Semaphore Error

[rushik]

Hello all,

I m facing an interesting problem related to semaphore in php.

We are using a huge business application running on LAMP. For database
operations we are maintaining centralized DB manager classes in php
which perform all the single table related activity. Before inserting
new record we are acquiring semaphore on specific key (all the tables
are having seprate sem keys), insert the record and release the
semaphore.

From past few days we are getting error "Warning: sem_get()

[function.sem-get]: failed for key ___: No space left on device", i've
gone to linux console check thru ipcs command whether semaphore is
there or not ?? ___ sem was there i've removed that by ipcrm, it
started working.

Now the problem is, I m acquiring sem on key say 774, then i m not able
to use sem keys 775, 776, 777 etc, I really dont know the reason.

I've made one test page having a loop in which i'd tried to acquire
semaphore from a certain range starts from 10 to 200, i also display
the result whether semaphore acquire is succeed or not..?? I've
executed the script and got the random result. on some keys i've
succeed and on some i've got problem with the above error message.

I'm searching the problem on google but i m not getting proper
solution. Can anyone has faced the same or related problem like this?

Thanks
Rushik.

[Colin McKinnon]

rushik wrote:

We are using a huge business application running on LAMP. For database
operations we are maintaining centralized DB manager classes in php
which perform all the single table related activity. Before inserting
new record we are acquiring semaphore on specific key (all the tables
are having seprate sem keys), insert the record and release the
semaphore.

Why? MySQL is quite capable of isolating DML operations.

From past few days we are getting error "Warning: sem_get()

[function.sem-get]: failed for key ___: No space left on device", i've
gone to linux console check thru ipcs command whether semaphore is
there or not ?? ___ sem was there i've removed that by ipcrm, it
started working.

(/me does not like IPC)

How many semaphores have you got in use? It might be useful to include (a
sample of) the output of ipcs or 'cat /proc/sysvipc/shm'. AIR there are
hard limits compiled into the kernel.
Now the problem is, I m acquiring sem on key say 774, then i m not able
to use sem keys 775, 776, 777 etc, I really dont know the reason.

eh? I've only seen mapping filenames to keys using ftok.

HTH

C.