[sr-dev] [kamailio/kamailio] Module snmpstats reporting inconsistent call success metrics on intense peaks of failed calls (Issue #4006)

<!-- Kamailio Project uses GitHub Issues only for bugs in the code or feature requests. Please use this template only for bug reports. If you have questions about using Kamailio or related to its configuration file, ask on sr-users mailing list: * https://lists.kamailio.org/mailman3/postorius/lists/sr-users.lists.kamailio… If you have questions about developing extensions to Kamailio or its existing C code, ask on sr-dev mailing list: * https://lists.kamailio.org/mailman3/postorius/lists/sr-dev.lists.kamailio.o… Please try to fill this template as much as possible for any issue. It helps the developers to troubleshoot the issue. Note that an issue report may be closed automatically after about 2 months if there is no interest from developers or community users on pursuing it, being considered expired. In such case, it can be reopened by writing a comment that includes the token `/notexpired`. About two weeks before considered expired, the issue is marked with the label `stale`, trying to notify the submitter and everyone else that might be interested in it. To remove the label `stale`, write a comment that includes the token `/notstale`. Also, any comment postpone the `expire` timeline, being considered that there is interest in pursuing the issue. If there is no content to be filled in a section, the entire section can be removed. You can delete the comments from the template sections when filling. You can delete next line and everything above before submitting (it is a comment). --> ### Description We are plotting the call success rate on each of our proxies. Using the Kamailio snmpstats module, we try to obtain three counters in order to plot them on a graph: - Total Calls - Active Calls - Error Calls Most of the time, everything works well and we obtain sensible values: `snmpwalk -c mycommunity -v 2c W.X.Y.Z 1.3.6.1.4.1.34352.3.1.3.1.3.2 -O n` .1.3.6.1.4.1.34352.3.1.3.1.3.2.2.0 = Gauge32: 95 -> Active Calls .1.3.6.1.4.1.34352.3.1.3.1.3.2.3.0 = Gauge32: 214 -> Error calls However, **when our proxies are facing intense peaks of failed calls in a short timespan**, sometimes, the **"Error Calls"** counter returns a value **higher than "Total Calls"**. As a result, **"Active Calls"** suddenly reaches a value close to the **maximum of a _Gauge32_** (because ${TotalCalls} - {ErrorCalls} < 0$). `snmpwalk -c mycommunity -v 2c W.X.Y.Z 1.3.6.1.4.1.34352.3.1.3.1.3.2 -O n` .1.3.6.1.4.1.34352.3.1.3.1.3.2.2.0 = Gauge32: 4294967226 -> Active Calls .1.3.6.1.4.1.34352.3.1.3.1.3.2.3.0 = Gauge32: 223 -> Error calls As a result, our graphs make no more sense. ### Troubleshooting There seems to be a bug causing Total calls to be lower than Error calls when a high number of failed calls are received in a short time window. Moreover, there is an integer overflow resulting to the negative result of the substraction being converted to a _Gauge32_. Maybe setting it to 0 in case of a negative result would be safer ? #### Reproduction Using the following configuration for the snmpstats module of your Kamailio proxy: ``` # -------- snmpstats params ------- modparam("snmpstats", "snmpgetPath", "/usr/bin/") modparam("snmpstats", "snmpCommunity", "mycommunity") modparam("snmpstats", "sipEntityType", "proxyServer") ``` On intense peaks of failed calls, get the call success metrics using `snmpwalk` : `snmpwalk -c mycommunity -v 2c W.X.Y.Z 1.3.6.1.4.1.34352.3.1.3.1.3.2 -O n` .1.3.6.1.4.1.34352.3.1.3.1.3.2.2.0 = Gauge32: 4294967226 -> Active Calls .1.3.6.1.4.1.34352.3.1.3.1.3.2.3.0 = Gauge32: 223-> Error calls ### Additional Information **Kamailio Version**: `kamailio -v` flags: USE_TCP, USE_TLS, USE_SCTP, TLS_HOOKS, USE_RAW_SOCKS, DISABLE_NAGLE, USE_ MCAST, DNS_IP_HACK, SHM_MMAP, PKG_MALLOC, Q_MALLOC, F_MALLOC, TLSF_MALLOC, DBG_S R_MEMORY, USE_FUTEX, FAST_LOCK-ADAPTIVE_WAIT, USE_DNS_CACHE, USE_DNS_FAILOVER, U SE_NAPTR, USE_DST_BLOCKLIST, HAVE_RESOLV_RES ADAPTIVE_WAIT_LOOPS 1024, MAX_RECV_BUFFER_SIZE 262144, MAX_URI_SIZE 1024, BUF_SI ZE 65535, DEFAULT PKG_SIZE 64MB poll method support: poll, epoll_lt, epoll_et, sigio_rt, select. id: a004cf compiled on 16:10:41 May 22 2023 with gcc 4.4.7 * **Operating System**: `uname -r` `lsb_release -a` Distributor ID: RedHatEnterpriseServer Description: Red Hat Enterprise Linux Server release 6.3 (Santiago) Release: 6.3 Codename: Santiago -- Reply to this email directly or view it on GitHub: https://github.com/kamailio/kamailio/issues/4006 You are receiving this because you are subscribed to this thread. Message ID: &lt;kamailio/kamailio/issues/4006(a)github.com&gt;