trying to track down the source of numerous sleeping threads on mysql as viewed via mytop I found the source to be phpgraphy.
For some reason when the initial page is displayed phpgraphy creates two threads in mysql and even when the webbrowser is closed these threads remain. Here's an example of the mytop display during very low traffic:
MySQL on localhost (5.0.60-log) up 9+03:25:57 [12:57:20]
Queries: 8.4M qps: 11 Slow: 0.0 Se/In/Up/De(%): 00/00/00/00
qps now: 2 Slow qps: 0.0 Threads: 4 ( 1/ 0) 00/00/00/00
Key Efficiency: 99.9% Bps in/out: 0.0/ 0.0 Now in/out: 8.4/ 1.3k
Id User Host/IP DB Time Cmd Query or State
-- ---- ------- -- ---- --- ----------
227029 tritontid localhost tritontide 4215 Sleep
227122 tritontid localhost tritontide 5025 Sleep
227120 tritontid localhost tritontide 5038 Sleep
226874 tritontid localhost tritontide 6062 Sleep
all of those threads were created by opening phpgraphy and persist after the browser is closed. Note that one of them has been running for 6000+ seconds
I looked into what could be causing this and I see that phpgraphy is using mysql_pconnect to open database connections.
Here's why this is a problem , see note 1:
also see the top user contributed note here:
Using mysql_pconnect call can cause the equivalent of a DOS on the server when high trafiic occurs for the site using phpgraphy as all mysql threads get used by dead connections.
I hope you will consider not using mysql_pconnect in future releases.
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