Back-patch checkpoint clarification docs and pg_basebackup updates

This backpatches 51e26c9 and 7220c7b, including both documentation
updates clarifying the checkpoints at the beginning of base backups and
the messages in verbose and progress mdoe of pg_basebackup.

Author: Michael Banck
Discussion: https://postgr.es/m/21444.1488142764%40sss.pgh.pa.us

3 files changed, 22 insertions, 2 deletions

diff --git a/doc/src/sgml/backup.sgml b/doc/src/sgml/backup.sgml
index 8c0bb1f6a20..03c0dbf1cd0 100644
--- a/doc/src/sgml/backup.sgml
+++ b/doc/src/sgml/backup.sgml
@@ -862,7 +862,8 @@ SELECT pg_start_backup('label', false, false);
      <xref linkend="guc-checkpoint-completion-target">).  This is
      usually what you want, because it minimizes the impact on query
      processing.  If you want to start the backup as soon as
-     possible, change the second parameter to <literal>true</>.
+     possible, change the second parameter to <literal>true</>, which will
+     issue an immediate checkpoint using as much I/O as available.
     </para>
 
     <para>
diff --git a/doc/src/sgml/ref/pg_basebackup.sgml b/doc/src/sgml/ref/pg_basebackup.sgml
index 95c801627b3..134b2982368 100644
--- a/doc/src/sgml/ref/pg_basebackup.sgml
+++ b/doc/src/sgml/ref/pg_basebackup.sgml
@@ -382,7 +382,7 @@ PostgreSQL documentation
       <term><option>--checkpoint=<replaceable class="parameter">fast|spread</replaceable></option></term>
       <listitem>
        <para>
-        Sets checkpoint mode to fast or spread (default) (see <xref linkend="backup-lowlevel-base-backup">).
+        Sets checkpoint mode to fast (immediate) or spread (default) (see <xref linkend="backup-lowlevel-base-backup">).
        </para>
       </listitem>
      </varlistentry>
@@ -590,6 +590,14 @@ PostgreSQL documentation
   <title>Notes</title>
 
   <para>
+   At the beginning of the backup, a checkpoint needs to be written on the
+   server the backup is taken from.  Especially if the option
+   <literal>--checkpoint=fast</literal> is not used, this can take some time
+   during which <application>pg_basebackup</application> will be appear
+   to be idle.
+  </para>
+
+  <para>
    The backup will include all files in the data directory and tablespaces,
    including the configuration files and any additional files placed in the
    directory by third parties. But only regular files and directories are
diff --git a/src/bin/pg_basebackup/pg_basebackup.c b/src/bin/pg_basebackup/pg_basebackup.c
index a5bc3225337..613f2e159c3 100644
--- a/src/bin/pg_basebackup/pg_basebackup.c
+++ b/src/bin/pg_basebackup/pg_basebackup.c
@@ -1661,6 +1661,14 @@ BaseBackup(void)
 	if (maxrate > 0)
 		maxrate_clause = psprintf("MAX_RATE %u", maxrate);
 
+	if (verbose)
+		fprintf(stderr,
+				_("%s: initiating base backup, waiting for checkpoint to complete\n"),
+				progname);
+
+	if (showprogress && !verbose)
+		fprintf(stderr, "waiting for checkpoint\r");
+
 	basebkp =
 		psprintf("BASE_BACKUP LABEL '%s' %s %s %s %s %s %s",
 				 escaped_label,
@@ -1698,6 +1706,9 @@ BaseBackup(void)
 
 	strlcpy(xlogstart, PQgetvalue(res, 0, 0), sizeof(xlogstart));
 
+	if (verbose)
+		fprintf(stderr, _("%s: checkpoint completed\n"), progname);
+
 	/*
 	 * 9.3 and later sends the TLI of the starting point. With older servers,
 	 * assume it's the same as the latest timeline reported by