this the tables of <literal>pub1</literal> will start replicating.
+<programlisting>
+test_sub=# ALTER SUBSCRIPTION sub1 ENABLE;
+ALTER SUBSCRIPTION
+test_sub=# ALTER SUBSCRIPTION sub1 REFRESH PUBLICATION;
+ALTER SUBSCRIPTION
+</programlisting></para>
+     </listitem>
+    </itemizedlist>
+   </para>
+
+   <para>
+    Example 2: Where the subscription says <literal>connect = false</literal>,
+    but also specifies the <literal>slot_name</literal>
+    <itemizedlist>
+     <listitem>
+      <para>
+       Create the subscription.
+<programlisting>
+test_sub=# CREATE SUBSCRIPTION sub1
+test_sub-# CONNECTION 'host=localhost dbname=test_pub'
+test_sub-# PUBLICATION pub1
+test_sub-# WITH (connect=false, slot_name='myslot');
+WARNING:  subscription was created, but is not connected
+HINT:  To initiate replication, you must manually create the replication slot, enable the subscription, and refresh the subscription.
+CREATE SUBSCRIPTION
+</programlisting></para>
+     </listitem>
+     <listitem>
+      <para>
+       On the publisher, manually create a slot using the same name that was
+       specified during <literal>CREATE SUBSCRIPTION</literal>, e.g. "myslot".
+<programlisting>
+test_pub=# SELECT * FROM pg_create_logical_replication_slot('myslot', 'pgoutput');
+ slot_name |    lsn
+-----------+-----------
+ myslot    | 0/19059A0
+(1 row)
+</programlisting></para>
+     </listitem>
+     <listitem>
+      <para>
+       On the subscriber, the remaining subscription activation steps are the
+       same as before.
+<programlisting>
+test_sub=# ALTER SUBSCRIPTION sub1 ENABLE;
+ALTER SUBSCRIPTION
+test_sub=# ALTER SUBSCRIPTION sub1 REFRESH PUBLICATION;
+ALTER SUBSCRIPTION
+</programlisting></para>
+     </listitem>
+    </itemizedlist>
+   </para>
+
+   <para>
+    Example 3: Where the subscription specifies <literal>slot_name = NONE</literal>
+    <itemizedlist>
+     <listitem>
+      <para>
+       Create the subscription. When <literal>slot_name = NONE</literal> then
+       <literal>enabled = false</literal>, and
+       <literal>create_slot = false</literal> are also needed.
+<programlisting>
+test_sub=# CREATE SUBSCRIPTION sub1
+test_sub-# CONNECTION 'host=localhost dbname=test_pub'
+test_sub-# PUBLICATION pub1
+test_sub-# WITH (slot_name=NONE, enabled=false, create_slot=false);
+CREATE SUBSCRIPTION
+</programlisting></para>
+     </listitem>
+     <listitem>
+      <para>
+       On the publisher, manually create a slot using any name, e.g. "myslot".
+<programlisting>
+test_pub=# SELECT * FROM pg_create_logical_replication_slot('myslot', 'pgoutput');
+ slot_name |    lsn
+-----------+-----------
+ myslot    | 0/1905930
+(1 row)
+</programlisting></para>
+     </listitem>
+     <listitem>
+      <para>
+       On the subscriber, associate the subscription with the slot name just
+       created.
+<programlisting>
+test_sub=# ALTER SUBSCRIPTION sub1 SET (slot_name='myslot');
+ALTER SUBSCRIPTION
+</programlisting></para>
+     </listitem>
+     <listitem>
+      <para>
+       The remaining subscription activation steps are same as before.
+<programlisting>
+test_sub=# ALTER SUBSCRIPTION sub1 ENABLE;
+ALTER SUBSCRIPTION
+test_sub=# ALTER SUBSCRIPTION sub1 REFRESH PUBLICATION;
+ALTER SUBSCRIPTION
+</programlisting></para>
+     </listitem>
+    </itemizedlist>
+   </para>
+  </sect2>
+
  </sect1>
 
  <sect1 id="logical-replication-row-filter">

diff --git a/doc/src/sgml/ref/create_subscription.sgml b/doc/src/sgml/ref/create_subscription.sgml
index bd12e71e33603eec5c4b55e8c1537b2cc0cc438e..f9a1776380bfc6058cdf7a1331bcf3c1d77228fa 100644 (file)
--- a/doc/src/sgml/ref/create_subscription.sgml
+++ b/doc/src/sgml/ref/create_subscription.sgml
@@ -120,11 +120,11 @@ CREATE SUBSCRIPTION <replaceable class="parameter">subscription_name</replaceabl
 
          <para>
           Since no connection is made when this option is
-          <literal>false</literal>, no tables are subscribed, and so
-          after you enable the subscription nothing will be replicated.
-          You will need to then run
-          <literal>ALTER SUBSCRIPTION ... REFRESH PUBLICATION</literal>
-          for tables to be subscribed.
+          <literal>false</literal>, no tables are subscribed. To initiate
+          replication, you must manually create the replication slot, enable
+          the subscription, and refresh the subscription. See
+          <xref linkend="logical-replication-subscription-examples-deferred-slot"/>
+          for examples.
          </para>
         </listitem>
        </varlistentry>
@@ -135,8 +135,12 @@ CREATE SUBSCRIPTION <replaceable class="parameter">subscription_name</replaceabl
          <para>
           Specifies whether the command should create the replication slot on
           the publisher.  The default is <literal>true</literal>.
+         </para>
+         <para>
           If set to <literal>false</literal>, you are responsible for
-          creating the publisher's slot in some other way.
+          creating the publisher's slot in some other way. See
+          <xref linkend="logical-replication-subscription-examples-deferred-slot"/>
+          for examples.
          </para>
         </listitem>
        </varlistentry>
@@ -162,11 +166,13 @@ CREATE SUBSCRIPTION <replaceable class="parameter">subscription_name</replaceabl
 
          <para>
           Setting <literal>slot_name</literal> to <literal>NONE</literal>
-          means there will be no replication slot
-          associated with the subscription.  Use this when you will be
-          creating the replication slot later manually.  Such
-          subscriptions must also have both <literal>enabled</literal> and
-          <literal>create_slot</literal> set to <literal>false</literal>.
+          means there will be no replication slot associated with the
+          subscription. Such subscriptions must also have both
+          <literal>enabled</literal> and <literal>create_slot</literal> set to
+          <literal>false</literal>.  Use this when you will be creating the
+          replication slot later manually. See
+          <xref linkend="logical-replication-subscription-examples-deferred-slot"/>
+          for examples.
          </para>
         </listitem>
        </varlistentry>
@@ -357,8 +363,10 @@ CREATE SUBSCRIPTION <replaceable class="parameter">subscription_name</replaceabl
    replication slot separately (using the
    function <function>pg_create_logical_replication_slot</function> with the
    plugin name <literal>pgoutput</literal>) and create the subscription using
-   the parameter <literal>create_slot = false</literal>.  This is an
-   implementation restriction that might be lifted in a future release.
+   the parameter <literal>create_slot = false</literal>.  See
+   <xref linkend="logical-replication-subscription-examples-deferred-slot"/>
+   for examples. This is an implementation restriction that might be lifted in a
+   future release.
   </para>
 
   <para>