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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 |
26 | Note that this module must be linked against exactly the same (shared, |
26 | F<libmysqlclient> library as DBD::mysql, otherwise it will not work. |
27 | possibly not working with all OSes) F<libmysqlclient> library as |
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28 | DBD::mysql, otherwise it will not work. |
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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. |
27 | |
40 | |
28 | Also, while this module makes database handles non-blocking, you still |
41 | Also, while this module makes database handles non-blocking, you still |
29 | 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 |
30 | 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 |
31 | database connections, one for each thread that runs queries. Not doing so |
44 | database connections, one for each thread that runs queries. Not doing |
32 | 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. |
33 | |
47 | |
34 | 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 |
35 | can freely share the database handles between threads, of course. |
49 | can freely share the database handles between threads, of course. |
36 | |
50 | |
37 | Also, this module uses a number of "unclean" techniques (patching an |
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38 | internal libmysql structure for one thing) and was hacked within a few |
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39 | hours on a long flight to Malaysia. |
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40 | |
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41 | It does, however, check whether it indeed got the structure layout |
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42 | correct, so you should expect perl exceptions or early crashes as opposed |
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43 | to data corruption when something goes wrong during patching. |
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44 | |
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45 | =head2 SPEED |
51 | =head2 SPEED |
46 | |
52 | |
47 | 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 |
48 | enough, it adds no overhead to the standard libmysql communication |
54 | enough, it adds no overhead to the standard libmysql communication |
49 | routines (which are very badly written, btw.). |
55 | routines (which are very badly written, btw.). In fact, since it has a |
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56 | more efficient buffering and allows requests to run in parallel, it often |
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57 | decreases the actual time to run many queries considerably. |
50 | |
58 | |
51 | For very fast queries ("select 0"), this module can add noticable overhead |
59 | For very fast queries ("select 0"), this module can add noticable overhead |
52 | (around 15%) as it tries to switch to other coroutines when mysqld doesn't |
60 | (around 15%, 7% when EV can be used) as it tries to switch to other |
53 | deliver the data instantly. |
61 | coroutines when mysqld doesn't deliver the data immediately, although, |
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62 | again, when running queries in parallel, they will usually execute faster. |
54 | |
63 | |
55 | For most types of queries, there will be no overhead, especially on |
64 | For most types of queries, there will be no extra latency, especially on |
56 | multicore systems where your perl process can do other things while mysqld |
65 | multicore systems where your perl process can do other things while mysqld |
57 | does its stuff. |
66 | does its stuff. |
58 | |
67 | |
59 | =head2 LIMITATIONS |
68 | =head2 LIMITATIONS |
60 | |
69 | |
61 | This module only supports "standard" mysql connection handles - this |
70 | This module only supports "standard" mysql connection handles - this |
62 | means unix domain or TCP sockets, and excludes SSL/TLS connections, named |
71 | means unix domain or TCP sockets, and excludes SSL/TLS connections, named |
63 | pipes (windows) and shared memory (also windows). No support for these |
72 | pipes (windows) and shared memory (also windows). No support for these |
64 | connection types is planned, either. |
73 | connection types is planned, either. |
65 | |
74 | |
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75 | =head1 CANCELLATION |
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76 | |
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77 | Cancelling a thread that is within a mysql query will likely make the |
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78 | handle unusable. As far as Coro::Mysql is concerned, the handle can be |
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79 | safely destroyed, but it's not clear how mysql itself will react to a |
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80 | cancellation. |
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81 | |
66 | =head1 FUNCTIONS |
82 | =head1 FUNCTIONS |
67 | |
83 | |
68 | Coro::Mysql offers a single user-accessible function: |
84 | Coro::Mysql offers a single user-accessible function: |
69 | |
85 | |
70 | =over 4 |
86 | =over 4 |
… | |
… | |
78 | |
94 | |
79 | use Scalar::Util (); |
95 | use Scalar::Util (); |
80 | use Carp qw(croak); |
96 | use Carp qw(croak); |
81 | |
97 | |
82 | use Guard; |
98 | use Guard; |
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99 | use AnyEvent (); |
83 | use Coro::Handle (); |
100 | use Coro (); |
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101 | use Coro::AnyEvent (); # not necessary with newer Coro versions |
84 | |
102 | |
85 | # we need this extra indirection, as Coro doesn't support |
103 | # we need this extra indirection, as Coro doesn't support |
86 | # calling SLF-like functions via call_sv. |
104 | # calling SLF-like functions via call_sv. |
87 | |
105 | |
88 | sub readable { &Coro::Handle::FH::readable } |
106 | sub readable { &Coro::Handle::FH::readable } |
89 | sub writable { &Coro::Handle::FH::writable } |
107 | sub writable { &Coro::Handle::FH::writable } |
90 | |
108 | |
91 | BEGIN { |
109 | BEGIN { |
92 | our $VERSION = '1.02'; |
110 | our $VERSION = '1.23'; |
93 | |
111 | |
94 | require XSLoader; |
112 | require XSLoader; |
95 | XSLoader::load Coro::Mysql::, $VERSION; |
113 | XSLoader::load Coro::Mysql::, $VERSION; |
96 | } |
114 | } |
97 | |
115 | |
… | |
… | |
106 | 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 |
107 | 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 |
108 | returned unchanged. That means it is harmless when applied to database |
126 | returned unchanged. That means it is harmless when applied to database |
109 | handles of other databases. |
127 | handles of other databases. |
110 | |
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 $DBI::errstr; |
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133 | |
111 | =cut |
134 | =cut |
112 | |
135 | |
113 | sub unblock { |
136 | sub unblock { |
114 | my ($DBH) = @_; |
137 | my ($DBH) = @_; |
115 | |
138 | |
116 | if ($DBH->{Driver}{Name} eq "mysql") { |
139 | if ($DBH && $DBH->{Driver}{Name} eq "mysql") { |
117 | my $sock = $DBH->{sock}; |
140 | my $sock = $DBH->{sock}; |
118 | |
141 | |
119 | open my $fh, "+>&" . $DBH->{sockfd} |
142 | open my $fh, "+>&" . $DBH->{sockfd} |
120 | or croak "Coro::Mysql unable to clone mysql fd"; |
143 | or croak "Coro::Mysql unable to clone mysql fd"; |
121 | |
144 | |
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145 | if (AnyEvent::detect ne "AnyEvent::Impl::EV" || !_use_ev) { |
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146 | require Coro::Handle; |
122 | $fh = Coro::Handle::unblock $fh; |
147 | $fh = Coro::Handle::unblock ($fh); |
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148 | } |
123 | |
149 | |
124 | _patch $sock, $DBH->{sockfd}, $fh, tied ${$fh}; |
150 | _patch $sock, $DBH->{sockfd}, $DBH->{mysql_clientversion}, $fh, tied *$$fh; |
125 | } |
151 | } |
126 | |
152 | |
127 | $DBH |
153 | $DBH |
128 | } |
154 | } |
129 | |
155 | |
… | |
… | |
144 | use PApp::SQL; |
170 | use PApp::SQL; |
145 | |
171 | |
146 | sub with_db($$$&) { |
172 | sub with_db($$$&) { |
147 | my ($database, $user, $pass, $cb) = @_; |
173 | my ($database, $user, $pass, $cb) = @_; |
148 | |
174 | |
149 | my $dbh = Coro::Mysql::unblock DBI->connect ($database, $user, $pass) |
175 | my $dbh = DBI->connect ($database, $user, $pass)->Coro::Mysql::unblock |
150 | or die $DBI::errstr; |
176 | or die $DBI::errstr; |
151 | |
177 | |
152 | Coro::on_enter { $PApp::SQL::DBH = $dbh }; |
178 | Coro::on_enter { $PApp::SQL::DBH = $dbh }; |
153 | |
179 | |
154 | $cb->(); |
180 | $cb->(); |
… | |
… | |
179 | |
205 | |
180 | =head1 SEE ALSO |
206 | =head1 SEE ALSO |
181 | |
207 | |
182 | 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). |
183 | |
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 | |
184 | =head1 AUTHOR |
216 | =head1 AUTHOR |
185 | |
217 | |
186 | Marc Lehmann <schmorp@schmorp.de> |
218 | Marc Lehmann <schmorp@schmorp.de> |
187 | http://home.schmorp.de/ |
219 | http://home.schmorp.de/ |
188 | |
220 | |