[collectd] [PATCH] Add option to close snmp sessions

[Teet Talviste]

If MaxHostsBCS is defined in snmp plugin config section, and it's less
than host count in the config file, then collectd closes the snmp
session after each read. I'm not sure, if this implementation is the
best, simple boolean would have been maybe simpler to understand.
I would advise setting this to ~900 or less.

Btw. if anyone comes up with better name for MaxHostsBCS (max hosts
before closing sessions), then we should use that, i just didn't have
enought time to dwell on this.
---
 src/snmp.c |   33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/src/snmp.c b/src/snmp.c
index 7a84851..cc6087c 100644
--- a/src/snmp.c
+++ b/src/snmp.c
@@ -97,6 +97,7 @@ typedef struct csnmp_table_values_s csnmp_table_values_t;
  * Private variables
  */
 static data_definition_t *data_head = NULL;
+static int close_host_sessions = 0;
 
 /*
  * Prototypes
@@ -653,6 +654,10 @@ static int csnmp_config (oconfig_item_t *ci)
 {
   int i;
 
+  /* maxhostbcs - close host sessions if hostcount exceeds it */
+  int hostcount = 0;
+  int maxhostbcs = -1;
+
   call_snmp_init_once ();
 
   for (i = 0; i < ci->children_num; i++)
@@ -661,13 +666,38 @@ static int csnmp_config (oconfig_item_t *ci)
     if (strcasecmp ("Data", child->key) == 0)
       csnmp_config_add_data (child);
     else if (strcasecmp ("Host", child->key) == 0)
+    {
       csnmp_config_add_host (child);
+      hostcount++;
+    }
+    else if (strcasecmp ("MaxHostsBCS", child->key) == 0)
+    {
+      if ((child->values_num != 1) || (child->values[0].type != OCONFIG_TYPE_NUMBER))
+      {
+        WARNING ("snmp plugin: The `MaxHostsBCS' option needs "
+                 "exactly one integer argument.");
+        return (-1);
+      }
+      if (child->values[0].type == OCONFIG_TYPE_NUMBER)
+      {
+	maxhostbcs = (int) child->values[0].value.number;
+      }
+    }
     else
     {
       WARNING ("snmp plugin: Ignoring unknown config option `%s'.", child->key);
     }
   } /* for (ci->children) */
 
+  /* set close_host_sessions to 1, this is looked at in csnmp_read_host
+   * and if true, csnmp_host_close_session is called after the read
+   */
+  if (maxhostbcs >= 0 && hostcount > maxhostbcs)
+  {
+    WARNING ("snmp plugin: Enabling maxhostbcs.");
+    close_host_sessions = 1;
+  }
+
   return (0);
 } /* int csnmp_config */
 
@@ -1559,6 +1589,9 @@ static int csnmp_read_host (user_data_t *ud)
 	CDTIME_T_TO_DOUBLE (time_end - time_start));
   }
 
+  if (close_host_sessions)
+    csnmp_host_close_session (host);
+
   if (success == 0)
     return (-1);
 
-- 
1.7.9.4