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<div class="sect1" lang="en" xml:lang="en">
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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="id3666734"></a>Parameters</h3>
</div>
</div>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="id3666140"></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 <code class="literal">DB_EVENT_PANIC</code>,
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>
<p>
This event is generated when the replication
role changes to client, either from master or
from being unset. The role is unset when an
environment is first created and after an
environment is recovered. This event is not
generated when restarting replication in an
environment that was previously a client and
was opened without recovery.
</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>
<p>
This event is generated when the replication
role changes to master, either from client or
from being unset. The role is unset when an
environment is first created and after an
environment is recovered. This event is not
generated when restarting replication in an
environment that was previously a master and
was opened without recovery.
</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_DUPMASTER"></a>
<code class="literal">DB_EVENT_REP_DUPMASTER</code>
</p>
<p>
Replication Manager has detected a
duplicate master situation, and has changed
the local site to the client role as a
result. If the
<a class="link" href="repconfig.html#config_DB_REPMGR_CONF_ELECTIONS">DB_REPMGR_CONF_ELECTIONS</a>
configuration parameter has been turned off, the
application should now choose and assign
the correct master site. If
<code class="literal">DB_REPMGR_CONF_ELECTIONS</code> is
turned on, the application may ignore this event.
</p>
<p>
The <code class="literal">DB_EVENT_REP_DUPMASTER</code> event is provided
only to applications configured for the replication manager.
</p>
</li>
<li>
<p><a id="event_notify_DB_EVENT_REP_ELECTION_FAILED"></a>
<code class="literal">DB_EVENT_REP_ELECTION_FAILED</code>
</p>
<p>
Replication Manager tried to run an
election to choose a master site, but the
election failed due to lack of timely
participation by a sufficient number of
other sites. Replication Manager will
automatically retry the election later.
This event is for information only.
</p>
<p>
The <code class="literal">DB_EVENT_REP_ELECTION_FAILED</code>
event is provided only to applications
configured for the replication manager.
</p>
</li>
<li>
<p><a id="event_notify_DB_EVENT_REP_MASTER_FAILURE"></a>
<code class="literal">DB_EVENT_REP_MASTER_FAILURE</code>
</p>
<p>
A Replication Manager client site has
detected the loss of connection to the
master site. If the
<a class="link" href="repconfig.html#config_DB_REPMGR_CONF_ELECTIONS">DB_REPMGR_CONF_ELECTIONS</a>
configuration parameter is turned on,
Replication Manager will automatically
start an election in order to choose a new
master. In this case, this event may be
ignored.
</p>
<p>
When <code class="literal">DB_REPMGR_CONF_ELECTIONS</code>
is turned off, the application should
choose and assign a new master. Failure to
do so means that your replication group has
no master, and so it cannot service write
requests.
</p>
<p>
The <code class="literal">DB_EVENT_REP_MASTER_FAILURE</code>
event is provided only to applications
configured for the replication manager.
</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 <code class="literal">DB_EVENT_REP_PERM_FAILED</code>
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="id3666636"></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="id3667182"></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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