From 63692ccacf464757638708b8ec7ed6c517d48b58 Mon Sep 17 00:00:00 2001
From: Konstantin Osipov <kostja@tarantool.org>
Date: Wed, 25 Apr 2012 23:48:11 +0400
Subject: [PATCH] Update the manual and the configuration file
Update the manual and the configuration file
to reflect the new WAL writer architecture.
---
cfg/core_cfg.cfg_tmpl | 5 ++---
doc/user/configuration-reference.xml | 16 ----------------
doc/user/persistence-architecture.xml | 25 ++++++++-----------------
3 files changed, 10 insertions(+), 36 deletions(-)
diff --git a/cfg/core_cfg.cfg_tmpl b/cfg/core_cfg.cfg_tmpl
index 3a019a52e2..d030d1217a 100644
--- a/cfg/core_cfg.cfg_tmpl
+++ b/cfg/core_cfg.cfg_tmpl
@@ -68,9 +68,8 @@ snap_io_rate_limit=0.0, ro
# Write no more rows in WAL
rows_per_wal=500000, ro
-# Size of the WAL writer request queue: how many outstanding
-# requests for write to disk it can have.
-# Rule of thumb is to set this to the average connection count.
+# OBSOLETE
+# Starting from 1.4.5, this variable has no effect.
wal_writer_inbox_size=16384, ro
# Defines fiber/data synchronization fsync(2) policy:
diff --git a/doc/user/configuration-reference.xml b/doc/user/configuration-reference.xml
index 311ab5cf7b..4bbb6a7977 100644
--- a/doc/user/configuration-reference.xml
+++ b/doc/user/configuration-reference.xml
@@ -529,22 +529,6 @@ tarantool_box: primary@sessions pri:33013 sec:33014 adm:33015</programlisting>
locations and moving snapshots to a separate disk.</entry>
</row>
- <row>
- <entry xml:id="wal_writer_inbox_size" xreflabel="wal_writer_inbox_size">wal_writer_inbox_size</entry>
- <entry>integer</entry>
- <entry>128</entry>
- <entry>no</entry>
- <entry>no</entry>
- <entry>WAL writer is a separate process whose sole
- purpose is to write the change log to disk. Every
- incoming data change is sent to this process and
- queued for write. This parameter affects the size of the
- user space buffer that WAL writer uses to queue
- write requests. By default, up to 128 client
- connections can have pending updates waiting on disk.
- </entry>
- </row>
-
<row>
<entry>wal_fsync_delay</entry>
<entry>float</entry>
diff --git a/doc/user/persistence-architecture.xml b/doc/user/persistence-architecture.xml
index 2147c53658..5db4d1f3f0 100644
--- a/doc/user/persistence-architecture.xml
+++ b/doc/user/persistence-architecture.xml
@@ -45,7 +45,7 @@ example:
</para></listitem>
<listitem><para>
A message is sent to a separate <quote>wal_writer</quote>
- process requesting that the change is recorded in the WAL.
+ thread requesting that the change is recorded in the WAL.
The fiber associate with the current connection is scheduled
off CPU until an acknowledgment is received from the WAL
writer.
@@ -60,24 +60,15 @@ example:
</para>
<para>
-Communication between master and WAL writer processes is asynchronous.
-It is implemented using 'inbox' paradigm, similar to
-process inboxes in Erlang, from which it was derived.
-Asynchronous but reliable message passing between processes
-allows Tarantool to continue handling requests regardless of disk
-throughput. SELECT performance, provided SELECTs are run in their
-own connections, is unaffected by disk load.
+Communication between master and WAL writer threads is asynchronous.
+It is implemented using an asynchronous FIFO queue.
+Asynchronous but reliable message passing between the master
+and WAL writer threads allows Tarantool to continue handling
+requests regardless of disk throughput. SELECT performance,
+provided SELECTs are run in their own connections, is unaffected
+by disk load.
</para>
-<para>
-The size of each process' inbox is fixed. In particular,
-the WAL writer inbox can hold only <olink targetptr="wal_writer_inbox_size"/>
-messages. This can pose a practical problem when thousands of
-connections perform updates — the WAL writer inbox can become full.
-Once this happens, the server aborts any update for which
-sending a WAL message has failed with <olink targetptr="ER_WAL_IO"/>
-error.
-</para>
</section>
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