Agent Module retain variable during calls

[zhjim]

Hi there,

playing around with the module extension of version 2.2 I came upon a strange behaviour I have no idea how to explain. I want to retain the value of a variable through out calls to item retrival. Just incrementing the value in the function and returning that new value. Sometime its all good and the correct value gets returned. Just most of the time the value seems to jump back to an older value and then gets incremented further. Or stays as it for some 2 - 3 calls and then increment.

Is it even possible to retain a value over succesive get item value calls? Do I miss something obvious?
Also the README file in the modules directory of the source put that line to compile the dummy-module.c as

gcc -shared -o dummy.so dummy.c -I../../../include 

I had to use

gcc -fPIC -shared ./simple.c -I../../zabbix-2.2.0/include 

to get the module compiled.

Here goes the code and some explanation what I like to have:
At first I wanted to get the status variables of an apache server. Started out writing a simple socket application that gets and parses the values from the server. I save the variable inside a struct which I refer to over a pointer in the main function. As I did not like to get all the stat vars from the server on every call to the item functions I created a bit mask and only get new values if the same variable is accesed a second time. I then incorperated this into the dummy module and got me two get item value functions. But this did not work out due to the value jumping around (also the pointer to the struct remained constant). I now shrinked the module down to very basic functions. But still the value jumps

#include <stdbool.h>

// defines various includes. Depending on --configure options
// also has include for libcurl
#include "sysinc.h"

// holds the structs for request and response
// as well as result defines
#include "module.h"

// modules.c loads the modules and
// has some infos what is needed for a working module

// variable declaration
static int item_timeout = 0;
static unsigned int req_tot = 0;
static unsigned int uptime = 100;
bool old;

// return value
void debug(char* msg);
int getrtot(char* server);
int getUp(char* server);

// prototypes for key functions
int zbx_module_apache_stats_rtot(AGENT_REQUEST *request, AGENT_RESULT *result);
int zbx_module_apache_stats_up(AGENT_REQUEST *request, AGENT_RESULT *result);

// array with keys of the module
static ZBX_METRIC keys[] =
/* Keyname, flags, function to call, test parameters */
{
        {"apache.status.requests.total", 0, zbx_module_apache_stats_rtot, 0},
        {"apache.status.uptime", 0, zbx_module_apache_stats_up, 0},
        {NULL}
};

// function mandatory (src/libs/zbxmodules/modules.c)
// init function of module
// load config and alike
int zbx_module_init(){
bool okay = false;
char msg[255];
debug("module_init: called\n");

        // Init variables
        req_tot = 0;
        uptime = 100;
        old = true;

        // All good so module can finish loading
        okay = true;

        if ( okay ) {
                return ZBX_MODULE_OK;           // see include/module.h for possible values
        } else {
                return ZBX_MODULE_FAIL;
        }
}
// function mandatory (src/libs/zbxmodules/modules.c
// cleaner
int zbx_module_uninit(){

        return ZBX_MODULE_OK;
}

// function mandatory (src/libs/zbxmodules/modules.c
// return api version of module
int zbx_module_api_version(){
        return ZBX_MODULE_API_VERSION_ONE;
}

// function non-mandatory
// sets timeout of items
void zbx_module_item_timeout(int timeout){
        item_timeout = timeout;
}

// function mandatory (src/libs/zbxmodules/modules.c
// returns list to keys of module
ZBX_METRIC *zbx_module_item_list(){
        return keys;
}

// Structure can be found in include/module.h
// As well as the different return types
// key function

int zbx_module_apache_stats_rtot(AGENT_REQUEST *request, AGENT_RESULT *result){
bool okay = false;
int value;
char *server;
debug("stats_rtot: called\n");

        if ( (value = getrtot(server)) != -1 ){
                debug("stats_rtot: value okay\n");
                okay = true;
                SET_UI64_RESULT(result, value);
        }

        if ( okay ) {
                debug("stats_rtot: return ok\n");
                return SYSINFO_RET_OK;
        } else {
                debug("stats_rtot: return false\n");
                SET_MSG_RESULT(result, strdup("Unkown error"));
                return SYSINFO_RET_FAIL;
        }
}
int zbx_module_apache_stats_up(AGENT_REQUEST *request, AGENT_RESULT *result){
bool okay = false;
int value;
char *server;
debug("stats_up: called\n");

        if ( (value = getUp(server)) != -1 ){
                debug("stats_up: value okay\n");
                okay = true;
                SET_UI64_RESULT(result, value);
        }

        if ( okay ) {
                debug("stats_up: return ok\n");
                return SYSINFO_RET_OK;
        } else {
                debug("stats_up: return false\n");
                SET_MSG_RESULT(result, strdup("Unkown error"));
                return SYSINFO_RET_FAIL;
        }
}


void debug(char* msg){
FILE *debug = fopen( "/tmp/apache.so.log", "a");

        fprintf(debug, "%s", msg);
        fclose(debug);

}

// Parses lines of status page and puts in struct apstat
//
// returns 0 on success
// returns 1 on parse error
int getrtot(char* server){
char msg[255];
sprintf(msg, "rtot: start: old =  %d, req_tot = %d\n", old, req_tot);
debug(msg);

        // Check if we need new values
        if ( old ){
                debug("new values\n");
                req_tot++;
                uptime+=100;
        }

        // set Flag
        old  = true;

sprintf(msg, "rtot: end: old =  %d, req_tot = %d\n", old, req_tot);
debug(msg);

        return req_tot;
}


int getUp(char* server){
char msg[255];
sprintf(msg, "UP: old = %d, uptime = %d\n", old, uptime);
debug(msg);

        return uptime;

} 

[zhjim]

I found out what the problem with the approach I'm taking is. Its the threads. In default configuration you have 3 agent threads running and each of them gets called in turn. So the initial values are set on all 3 threads. Then I ask for my item and thread one answers it and has its value set to the new values. Next time I ask its thread 2 turn but he has the initial values from module load so he returns those and not the values I expected.

If one would only use one agent thread it all goes well. At least it did with my tests.

Is there anyway to have the threads refer to the same variables? I guess this would be a change either to how modules are loaded or how the threads get created.