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

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

@@ -1273,6 +1273,15 @@ Parent Proxy Configuration
 
    See :ref:`admin-performance-timeouts` for more discussion on |TS| timeouts.
 
+.. 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

@@ -140,6 +140,7 @@ c:member:`TS_CONFIG_HTTP_NUMBER_OF_REDIRECTIONS`                    :ts:cv:`prox
 c:member:`TS_CONFIG_HTTP_ORIGIN_MAX_CONNECTIONS`                    :ts:cv:`proxy.config.http.origin_max_connections`
 c:member:`TS_CONFIG_HTTP_ORIGIN_MAX_CONNECTIONS_QUEUE`              :ts:cv:`proxy.config.http.origin_max_connections_queue`
 c:member:`TS_CONFIG_HTTP_PARENT_PROXY_TOTAL_CONNECT_ATTEMPTS`       :ts:cv:`proxy.config.http.parent_proxy.total_connect_attempts`
+c:member:`TS_CONFIG_PARENT_FAILURES_UPDATE_HOSTDB`                  :ts:cv:`proxy.config.http.parent_proxy.mark_down_hostdb`
 c:member:`TS_CONFIG_HTTP_POST_CHECK_CONTENT_LENGTH_ENABLED`         :ts:cv:`proxy.config.http.post.check.content_length.enabled`
 c:member:`TS_CONFIG_HTTP_POST_CONNECT_ATTEMPTS_TIMEOUT`             :ts:cv:`proxy.config.http.post_connect_attempts_timeout`
 c:member:`TS_CONFIG_HTTP_REDIRECT_USE_ORIG_CACHE_KEY`               :ts:cv:`proxy.config.http.redirect_use_orig_cache_key`

lib/ts/apidefs.h.in

@@ -745,6 +745,7 @@ typedef enum {
   TS_CONFIG_HTTP_FORWARD_CONNECT_METHOD,
   TS_CONFIG_SSL_CERT_FILENAME,
   TS_CONFIG_SSL_CERT_FILEPATH,
+  TS_CONFIG_PARENT_FAILURES_UPDATE_HOSTDB,
   TS_CONFIG_LAST_ENTRY
 } TSOverridableConfigKey;
 

mgmt/RecordsConfig.cc

@@ -518,6 +518,8 @@ static const RecordElement RecordsConfig[] =
   ,
   {RECT_CONFIG, "proxy.config.http.parent_proxy.connect_attempts_timeout", RECD_INT, "30", RECU_DYNAMIC, RR_NULL, RECC_NULL, nullptr, 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

@@ -124,6 +124,7 @@ typedef enum {
   TS_LUA_CONFIG_HTTP_FORWARD_CONNECT_METHOD                   = TS_CONFIG_HTTP_FORWARD_CONNECT_METHOD,
   TS_LUA_CONFIG_SSL_CERT_FILENAME                             = TS_CONFIG_SSL_CERT_FILENAME,
   TS_LUA_CONFIG_SSL_CERT_FILEPATH                             = TS_CONFIG_SSL_CERT_FILEPATH,
+  TS_LUA_CONFIG_PARENT_FAILURES_UPDATE_HOSTDB                 = TS_CONFIG_PARENT_FAILURES_UPDATE_HOSTDB,
 } TSLuaOverridableConfigKey;
 
 typedef enum {
@@ -238,6 +239,7 @@ ts_lua_var_item ts_lua_http_config_vars[] = {
   TS_LUA_MAKE_VAR_ITEM(TS_LUA_CONFIG_HTTP_FORWARD_CONNECT_METHOD),
   TS_LUA_MAKE_VAR_ITEM(TS_LUA_CONFIG_SSL_CERT_FILENAME),
   TS_LUA_MAKE_VAR_ITEM(TS_LUA_CONFIG_SSL_CERT_FILEPATH),
+  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

@@ -8150,6 +8150,9 @@ _conf_to_memberp(TSOverridableConfigKey conf, OverridableHttpConfigParams *overr
     typ = OVERRIDABLE_TYPE_STRING;
     ret = &overridableHttpConfig->client_cert_filepath;
     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:
@@ -8769,6 +8772,11 @@ 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

@@ -7621,6 +7621,7 @@ const char *SDK_Overridable_Configs[TS_CONFIG_LAST_ENTRY] = {
   "proxy.config.http.forward_connect_method",
   "proxy.config.ssl.client.cert.filename",
   "proxy.config.ssl.client.cert.path",
+  "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

@@ -972,6 +972,7 @@ 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");
@@ -1255,6 +1256,7 @@ 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

@@ -410,6 +410,7 @@ struct OverridableHttpConfigParams {
       flow_control_enabled(0),
       normalize_ae_gzip(0),
       srv_enabled(0),
+      parent_failures_update_hostdb(0),
       cache_open_write_fail_action(0),
       post_check_content_length_enabled(1),
       redirection_enabled(0),
@@ -563,6 +564,7 @@ struct OverridableHttpConfigParams {
   // hostdb/dns variables //
   //////////////////////////
   MgmtByte srv_enabled;
+  MgmtByte parent_failures_update_hostdb;
 
   MgmtByte cache_open_write_fail_action;
 

proxy/http/HttpTransact.cc

@@ -3571,7 +3571,11 @@ 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,