1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
|
<?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>DbEnv::set_event_notify()</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="env.html" title="Chapter 5. The DbEnv Handle" />
<link rel="prev" href="envset_encrypt.html" title="DbEnv::set_encrypt()" />
<link rel="next" href="envset_errcall.html" title="DbEnv::set_errcall()" />
</head>
<body>
<div class="navheader">
<table width="100%" summary="Navigation header">
<tr>
<th colspan="3" align="center">DbEnv::set_event_notify()</th>
</tr>
<tr>
<td width="20%" align="left"><a accesskey="p" href="envset_encrypt.html">Prev</a> </td>
<th width="60%" align="center">Chapter 5.
The DbEnv Handle
</th>
<td width="20%" align="right"> <a accesskey="n" href="envset_errcall.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="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="idp52006520"></a>Parameters</h3>
</div>
</div>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idp52017192"></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_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_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="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_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="idp51996344"></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="idp51991416"></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>
</div>
<div class="navfooter">
<hr />
<table width="100%" summary="Navigation footer">
<tr>
<td width="40%" align="left"><a accesskey="p" href="envset_encrypt.html">Prev</a> </td>
<td width="20%" align="center">
<a accesskey="u" href="env.html">Up</a>
</td>
<td width="40%" align="right"> <a accesskey="n" href="envset_errcall.html">Next</a></td>
</tr>
<tr>
<td width="40%" align="left" valign="top">DbEnv::set_encrypt() </td>
<td width="20%" align="center">
<a accesskey="h" href="index.html">Home</a>
</td>
<td width="40%" align="right" valign="top"> DbEnv::set_errcall()</td>
</tr>
</table>
</div>
</body>
</html>
|
