From 70373f8cb0a3fe404c1e51e0ade0c98b83aa0014 Mon Sep 17 00:00:00 2001
From: Dan Gudmundsson <dgud@erlang.org>
Date: Wed, 12 Feb 2014 14:50:49 +0100
Subject: mnesia: Add explicit sync_log command
For performance reasons the file data is not synced to disk in mnesia,
data loss can happen between each dump.
mnesia:dump_log() can be used explicitly to ensure data is written to disk.
But that can take a long time, so mnesia:sync_log() which just
sync the log have been added.
---
lib/mnesia/doc/src/mnesia.xml | 26 ++++++++++++++++++++++----
lib/mnesia/src/mnesia.erl | 6 +++++-
lib/mnesia/src/mnesia_monitor.erl | 7 +++++++
lib/mnesia/test/mnesia_nice_coverage_test.erl | 3 ++-
4 files changed, 36 insertions(+), 6 deletions(-)
diff --git a/lib/mnesia/doc/src/mnesia.xml b/lib/mnesia/doc/src/mnesia.xml
index 914ec77721..72e9bd7e8f 100644
--- a/lib/mnesia/doc/src/mnesia.xml
+++ b/lib/mnesia/doc/src/mnesia.xml
@@ -4,7 +4,7 @@
<erlref>
<header>
<copyright>
- <year>1996</year><year>2013</year>
+ <year>1996</year><year>2014</year>
<holder>Ericsson AB. All Rights Reserved.</holder>
</copyright>
<legalnotice>
@@ -1204,7 +1204,11 @@ mnesia:create_table(person,
<desc>
<p>Performs a user initiated dump of the local log file.
This is usually not necessary since Mnesia, by default,
- manages this automatically.</p>
+ manages this automatically.
+ See configuration parameters
+ <seealso marker="#dump_log_time_threshold">dump_log_time_threshold</seealso> and
+ <seealso marker="#dump_log_write_threshold">dump_log_write_threshold</seealso>.
+ </p>
</desc>
</func>
<func>
@@ -2207,6 +2211,18 @@ mnesia:create_table(employee,
Mnesia User's Guide for more details.</p>
</desc>
</func>
+ <func>
+ <name>sync_log() -> ok | {error, Reason} </name>
+ <fsummary>Perform a file sync of the local log file.</fsummary>
+ <desc>
+ <p>Ensures that the local transaction log file is synced to disk.
+ On a single node system data written to disk tables, since the last dump,
+ can be lost in case of a power outage.
+ See <seealso marker="#dump_log/0">dump_log/0</seealso>.
+ </p>
+ </desc>
+ </func>
+
<func>
<name>sync_transaction(Fun, [[, Args], Retries]) -> {aborted, Reason} | {atomic, ResultOfFun} </name>
<fsummary>Synchronously execute a transaction.</fsummary>
@@ -2445,7 +2461,7 @@ mnesia:create_table(employee,
<name>table(Tab [,[Option]]) -> QueryHandle </name>
<fsummary>Return a QLC query handle.</fsummary>
<desc>
- <p> <marker id="qlc_table"></marker>
+ <p><marker id="qlc_table"></marker>
Returns a QLC (Query List Comprehension) query handle, see
<seealso marker="stdlib:qlc">qlc(3)</seealso>.The module <c>qlc</c> implements a query language, it
can use mnesia tables as sources of data. Calling
@@ -3015,6 +3031,7 @@ raise(Name, Amount) ->
performed on the original data file. The default is <c>true</c></p>
</item>
<item>
+ <marker id=" dump_log_write_threshold"></marker>
<p><c>-mnesia dump_log_write_threshold Max</c>, where
<c>Max</c> is an integer which specifies the maximum number of writes
allowed to the transaction log before a new dump of the log
@@ -3022,13 +3039,14 @@ raise(Name, Amount) ->
</p>
</item>
<item>
+ <marker id=" dump_log_time_threshold"></marker>
<p><c>-mnesia dump_log_time_threshold Max</c>,
where <c>Max</c> is an integer which
specifies the dump log interval in milliseconds. It defaults
to 3 minutes. If a dump has not been performed within
<c>dump_log_time_threshold</c> milliseconds, then a new dump is
performed regardless of how many writes have been
- performed.
+ performed.
</p>
</item>
<item>
diff --git a/lib/mnesia/src/mnesia.erl b/lib/mnesia/src/mnesia.erl
index 70466d10d7..b791e1221f 100644
--- a/lib/mnesia/src/mnesia.erl
+++ b/lib/mnesia/src/mnesia.erl
@@ -104,7 +104,8 @@
set_master_nodes/1, set_master_nodes/2,
%% Misc admin
- dump_log/0, subscribe/1, unsubscribe/1, report_event/1,
+ dump_log/0, sync_log/0,
+ subscribe/1, unsubscribe/1, report_event/1,
%% Snmp
snmp_open_table/2, snmp_close_table/1,
@@ -2554,6 +2555,9 @@ set_master_nodes(Tab, Nodes) ->
dump_log() ->
mnesia_controller:sync_dump_log(user).
+sync_log() ->
+ mnesia_monitor:sync_log(latest_log).
+
subscribe(What) ->
mnesia_subscr:subscribe(self(), What).
diff --git a/lib/mnesia/src/mnesia_monitor.erl b/lib/mnesia/src/mnesia_monitor.erl
index c7b905a1bf..7b56613ad7 100644
--- a/lib/mnesia/src/mnesia_monitor.erl
+++ b/lib/mnesia/src/mnesia_monitor.erl
@@ -44,6 +44,7 @@
set_env/2,
start/0,
start_proc/4,
+ sync_log/1,
terminate_proc/3,
unsafe_close_dets/1,
unsafe_close_log/1,
@@ -118,6 +119,9 @@ open_log(Args) ->
reopen_log(Name, Fname, Head) ->
unsafe_call({reopen_log, Name, Fname, Head}).
+sync_log(Name) ->
+ unsafe_call({sync_log, Name}).
+
close_log(Name) ->
unsafe_call({close_log, Name}).
@@ -382,6 +386,9 @@ handle_call({reopen_log, Name, Fname, Head}, _From, State) ->
{noreply, State}
end;
+handle_call({sync_log, Name}, _From, State) ->
+ {reply, disk_log:sync(Name), State};
+
handle_call({close_log, Name}, _From, State) ->
case disk_log:close(Name) of
ok ->
diff --git a/lib/mnesia/test/mnesia_nice_coverage_test.erl b/lib/mnesia/test/mnesia_nice_coverage_test.erl
index 78eab67b11..4b28ac634f 100644
--- a/lib/mnesia/test/mnesia_nice_coverage_test.erl
+++ b/lib/mnesia/test/mnesia_nice_coverage_test.erl
@@ -1,7 +1,7 @@
%%
%% %CopyrightBegin%
%%
-%% Copyright Ericsson AB 1996-2010. All Rights Reserved.
+%% Copyright Ericsson AB 1996-2014. All Rights Reserved.
%%
%% The contents of this file are subject to the Erlang Public License,
%% Version 1.1, (the "License"); you may not use this file except in
@@ -189,6 +189,7 @@ adm(Attrs, Node1, Node2) ->
?match({atomic, ok}, mnesia:move_table_copy(nice_tab, Node2, Node1)),
?match(yes, mnesia:force_load_table(nice_counter_tab)),
+ ?match(ok, mnesia:sync_log()),
?match(dumped, mnesia:dump_log()),
ok.
--
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