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12 | |
12 | |
13 | (Note that in this manual, "thread" refers to real threads as implemented |
13 | (Note that in this manual, "thread" refers to real threads as implemented |
14 | by the Coro module, not to the built-in windows process emulation which |
14 | by the Coro module, not to the built-in windows process emulation which |
15 | unfortunately is also called "threads") |
15 | unfortunately is also called "threads") |
16 | |
16 | |
17 | This module "patches" DBD::mysql database handles so that they do not |
17 | This module replaces the I/O handlers for a database connection, with the |
18 | block the whole process, but only the thread that they are used in. |
18 | effect that "patched" database handles no longer block the all threads of |
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19 | a process, but only the thread that does the request. |
19 | |
20 | |
20 | This can be used to make parallel sql requests using Coro, or to do other |
21 | This can be used to make parallel sql requests using Coro, or to do other |
21 | stuff while mysql is rumbling in the background. |
22 | stuff while mysql is rumbling in the background. |
22 | |
23 | |
23 | =head2 CAVEAT |
24 | =head2 CAVEAT |
24 | |
25 | |
25 | Note that this module must be linked against exactly the same (shared, |
26 | Note that this module must be linked against exactly the same (shared, |
26 | possibly not working with all OSes) F<libmysqlclient> library as |
27 | possibly not working with all OSes) F<libmysqlclient> library as |
27 | DBD::mysql, otherwise it will not work. |
28 | DBD::mysql, otherwise it will not work. |
28 | |
29 | |
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30 | Also, this module requires a header file that apparently isn't installed |
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31 | everywhere (F<violite.h>), and therefore comes with it's own copy, which |
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32 | might or might not be compatible to the F<violite.h> of your library - |
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33 | when in doubt, make sure all the libmysqlclient header files are installed |
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34 | and delete the F<violite.h> header that comes with this module. |
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35 | |
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36 | On the good side, this module does a multitude of checks to ensure that |
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37 | the libray versions match on the binary level, so on incompatibilities you |
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38 | should expect an exception when trying to unblock a handle, rather than |
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39 | data corruption. |
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40 | |
29 | Also, while this module makes database handles non-blocking, you still |
41 | Also, while this module makes database handles non-blocking, you still |
30 | cannot run multiple requests in parallel on the same database handle. If |
42 | cannot run multiple requests in parallel on the same database handle. If |
31 | you want to run multiple queries in parallel, you have to create multiple |
43 | you want to run multiple queries in parallel, you have to create multiple |
32 | database connections, one for each thread that runs queries. Not doing so |
44 | database connections, one for each thread that runs queries. Not doing |
33 | can corrupt your data - use a Coro::Semaphore when in doubt. |
45 | so can corrupt your data - use a Coro::Semaphore to protetc access to a |
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46 | shared database handle when in doubt. |
34 | |
47 | |
35 | If you make sure that you never run two or more requests in parallel, you |
48 | If you make sure that you never run two or more requests in parallel, you |
36 | can freely share the database handles between threads, of course. |
49 | can freely share the database handles between threads, of course. |
37 | |
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38 | Also, this module uses a number of "unclean" techniques (patching an |
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39 | internal libmysql structure for one thing) and was initially hacked within |
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40 | a few hours on a long flight to Malaysia. |
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41 | |
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42 | It does, however, check whether it indeed got the structure layout |
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43 | correct, so you should expect perl exceptions or early crashes as opposed |
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44 | to data corruption when something goes wrong during patching. |
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45 | |
50 | |
46 | =head2 SPEED |
51 | =head2 SPEED |
47 | |
52 | |
48 | This module is implemented in XS, and as long as mysqld replies quickly |
53 | This module is implemented in XS, and as long as mysqld replies quickly |
49 | enough, it adds no overhead to the standard libmysql communication |
54 | enough, it adds no overhead to the standard libmysql communication |
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100 | |
105 | |
101 | sub readable { &Coro::Handle::FH::readable } |
106 | sub readable { &Coro::Handle::FH::readable } |
102 | sub writable { &Coro::Handle::FH::writable } |
107 | sub writable { &Coro::Handle::FH::writable } |
103 | |
108 | |
104 | BEGIN { |
109 | BEGIN { |
105 | our $VERSION = '1.02'; |
110 | our $VERSION = '1.21'; |
106 | |
111 | |
107 | require XSLoader; |
112 | require XSLoader; |
108 | XSLoader::load Coro::Mysql::, $VERSION; |
113 | XSLoader::load Coro::Mysql::, $VERSION; |
109 | } |
114 | } |
110 | |
115 | |
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119 | It is safe to call this function on any database handle (or just about any |
124 | It is safe to call this function on any database handle (or just about any |
120 | value), but it will only do anything to L<DBD::mysql> handles, others are |
125 | value), but it will only do anything to L<DBD::mysql> handles, others are |
121 | returned unchanged. That means it is harmless when applied to database |
126 | returned unchanged. That means it is harmless when applied to database |
122 | handles of other databases. |
127 | handles of other databases. |
123 | |
128 | |
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129 | It is also safe to pass C<undef>, so code like this is works as expected: |
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130 | |
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131 | my $dbh = DBI->connect ($database, $user, $pass)->Coro::Mysql::unblock |
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132 | or die $DBI::errstr; |
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133 | |
124 | =cut |
134 | =cut |
125 | |
135 | |
126 | sub unblock { |
136 | sub unblock { |
127 | my ($DBH) = @_; |
137 | my ($DBH) = @_; |
128 | |
138 | |
129 | if ($DBH->{Driver}{Name} eq "mysql") { |
139 | if ($DBH && $DBH->{Driver}{Name} eq "mysql") { |
130 | my $sock = $DBH->{sock}; |
140 | my $sock = $DBH->{sock}; |
131 | |
141 | |
132 | open my $fh, "+>&" . $DBH->{sockfd} |
142 | open my $fh, "+>&" . $DBH->{sockfd} |
133 | or croak "Coro::Mysql unable to clone mysql fd"; |
143 | or croak "Coro::Mysql unable to clone mysql fd"; |
134 | |
144 | |
135 | if (AnyEvent::detect ne "AnyEvent::Impl::EV" || !_use_ev) { |
145 | if (AnyEvent::detect ne "AnyEvent::Impl::EV" || !_use_ev) { |
136 | require Coro::Handle; |
146 | require Coro::Handle; |
137 | $fh = Coro::Handle::unblock ($fh); |
147 | $fh = Coro::Handle::unblock ($fh); |
138 | } |
148 | } |
139 | |
149 | |
140 | _patch $sock, $DBH->{sockfd}, $fh, tied ${$fh}; |
150 | _patch $sock, $DBH->{sockfd}, $DBH->{mysql_clientversion}, $fh, tied ${$fh}; |
141 | } |
151 | } |
142 | |
152 | |
143 | $DBH |
153 | $DBH |
144 | } |
154 | } |
145 | |
155 | |
… | |
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195 | |
205 | |
196 | =head1 SEE ALSO |
206 | =head1 SEE ALSO |
197 | |
207 | |
198 | L<Coro>, L<PApp::SQL> (a user friendly but efficient wrapper around DBI). |
208 | L<Coro>, L<PApp::SQL> (a user friendly but efficient wrapper around DBI). |
199 | |
209 | |
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210 | =head1 HISTORY |
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211 | |
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212 | This module was initially hacked together within a few hours on a long |
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213 | flight to Malaysia, and seems to have worked ever since, with minor |
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214 | adjustments for newer libmysqlclient libraries. |
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215 | |
200 | =head1 AUTHOR |
216 | =head1 AUTHOR |
201 | |
217 | |
202 | Marc Lehmann <schmorp@schmorp.de> |
218 | Marc Lehmann <schmorp@schmorp.de> |
203 | http://home.schmorp.de/ |
219 | http://home.schmorp.de/ |
204 | |
220 | |