[PATCH] Add display of parent and child hosts to extinfo.cgi

[Andreas Ericsson]

psychotrahe at gmx.de wrote:
> From: Matthias Eble <matthias.eble at mailing.kaufland-informationssysteme.com>
> 
> When extinfo.cgi displays a host's status, parent and/or child hosts
> get displayed also. New cgi.cfg variables have been added to prevent
> flooding in case of too many parents/children:
>   child_host_display_len
>   parent_host_display_len
> ---
> 
> Hi all,
> 
> so after some tinkering I thought that it'd be a good idea to display
> parent/child hosts on extinfo.cgi rather linking to config.cgi.
> So here's the patch including doc updates.
> 

Nice work, and nicely submitted patch. Comments inline:

> +
> +				if (temp_host->parent_hosts != NULL) {
> +					/* display parent hosts */
> +					printf("<DIV CLASS='data'>Parent Hosts:</DIV>\n");
> +					printf("<DIV CLASS='dataTitle'>\n");
> +					for(temp_parenthost=temp_host->parent_hosts;temp_parenthost!=NULL;temp_parenthost=temp_parenthost->next){
> +						len += strlen(temp_parenthost->host_name);
> +						if(len > parent_host_display_len && !display_all_parents) {
> +							printf("<A HREF='%s?%s&display_all_parents'>...</A>",EXTINFO_CGI,query_string);
> +							break;
> +						}
> +						printf("<A HREF='%s?host=%s'>%s</A>\n",STATUS_CGI, url_encode(temp_parenthost->host_name),temp_parenthost->host_name);
> +					}
> +					printf("</DIV><BR>\n");
> +				}
> +

The section above is quite alright, but...

> +				len=0;
> +				/* look up and display child hosts */
> +				for(temp_host2=host_list;temp_host2!=NULL;temp_host2=temp_host2->next){
> +					if(len > child_host_display_len && !display_all_children) {
> +						printf("<A HREF='%s?%s&display_all_children'>...</A>", EXTINFO_CGI, query_string);
> +						break;
> +					}
> +					if (temp_host2->parent_hosts != NULL) {
> +						for(temp_parenthost=temp_host2->parent_hosts;temp_parenthost!=NULL;temp_parenthost=temp_parenthost->next){
> +							if(!strcmp(temp_host->name, temp_parenthost->host_name)) {
> +								if(len == 0){
> +									printf("<DIV CLASS='data'>Child Hosts:</DIV>\n");
> +									printf("<DIV CLASS='dataTitle'>\n");
> +								}
> +								len += strlen(temp_parenthost->host_name);
> +								printf("<A HREF='%s?host=%s'>%s</A>\n",STATUS_CGI,url_encode(temp_host2->name),temp_host2->name);
> +							}
> +						}
> +					}
> +				}

... this really isn't. In a *best* case scenario (where each parent is a
parent to only one host), this exhibits O(hosts*2) performance, which I
have a hard time accepting. Especially in view of Jean Gabès' recent
patch, which makes Nagios scale to truly huge networks. I think a better
solution would be to waste some memory for the host we're showing and
plug in the host->child_hosts logic into the CGI's as well, but only
for the host we're currently showing.

The rest of the patch looks good though, although I'd personally have
used a "max_show_{parent,child}_hosts=number-of-hosts-to-show" variable
for this, since the sort-order of the hosts will sometimes affect how
many parents are shown.

Would you care to amend the patch, or would you prefer if I strip out
the child-drawing stuff and only apply the parent-drawing logic for
now?

-- 
Andreas Ericsson                   andreas.ericsson at op5.se
OP5 AB                             www.op5.se
Tel: +46 8-230225                  Fax: +46 8-230231

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