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<th colspan="3" align="center">DbEnv::set_event_notify()</th>
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<div class="sect1" lang="en" xml:lang="en">
<div class="titlepage">
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<div>
<h2 class="title" style="clear: both"><a id="envevent_notify"></a>DbEnv::set_event_notify()</h2>
</div>
</div>
</div>
<pre class="programlisting">#include <db_cxx.h>
int
DbEnv::set_event_notify(
void (*db_event_fcn)(DB_ENV *dbenv, u_int32_t event,
void *event_info));</pre>
<p>
The <code class="methodname">DbEnv::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">DbEnv::set_event_notify()</code> method
configures operations performed using the specified
<a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a> handle, not all operations
performed on the underlying database environment.
</p>
<p>
The <code class="methodname">DbEnv::set_event_notify()</code> method may
be called at any time during the life of the application.
</p>
<p>
The <code class="methodname">DbEnv::set_event_notify()</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="idp7249024"></a>Parameters</h3>
</div>
</div>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idp7244960"></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="DbEnv::open()">DbEnv::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="DbEnv::open()">DbEnv::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_CONNECT_BROKEN"></a>
<code class="literal">DB_EVENT_REP_CONNECT_BROKEN</code>
</p>
<p>
A previously established replication message connection between the
local site and a remote site has been broken. This event supplies
the EID of the remote site, and an integer error code that
identifies the reason the connection was broken.
</p>
<p>
A non-zero error code indicates an unexpected
condition such as a hardware failure or a
protocol error. An application might respond
by emitting an informational message or passing
this information to other parts of the
application using the
<code class="literal">app_private</code>
field. A zero error code indicates that the
connection was cleanly closed by the other end.
Replication Manager retries broken connections
periodically until they are restored.
</p>
</li>
<li>
<p><a id="event_notify_DB_EVENT_REP_CONNECT_ESTD"></a>
<code class="literal">DB_EVENT_REP_CONNECT_ESTD</code>
</p>
<p>
A replication message connection has been established between the
local site and a remote site. This event supplied the EID of the
remote site.
</p>
</li>
<li>
<p><a id="event_notify_DB_EVENT_REP_CONNECT_TRY_FAILED"></a>
<code class="literal">DB_EVENT_REP_CONNECT_TRY_FAILED</code>
</p>
<p>
An attempt to establish a connection between the local site and a
remote site has failed. This event supplies the EID of the remote
site, and an integer error code that identifies the reason the
connection attempt failed.
</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_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="DbEnv::rep_start()">DbEnv::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="DbEnv::rep_start()">DbEnv::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_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_ELECTION_STARTED"></a>
<code class="literal">DB_EVENT_REP_ELECTION_STARTED</code>
</p>
<p>
Replication Manager has started an election
to choose a master site.
</p>
</li>
<li>
<p><a id="event_notify_DB_EVENT_REP_INIT_DONE"></a>
<code class="literal">DB_EVENT_REP_INIT_DONE</code>
</p>
<p>
Replication Manager has completed an
internal initialization procedure.
</p>
</li>
<li>
<p><a id="event_notify_DB_EVENT_REP_JOIN_FAILURE"></a>
<code class="literal">DB_EVENT_REP_JOIN_FAILURE</code>
</p>
<p>
The local client site is unable to synchronize with a new master,
possibly because the client has turned off automatic internal
initialization by setting the
<a class="link" href="repconfig.html#config_DB_REP_CONF_AUTOINIT">DB_REP_CONF_AUTOINIT</a>
flag to <code class="literal">0</code>.
</p>
</li>
<li>
<p><a id="event_notify_DB_EVENT_REP_LOCAL_SITE_REMOVED"></a>
<code class="literal">DB_EVENT_REP_LOCAL_SITE_REMOVED</code>
</p>
<p>
The local site has been
removed from the replication group.
</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_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_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="DbEnv::repmgr_set_ack_policy()">DbEnv::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_SITE_ADDED"></a>
<code class="literal">DB_EVENT_REP_SITE_ADDED</code>
</p>
<p>
A new site has joined the group.
The
<span class="bold"><strong>event_info</strong></span> parameter points to an
integer containing the environment ID of the new site.
</p>
</li>
<li>
<p><a id="event_notify_DB_EVENT_REP_SITE_REMOVED"></a>
<code class="literal">DB_EVENT_REP_SITE_REMOVED</code>
</p>
<p>
An existing remote site has been removed from the group. The
<span class="bold"><strong>event_info</strong></span> parameter points to an
integer containing the environment ID of the site that was removed.
</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="idp7269232"></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="idp7228840"></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>
</div>
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