can I use a .txt database with concurrent users?

Anon

I want to grab data from a form & dump it into a .txt file. I don't need to retreive data from the file or do any database functions on it. I just want to keep a log that I will retreive & empty every so often.
My knowledge of cgi is, well, non-existant, so I would prefer not to go that route at the moment.
Question: Can I open & append to a .txt file with multiple concurrent users? Or would it crash? I am anticipating 300+- hits/day.

Anon

Well if you used diferent files it'd be ok, but if you're using the same big master file for every request you might run into overlap problems if two users used the script at the same time. If thats not a concern then I say go for it, but usualy it is so I'd go with either separate files or a database solution.

Anon

I'd say you're safe. Even if you had 300 hits per hour, you'd be safe.

Imagine 300 hits per HOUR, that's 5 hits per minute, or one hit every 12 seconds on average. Typically appending operations like this take less than a second, so the odds of corruption/missed writes are slim. If you're worried, see <http://www.php.net/manual/function.flock.php> for info on file locking.

Anon

I'd say you're safe. Even if you had 300 hits per hour, you'd be safe.

No way; I take it you've never made the acquaintance of the famous Mr. Murphy? The hidden assumption behind your assurance is the assertion that these hits are virtually guaranteed to be spaced out, but of course there's no way to know this in advance.

But your recommendation of flock() is not a bad idea: just open the file in append mode, then flock() it before writing.

Anon

Of course if another user tries to use the script at the same time just remember to toss i some error checking, maybe a loop to make the script wait for the file to be unlocked? Might lag a bit but it shouldn't be waiting more than a couple of miliseconds.

Anon

Calculated risks are often necessary. Considering the application will get typically 30 hits per day, I would balance the time spent vs. the return.

I often work on projects and think of ways to improve the design once I'm elbow deep in the project. This time invariably adds up and when a dollar ammount (or pound/yen/euro/DM/whatever) is attached to this time, someone is going to loose.

If you think about it, after the time implmenting the locking, write the status checking code, and the handful of other tasks that would certainly pop up is added together, you have to ask yourself, "Why didn't I use a database?"

Someone once told me an anacronym, K.I.S.S. which stands for, Keep It Simple Stupid! I think this ceratinly applies here.

By all means, I do not encourage sloppy coding, I do encourage setting realistic limitations on the functionality of an application. This requires balance between functionality and cost (in time).

On a philisophical note, what technique is used in log files to prevent these types of problems?

Anon

If you think about it, after the time implmenting the locking, write
the status checking code, and the handful of other tasks that would
certainly pop up is added together, you have to ask yourself, "Why
didn't I use a database?"

Well, I wasn't advocating the use of text files in the first place, but only saying "If you must do this, at least consider how to do it safely." However, I can easily foresee some of the obvious answers to the question, "Why didn't I use a database?":

You don't "own" the machine, and don't have permission to install a
database and/or can't talk the person who does have the authority
to do so
You do own the machine, but rightly suspect that installing a database
and getting it set up will, in fact, be a bit less trivial than simply adding
a loop and a call to flock() to your existing code.

On a philisophical note, what technique is used in log files to prevent
these types of problems?

Lots of variety here, including

Lockfiles
Semaphores (on platforms that support them)
File locking (our good old flock()!)
On local files on unix systems, depending on the atomic nature of write()
(note, not fwrite()!) to safely append single lines to a log file.

I have no idea which method(s) Apache uses...

Anon

I'm thinking Apache uses file locking semantics... just lock the file and be done with it.

It's just a log for ... b.....

But make it standard and keep it simple,
comma-delimit if you can, and that way you can parse it later on.

Michael