set custom loglevel for external libraries

[Daniel P. Berrangé]

On Thu, Jul 22, 2021 at 04:39:24PM +0200, Olaf Hering wrote:
> Thanks for your reply, I had no time to look at this until now.
> 
> Am Wed, 16 Jun 2021 11:44:10 +0100
> schrieb Daniel P. Berrangé <berrange at redhat.com>:
> 
> > Anyway if you used a virLogSource object, then turning on debugging
> > exclusively for libxl library messages would be as simple as
> > 
> >   log_filters="1:libxl.libxl_library"
> > 
> > without affecting the global libvirt logging behaviour
> 
> It seems log_filters= does not allow arbitrary numbers.
> virLogParseFilter would just allow values from 1 to 4.
> Such extra logfilter needs to handle a xentoollog_level, values from 1 to 9 (>XTL_NONE and <XTL_NUM_LEVELS).
> 
> How should this be expressed in a config setting?

Do we actually need to care about every single level, as opposed to
just doing a sparse mapping where we squash several xen levels into
one libvirt level, as the code below shows ?

> 
> Perhaps just go the easy route and obtain a value from environment?
> 
> --- a/src/libxl/libxl_conf.c
> +++ b/src/libxl/libxl_conf.c
> @@ -1829,7 +1829,7 @@ libxlDriverConfigInit(libxlDriverConfig *cfg)
>          return -1;
>      }
>  
> -    cfg->logger = libxlLoggerNew(cfg->logDir, virLogGetDefaultPriority());
> +    cfg->logger = libxlLoggerNew(cfg->logDir);
>      if (!cfg->logger) {
>          VIR_ERROR(_("cannot create logger for libxenlight, disabling driver"));
>          return -1;
> --- a/src/libxl/libxl_logger.c
> +++ b/src/libxl/libxl_logger.c
> @@ -129,25 +129,33 @@ libvirt_destroy(xentoollog_logger *logger_in)
>  
>  
>  libxlLogger *
> -libxlLoggerNew(const char *logDir, virLogPriority minLevel)
> +libxlLoggerNew(const char *logDir)
>  {
>      xentoollog_logger_libvirt logger;
>      g_autofree char *path = NULL;
> -
> -    switch (minLevel) {
> -    case VIR_LOG_DEBUG:
> -        logger.minLevel = XTL_DEBUG;
> -        break;
> -    case VIR_LOG_INFO:
> -        logger.minLevel = XTL_INFO;
> -        break;
> -    case VIR_LOG_WARN:
> -        logger.minLevel = XTL_WARN;
> -        break;
> -    case VIR_LOG_ERROR:
> -        logger.minLevel = XTL_ERROR;
> -        break;
> +    char *xenlight_minlevel = getenv("xenlight_minlevel");
> +    int minlevel;
> +
> +    if (!(xenlight_minlevel && *xenlight_minlevel &&
> +        virStrToLong_i(xenlight_minlevel, NULL, 10, &minlevel) >= 0 &&
> +        minlevel > XTL_NONE && minlevel < XTL_NUM_LEVELS)) {
> +        minlevel = virLogGetDefaultPriority();
> +        switch (minlevel) {
> +        case VIR_LOG_DEBUG:
> +            minlevel = XTL_DEBUG;
> +            break;
> +        case VIR_LOG_INFO:
> +            minlevel = XTL_INFO;
> +            break;
> +        case VIR_LOG_WARN:
> +            minlevel = XTL_WARN;
> +            break;
> +        case VIR_LOG_ERROR:
> +            minlevel = XTL_ERROR;
> +            break;
> +        }
>      }
> +    logger.minLevel = minlevel;
>      logger.logDir = logDir;
>  
>      if ((logger.files = virHashNew(libxlLoggerFileFree)) == NULL)
> --- a/src/libxl/libxl_logger.h
> +++ b/src/libxl/libxl_logger.h
> @@ -24,8 +24,7 @@
>  
>  typedef struct xentoollog_logger_libvirt libxlLogger;
>  
> -libxlLogger *libxlLoggerNew(const char *logDir,
> -                              virLogPriority minLevel);
> +libxlLogger *libxlLoggerNew(const char *logDir);
>  void libxlLoggerFree(libxlLogger *logger);
>  
>  void libxlLoggerOpenFile(libxlLogger *logger, int id, const char *name,
> 
> 
> Olaf



Regards,
Daniel
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