Bug#23921: random failure of user_limits.test

mysqltest disconnect/connect-combo could be so
quick that connect would hit the server before
it had processed the disconnect. Since that
resulted in one more concurrent connection than
we meant to have, global or per-user
max-user-connections could be exceeded.
This could lead to "random" failures in tests
that set those limits.

client/mysqltest.c

@@ -163,6 +163,8 @@ static ulonglong timer_now(void);
 
 static ulonglong progress_start= 0;
 
+static ulong connection_retry_sleep= 100000; /* Microseconds */
+
 /* Precompiled re's */
 static my_regex_t ps_re;     /* the query can be run using PS protocol */
 static my_regex_t sp_re;     /* the query can be run as a SP */
@@ -482,6 +484,9 @@ void replace_dynstr_append(DYNAMIC_STRING *ds, const char *val);
 void replace_dynstr_append_uint(DYNAMIC_STRING *ds, uint val);
 void dynstr_append_sorted(DYNAMIC_STRING* ds, DYNAMIC_STRING* ds_input);
 
+static int match_expected_error(struct st_command *command,
+                                unsigned int err_errno,
+                                const char *err_sqlstate);
 void handle_error(struct st_command*,
                   unsigned int err_errno, const char *err_error,
                   const char *err_sqlstate, DYNAMIC_STRING *ds);
@@ -835,30 +840,26 @@ void check_command_args(struct st_command *command,
   DBUG_VOID_RETURN;
 }
 
-
 void handle_command_error(struct st_command *command, uint error)
 {
   DBUG_ENTER("handle_command_error");
   DBUG_PRINT("enter", ("error: %d", error));
   if (error != 0)
   {
-    uint i;
+    int i;
 
     if (command->abort_on_error)
       die("command \"%.*s\" failed with error %d",
           command->first_word_len, command->query, error);
-    for (i= 0; i < command->expected_errors.count; i++)
-    {
-      DBUG_PRINT("info", ("expected error: %d",
-                          command->expected_errors.err[i].code.errnum));
-      if ((command->expected_errors.err[i].type == ERR_ERRNO) &&
-          (command->expected_errors.err[i].code.errnum == error))
+
+    i= match_expected_error(command, error, NULL);
+
+    if (i >= 0)
     {
       DBUG_PRINT("info", ("command \"%.*s\" failed with expected error: %d",
                           command->first_word_len, command->query, error));
       DBUG_VOID_RETURN;
     }
-    }
     die("command \"%.*s\" failed with wrong error: %d",
         command->first_word_len, command->query, error);
   }
@@ -2452,8 +2453,8 @@ void do_exec(struct st_command *command)
   error= pclose(res_file);
   if (error > 0)
   {
-    uint status= WEXITSTATUS(error), i;
-    my_bool ok= 0;
+    uint status= WEXITSTATUS(error);
+    int i;
 
     if (command->abort_on_error)
     {
@@ -2465,19 +2466,13 @@ void do_exec(struct st_command *command)
 
     DBUG_PRINT("info",
                ("error: %d, status: %d", error, status));
-    for (i= 0; i < command->expected_errors.count; i++)
-    {
-      DBUG_PRINT("info", ("expected error: %d",
-                          command->expected_errors.err[i].code.errnum));
-      if ((command->expected_errors.err[i].type == ERR_ERRNO) &&
-          (command->expected_errors.err[i].code.errnum == status))
-      {
-        ok= 1;
+
+    i= match_expected_error(command, status, NULL);
+
+    if (i >= 0)
       DBUG_PRINT("info", ("command \"%s\" failed with expected error: %d",
                           command->first_argument, status));
-      }
-    }
-    if (!ok)
+    else
     {
       dynstr_free(&ds_cmd);
       die("command \"%s\" failed with wrong error: %d",
@@ -4157,7 +4152,6 @@ void safe_connect(MYSQL* mysql, const char *name, const char *host,
                   int port, const char *sock)
 {
   int failed_attempts= 0;
-  static ulong connection_retry_sleep= 100000; /* Microseconds */
 
   DBUG_ENTER("safe_connect");
   while(!mysql_real_connect(mysql, host,user, pass, db, port, sock,
@@ -4224,6 +4218,7 @@ int connect_n_handle_errors(struct st_command *command,
                             const char* db, int port, const char* sock)
 {
   DYNAMIC_STRING *ds;
+  int failed_attempts= 0;
 
   ds= &ds_res;
 
@@ -4252,9 +4247,41 @@ int connect_n_handle_errors(struct st_command *command,
     dynstr_append_mem(ds, delimiter, delimiter_length);
     dynstr_append_mem(ds, "\n", 1);
   }
-  if (!mysql_real_connect(con, host, user, pass, db, port, sock ? sock: 0,
+  while (!mysql_real_connect(con, host, user, pass, db, port, sock ? sock: 0,
                           CLIENT_MULTI_STATEMENTS))
   {
+    /*
+      If we have used up all our connections check whether this
+      is expected (by --error). If so, handle the error right away.
+      Otherwise, give it some extra time to rule out race-conditions.
+      If extra-time doesn't help, we have an unexpected error and
+      must abort -- just proceeding to handle_error() when second
+      and third chances are used up will handle that for us.
+
+      There are various user-limits of which only max_user_connections
+      and max_connections_per_hour apply at connect time. For the
+      the second to create a race in our logic, we'd need a limits
+      test that runs without a FLUSH for longer than an hour, so we'll
+      stay clear of trying to work out which exact user-limit was
+      exceeded.
+    */
+
+    if (((mysql_errno(con) == ER_TOO_MANY_USER_CONNECTIONS) ||
+         (mysql_errno(con) == ER_USER_LIMIT_REACHED)) &&
+        (failed_attempts++ < opt_max_connect_retries))
+    {
+      int i;
+
+      i= match_expected_error(command, mysql_errno(con), mysql_sqlstate(con));
+
+      if (i >= 0)
+        goto do_handle_error;                 /* expected error, handle */
+
+      my_sleep(connection_retry_sleep);       /* unexpected error, wait */
+      continue;                               /* and give it 1 more chance */
+    }
+
+do_handle_error:
     var_set_errno(mysql_errno(con));
     handle_error(command, mysql_errno(con), mysql_error(con),
 		 mysql_sqlstate(con), ds);
@@ -6015,6 +6042,56 @@ void run_query_normal(struct st_connection *cn, struct st_command *command,
 }
 
 
+/*
+  Check whether given error is in list of expected errors
+
+  SYNOPSIS
+    match_expected_error()
+
+  PARAMETERS
+    command        the current command (and its expect-list)
+    err_errno      error number of the error that actually occurred
+    err_sqlstate   SQL-state that was thrown, or NULL for impossible
+                   (file-ops, diff, etc.)
+
+  RETURNS
+    -1 for not in list, index in list of expected errors otherwise
+
+  NOTE
+    If caller needs to know whether the list was empty, they should
+    check command->expected_errors.count.
+*/
+
+static int match_expected_error(struct st_command *command,
+                                unsigned int err_errno,
+                                const char *err_sqlstate)
+{
+  uint i;
+
+  for (i= 0 ; (uint) i < command->expected_errors.count ; i++)
+  {
+    if ((command->expected_errors.err[i].type == ERR_ERRNO) &&
+        (command->expected_errors.err[i].code.errnum == err_errno))
+      return i;
+
+    if (command->expected_errors.err[i].type == ERR_SQLSTATE)
+    {
+      /*
+        NULL is quite likely, but not in conjunction with a SQL-state expect!
+      */
+      if (unlikely(err_sqlstate == NULL))
+        die("expecting a SQL-state (%s) from query '%s' which cannot produce one...",
+            command->expected_errors.err[i].code.sqlstate, command->query);
+
+      if (strncmp(command->expected_errors.err[i].code.sqlstate,
+                  err_sqlstate, SQLSTATE_LENGTH) == 0)
+        return i;
+    }
+  }
+  return -1;
+}
+
+
 /*
   Handle errors which occurred during execution
 
@@ -6035,7 +6112,7 @@ void handle_error(struct st_command *command,
                   unsigned int err_errno, const char *err_error,
                   const char *err_sqlstate, DYNAMIC_STRING *ds)
 {
-  uint i;
+  int i;
 
   DBUG_ENTER("handle_error");
 
@@ -6061,13 +6138,10 @@ void handle_error(struct st_command *command,
 
   DBUG_PRINT("info", ("expected_errors.count: %d",
                       command->expected_errors.count));
-  for (i= 0 ; (uint) i < command->expected_errors.count ; i++)
-  {
-    if (((command->expected_errors.err[i].type == ERR_ERRNO) &&
-         (command->expected_errors.err[i].code.errnum == err_errno)) ||
-        ((command->expected_errors.err[i].type == ERR_SQLSTATE) &&
-         (strncmp(command->expected_errors.err[i].code.sqlstate,
-                  err_sqlstate, SQLSTATE_LENGTH) == 0)))
+
+  i= match_expected_error(command, err_errno, err_sqlstate);
+
+  if (i >= 0)
   {
     if (!disable_result_log)
     {
@@ -6089,7 +6163,6 @@ void handle_error(struct st_command *command,
     /* OK */
     DBUG_VOID_RETURN;
   }
-  }
 
   DBUG_PRINT("info",("i: %d  expected_errors: %d", i,
                      command->expected_errors.count));
@@ -6103,7 +6176,7 @@ void handle_error(struct st_command *command,
     dynstr_append_mem(ds, "\n", 1);
   }
 
-  if (i)
+  if (command->expected_errors.count > 0)
   {
     if (command->expected_errors.err[0].type == ERR_ERRNO)
       die("query '%s' failed with wrong errno %d: '%s', instead of %d...",

mysql-test/r/mysqltest.result

@@ -14,6 +14,7 @@ select otto from (select 1 as otto) as t1;
 otto
 1
 mysqltest: At line 1: query 'select otto from (select 1 as otto) as t1' succeeded - should have failed with sqlstate 42S22...
+mysqltest: At line 1: expecting a SQL-state (00000) from query 'remove_file /misc/mysql/forest/23921/51-23921/mysql-test/var/tmp/test_nonexistent.tmp' which cannot produce one...
 select friedrich from (select 1 as otto) as t1;
 ERROR 42S22: Unknown column 'friedrich' in 'field list'
 mysqltest: At line 1: query 'select friedrich from (select 1 as otto) as t1' failed with wrong sqlstate 42S22: 'Unknown column 'friedrich' in 'field list'', instead of 00000...

mysql-test/t/disabled.def

@@ -11,7 +11,6 @@
 ##############################################################################
 federated_transactions   : Bug#29523 Transactions do not work
 csv_alter_table      : Bug#33696 2008-01-21 pcrews no .result file - bug allows NULL columns in CSV tables
-user_limits     : Bug#23921 random failure of user_limits.test
 thread_cache_size_func : Bug#36733 main.thread_cache_size_func fails randomly
 binlog_cache_size_basic_32            : Bug #36522: Some tests of system variables have diffs on 64bit platorms
 bulk_insert_buffer_size_basic_32      : Bug #36522: Some tests of system variables have diffs on 64bit platorms

mysql-test/t/mysqltest.test

@@ -91,6 +91,8 @@ select otto from (select 1 as otto) as t1;
 --error 1
 --exec echo "error S42S22; select otto from (select 1 as otto) as t1;" | $MYSQL_TEST  2>&1
 
+--error 1
+--exec echo "error S00000; remove_file $MYSQLTEST_VARDIR/tmp/test_nonexistent.tmp;" | $MYSQL_TEST  2>&1
 
 
 # ----------------------------------------------------------------------------