SNMP statistic module, interprocess buffer. More...

#include "../../str.h"
#include "../../locking.h"
#include "snmpstats_globals.h"
#include "hashTable.h"
#include "../usrloc/ucontact.h"

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Functions

void consumeInterprocessBuffer (void)
Interprocess Buffer consumption Function.
void handleContactCallbacks (ucontact_t *contactInfo, int type, void *param)
USRLOC Callback Handler:
int initInterprocessBuffers (void)
Initialize shared memory used to buffer communication between the usrloc module and the SNMPStats module.

Variables

interprocessBuffer_t * frontRegUserTableBuffer
All interprocess communication is stored between these two declarations.
hashSlot_t * hashTable
The hash table:
gen_lock_t * interprocessCBLock
This is to protect the potential racecondition in which a command is added to the buffer while it is being consumed.

Detailed Description

The SNMPStats module exposes user information through openserSIPRegUserTable, openserSIPContactTable, and openserSIPRegUserLookupTable. These tables are populated through callback mechanisms from the usrloc module. Unfortunately the NetSNMP table population code is very slow when dealing with large amounts of data. Because we don't want to experience a performance hit when registering users, we make use of the interprocess buffer. Specifically, instead of adding/removing users/contacts from the SNMP tables directly, the callbacks add an add/delete command to the interprocessBuffer.

When an snmp request is recieved by the SNMPStats sub-process, it will consume this interprocess buffer, adding and deleting users. When it is finished, it can service the SNMP request.

This doesn't remove the NetSNMP inefficiency of course, but it does move it to a non-critical path. Such an approach allows SNMP support with almost no overhead to the rest of the server.

Module: SNMPSTATS :: The Kamailio snmpstats Module

Definition in file interprocess_buffer.h.

Function Documentation

void consumeInterprocessBuffer ( void )

This function will iterate over every element of the interprocess buffer, and add or remove the specified contacts and users. Whether the contacts are added or removed is dependent on if the original element was added as a result of a UL_CONTACT_INSERT or UL_CONTACT_EXPIRE callback.

The function will free any memory occupied by the interprocess buffer.

Note:: This function is believed to be thread safe. Specifically, it protects corruption of the interprocess buffer through the interprocessCBLock. This ensures no corruption of the buffer by race conditions. The lock has been designed to be occupied for as short a period as possible, so as to prevent long waits. Specifically, once we start consumption of the list, other processes are free to continue even before we are done. This is made possible by simply changing the head of the interprocess buffer, and then releasing the lock.

Definition at line 219 of file interprocess_buffer.c.

References executeInterprocessBufferCmd(), frontRegUserTableBuffer, and interprocessCBLock.

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void handleContactCallbacks	(	ucontact_t *	contactInfo,
		int	type,
		void *	param
	)

This function should be registered to receive callbacks from the usrloc module. It can be called for any of the callbacks listed in ul_callback.h. The callback type will be passed in 'type', and the contact the callback applies to will be supplied in 'contactInfo. This information will be copied into the interprocess buffer. The interprocess buffer will be consumed at a later time, when consumeInterprocessBuffer() is called.

This callback is thread safe with respect to the consumeInterprocessBuffer() function. Specifically, the interprocess buffer should not be corrupted by any race conditions between this function and the consumeInterprocessBuffer() function.

Definition at line 147 of file interprocess_buffer.c.

References ucontact::aor, ucontact::c, contact, convertStrToCharString(), frontRegUserTableBuffer, interprocessCBLock, ucontact::next, and _str::s.

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