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POAnalysing connections to diagnose "too many connections" error
 

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  1. POAnalysing connections to diagnose "too many connections" error
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    <p>My website is currently receiving the following error message: <code>Error establishing a database connection</code>. If I go on /phpma, I receive this: <code>#1040 - Too many connections</code>.</p> <p>If I restart <code>mysqld</code>, the problem temporarily goes away.</p> <p>Unfortunately, it has now come back three times.</p> <p>My dedicated box is also down to less than 1Gb of memory, from 8Gb.</p> <pre><code>Total Memory 8181984 kB Free Memory 99344 kB Total Swap Memory 1051064 kB Free Swap Memory 0 kB </code></pre> <p>If I go into <code>mysql</code> on the server and perform <code>SHOW PROCESSLIST</code>, I receive the following information:</p> <pre><code>| 17181 | my_db | localhost | my_db | Query | 35117 | Waiting for table level lock | SELECT wp_posts.* FROM wp_posts WHERE 1=1 AND wp_posts.post_name = 'boraras-brigittae' AND wp_po | | 17182 | my_db | localhost | my_db | Query | 35118 | Waiting for table level lock | SELECT post_modified_gmt FROM wp_posts WHERE post_status = 'publish' AND post_type IN ('post', 'page | | 17183 | my_db | localhost | my_db | Query | 35117 | Waiting for table level lock | SELECT wp_posts.* FROM wp_posts WHERE 1=1 AND wp_posts.post_name = 'boraras-brigittae' AND wp_po | | 17184 | my_db | localhost | my_db | Query | 35117 | Waiting for table level lock | SELECT wp_posts.* FROM wp_posts WHERE 1=1 AND wp_posts.post_name = 'boraras-brigittae' AND wp_po | | 17185 | my_db | localhost | my_db | Query | 35041 | Waiting for table level lock | SELECT wp_posts.* FROM wp_posts WHERE 1=1 AND wp_posts.post_name = 'akysis-vespa' AND wp_posts.p | | 17186 | my_db | localhost | my_db | Query | 35050 | Waiting for table level lock | SELECT ID, post_name, post_parent FROM wp_posts WHERE post_name IN ('images','profiledotline-gif') A | | 17187 | my_db | localhost | my_db | Query | 35050 | Waiting for table level lock | SELECT ID, post_name, post_parent FROM wp_posts WHERE post_name IN ('images','picarrow-gif') AND (po | | 17188 | my_db | localhost | my_db | Query | 35043 | Waiting for table level lock | SELECT post_modified_gmt FROM wp_posts WHERE post_status = 'publish' AND post_type IN ('post', 'page | | 17189 | my_db | localhost | my_db | Query | 35041 | Waiting for table level lock | SELECT ID, post_name, post_parent FROM wp_posts WHERE post_name IN ('m','marginal') AND (post_type = | | 17190 | my_db | localhost | my_db | Query | 34989 | Waiting for table level lock | SELECT wp_posts.* FROM wp_posts WHERE 1=1 AND wp_posts.post_name = 'piaractus-brachypomus' AND w | | 17191 | my_db | localhost | my_db | Query | 34989 | Waiting for table level lock | SELECT ID, post_name, post_parent FROM wp_posts WHERE post_name IN ('w','wet-dry-filter') AND (post_ | | 17192 | my_db | localhost | my_db | Query | 34990 | Waiting for table level lock | SELECT SQL_CALC_FOUND_ROWS wp_posts.ID FROM wp_posts WHERE 1=1 AND wp_posts.post_type = 'post' AN | | 17193 | my_db | localhost | my_db | Query | 34954 | Waiting for table level lock | SELECT wp_posts.* FROM wp_posts WHERE 1=1 AND wp_posts.post_name = 'corydoras-sterbai' AND wp_po | | 17194 | my_db | localhost | my_db | Query | 34954 | Waiting for table level lock | SELECT wp_posts.* FROM wp_posts WHERE 1=1 AND wp_posts.post_name = 'piaractus-brachypomus' AND w | | 17195 | my_db | localhost | my_db | Query | 34955 | Waiting for table level lock | SELECT SQL_CALC_FOUND_ROWS wp_posts.ID FROM wp_posts WHERE 1=1 AND wp_posts.post_type = 'post' AN | | 17196 | my_db | localhost | my_db | Query | 34954 | Waiting for table level lock | SELECT wp_posts.* FROM wp_posts WHERE 1=1 AND wp_posts.post_name = 'piaractus-brachypomus' AND w | | 17197 | my_db | localhost | my_db | Query | 34897 | Waiting for table level lock | SELECT SQL_CALC_FOUND_ROWS wp_posts.ID FROM wp_posts WHERE 1=1 AND wp_posts.post_type = 'post' AN | | 17198 | my_db | localhost | my_db | Query | 34955 | Waiting for table level lock | SELECT SQL_CALC_FOUND_ROWS wp_posts.ID FROM wp_posts WHERE 1=1 AND wp_posts.post_type = 'post' AN | | 17199 | my_db | localhost | my_db | Query | 34898 | Waiting for table level lock | SELECT post_modified_gmt FROM wp_posts WHERE post_status = 'publish' AND post_type IN ('post', 'page | | 17200 | my_db | localhost | my_db | Query | 34897 | Waiting for table level lock | SELECT SQL_CALC_FOUND_ROWS wp_posts.ID FROM wp_posts WHERE 1=1 AND wp_posts.post_type = 'post' AN | | 17201 | my_db | localhost | my_db | Query | 34898 | Waiting for table level lock | SELECT ID, post_name, post_parent FROM wp_posts WHERE post_name IN ('forums','lofiversion','index-ph | | 17202 | my_db | localhost | my_db | Query | 34897 | Waiting for table level lock | SELECT ID, post_name, post_parent FROM wp_posts WHERE post_name IN ('forums') AND (post_type = 'page | | 17204 | my_db | localhost | my_db | Query | 34897 | Waiting for table level lock | SELECT post_modified_gmt FROM wp_posts WHERE post_status = 'publish' AND post_type IN ('post', 'page | | 17205 | my_db | localhost | my_db | Query | 34897 | Waiting for table level lock | SELECT wp_posts.* FROM wp_posts WHERE 1=1 AND wp_posts.post_name = 'sawbwa-resplendens' AND wp_p | | 17206 | my_db | localhost | my_db | Query | 34897 | Waiting for table level lock | SELECT wp_posts.* FROM wp_posts WHERE 1=1 AND wp_posts.post_name = 'badis-sp-buxar' AND wp_posts | | 17207 | my_db | localhost | my_db | Query | 34898 | Waiting for table level lock | SELECT wp_posts.* FROM wp_posts WHERE 1=1 AND wp_posts.post_name = 'melanotaenia-boesemani' AND | | 17208 | my_db | localhost | my_db | Query | 34898 | Waiting for table level lock | SELECT wp_posts.* FROM wp_posts WHERE 1=1 AND wp_posts.post_name = 'betta-prima' AND wp_posts.po | | 17209 | my_db | localhost | my_db | Query | 34865 | Waiting for table level lock | SELECT ID, post_name, post_parent FROM wp_posts WHERE post_name IN ('forums') AND (post_type = 'page | | 17210 | my_db | localhost | my_db | Query | 34897 | Waiting for table level lock | SELECT SQL_CALC_FOUND_ROWS wp_posts.ID FROM wp_posts WHERE 1=1 AND wp_posts.post_type = 'post' AN | | 17211 | my_db | localhost | my_db | Query | 34898 | Waiting for table level lock | SELECT post_modified_gmt FROM wp_posts WHERE post_status = 'publish' AND post_type IN ('post', 'page | | 17213 | my_db | localhost | my_db | Query | 34864 | Waiting for table level lock | SELECT wp_posts.* FROM wp_posts WHERE 1=1 AND wp_posts.post_name = 'piaractus-brachypomus' AND w | | 17214 | my_db | localhost | my_db | Query | 34864 | Waiting for table level lock | SELECT SQL_CALC_FOUND_ROWS wp_posts.ID FROM wp_posts WHERE 1=1 AND wp_posts.post_type = 'post' AN | | 17215 | my_db | localhost | my_db | Query | 34864 | Waiting for table level lock | SELECT ID, post_name, post_parent FROM wp_posts WHERE post_name IN ('knowledge-base') AND (post_type | | 17216 | my_db | localhost | my_db | Query | 34865 | Waiting for table level lock | SELECT SQL_CALC_FOUND_ROWS wp_posts.ID FROM wp_posts WHERE 1=1 AND wp_posts.post_type = 'post' AN | | 17217 | my_db | localhost | my_db | Query | 34864 | Waiting for table level lock | SELECT wp_posts.* FROM wp_posts WHERE 1=1 AND wp_posts.post_name = 'piaractus-brachypomus' AND w | | 17218 | my_db | localhost | my_db | Query | 34864 | Waiting for table level lock | SELECT wp_posts.* FROM wp_posts WHERE 1=1 AND wp_posts.post_name = 'badis-sp-buxar' AND wp_posts | | 17219 | my_db | localhost | my_db | Query | 34864 | Waiting for table level lock | SELECT ID, post_name, post_parent FROM wp_posts WHERE post_name IN ('forums','lofiversion','index-ph | | 17220 | my_db | localhost | my_db | Query | 34864 | Waiting for table level lock | SELECT wp_posts.* FROM wp_posts WHERE 1=1 AND wp_posts.post_name = 'betta-prima' AND wp_posts.po | | 17221 | my_db | localhost | my_db | Query | 34864 | Waiting for table level lock | SELECT SQL_CALC_FOUND_ROWS wp_posts.ID FROM wp_posts WHERE 1=1 AND wp_posts.post_type = 'post' AN | | 17222 | my_db | localhost | my_db | Query | 34865 | Waiting for table level lock | SELECT wp_posts.* FROM wp_posts WHERE 1=1 AND wp_posts.post_name = 'piaractus-brachypomus' AND w | | 17223 | my_db | localhost | my_db | Query | 34864 | Waiting for table level lock | SELECT wp_posts.* FROM wp_posts WHERE 1=1 AND wp_posts.post_name = 'piaractus-brachypomus' AND w | | 17224 | my_db | localhost | my_db | Query | 34865 | Waiting for table level lock | SELECT wp_posts.* FROM wp_posts WHERE 1=1 AND wp_posts.post_name = 'hemichromis-lifalili' AND wp | | 17225 | my_db | localhost | my_db | Query | 34864 | Waiting for table level lock | SELECT post_modified_gmt FROM wp_posts WHERE post_status = 'publish' AND post_type IN ('post', 'page | | 17226 | my_db | localhost | my_db | Query | 34862 | Waiting for table level lock | SELECT wp_posts.* FROM wp_posts WHERE 1=1 AND wp_posts.post_name = 'apistogramma-borellii' AND w | | 17227 | my_db | localhost | my_db | Query | 34863 | Waiting for table level lock | SELECT wp_posts.* FROM wp_posts WHERE 1=1 AND wp_posts.post_name = 'melanotaenia-lacustris' AND | | 17228 | my_db | localhost | my_db | Query | 34862 | Waiting for table level lock | SELECT wp_posts.* FROM wp_posts WHERE 1=1 AND wp_posts.post_name = 'melanotaenia-lacustris' AND | | 17229 | my_db | localhost | my_db | Query | 34861 | Waiting for table level lock | SELECT wp_posts.* FROM wp_posts WHERE 1=1 AND wp_posts.post_name = 'mikrogeophagus-altispinosus' | | 17230 | my_db | localhost | my_db | Query | 34861 | Waiting for table level lock | SELECT wp_posts.* FROM wp_posts WHERE 1=1 AND wp_posts.ID = 25503 AND wp_posts.post_type = 'atta | | 17231 | my_db | localhost | my_db | Query | 34803 | Waiting for table level lock | SELECT wp_posts.* FROM wp_posts WHERE 1=1 AND wp_posts.post_name = 'piaractus-brachypomus' AND w | | 17232 | my_db | localhost | my_db | Query | 34803 | Waiting for table level lock | SELECT SQL_CALC_FOUND_ROWS wp_posts.ID FROM wp_posts WHERE 1=1 AND wp_posts.post_type = 'post' AN | | 17233 | my_db | localhost | my_db | Query | 34803 | Waiting for table level lock | SELECT ID, post_name, post_parent FROM wp_posts WHERE post_name IN ('knowledge-base') AND (post_type | | 17234 | my_db | localhost | my_db | Query | 34803 | Waiting for table level lock | SELECT post_modified_gmt FROM wp_posts WHERE post_status = 'publish' AND post_type IN ('post', 'page | | 17235 | my_db | localhost | my_db | Query | 34803 | Waiting for table level lock | SELECT ID, post_name, post_parent FROM wp_posts WHERE post_name IN ('forums') AND (post_type = 'page | | 17236 | my_db | localhost | my_db | Query | 34803 | Waiting for table level lock | SELECT SQL_CALC_FOUND_ROWS wp_posts.ID FROM wp_posts WHERE 1=1 AND wp_posts.post_type = 'post' AN | | 17237 | my_db | localhost | my_db | Query | 34803 | Waiting for table level lock | SELECT ID, post_name, post_parent FROM wp_posts WHERE post_name IN ('forums') AND (post_type = 'page | | 17238 | my_db | localhost | my_db | Query | 34788 | Waiting for table level lock | SELECT ID, post_name, post_parent FROM wp_posts WHERE post_name IN ('m','migrate') AND (post_type = | | 17239 | my_db | localhost | my_db | Query | 34788 | Waiting for table level lock | SELECT wp_posts.* FROM wp_posts WHERE 1=1 AND wp_posts.post_name = 'hemichromis-lifalili' AND wp | | 17240 | my_db | localhost | my_db | Query | 34788 | Waiting for table level lock | SELECT post_modified_gmt FROM wp_posts WHERE post_status = 'publish' AND post_type IN ('post', 'page | | 17241 | my_db | localhost | my_db | Query | 34788 | Waiting for table level lock | SELECT ID, post_name, post_parent FROM wp_posts WHERE post_name IN ('forums') AND (post_type = 'page | | 17242 | my_db | localhost | my_db | Query | 34788 | Waiting for table level lock | SELECT SQL_CALC_FOUND_ROWS wp_posts.ID FROM wp_posts WHERE 1=1 AND wp_posts.post_type = 'post' AN | | 17243 | my_db | localhost | my_db | Query | 34788 | Waiting for table level lock | SELECT post_modified_gmt FROM wp_posts WHERE post_status = 'publish' AND post_type IN ('post', 'page | | 17244 | my_db | localhost | my_db | Query | 34788 | Waiting for table level lock | SELECT ID, post_name, post_parent FROM wp_posts WHERE post_name IN ('forums','lofiversion','index-ph | | 17245 | my_db | localhost | my_db | Query | 34788 | Waiting for table level lock | SELECT post_modified_gmt FROM wp_posts WHERE post_status = 'publish' AND post_type IN ('post', 'page | | 17246 | my_db | localhost | my_db | Query | 34788 | Waiting for table level lock | SELECT post_modified_gmt FROM wp_posts WHERE post_status = 'publish' AND post_type IN ('post', 'page | | 17247 | my_db | localhost | my_db | Query | 34788 | Waiting for table level lock | SELECT ID, post_name, post_parent FROM wp_posts WHERE post_name IN ('forums') AND (post_type = 'page | | 17248 | my_db | localhost | my_db | Query | 34788 | Waiting for table level lock | SELECT wp_posts.* FROM wp_posts WHERE 1=1 AND wp_posts.post_name = 'geophagus-brokopondo' AND wp | | 17249 | my_db | localhost | my_db | Query | 34788 | Waiting for table level lock | SELECT wp_posts.* FROM wp_posts WHERE 1=1 AND wp_posts.post_name = 'hyphessobrycon-amandae' AND | | 17253 | my_db | localhost | my_db | Query | 34788 | Waiting for table level lock | SELECT SQL_CALC_FOUND_ROWS wp_posts.ID FROM wp_posts WHERE 1=1 AND wp_posts.post_type = 'post' AN | | 17255 | my_db | localhost | my_db | Query | 34786 | Waiting for table level lock | SELECT ID, post_name, post_parent FROM wp_posts WHERE post_name IN ('knowledge-base') AND (post_type | | 17260 | my_db | localhost | my_db | Query | 34786 | Waiting for table level lock | SELECT ID, post_name, post_parent FROM wp_posts WHERE post_name IN ('s','silver-sand') AND (post_typ | | 17262 | my_db | localhost | my_db | Query | 34786 | Waiting for table level lock | SELECT ID, post_name, post_parent FROM wp_posts WHERE post_name IN ('forums') AND (post_type = 'page | | 25505 | root | localhost | NULL | Query | 2 | NULL | SHOW PROCESSLIST </code></pre> <p>I tried running <code>mysql</code> with the <code>--log-slow-queries[slow-queries]</code> flag but it doesn't seem to have done anything - I can't find a file called <code>slow-queries</code> anywhere on my box, at least.</p> <p>I'm guessing this is a suspect query somewhere, but I have no idea where to begin looking!</p> <hr> <p><strong>EDIT: Hits and settings</strong></p> <ul> <li>MySQL is currently running a max of 500 simultaneous connections</li> <li>PHP's memory limit is quite high (around 1Gb) as I was trying some performance testing on scripts</li> <li>This website alone (there are others on the box; all are currently affected by this error) receives around 30,000 unique visitors and 250,000 hits per week</li> </ul>
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    1. COHow many hits is this website receiving a second? If you raise the connection limit does it go away or does it just take longer for the problem to occur?
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    2. COI've added this information to my OP. The max_connections has been the default value for around 5 years as the website has been built up, but this has suddenly just happened pretty much overnight. Last night I raised the max_connections setting to 500 and the same problem occurred this morning when I woke up.
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