Re: Show application performance/errors from pseudo file

[Daniel Hilst Selli <danielhilst@gmail.com>]

On 10/17/2014 04:00 PM, Daniel Hilst Selli wrote:
> On 10/17/2014 03:59 PM, Daniel Hilst Selli wrote:
>> On 10/16/2014 05:31 PM, Yichao Yu wrote:
>>> Resend as plain text.
>>>
>>> On Thu, Oct 16, 2014 at 4:01 PM, Yichao Yu <yyc1992@gmail.com> wrote:
>>>>
>>>>
>>>> On Thu, Oct 16, 2014 at 3:50 PM, Daniel Hilst Selli <danielhilst@gmail.com>
>>>> wrote:
>>>>>
>>>>> I'm writing a new application and would be nice to have a pseudo file
>>>>> showing its status, just the way that procfs does with kernel.
>>>>> I'm looking for sugestions, I want to `cat' files contents and have
>>>>> something similar to /proc/meminfo
>>>>>
>>>>> First I think using named pipes, but, AFAIK, pipes would retain data
>>>>> writed until someone read it, what I thought is a kind of read
>>>>> hook that only show data when asked for. Here are a few requisites,
>>>>>
>>>>> - Don't retain data
>>>>> - Don't generate disk I/O
>>>>> - Vanish when application stops
>>>>> - Work with a simple cat or something similar..
>>>>
>>>>
>>>> You should have a look at fuse[1].
>>>>
>>>> [1] http://fuse.sourceforge.net/
>>>>
>>>>>
>>>>>
>>>>> With that in mind I think about using unix domain sockets.. it seems to
>>>>> fit all requisites, for
>>>>> the fourth requisite I could use netcat, that is almost cat,
>>>>>
>>>>> Cheers
>>>>> --
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>>>>
>>>>
>>
>> Seems god, a little overkill for so simple stuff but adds nice features, I'm taking
>> a look on further options..
>>
>> Cheers
> good*

Looking further I found that named pipes will block on open() calls, until
the other end open it too. So I still can implement this with named pipes.

Here is the pseudo code implementation I use. (Yes I'm using threads)

void *stats_handler(void *unused)
{
	for (;;) {
		int fd = open(FIFO_PATH, O_WRONLY); /* should block here */

                 /* handle open error */

		write(fd, statistics_buffer, statistics_buffer_len);

		close(fd);

		sleep(1); /* avoid flooders :-P */
	}
}

void stats_init(void)
{
	pthread_t stat_id;

	mkfifo(FIFO_PATH, 0755);
	/* handle mkfifo errors */
	pthread_create(&stat_id, NULL, stats_handler, NULL);
}

int main(void)
{
	...
	stats_init();
	...
}


After that I can just `cat FIFO_PATH' to see my statistics :D

Thanks for all and best regards!