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<h2 class="title" style="clear: both"><a id="envevent_notify"></a>DB_ENV->set_event_notify()</h2>
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<pre class="programlisting">#include <db.h>
int
DB_ENV->set_event_notify(DB_ENV *dbenv,
void (*db_event_fcn)(DB_ENV *dbenv, u_int32_t event,
void *event_info)); </pre>
<p>
The <code class="methodname">DB_ENV->set_event_notify()</code> method configures a callback function
which is called to notify the process of specific Berkeley DB events.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<h3 class="title">Note</h3>
<p>
Berkeley DB is not re-entrant. Callback functions should not attempt to make library calls (for
example, to release locks or close open handles). Re-entering Berkeley DB is not guaranteed to work
correctly, and the results are undefined.
</p>
</div>
<p>
The <code class="methodname">DB_ENV->set_event_notify()</code> method configures operations performed
using the specified <a class="link" href="env.html" title="Chapter 5. The DB_ENV Handle">DB_ENV</a> handle, not all
operations performed on the underlying database environment.
</p>
<p>
The <code class="methodname">DB_ENV->set_event_notify()</code> method may be called at any time
during the life of the application.
</p>
<p>
The <code class="methodname">DB_ENV->set_event_notify()</code> <span>
<span>
method returns a non-zero error value on failure and 0 on success.
</span>
</span>
</p>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="id1667776"></a>Parameters</h3>
</div>
</div>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="id1667783"></a>db_event_fcn</h4>
</div>
</div>
</div>
<p>
The <span class="bold"><strong>db_event_fcn</strong></span> parameter is the
application's event notification function. The function takes three
parameters:
</p>
<div class="itemizedlist">
<ul type="disc">
<li>
<p>
<code class="literal">dbenv</code>
</p>
<p>
The <span class="bold"><strong>dbenv</strong></span> parameter is the enclosing
database environment handle.
</p>
</li>
<li>
<p>
<code class="literal">event</code>
</p>
<p>
The <span class="bold"><strong>event</strong></span> parameter is one of the
following values:
</p>
<div class="itemizedlist">
<ul type="circle">
<li>
<p><a id="event_notify_DB_EVENT_PANIC"></a>
<code class="literal">DB_EVENT_PANIC</code>
</p>
<p>
Errors can occur in the Berkeley DB library where the only solution is
to shut down the application and run recovery (for example, if
Berkeley DB is unable to allocate heap memory). In such cases, the
Berkeley DB methods will return
<a href="../../programmer_reference/program_errorret.html#program_errorret.DB_RUNRECOVERY" class="olink">DB_RUNRECOVERY</a>.
It is often easier to simply exit the application when such errors
occur rather than gracefully return up the stack.
</p>
<p>
When <span class="bold"><strong>event</strong></span> is set to DB_EVENT_PANIC,
the database environment has failed. All threads of control in the
database environment should exit the environment, and recovery should
be run.
</p>
</li>
<li>
<p><a id="event_notify_DB_EVENT_REG_ALIVE"></a>
<code class="literal">DB_EVENT_REG_ALIVE</code>
</p>
<p>
Recovery is needed in an environment where the
<a class="link" href="envopen.html#envopen_DB_REGISTER">DB_REGISTER</a>
flag was specified on the
<a class="xref" href="envopen.html" title="DB_ENV->open()">DB_ENV->open()</a> method and there is
a process attached to the environment. The callback function is triggered
once for each process attached.
</p>
<p>
The <span class="bold"><strong>event_info</strong></span> parameter points to a pid_t value
containing the process identifier (pid) of the process the Berkeley DB library
detects is attached to the environment.
</p>
</li>
<li>
<p><a id="event_notify_DB_EVENT_REG_PANIC"></a>
<code class="literal">DB_EVENT_REG_PANIC</code>
</p>
<p>
Recovery is needed in an environment where the
<a class="link" href="envopen.html#envopen_DB_REGISTER">DB_REGISTER</a>
flag was specified
on the <a class="xref" href="envopen.html" title="DB_ENV->open()">DB_ENV->open()</a> method. All threads
of control in the database environment should exit the environment.
</p>
<p>
This event is different than the <code class="literal">DB_EVENT_PANIC</code> event
because it can only be triggered when <code class="literal">DB_REGISTER</code> was
specified. It can be used to distinguish between the case when a process
dies in the environment and recovery is initiated versus the case when an
error happened (for example, if Berkeley DB is unable to allocate heap
memory)
</p>
</li>
<li>
<p><a id="event_notify_DB_EVENT_REP_CLIENT"></a>
<code class="literal">DB_EVENT_REP_CLIENT</code>
</p>
<p>
The local site is now a replication client.
</p>
</li>
<li>
<p><a id="event_notify_DB_EVENT_REP_ELECTED"></a>
<code class="literal">DB_EVENT_REP_ELECTED</code>
</p>
<p>
The local replication site has just won an election. An application
using the Base replication API should arrange for a call to the
<a class="xref" href="repstart.html" title="DB_ENV->rep_start()">DB_ENV->rep_start()</a> method
after receiving this event, to reconfigure the local environment as a
replication master.
</p>
<p>
Replication Manager applications may safely ignore this event. The
Replication Manager calls <a class="xref" href="repstart.html" title="DB_ENV->rep_start()">DB_ENV->rep_start()</a>
automatically on behalf of the application when appropriate (resulting
in firing of the DB_EVENT_REP_MASTER event).
</p>
</li>
<li>
<p><a id="event_notify_DB_EVENT_REP_MASTER"></a>
<code class="literal">DB_EVENT_REP_MASTER</code>
</p>
<p>
The local site is now the master site of its replication group. It is
the application's responsibility to begin acting as the master
environment.
</p>
</li>
<li>
<p><a id="event_notify_DB_EVENT_REP_NEWMASTER"></a>
<code class="literal">DB_EVENT_REP_NEWMASTER</code>
</p>
<p>
The replication group of which this site is a member has just
established a new master; the local site is not the new master. The
<span class="bold"><strong>event_info</strong></span> parameter points to an
integer containing the environment ID of the new master.
</p>
</li>
<li>
<p><a id="event_notify_DB_EVENT_REP_PERM_FAILED"></a>
<code class="literal">DB_EVENT_REP_PERM_FAILED</code>
</p>
<p>
The replication manager did not receive enough acknowledgements (based
on the acknowledgement policy configured with
<a class="xref" href="repmgrset_ack_policy.html" title="DB_ENV->repmgr_set_ack_policy()">DB_ENV->repmgr_set_ack_policy()</a> )
to ensure a transaction's durability within the replication group.
The transaction will be flushed to the master's local disk storage for
durability.
</p>
<p>
The DB_EVENT_REP_PERM_FAILED event is provided only to applications
configured for the replication manager.
</p>
</li>
<li>
<p><a id="event_notify_DB_EVENT_REP_STARTUPDONE"></a>
<code class="literal">DB_EVENT_REP_STARTUPDONE</code>
</p>
<p>
The client has completed startup synchronization and is now processing
live log records received from the master.
</p>
</li>
<li>
<p><a id="event_notify_DB_EVENT_WRITE_FAILED"></a>
<code class="literal">DB_EVENT_WRITE_FAILED</code>
</p>
<p>
A Berkeley DB write to stable storage failed.
</p>
</li>
</ul>
</div>
</li>
<li>
<p>
<code class="literal">event_info</code>
</p>
<p>
The <span class="bold"><strong>event_info</strong></span> parameter may
reference memory which contains additional information describing an
event. By default, <span class="bold"><strong>event_info</strong></span> is
NULL; specific events may pass non-NULL values, in which case the
event will also describe the memory's structure.
</p>
</li>
</ul>
</div>
</div>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="id1667981"></a>Class</h3>
</div>
</div>
</div>
<p>
<a class="link" href="env.html" title="Chapter 5. The DB_ENV Handle">DB_ENV</a>
</p>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="id1668370"></a>See Also</h3>
</div>
</div>
</div>
<p>
<a class="xref" href="env.html#envlist" title="Database Environments and Related Methods">Database Environments and Related Methods</a>
</p>
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