fix(tcp failure) disabling tcp check on http(s) checks is not allowed

README.md

@@ -106,6 +106,8 @@ Versioning is strictly based on [Semantic Versioning](https://semver.org/)
   and `post_local` won't anymore call `poll` on a running worker automatically,
   for more information, see:
   https://github.com/Kong/lua-resty-worker-events#200-16-september-2020
+* BREAKING: tcp_failures can no longer be 0 on http(s) checks (unless http(s)_failures
+  are also set to 0) [#55](https://github.com/Kong/lua-resty-healthcheck/pull/55)
 * feature: Added support for https_sni [#49](https://github.com/Kong/lua-resty-healthcheck/pull/49)
 * fix: properly log line numbers by using tail calls [#29](https://github.com/Kong/lua-resty-healthcheck/pull/29)
 * fix: when not providing a hostname, use IP [#48](https://github.com/Kong/lua-resty-healthcheck/pull/48)

lib/resty/healthcheck.lua

@@ -1363,6 +1363,22 @@ function _M.new(opts)
   assert(self.checks.passive.unhealthy.http_failures < 255, "checks.passive.unhealthy.http_failures must be at most 254")
   assert(self.checks.passive.unhealthy.timeouts < 255,      "checks.passive.unhealthy.timeouts must be at most 254")
 
+  -- since counter types are independent (tcp failure does not also increment http failure)
+  -- a TCP threshold of 0 is not allowed for enabled http checks.
+  -- It would make tcp failures go unnoticed because the http failure counter is not
+  -- incremented and a tcp threshold of 0 means disabled, and hence it would never trip.
+  -- See https://github.com/Kong/lua-resty-healthcheck/issues/30
+  if self.checks.passive.type == "http" or self.checks.passive.type == "https" then
+    if self.checks.passive.unhealthy.http_failures > 0 then
+      assert(self.checks.passive.unhealthy.tcp_failures > 0, "self.checks.passive.unhealthy.tcp_failures must be >0 for http(s) checks with http_failures >0")
+    end
+  end
+  if self.checks.active.type == "http" or self.checks.active.type == "https" then
+    if self.checks.active.unhealthy.http_failures > 0 then
+      assert(self.checks.active.unhealthy.tcp_failures > 0, "self.checks.active.unhealthy.tcp_failures must be > 0 for http(s) checks with http_failures >0")
+    end
+  end
+
   if opts.test then
     self.test_get_counter = test_get_counter
   end

t/07-report_tcp_failure.t

@@ -130,7 +130,7 @@ qq{
                         unhealthy  = {
                             interval = 999, -- we don't want active checks
                             tcp_failures = 0,
-                            http_failures = 5,
+                            http_failures = 0,
                         }
                     },
                     passive = {
@@ -208,7 +208,7 @@ qq{
                         },
                         unhealthy  = {
                             tcp_failures = 0,
-                            http_failures = 5,
+                            http_failures = 0,
                         }
                     }
                 }