diff options
Diffstat (limited to 'lib/mnesia/doc')
| -rw-r--r-- | lib/mnesia/doc/src/Mnesia_chap7.xmlsrc | 9 | ||||
| -rw-r--r-- | lib/mnesia/doc/src/mnesia.xml | 34 | ||||
| -rw-r--r-- | lib/mnesia/doc/src/notes.xml | 36 |
3 files changed, 74 insertions, 5 deletions
diff --git a/lib/mnesia/doc/src/Mnesia_chap7.xmlsrc b/lib/mnesia/doc/src/Mnesia_chap7.xmlsrc index 7078499fbf..ae41a216f4 100644 --- a/lib/mnesia/doc/src/Mnesia_chap7.xmlsrc +++ b/lib/mnesia/doc/src/Mnesia_chap7.xmlsrc @@ -4,7 +4,7 @@ <chapter> <header> <copyright> - <year>1997</year><year>2009</year> + <year>1997</year><year>2011</year> <holder>Ericsson AB. All Rights Reserved.</holder> </copyright> <legalnotice> @@ -473,6 +473,13 @@ dets:close(N). </pre> <c>mnesia:table_info(Tab, master_nodes)</c> may be used to obtain information about the potential master nodes. </p> + <p>Determining which data to keep after communication failure is outside + the scope of Mnesia. One approach would be to determine which "island" + contains a majority of the nodes. Using the <c>{majority,true}</c> option + for critical tables can be a way of ensuring that nodes that are not part + of a "majority island" are not able to update those tables. Note that this + constitutes a reduction in service on the minority nodes. This would be + a tradeoff in favour of higher consistency guarantees.</p> <p>The function <c>mnesia:force_load_table(Tab)</c> may be used to force load the table regardless of which table load mechanism is activated. diff --git a/lib/mnesia/doc/src/mnesia.xml b/lib/mnesia/doc/src/mnesia.xml index 16e78ea0af..7a8f796cee 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>2010</year> + <year>1996</year><year>2011</year> <holder>Ericsson AB. All Rights Reserved.</holder> </copyright> <legalnotice> @@ -161,6 +161,14 @@ If a new item is inserted with the same key as </p> </item> <item> + <p><c>majority</c> This attribute can be either <c>true</c> or + <c>false</c> (default is <c>false</c>). When <c>true</c>, a majority + of the table replicas must be available for an update to succeed. + Majority checking can be enabled on tables with mission-critical data, + where it is vital to avoid inconsistencies due to network splits. + </p> + </item> + <item> <p><c>snmp</c> Each (set based) Mnesia table can be automatically turned into an SNMP ordered table as well. This property specifies the types of the SNMP keys. @@ -650,6 +658,17 @@ mnesia:change_table_copy_type(person, node(), disc_copies) </desc> </func> <func> + <name>change_table_majority(Tab, Majority) -> {aborted, R} | {atomic, ok}</name> + <fsummary>Change the majority check setting for the table.</fsummary> + <desc> + <p><c>Majority</c> must be a boolean; the default is <c>false</c>. + When <c>true</c>, a majority of the table's replicas must be available + for an update to succeed. When used on fragmented tables, <c>Tab</c> + must be the name base table. Directly changing the majority setting on + individual fragments is not allowed.</p> + </desc> + </func> + <func> <name>clear_table(Tab) -> {aborted, R} | {atomic, ok}</name> <fsummary>Deletes all entries in a table.</fsummary> <desc> @@ -753,6 +772,14 @@ mnesia:change_table_copy_type(person, node(), disc_copies) priority will be loaded first at startup. </p> </item> + <item> + <p><c>{majority, Flag}</c>, where <c>Flag</c> must be a boolean. + If <c>true</c>, any (non-dirty) update to the table will abort unless + a majority of the table's replicas are available for the commit. + When used on a fragmented table, all fragments will be given + the same majority setting. + </p> + </item> <item> <p><c>{ram_copies, Nodelist}</c>, where <c>Nodelist</c> is a list of the nodes where this table @@ -1737,7 +1764,10 @@ mnesia:create_table(person, <c>write</c> and <c>sticky_write</c> are supported. </p> <p>If the user wants to update the record it is more efficient to - use <c>write/sticky_write</c> as the LockKind. + use <c>write/sticky_write</c> as the LockKind. If majority checking + is active on the table, it will be checked as soon as a write lock is + attempted. This can be used to quickly abort if the majority condition + isn't met. </p> </desc> </func> diff --git a/lib/mnesia/doc/src/notes.xml b/lib/mnesia/doc/src/notes.xml index 19574a1434..7f50dc049a 100644 --- a/lib/mnesia/doc/src/notes.xml +++ b/lib/mnesia/doc/src/notes.xml @@ -4,7 +4,7 @@ <chapter> <header> <copyright> - <year>1996</year><year>2010</year> + <year>1996</year><year>2011</year> <holder>Ericsson AB. All Rights Reserved.</holder> </copyright> <legalnotice> @@ -38,7 +38,39 @@ thus constitutes one section in this document. The title of each section is the version number of Mnesia.</p> - <section><title>Mnesia 4.4.18</title> + <section><title>Mnesia 4.4.19</title> + + <section><title>Fixed Bugs and Malfunctions</title> + <list> + <item> + <p> + Mnesia could crash if mnesia:add_table_index/2 was + invoked before the table was loaded on all nodes.</p> + <p> + Own Id: OTP-9285 Aux Id: seq11844 </p> + </item> + <item> + <p> + Add {majority, boolean()} per-table option.</p> + <p> + With {majority, true} set for a table, write transactions + will abort if they cannot commit to a majority of the + nodes that have a copy of the table. Currently, the + implementation hooks into the prepare_commit, and forces + an asymmetric transaction if the commit set affects any + table with the majority flag set. In the commit itself, + the transaction will abort if it cannot satisfy the + majority requirement for all tables involved in the + transaction.(Thanks to Ulf Wiger)</p> + <p> + Own Id: OTP-9304</p> + </item> + </list> + </section> + +</section> + +<section><title>Mnesia 4.4.18</title> <section><title>Fixed Bugs and Malfunctions</title> <list> |