re-wrote /proc/net/snmp using ARL; added alarm for max TCP connections

conf.d/Makefile.am

@@ -102,6 +102,7 @@ dist_healthconfig_DATA = \
     health.d/softnet.conf \
     health.d/squid.conf \
     health.d/swap.conf \
+    health.d/tcp_conn.conf \
     health.d/tcp_listen.conf \
     health.d/tcp_orphans.conf \
     health.d/tcp_resets.conf \

conf.d/health.d/tcp_conn.conf

@@ -0,0 +1,19 @@
+
+#
+# ${tcp_max_connections} may be nan or -1 if the system
+# supports dynamic threshold for TCP connections.
+# In this case, the alarm will always be zero.
+#
+
+   alarm: tcp_connections
+      on: ipv4.tcpsock
+      os: linux
+   hosts: *
+    calc: (${tcp_max_connections} > 0) ? ( ${connections} * 100 / ${tcp_max_connections} ) : 0
+   units: %
+   every: 10s
+    warn: $this > (($status >= $WARNING ) ? ( 60 ) : ( 80 ))
+    crit: $this > (($status >= $CRITICAL) ? ( 80 ) : ( 90 ))
+   delay: up 0 down 5m multiplier 1.5 max 1h
+    info: the percentage of IPv4 TCP connections over the max allowed
+      to: sysadmin

conf.d/health.d/tcp_orphans.conf

@@ -7,7 +7,7 @@
 # so we alarm warning at 25% and critical at 50%
 #
 
-   alarm: tcp_orphans_percentage
+   alarm: tcp_orphans
       on: ipv4.sockstat_tcp_sockets
       os: linux
    hosts: *
@@ -17,5 +17,5 @@
     warn: $this > (($status >= $WARNING ) ? ( 20 ) : ( 25 ))
     crit: $this > (($status >= $CRITICAL) ? ( 25 ) : ( 50 ))
    delay: up 0 down 5m multiplier 1.5 max 1h
-    info: the percentage of orphan IPv4 TCP sockets over the max allowed (this may lead to out-of-socket-memory errors)
+    info: the percentage of orphan IPv4 TCP sockets over the max allowed (this may lead to too-many-orphans errors)
       to: sysadmin

src/adaptive_resortable_list.c

@@ -2,7 +2,7 @@
 
 // the default processor() of the ARL
 // can be overwritten at arl_create()
-static inline void arl_callback_str2ull(const char *name, uint32_t hash, const char *value, void *dst) {
+inline void arl_callback_str2ull(const char *name, uint32_t hash, const char *value, void *dst) {
     (void)name;
     (void)hash;
 
@@ -11,6 +11,15 @@ static inline void arl_callback_str2ull(const char *name, uint32_t hash, const c
     // fprintf(stderr, "name '%s' with hash %u and value '%s' is %llu\n", name, hash, value, *d);
 }
 
+inline void arl_callback_str2kernel_uint_t(const char *name, uint32_t hash, const char *value, void *dst) {
+    (void)name;
+    (void)hash;
+
+    register kernel_uint_t *d = dst;
+    *d = str2kernel_uint_t(value);
+    // fprintf(stderr, "name '%s' with hash %u and value '%s' is %llu\n", name, hash, value, (unsigned long long)*d);
+}
+
 // create a new ARL
 ARL_BASE *arl_create(const char *name, void (*processor)(const char *, uint32_t, const char *, void *), size_t rechecks) {
     ARL_BASE *base = callocz(1, sizeof(ARL_BASE));

src/adaptive_resortable_list.h

@@ -110,6 +110,9 @@ extern int arl_find_or_create_and_relink(ARL_BASE *base, const char *s, const ch
 // begin an ARL iteration
 extern void arl_begin(ARL_BASE *base);
 
+extern void arl_callback_str2ull(const char *name, uint32_t hash, const char *value, void *dst);
+extern void arl_callback_str2kernel_uint_t(const char *name, uint32_t hash, const char *value, void *dst);
+
 // check a keyword against the ARL
 // this is to be called for each keyword read from source data
 // s = the keyword, as collected