Re: [Xen-devel] [PATCH] xenconsoled: add ability to log guest consoles

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2010-05-20 at 14:04 +0100, Keir Fraser wrote:
> We already have a logging capability in xenconsoled, albeit enabled globally
> via a command-line switch and no direct control over log-file naming.

I didn't know about that option, very useful ;-)

> But do we really need a second method?

I don't think so, this was just a patch that's been hanging around for
years.

Ian.

> 
>  K.
> 
> On 20/05/2010 13:08, "Ian Campbell" <ian.campbell@xxxxxxxxxx> wrote:
> 
> > This is useful as a debugging aid when guests die too quickly to catch
> > their console or produce so much spew that the ring has been recycled
> > etc.
> > 
> > Logging is enable by writing the filename of the logfile to the node
> > /local/logconsole/<domid> in xenstore.
> > 
> > Writing the empty string or removing the node stops logging.
> > 
> > Writing the same path to the node causes the daemon to close and
> > reopen the file -- this can be used to logrotate the file.
> > 
> > The /local/logconsole directory should not be removed as otherwise all
> > console logging will not work until xenconsoled is restarted.
> > 
> > Logging can also be enabled by writing a filename containing %d to the
> > node /local/logconsole/@ in xenstore.  This enables logging for
> > domains for which no /local/logconsole/<domid> node exists.  The
> > filename is expanded by replacing %d with the domain id.
> > 
> > Original patch by Christian Limpach.
> > 
> > Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
> > 
> > diff -r 2c5201796a2c -r 4997d5743bc3 tools/console/daemon/io.c
> > --- a/tools/console/daemon/io.c Thu May 20 12:55:56 2010 +0100
> > +++ b/tools/console/daemon/io.c Thu May 20 13:07:25 2010 +0100
> > @@ -97,7 +97,11 @@
> > struct xencons_interface *interface;
> > int event_count;
> > long long next_period;
> > + FILE *logfile;
> >  };
> > +
> > +static void update_logconsole(struct domain *);
> > +static char *wildcard_logfile = NULL;
> >  
> >  static struct domain *dom_head;
> >  
> > @@ -152,6 +156,7 @@
> > struct buffer *buffer = &dom->buffer;
> > XENCONS_RING_IDX cons, prod, size;
> > struct xencons_interface *intf = dom->interface;
> > + size_t begin;
> >  
> > cons = intf->out_cons;
> > prod = intf->out_prod;
> > @@ -170,9 +175,15 @@
> > }
> > }
> >  
> > + begin = buffer->size;
> > while (cons != prod)
> > buffer->data[buffer->size++] = intf->out[
> > MASK_XENCONS_IDX(cons++, intf->out)];
> > + if (dom->logfile && buffer->size != begin) {
> > +  fwrite(&buffer->data[begin], buffer->size - begin, 1,
> > +         dom->logfile);
> > +  fflush(dom->logfile);
> > + }
> >  
> > xen_mb();
> > intf->out_cons = cons;
> > @@ -699,6 +710,9 @@
> > if (!watch_domain(dom, true))
> > goto out;
> >  
> > + dom->logfile = NULL;
> > + update_logconsole(dom);
> > +
> > dom->next = dom_head;
> > dom_head = dom;
> >  
> > @@ -725,12 +739,17 @@
> >  static void remove_domain(struct domain *dom)
> >  {
> > struct domain **pp;
> > + FILE *oldfile;
> >  
> > dolog(LOG_DEBUG, "Removing domain-%d", dom->domid);
> >  
> > for (pp = &dom_head; *pp; pp = &(*pp)->next) {
> > if (dom == *pp) {
> > *pp = dom->next;
> > +   oldfile = dom->logfile;
> > +   dom->logfile = NULL;
> > +   if (oldfile)
> > +    fclose(oldfile);
> > free(dom);
> > break;
> > }
> > @@ -782,6 +801,36 @@
> > }
> > domid = dominfo.domid + 1;
> > }
> > +}
> > +
> > +static void update_logconsole(struct domain *dom)
> > +{
> > + char *fname = NULL, *path = NULL;
> > + FILE *oldfile;
> > +
> > + oldfile = dom->logfile;
> > +
> > + if (asprintf(&path, "/local/logconsole/%d", dom->domid) == -1)
> > +  goto out;
> > +
> > + fname = xs_read(xs, XBT_NULL, path, NULL);
> > + if (!fname && wildcard_logfile)
> > +  asprintf(&fname, wildcard_logfile, dom->domid);
> > + if (!fname || !fname[0])
> > +  goto out;
> > +
> > + dom->logfile = fopen(fname, "a");
> > + if (!dom->logfile)
> > +  dolog(LOG_ERR, "fopen %s failed", fname);
> > +
> > + out:
> > + if (oldfile && dom->logfile == oldfile) {
> > +  dom->logfile = NULL;
> > +  fclose(oldfile);
> > + }
> > + free(fname);
> > + free(path);
> > + return;
> >  }
> >  
> >  static int ring_free_bytes(struct domain *dom)
> > @@ -909,6 +958,19 @@
> >   been removed, so dom may be NULL here. */
> > if (dom && dom->is_dead == false)
> > domain_create_ring(dom);
> > + } else if (!strcmp(vec[XS_WATCH_TOKEN], "logconsole")) {
> > +  if (sscanf(vec[XS_WATCH_PATH], "/local/logconsole/%u",
> > +      &domid) == 1) {
> > +   dom = lookup_domain(domid);
> > +   if (dom && dom->is_dead == false)
> > +    update_logconsole(dom);
> > +  } else if (!strcmp(vec[XS_WATCH_PATH],
> > +       "/local/logconsole/@")) {
> > +   free(wildcard_logfile);
> > +   wildcard_logfile = xs_read(xs, XBT_NULL,
> > +         "/local/logconsole/@",
> > +         NULL);
> > +  }
> > }
> >  
> > free(vec);
> > @@ -1128,6 +1190,17 @@
> > log_hv_evtchn = -1;
> >  }
> >  
> > +void watch_logconsole(void)
> > +{
> > +      bool success;
> > +
> > +      success = xs_watch(xs, "/local/logconsole", "logconsole");
> > +      if (!success)
> > +              dolog(LOG_ERR, "logconsole watch failed");
> > +      wildcard_logfile = xs_read(xs, XBT_NULL, "/local/logconsole/@", 
> > NULL);
> > +}
> > +
> > +
> >  /*
> >   * Local variables:
> >   *  c-file-style: "linux"
> > diff -r 2c5201796a2c -r 4997d5743bc3 tools/console/daemon/io.h
> > --- a/tools/console/daemon/io.h Thu May 20 12:55:56 2010 +0100
> > +++ b/tools/console/daemon/io.h Thu May 20 13:07:25 2010 +0100
> > @@ -23,5 +23,6 @@
> >  
> >  void enum_domains(void);
> >  void handle_io(void);
> > +void watch_logconsole(void);
> >  
> >  #endif
> > diff -r 2c5201796a2c -r 4997d5743bc3 tools/console/daemon/main.c
> > --- a/tools/console/daemon/main.c Thu May 20 12:55:56 2010 +0100
> > +++ b/tools/console/daemon/main.c Thu May 20 13:07:25 2010 +0100
> > @@ -159,6 +159,8 @@
> > if (!xen_setup())
> > exit(1);
> >  
> > + watch_logconsole();
> > +
> > enum_domains();
> >  
> > handle_io();
> > 
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@xxxxxxxxxxxxxxxxxxx
> > http://lists.xensource.com/xen-devel
> 
> 



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