apache plugin: Use the HTTP header to determine the server software.

On Wed, Apr 22, 2009 at 1:53 PM, Florian Forster <octo@verplant.org> wrote:
> I think we have two options left:
>
>  - Set a header callback using the CURLOPT_HEADERFUNCTION option and
>   look for the <91>Server<92> header field. If it contains <93>lighttpd<94>, assume
>   lighttpd, Apache otherwise.
>
>  - Let the user configure which server software he's using.
>
> The two could be combined, of course: Use the user's setting if he has
> given one, (try to) determine the server software automatically if not.
>
> What do you think?
yeah this sounds good. While I thought about parsing the headers
initially but then the server headers can easily be changed, so I
wasn't sure about this approach earlier. Combing this with the user
specified server configuration value seems like the best solution.

Do find the patch attached. I am using st->server_type variable which
will be set to APACHE or LIGHTTPD based on the following logic:
- If the user has specified Server element in the conf file and it is
"apache" or "lighttpd", then set  st->server_type variable
appropriately, otherwise ignore the Server value
- Parse the headers (only if the Server element is NULL or invalid) to
determine the type and set the st->server_type variable accordingly
- if  st->server_type is not set as yet, then default it to apache

Regards
Amit

Signed-off-by: Florian Forster <octo@huhu.verplant.org>

diff --git a/src/apache.c b/src/apache.c
index c11f55d..69633d6 100644 (file)
--- a/src/apache.c
+++ b/src/apache.c
@@ -31,14 +31,16 @@
 
 #include <curl/curl.h>
 
-enum server_type
+enum server_enum
 {
        APACHE = 0,
        LIGHTTPD
 };
 
+
 struct apache_s
 {
+       int server_type;
        char *name;
        char *host;
        char *url;
@@ -47,6 +49,7 @@ struct apache_s
        int   verify_peer;
        int   verify_host;
        char *cacert;
+       char *server; // user specific server type
        char *apache_buffer;
        char apache_curl_error[CURL_ERROR_SIZE];
        size_t apache_buffer_size;
@@ -70,6 +73,7 @@ static void apache_free (apache_t *st)
        sfree (st->user);
        sfree (st->pass);
        sfree (st->cacert);
+       sfree (st->server);
        sfree (st->apache_buffer);
        if (st->curl) {
                curl_easy_cleanup(st->curl);
@@ -116,6 +120,32 @@ static size_t apache_curl_callback (void *buf, size_t size, size_t nmemb,
        return (len);
 } /* int apache_curl_callback */
 
+static size_t apache_header_callback (void *buf, size_t size, size_t nmemb,
+               void *user_data)
+{
+       size_t len = size * nmemb;
+       apache_t *st;
+
+       st = user_data;
+       if (st == NULL)
+       {
+               ERROR ("apache plugin: apache_header_callback: "
+                               "user_data pointer is NULL.");
+               return (0);
+       }
+
+       if (len <= 0)
+               return len;
+
+       // look for the Server header
+       if ((strstr(buf, "Server: ") != NULL) &&
+                       (strstr(buf, "lighttpd") != NULL)) {
+               st->server_type = LIGHTTPD;
+       }
+
+       return len;
+} /* apache_header_callback */
+
 /* Configuration handling functiions
  * <Plugin apache>
  *   <Instance "instance_name">
@@ -241,6 +271,8 @@ static int config_add (oconfig_item_t *ci)
                        status = config_set_boolean (&st->verify_host, child);
                else if (strcasecmp ("CACert", child->key) == 0)
                        status = config_set_string (&st->cacert, child);
+               else if (strcasecmp ("Server", child->key) == 0)
+                       status = config_set_string (&st->server, child);
                else
                {
                        WARNING ("apache plugin: Option `%s' not allowed here.",
@@ -370,6 +402,26 @@ static int init_host (apache_t *st) /* {{{ */
 
        curl_easy_setopt (st->curl, CURLOPT_WRITEFUNCTION, apache_curl_callback);
        curl_easy_setopt (st->curl, CURLOPT_WRITEDATA, st);
+
+       st->server_type = -1; // not set as yet
+       // if the user specified string doesn't match apache or lighttpd, then
+       // ignore it. Headers will be parsed to find out the server type
+       if (st->server != NULL)
+       {
+               if (strcasecmp(st->server, "apache") == 0)
+                       st->server_type = APACHE;
+               else if (strcasecmp(st->server, "lighttpd") == 0)
+                       st->server_type = LIGHTTPD;
+       }
+
+       // if not found register a header callback to determine the
+       // server_type
+       if (st->server_type == -1)
+       {
+               curl_easy_setopt (st->curl, CURLOPT_HEADERFUNCTION, apache_header_callback);
+               curl_easy_setopt (st->curl, CURLOPT_WRITEHEADER, st);
+       }
+
        curl_easy_setopt (st->curl, CURLOPT_USERAGENT, PACKAGE_NAME"/"PACKAGE_VERSION);
        curl_easy_setopt (st->curl, CURLOPT_ERRORBUFFER, st->apache_curl_error);
 
@@ -460,7 +512,7 @@ static void submit_gauge (const char *type, const char *type_instance,
        submit_value (type, type_instance, v, st);
 } /* void submit_gauge */
 
-static void submit_scoreboard (char *buf, int server, apache_t *st)
+static void submit_scoreboard (char *buf, apache_t *st)
 {
        /*
         * Scoreboard Key:
@@ -496,7 +548,6 @@ static void submit_scoreboard (char *buf, int server, apache_t *st)
        long long response_end   = 0LL;
 
        int i;
-
        for (i = 0; buf[i] != '\0'; i++)
        {
                if (buf[i] == '.') open++;
@@ -519,7 +570,7 @@ static void submit_scoreboard (char *buf, int server, apache_t *st)
                else if (buf[i] == 'S') response_end++;
        }
 
-       if (server == APACHE)
+       if (st->server_type == APACHE)
        {
                submit_gauge ("apache_scoreboard", "open"     , open, st);
                submit_gauge ("apache_scoreboard", "waiting"  , waiting, st);
@@ -545,7 +596,6 @@ static void submit_scoreboard (char *buf, int server, apache_t *st)
                submit_gauge ("apache_scoreboard", "request_end"   , request_end, st);
                submit_gauge ("apache_scoreboard", "response_start", response_start, st);
                submit_gauge ("apache_scoreboard", "response_end"  , response_end, st);
-
        }
 }
 
@@ -560,7 +610,6 @@ static int apache_read_host (user_data_t *user_data) /* {{{ */
 
        char *fields[4];
        int   fields_num;
-       int server = LIGHTTPD; /* default is lighttpd */
 
        apache_t *st;
 
@@ -587,6 +636,10 @@ static int apache_read_host (user_data_t *user_data) /* {{{ */
                return (-1);
        }
 
+       // fallback - server_type to apache if not set at this time
+       if (st->server_type == -1)
+               st->server_type = APACHE;
+
        ptr = st->apache_buffer;
        saveptr = NULL;
        while ((lines[lines_num] = strtok_r (ptr, "\n\r", &saveptr)) != NULL)
@@ -615,17 +668,8 @@ static int apache_read_host (user_data_t *user_data) /* {{{ */
                }
                else if (fields_num == 2)
                {
-                       /* find out if the server is apache from the mod_status
-                        * output. apache mod_status output has additional
-                        * fields which lighttpd mod_status output doesn't have
-                        * e.g: ReqPerSec. submit_scoreboard needs server type
-                        * information and thus it is important to pick up a
-                        * field before scoreboard gets parsed to set the
-                        * server type */
-                       if (strcmp (fields[0], "ReqPerSec:") == 0)
-                               server = APACHE;
-                       else if (strcmp (fields[0], "Scoreboard:") == 0)
-                               submit_scoreboard (fields[1], server, st);
+                       if (strcmp (fields[0], "Scoreboard:") == 0)
+                               submit_scoreboard (fields[1], st);
                        else if (strcmp (fields[0], "BusyServers:") == 0)
                                submit_gauge ("apache_connections", NULL, atol (fields[1]), st);
                }