<?xml version="1.0" encoding="UTF-8" standalone="no"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> <title>DbChannel::send_request()</title> <link rel="stylesheet" href="apiReference.css" type="text/css" /> <meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /> <link rel="start" href="index.html" title="Berkeley DB C++ API Reference" /> <link rel="up" href="rep.html" title="Chapter 11. 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Replication Methods </th> <td width="20%" align="right"> <a accesskey="n" href="dbchannel_set_timeout.html">Next</a></td> </tr> </table> <hr /> </div> <div class="sect1" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h2 class="title" style="clear: both"><a id="dbchannel_send_request"></a>DbChannel::send_request()</h2> </div> </div> </div> <pre class="programlisting">#include <db_cxx.h> int DbChannel::send_request(Dbt *request, u_int32_t nrequest, Dbt *response, db_timeout_t timeout, u_int32_t flags);</pre> <p> The <code class="methodname">DbChannel::send_request()</code> method sends a message on the message channel. The message is sent synchronously; the method blocks waiting for a response before returning. If a response is not received within the timeout value configured for this request, this method returns with an error condition. </p> <p> If you do not want to block while waiting for a response from a remote site, use the <a class="xref" href="dbchannel_send_msg.html" title="DbChannel::send_msg()">DbChannel::send_msg()</a> method. </p> <p> The message sent by this method is received and handled at remote sites using a message dispatch callback, which is configured using the <a class="xref" href="repmgr_msg_dispatch.html" title="DbEnv::repmgr_msg_dispatch()">DbEnv::repmgr_msg_dispatch()</a> method. </p> <p> The <code class="methodname">DbChannel::send_request()</code> <span> <span> method either returns a non-zero error value or throws an exception that encapsulates a non-zero error value on failure, and returns 0 on success. </span> </span> </p> <div class="sect2" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h3 class="title"><a id="idp3981728"></a>Parameters</h3> </div> </div> </div> <div class="sect3" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h4 class="title"><a id="idp3982392"></a>request</h4> </div> </div> </div> <p> Refers to an array of Dbt handles. For more information, see <a class="xref" href="dbt.html" title="Chapter 4. The Dbt Handle"> The Dbt Handle </a>. </p> <p> Any flags provided to the Dbt handles used in this array are ignored. </p> </div> <div class="sect3" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h4 class="title"><a id="idp3984376"></a>nrequest</h4> </div> </div> </div> <p> Indicates how many elements are contained in the <code class="literal">msg</code> array. </p> </div> <div class="sect3" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h4 class="title"><a id="idp3981400"></a>response</h4> </div> </div> </div> <p> Points to a single Dbt handle, which is used to receive the response from the remote site. By default, the response is expected to be a single-part message. If there is a possibility that the response could be a multi-part message, specify <code class="literal">DB_MULTIPLE</code> to this method's <span class="bold"><strong>flags</strong></span> parameter. </p> <p> The response Dbt should specify one of the following flags: <code class="literal">DB_DBT_MALLOC</code>, <code class="literal">DB_DBT_REALLOC</code>, or <code class="literal">DB_DBT_USERMEM</code>. </p> <p> For more information on configuring and using Dbts, see <a class="xref" href="dbt.html" title="Chapter 4. The Dbt Handle"> The Dbt Handle </a>. </p> <p> Note that the response Dbt can be empty. In this way an application can send an acknowledgement even if there is no other information that needs to be sent. </p> </div> <div class="sect3" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h4 class="title"><a id="idp3976936"></a>timeout</h4> </div> </div> </div> <p> Configures the amount of time that may elapse while this method waits for a response from the remote site. If this timeout period elapses without a response, this method returns with an error condition. </p> <p> The timeout value must be specified as an unsigned 32-bit number of microseconds, limiting the maximum timeout to roughly 71 minutes. </p> <p> A timeout value of <code class="literal">0</code> indicates that the channel's default timeout value should be used. This default is configured using the <a class="xref" href="dbchannel_set_timeout.html" title="DbChannel::set_timeout()">DbChannel::set_timeout()</a> method. </p> </div> <div class="sect3" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h4 class="title"><a id="idp3984896"></a>flags</h4> </div> </div> </div> <p> This parameter must be set to either <code class="literal">DB_MULTIPLE</code> or 0. </p> <p> If there is a possibility that the response can consist of multiple Dbt handles, specify <code class="literal">DB_MULTIPLE</code> to this parameter. In that case, the response buffer is formatted for bulk operations. </p> </div> </div> <div class="sect2" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h3 class="title"><a id="idp3985976"></a>Errors</h3> </div> </div> </div> <p> The <code class="methodname">DbChannel::send_request()</code> <span> <span> method may fail and throw a <a class="link" href="dbexception.html" title="Chapter 6. The DbException Class">DbException</a> exception, encapsulating one of the following non-zero errors, or return one of the following non-zero errors: </span> </span> </p> <div class="sect3" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h4 class="title"><a id="idp3990496"></a>DB_BUFFER_SMALL</h4> </div> </div> </div> <p> <code class="literal">DB_MULTIPLE</code> was not specified for the response Dbt, but the remote site sent a response consisting of more than one Dbt; or a buffer supplied using <code class="literal">DB_DBT_USERMEM</code> was not large enough to contain the message response. </p> </div> <div class="sect3" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h4 class="title"><a id="idp3992952"></a>DB_NOSERVER</h4> </div> </div> </div> <p> A message was sent to a remote site that has not configured a message dispatch call-back function. Use the <a class="xref" href="repmgr_msg_dispatch.html" title="DbEnv::repmgr_msg_dispatch()">DbEnv::repmgr_msg_dispatch()</a> method at every site belonging to the replication group to configure a message dispatch call-back function. </p> </div> <div class="sect3" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h4 class="title"><a id="idp3971664"></a>EINVAL</h4> </div> </div> </div> <p> If this method is called from a Base API application, or if an invalid flag value or parameter was specified. </p> </div> </div> <div class="sect2" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h3 class="title"><a id="idp3989416"></a>Class</h3> </div> </div> </div> <p> <a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a> </p> </div> <div class="sect2" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h3 class="title"><a id="idp3982592"></a>See Also</h3> </div> </div> </div> <p> <a class="xref" href="rep.html#replist" title="Replication and Related Methods">Replication and Related Methods</a> </p> </div> </div> <div class="navfooter"> <hr /> <table width="100%" summary="Navigation footer"> <tr> <td width="40%" align="left"><a accesskey="p" href="dbchannel_send_msg.html">Prev</a> </td> <td width="20%" align="center"> <a accesskey="u" href="rep.html">Up</a> </td> <td width="40%" align="right"> <a accesskey="n" href="dbchannel_set_timeout.html">Next</a></td> </tr> <tr> <td width="40%" align="left" valign="top">DbChannel::send_msg() </td> <td width="20%" align="center"> <a accesskey="h" href="index.html">Home</a> </td> <td width="40%" align="right" valign="top"> DbChannel::set_timeout()</td> </tr> </table> </div> </body> </html>