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129 | .\" ======================================================================== | |
130 | .\" | |
131 | .IX Title "DBD::Proxy 3" | |
132 | .TH DBD::Proxy 3 "2002-10-01" "perl v5.8.0" "User Contributed Perl Documentation" | |
133 | .SH "NAME" | |
134 | DBD::Proxy \- A proxy driver for the DBI | |
135 | .SH "SYNOPSIS" | |
136 | .IX Header "SYNOPSIS" | |
137 | .Vb 1 | |
138 | \& use DBI; | |
139 | .Ve | |
140 | .PP | |
141 | .Vb 2 | |
142 | \& $dbh = DBI->connect("dbi:Proxy:hostname=$host;port=$port;dsn=$db", | |
143 | \& $user, $passwd); | |
144 | .Ve | |
145 | .PP | |
146 | .Vb 1 | |
147 | \& # See the DBI module documentation for full details | |
148 | .Ve | |
149 | .SH "DESCRIPTION" | |
150 | .IX Header "DESCRIPTION" | |
151 | DBD::Proxy is a Perl module for connecting to a database via a remote | |
152 | \&\s-1DBI\s0 driver. | |
153 | .PP | |
154 | This is of course not needed for \s-1DBI\s0 drivers which already | |
155 | support connecting to a remote database, but there are engines which | |
156 | don't offer network connectivity. | |
157 | .PP | |
158 | Another application is offering database access through a firewall, as | |
159 | the driver offers query based restrictions. For example you can | |
160 | restrict queries to exactly those that are used in a given \s-1CGI\s0 | |
161 | application. | |
162 | .PP | |
163 | Speaking of \s-1CGI\s0, another application is (or rather, will be) to reduce | |
164 | the database connect/disconnect overhead from \s-1CGI\s0 scripts by using | |
165 | proxying the connect_cached method. The proxy server will hold the | |
166 | database connections open in a cache. The \s-1CGI\s0 script then trades the | |
167 | database connect/disconnect overhead for the DBD::Proxy | |
168 | connect/disconnect overhead which is typically much less. | |
169 | \&\fINote that the connect_cached method is new and still experimental.\fR | |
170 | .SH "CONNECTING TO THE DATABASE" | |
171 | .IX Header "CONNECTING TO THE DATABASE" | |
172 | Before connecting to a remote database, you must ensure, that a Proxy | |
173 | server is running on the remote machine. There's no default port, so | |
174 | you have to ask your system administrator for the port number. See | |
175 | \&\fIDBI::ProxyServer\fR\|(3) for details. | |
176 | .PP | |
177 | Say, your Proxy server is running on machine \*(L"alpha\*(R", port 3334, and | |
178 | you'd like to connect to an \s-1ODBC\s0 database called \*(L"mydb\*(R" as user \*(L"joe\*(R" | |
179 | with password \*(L"hello\*(R". When using \s-1DBD::ODBC\s0 directly, you'd do a | |
180 | .PP | |
181 | .Vb 1 | |
182 | \& $dbh = DBI->connect("DBI:ODBC:mydb", "joe", "hello"); | |
183 | .Ve | |
184 | .PP | |
185 | With DBD::Proxy this becomes | |
186 | .PP | |
187 | .Vb 2 | |
188 | \& $dsn = "DBI:Proxy:hostname=alpha;port=3334;dsn=DBI:ODBC:mydb"; | |
189 | \& $dbh = DBI->connect($dsn, "joe", "hello"); | |
190 | .Ve | |
191 | .PP | |
192 | You see, this is mainly the same. The DBD::Proxy module will create a | |
193 | connection to the Proxy server on \*(L"alpha\*(R" which in turn will connect | |
194 | to the \s-1ODBC\s0 database. | |
195 | .PP | |
196 | Refer to the \s-1\fIDBI\s0\fR\|(3) documentation on the \f(CW\*(C`connect\*(C'\fR method for a way | |
197 | to automatically use DBD::Proxy without having to change your code. | |
198 | .PP | |
199 | DBD::Proxy's \s-1DSN\s0 string has the format | |
200 | .PP | |
201 | .Vb 1 | |
202 | \& $dsn = "DBI:Proxy:key1=val1; ... ;keyN=valN;dsn=valDSN"; | |
203 | .Ve | |
204 | .PP | |
205 | In other words, it is a collection of key/value pairs. The following | |
206 | keys are recognized: | |
207 | .IP "hostname" 4 | |
208 | .IX Item "hostname" | |
209 | .PD 0 | |
210 | .IP "port" 4 | |
211 | .IX Item "port" | |
212 | .PD | |
213 | Hostname and port of the Proxy server; these keys must be present, | |
214 | no defaults. Example: | |
215 | .Sp | |
216 | .Vb 1 | |
217 | \& hostname=alpha;port=3334 | |
218 | .Ve | |
219 | .IP "dsn" 4 | |
220 | .IX Item "dsn" | |
221 | The value of this attribute will be used as a dsn name by the Proxy | |
222 | server. Thus it must have the format \f(CW\*(C`DBI:driver:...\*(C'\fR, in particular | |
223 | it will contain colons. The \fIdsn\fR value may contain semicolons, hence | |
224 | this key *must* be the last and it's value will be the complete | |
225 | remaining part of the dsn. Example: | |
226 | .Sp | |
227 | .Vb 1 | |
228 | \& dsn=DBI:ODBC:mydb | |
229 | .Ve | |
230 | .IP "cipher" 4 | |
231 | .IX Item "cipher" | |
232 | .PD 0 | |
233 | .IP "key" 4 | |
234 | .IX Item "key" | |
235 | .IP "usercipher" 4 | |
236 | .IX Item "usercipher" | |
237 | .IP "userkey" 4 | |
238 | .IX Item "userkey" | |
239 | .PD | |
240 | By using these fields you can enable encryption. If you set, | |
241 | for example, | |
242 | .Sp | |
243 | .Vb 1 | |
244 | \& cipher=$class;key=$key | |
245 | .Ve | |
246 | .Sp | |
247 | (note the semicolon) then DBD::Proxy will create a new cipher object | |
248 | by executing | |
249 | .Sp | |
250 | .Vb 1 | |
251 | \& $cipherRef = $class->new(pack("H*", $key)); | |
252 | .Ve | |
253 | .Sp | |
254 | and pass this object to the RPC::PlClient module when creating a | |
255 | client. See \fIRPC::PlClient\fR\|(3). Example: | |
256 | .Sp | |
257 | .Vb 1 | |
258 | \& cipher=IDEA;key=97cd2375efa329aceef2098babdc9721 | |
259 | .Ve | |
260 | .Sp | |
261 | The usercipher/userkey attributes allow you to use two phase encryption: | |
262 | The cipher/key encryption will be used in the login and authorisation | |
263 | phase. Once the client is authorised, he will change to usercipher/userkey | |
264 | encryption. Thus the cipher/key pair is a \fBhost\fR based secret, typically | |
265 | less secure than the usercipher/userkey secret and readable by anyone. | |
266 | The usercipher/userkey secret is \fByour\fR private secret. | |
267 | .Sp | |
268 | Of course encryption requires an appropriately configured server. See | |
269 | <\fIDBD::ProxyServer\fR\|(3)/CONFIGURATION \s-1FILE\s0>. | |
270 | .IP "debug" 4 | |
271 | .IX Item "debug" | |
272 | Turn on debugging mode | |
273 | .IP "stderr" 4 | |
274 | .IX Item "stderr" | |
275 | This attribute will set the corresponding attribute of the RPC::PlClient | |
276 | object, thus logging will not use \fIsyslog()\fR, but redirected to stderr. | |
277 | This is the default under Windows. | |
278 | .Sp | |
279 | .Vb 1 | |
280 | \& stderr=1 | |
281 | .Ve | |
282 | .IP "logfile" 4 | |
283 | .IX Item "logfile" | |
284 | Similar to the stderr attribute, but output will be redirected to the | |
285 | given file. | |
286 | .Sp | |
287 | .Vb 1 | |
288 | \& logfile=/dev/null | |
289 | .Ve | |
290 | .IP "RowCacheSize" 4 | |
291 | .IX Item "RowCacheSize" | |
292 | The DBD::Proxy driver supports this attribute (which is \s-1DBI\s0 standard, | |
293 | as of \s-1DBI\s0 1.02). It's used to reduce network round-trips by fetching | |
294 | multiple rows in one go. The current default value is 20, but this may | |
295 | change. | |
296 | .IP "proxy_no_finish" 4 | |
297 | .IX Item "proxy_no_finish" | |
298 | This attribute can be used to reduce network traffic: If the | |
299 | application is calling \f(CW$sth\fR\->\fIfinish()\fR then the proxy tells the server | |
300 | to finish the remote statement handle. Of course this slows down things | |
301 | quite a lot, but is prefectly good for reducing memory usage with | |
302 | persistent connections. | |
303 | .Sp | |
304 | However, if you set the \fIproxy_no_finish\fR attribute to a \s-1TRUE\s0 value, | |
305 | either in the database handle or in the statement handle, then \fIfinish()\fR | |
306 | calls will be supressed. This is what you want, for example, in small | |
307 | and fast \s-1CGI\s0 applications. | |
308 | .IP "proxy_quote" 4 | |
309 | .IX Item "proxy_quote" | |
310 | This attribute can be used to reduce network traffic: By default calls | |
311 | to \f(CW$dbh\fR\->\fIquote()\fR are passed to the remote driver. Of course this slows | |
312 | down things quite a lot, but is the safest default behaviour. | |
313 | .Sp | |
314 | However, if you set the \fIproxy_quote\fR attribute to the value '\f(CW\*(C`local\*(C'\fR' | |
315 | either in the database handle or in the statement handle, and the call | |
316 | to quote has only one parameter, then the local default \s-1DBI\s0 quote | |
317 | method will be used (which will be faster but may be wrong). | |
318 | .SH "KNOWN ISSUES" | |
319 | .IX Header "KNOWN ISSUES" | |
320 | .Sh "Complex handle attributes" | |
321 | .IX Subsection "Complex handle attributes" | |
322 | Sometimes handles are having complex attributes like hash refs or | |
323 | array refs and not simple strings or integers. For example, with | |
324 | \&\s-1DBD::CSV\s0, you would like to write something like | |
325 | .PP | |
326 | .Vb 2 | |
327 | \& $dbh->{"csv_tables"}->{"passwd"} = | |
328 | \& { "sep_char" => ":", "eol" => "\en"; | |
329 | .Ve | |
330 | .PP | |
331 | The above example would advice the \s-1CSV\s0 driver to assume the file | |
332 | \&\*(L"passwd\*(R" to be in the format of the /etc/passwd file: Colons as | |
333 | separators and a line feed without carriage return as line | |
334 | terminator. | |
335 | .PP | |
336 | Surprisingly this example doesn't work with the proxy driver. To understand | |
337 | the reasons, you should consider the following: The Perl compiler is | |
338 | executing the above example in two steps: | |
339 | .IP "1.)" 4 | |
340 | .IX Item "1.)" | |
341 | The first step is fetching the value of the key \*(L"csv_tables\*(R" in the | |
342 | handle \f(CW$dbh\fR. The value returned is complex, a hash ref. | |
343 | .IP "2.)" 4 | |
344 | .IX Item "2.)" | |
345 | The second step is storing some value (the right hand side of the | |
346 | assignment) as the key \*(L"passwd\*(R" in the hash ref from step 1. | |
347 | .PP | |
348 | This becomes a little bit clearer, if we rewrite the above code: | |
349 | .PP | |
350 | .Vb 2 | |
351 | \& $tables = $dbh->{"csv_tables"}; | |
352 | \& $tables->{"passwd"} = { "sep_char" => ":", "eol" => "\en"; | |
353 | .Ve | |
354 | .PP | |
355 | While the examples work fine without the proxy, the fail due to a | |
356 | subtile difference in step 1: By \s-1DBI\s0 magic, the hash ref | |
357 | \&\f(CW$dbh\fR\->{'csv_tables'} is returned from the server to the client. | |
358 | The client creates a local copy. This local copy is the result of | |
359 | step 1. In other words, step 2 modifies a local copy of the hash ref, | |
360 | but not the server's hash ref. | |
361 | .PP | |
362 | The workaround is storing the modified local copy back to the server: | |
363 | .PP | |
364 | .Vb 3 | |
365 | \& $tables = $dbh->{"csv_tables"}; | |
366 | \& $tables->{"passwd"} = { "sep_char" => ":", "eol" => "\en"; | |
367 | \& $dbh->{"csv_tables"} = $tables; | |
368 | .Ve | |
369 | .SH "AUTHOR AND COPYRIGHT" | |
370 | .IX Header "AUTHOR AND COPYRIGHT" | |
371 | This module is Copyright (c) 1997, 1998 | |
372 | .PP | |
373 | .Vb 4 | |
374 | \& Jochen Wiedmann | |
375 | \& Am Eisteich 9 | |
376 | \& 72555 Metzingen | |
377 | \& Germany | |
378 | .Ve | |
379 | .PP | |
380 | .Vb 2 | |
381 | \& Email: joe@ispsoft.de | |
382 | \& Phone: +49 7123 14887 | |
383 | .Ve | |
384 | .PP | |
385 | The DBD::Proxy module is free software; you can redistribute it and/or | |
386 | modify it under the same terms as Perl itself. In particular permission | |
387 | is granted to Tim Bunce for distributing this as a part of the \s-1DBI\s0. | |
388 | .SH "SEE ALSO" | |
389 | .IX Header "SEE ALSO" | |
390 | \&\s-1\fIDBI\s0\fR\|(3), \fIRPC::PlClient\fR\|(3), \fIStorable\fR\|(3) |