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diff --git a/db/docs/ref/rep/comm.html b/db/docs/ref/rep/comm.html new file mode 100644 index 000000000..a58a11e0b --- /dev/null +++ b/db/docs/ref/rep/comm.html @@ -0,0 +1,71 @@ +<!--Id: comm.so,v 1.1 2001/10/13 19:56:23 bostic Exp --> +<!--Copyright 1997-2001 by Sleepycat Software, Inc.--> +<!--All rights reserved.--> +<html> +<head> +<title>Berkeley DB Reference Guide: Building the communications infrastructure</title> +<meta name="description" content="Berkeley DB: An embedded database programmatic toolkit."> +<meta name="keywords" content="embedded,database,programmatic,toolkit,b+tree,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,java,C,C++"> +</head> +<body bgcolor=white> +<table width="100%"><tr valign=top> +<td><h3><dl><dt>Berkeley DB Reference Guide:<dd>Berkeley DB Replication</dl></h3></td> +<td align=right><a href="../../ref/rep/app.html"><img src="../../images/prev.gif" alt="Prev"></a><a href="../../reftoc.html"><img src="../../images/ref.gif" alt="Ref"></a><a href="../../ref/rep/newsite.html"><img src="../../images/next.gif" alt="Next"></a> +</td></tr></table> +<p> +<h1 align=center>Building the communications infrastructure</h1> +<p>Replicated applications are typically written with one or more threads +of control looping on one or more communication channels. These threads +accept messages from remote environments for the local database +environment, and accept messages from the local environment for remote +environments. Messages from remote environments are passed to the local +database environment using the <a href="../../api_c/rep_message.html">DB_ENV->rep_process_message</a> function. Messages from the +local environment are passed to the application for transmission using +the callback interface specified to the <a href="../../api_c/rep_transport.html">DB_ENV->set_rep_transport</a> function. +<p>Both clients and servers establish communication channels by calling +the <a href="../../api_c/rep_transport.html">DB_ENV->set_rep_transport</a> function. This method specifies the <b>send</b> +interface, a callback interface used by Berkeley DB for sending messages to +other database environments in the replication group. The <b>send</b> +interface takes an environment ID and two opaque data objects. It is +the responsibility of the <b>send</b> interface to transmit the +information in the two data objects to the database environment +corresponding to the ID, with the receiving application then calling +the <a href="../../api_c/rep_message.html">DB_ENV->rep_process_message</a> function to process the message. +<p>The details of the transport mechanism are left entirely to the +application; the only requirement is that the data buffer and size of +each of the control and rec <a href="../../api_c/dbt.html">DBT</a>s passed to the <b>send</b> +function on the sending site be faithfully copied and delivered to the +receiving site by means of a call to <a href="../../api_c/rep_message.html">DB_ENV->rep_process_message</a> with +corresponding arguments. The <a href="../../api_c/rep_message.html">DB_ENV->rep_process_message</a> function is free-threaded; it +is safe to deliver any number of messages simultaneously, and from any +arbitrary thread or process in the Berkeley DB environment. +<p>There are a number of informational returns from the +<a href="../../api_c/rep_message.html">DB_ENV->rep_process_message</a> function: +<p><dl compact> +<p><dt><a href="../../api_c/rep_message.html#DB_REP_HOLDELECTION">DB_REP_HOLDELECTION</a><dd>When <a href="../../api_c/rep_message.html">DB_ENV->rep_process_message</a> returns <a href="../../api_c/rep_message.html#DB_REP_HOLDELECTION">DB_REP_HOLDELECTION</a>, it means +that another database environment in the replication group has called +for an election. The application should call the <a href="../../api_c/rep_elect.html">DB_ENV->rep_elect</a> function. +<p><dt><a href="../../api_c/rep_message.html#DB_REP_NEWMASTER">DB_REP_NEWMASTER</a><dd>When <a href="../../api_c/rep_message.html">DB_ENV->rep_process_message</a> returns <a href="../../api_c/rep_message.html#DB_REP_NEWMASTER">DB_REP_NEWMASTER</a>, it means that +a new master has been elected. The call will also return the local +environment's ID for that master. If the ID of the master has changed, +the application may need to reconfigure itself (for example, to redirect +update queries to the new master rather then the old one). If the new +master is the local environment, then the application must call the +<a href="../../api_c/rep_start.html">DB_ENV->rep_start</a> function, and to reconfigure the supporting Berkeley DB library as +a replication master. +<p><dt><a href="../../api_c/rep_message.html#DB_REP_NEWSITE">DB_REP_NEWSITE</a><dd>When <a href="../../api_c/rep_message.html">DB_ENV->rep_process_message</a> returns <a href="../../api_c/rep_message.html#DB_REP_NEWSITE">DB_REP_NEWSITE</a>, it means that +a message from a previously unknown member of the replication group has +been received. The application should reconfigure itself as necessary +so it is able to send messages to this site. +<p><dt><a href="../../api_c/rep_message.html#DB_REP_OUTDATED">DB_REP_OUTDATED</a><dd>When <a href="../../api_c/rep_message.html">DB_ENV->rep_process_message</a> returns <a href="../../api_c/rep_message.html#DB_REP_OUTDATED">DB_REP_OUTDATED</a>, it means that +the environment has been out-of-contact with the master for too long a +time, and the master no longer has sufficient logs in order to bring the +local client up-to-date. The application should shut down, and the +client reinitialized (see <a href="../../ref/rep/init.html">Initializing +a new site</a> for more information.) +</dl> +<table width="100%"><tr><td><br></td><td align=right><a href="../../ref/rep/app.html"><img src="../../images/prev.gif" alt="Prev"></a><a href="../../reftoc.html"><img src="../../images/ref.gif" alt="Ref"></a><a href="../../ref/rep/newsite.html"><img src="../../images/next.gif" alt="Next"></a> +</td></tr></table> +<p><font size=1><a href="http://www.sleepycat.com">Copyright Sleepycat Software</a></font> +</body> +</html> |