TS-4747: make marking parent proxies down in hostdb configurable.

doc/admin-guide/files/records.config.en.rst

@@ -1075,6 +1075,15 @@ Parent Proxy Configuration
 
    The timeout value (in seconds) for parent cache connection attempts.
 
+.. ts:cv:: CONFIG proxy.config.http.parent_proxy.mark_down_hostdb INT 0
+   :reloadable:
+   :overridable:
+
+   Enables (``1``) or disables (``0``) marking parent proxies down in hostdb when a connection
+   error is detected.  Normally parent selection manages parent proxies and will mark them as unavailable
+   as needed.  But when parents are defined in dns with multiple ip addresses, it may be useful to mark the
+   failing ip down in hostdb.  In this case you would enable these updates.
+
 .. ts:cv:: CONFIG proxy.config.http.forward.proxy_auth_to_parent INT 0
    :reloadable:
    :overridable:

doc/developer-guide/api/functions/TSHttpOverridableConfig.en.rst

@@ -151,6 +151,7 @@ The following configurations (from ``records.config``) are overridable.
 |   :ts:cv:`proxy.config.http.number_of_redirections`
 |   :ts:cv:`proxy.config.http.cache.max_open_write_retries`
 |   :ts:cv:`proxy.config.http.redirect_use_orig_cache_key`
+|   :ts:cv:`proxy.config.http.parent_proxy.mark_down_hostdb`
 
 Examples
 ========

lib/ts/apidefs.h.in

@@ -681,6 +681,7 @@ typedef enum {
   TS_CONFIG_HTTP_UNCACHEABLE_REQUESTS_BYPASS_PARENT,
   TS_CONFIG_HTTP_PARENT_PROXY_TOTAL_CONNECT_ATTEMPTS,
   TS_CONFIG_HTTP_TRANSACTION_ACTIVE_TIMEOUT_IN,
+  TS_CONFIG_PARENT_FAILURES_UPDATE_HOSTDB,
   TS_CONFIG_LAST_ENTRY
 } TSOverridableConfigKey;
 

mgmt/RecordsConfig.cc

@@ -517,7 +517,9 @@ static const RecordElement RecordsConfig[] =
   ,
   {RECT_CONFIG, "proxy.config.http.parent_proxy.connect_attempts_timeout", RECD_INT, "30", RECU_DYNAMIC, RR_NULL, RECC_NULL, NULL, RECA_NULL}
   ,
-  {RECT_CONFIG, "proxy.config.http.forward.proxy_auth_to_parent", RECD_INT, "0", RECU_DYNAMIC, RR_NULL, RECC_NULL, NULL, RECA_NULL}
+  {RECT_CONFIG, "proxy.config.http.parent_proxy.mark_down_hostdb", RECD_INT, "0", RECU_DYNAMIC, RR_NULL, RECC_INT, "[0-1]", RECA_NULL}
+  ,
+  {RECT_CONFIG, "proxy.config.http.forward.proxy_auth_to_parent", RECD_INT, "0", RECU_DYNAMIC, RR_NULL, RECC_NULL, nullptr, RECA_NULL}
   ,
 
   //        ###################################

plugins/experimental/ts_lua/ts_lua_http_config.c

@@ -120,6 +120,7 @@ typedef enum {
   TS_LUA_CONFIG_HTTP_PARENT_PROXY_TOTAL_CONNECT_ATTEMPTS      = TS_CONFIG_HTTP_PARENT_PROXY_TOTAL_CONNECT_ATTEMPTS,
   TS_LUA_CONFIG_HTTP_TRANSACTION_ACTIVE_TIMEOUT_IN            = TS_CONFIG_HTTP_TRANSACTION_ACTIVE_TIMEOUT_IN,
   TS_LUA_CONFIG_LAST_ENTRY                                    = TS_CONFIG_LAST_ENTRY,
+  TS_LUA_CONFIG_PARENT_FAILURES_UPDATE_HOSTDB                 = TS_CONFIG_PARENT_FAILURES_UPDATE_HOSTDB,
 } TSLuaOverridableConfigKey;
 
 typedef enum {
@@ -230,6 +231,7 @@ ts_lua_var_item ts_lua_http_config_vars[] = {
   TS_LUA_MAKE_VAR_ITEM(TS_LUA_CONFIG_HTTP_UNCACHEABLE_REQUESTS_BYPASS_PARENT),
   TS_LUA_MAKE_VAR_ITEM(TS_LUA_CONFIG_HTTP_PARENT_PROXY_TOTAL_CONNECT_ATTEMPTS),
   TS_LUA_MAKE_VAR_ITEM(TS_LUA_CONFIG_HTTP_TRANSACTION_ACTIVE_TIMEOUT_IN),
+  TS_LUA_MAKE_VAR_ITEM(TS_LUA_CONFIG_PARENT_FAILURES_UPDATE_HOSTDB),
   TS_LUA_MAKE_VAR_ITEM(TS_LUA_CONFIG_LAST_ENTRY),
 };
 

proxy/InkAPI.cc

@@ -7979,6 +7979,9 @@ _conf_to_memberp(TSOverridableConfigKey conf, OverridableHttpConfigParams *overr
     typ = OVERRIDABLE_TYPE_INT;
     ret = &overridableHttpConfig->transaction_active_timeout_in;
     break;
+  case TS_CONFIG_PARENT_FAILURES_UPDATE_HOSTDB:
+    ret = &overridableHttpConfig->parent_failures_update_hostdb;
+    break;
   // This helps avoiding compiler warnings, yet detect unhandled enum members.
   case TS_CONFIG_NULL:
   case TS_CONFIG_LAST_ENTRY:
@@ -8521,6 +8524,11 @@ TSHttpTxnConfigFind(const char *name, int length, TSOverridableConfigKey *conf,
 
   case 47:
     switch (name[length - 1]) {
+    case 'b':
+      if (!strncmp(name, "proxy.config.http.parent_proxy.mark_down_hostdb", length)) {
+        cnf = TS_CONFIG_PARENT_FAILURES_UPDATE_HOSTDB;
+      }
+      break;
     case 'd':
       if (!strncmp(name, "proxy.config.http.negative_revalidating_enabled", length))
         cnf = TS_CONFIG_HTTP_NEGATIVE_REVALIDATING_ENABLED;

proxy/InkAPITest.cc

@@ -7487,6 +7487,7 @@ const char *SDK_Overridable_Configs[TS_CONFIG_LAST_ENTRY] = {
   "proxy.config.http.uncacheable_requests_bypass_parent",
   "proxy.config.http.parent_proxy.total_connect_attempts",
   "proxy.config.http.transaction_active_timeout_in",
+  "proxy.config.http.parent_proxy.mark_down_hostdb",
 };
 
 REGRESSION_TEST(SDK_API_OVERRIDABLE_CONFIGS)(RegressionTest *test, int /* atype ATS_UNUSED */, int *pstatus)

proxy/http/HttpConfig.cc

@@ -959,6 +959,7 @@ HttpConfig::startup()
   HttpEstablishStaticConfigLongLong(c.oride.parent_connect_attempts, "proxy.config.http.parent_proxy.total_connect_attempts");
   HttpEstablishStaticConfigLongLong(c.per_parent_connect_attempts, "proxy.config.http.parent_proxy.per_parent_connect_attempts");
   HttpEstablishStaticConfigLongLong(c.parent_connect_timeout, "proxy.config.http.parent_proxy.connect_attempts_timeout");
+  HttpEstablishStaticConfigByte(c.oride.parent_failures_update_hostdb, "proxy.config.http.parent_proxy.mark_down_hostdb");
 
   HttpEstablishStaticConfigLongLong(c.oride.sock_recv_buffer_size_out, "proxy.config.net.sock_recv_buffer_size_out");
   HttpEstablishStaticConfigLongLong(c.oride.sock_send_buffer_size_out, "proxy.config.net.sock_send_buffer_size_out");
@@ -1232,6 +1233,7 @@ HttpConfig::reconfigure()
   params->oride.parent_connect_attempts                  = m_master.oride.parent_connect_attempts;
   params->per_parent_connect_attempts                    = m_master.per_parent_connect_attempts;
   params->parent_connect_timeout                         = m_master.parent_connect_timeout;
+  params->oride.parent_failures_update_hostdb            = m_master.oride.parent_failures_update_hostdb;
 
   params->oride.sock_recv_buffer_size_out = m_master.oride.sock_recv_buffer_size_out;
   params->oride.sock_send_buffer_size_out = m_master.oride.sock_send_buffer_size_out;

proxy/http/HttpConfig.h

@@ -402,6 +402,7 @@ struct OverridableHttpConfigParams {
       flow_control_enabled(0),
       accept_encoding_filter_enabled(0),
       normalize_ae_gzip(0),
+      parent_failures_update_hostdb(0),
       negative_caching_lifetime(1800),
       negative_revalidating_lifetime(1800),
       sock_recv_buffer_size_out(0),
@@ -555,6 +556,11 @@ struct OverridableHttpConfigParams {
   ////////////////////////////////
   MgmtByte normalize_ae_gzip;
 
+  //////////////////////////
+  // hostdb/dns variables //
+  //////////////////////////
+  MgmtByte parent_failures_update_hostdb;
+
   ////////////////////////////////
   //  Negative cache lifetimes  //
   ////////////////////////////////

proxy/http/HttpTransact.cc

@@ -3603,7 +3603,11 @@ HttpTransact::handle_response_from_parent(State *s)
       ink_assert(s->hdr_info.server_request.valid());
 
       s->current.server->connect_result = ENOTCONN;
-      s->state_machine->do_hostdb_update_if_necessary();
+      // only mark the parent down in hostdb if the configuration allows it,
+      // see proxy.config.http.parent_proxy.mark_down_hostdb in records.config.
+      if (s->txn_conf->parent_failures_update_hostdb) {
+        s->state_machine->do_hostdb_update_if_necessary();
+      }
 
       char addrbuf[INET6_ADDRSTRLEN];
       DebugTxn("http_trans", "[%d] failed to connect to parent %s", s->current.attempts,