Implementing features: generic logging interface.

[gbaligh]

What do you think about an Implementation of generic logging interface. This implementation must be thread-safe, Level support, use syslog, enable log by module.

void chilli_log_init(chilli_log_t *log);
void chilli_log(char const *fmt, ...) __attribute__ ((__format__ (printf, 1, 2)));
void chilli_llog(chilli_log_t *log, unsigned level, char const *fmt, ...) __attribute__ ((__format__ (printf, 3, 4)));
void chilli_vllog(chilli_log_t *log, unsigned level,  char const *fmt, va_list ap);
void chilli_log_set_level(chilli_log_t *log, unsigned level);

[ynezz]

Yep, it's clear from #119, that we need to improve logging.

This implementation must be thread-safe, Level support, use syslog, enable log by module.

What do you mean by thread-safe exactly? Are you going to have different settings for every thread, are you going to share some buffers etc? Isn't it overdesigned for our needs?

How are you going to solve enable log by module by the proposed API? I don't see it from the API. Do we need this? Isn't just a log level verbosity good enough (ERROR, VERBOSE, DEBUG...)?

What are you going to keep in struct chilli_log_t?

I would simply use ulog modified for our needs (adding DEBUG log level, removing kmsg logging etc.).

[gbaligh]

Yes, you are totally right for Thread-safe capability.

• Thread Safe, in my point of view, is needed when logging a status of a context, which must be protected (by mutex or other methods) to avoid incoherent logging. Of course, this is in case of threads and shared context.
• Log by module, will be helpful if we need to debug only some modules (DHCP, DNS, ARP, HTTP, MD5, ...). For implementation, it's not a big problem : We can create a log context for each module.
• I do not have any idea for the moment, in how to implement this module, but there I suppose that there is a big need. And I'm totally agree with any idea that will simplify logging, including the one you proposed using ulog
• My proposal :

struct chilli_log_s {
  char const  *log_name;
  unsigned  log_level;
  int  log_init;
};

/* Initialize a chilli_log_s structure */
#define CHILLI_LOG_INIT(name, level)  

#ifndef CHILLI_LOG
#define CHILLI_LOG       (chilli_log_default)
#else
struct chilli_log_s CHILLI_LOG[];
#endif

struct chilli_log_s chilli_log_default[];

void chilli_log(unsigned level, char const *fmt, ...) __attribute__ ((__format__ (printf, 1, 2))) 

/* in dhcp.c */
#define CHILLI_LOG_CTX  log_dhcp;
#include <chilli_log.h>
...
struct chilli_log_s log_dhcp[1] = { "DHCP", LOG_DEBUG, 1 };
...
chilli_log(LOG_INFO, "some INFO message");
/* Will print: [DHCP] - some INFO message */
...
chilli_log(LOG_DEBUG, "some DEBUG message");
/* Will print: [DHCP] - some DEBUG message */

/* in dns.c */
#define CHILLI_LOG_CTX  log_dns;
#include <chilli_log.h>
...
struct chilli_log_s log_dns[1] = { "DNS", LOG_DEBUG, 1 };
...
chilli_log(LOG_INFO, "some INFO message");
/* Will print: [DNS] - some INFO message */
...
chilli_log(LOG_DEBUG, "some DEBUG message");
/* Will print: [DNS] - some DEBUG message */