Switch back to MySQL-python for CentOS 8.0 and convert to python3 [no…

…n-RocksDB part]

Summary:
In order to get python tests to work in CentOS 8.0:
1. Default `python` has been removed in CentOS 8.0, so all invocations should explicitly call `python2` or `python3`.
2. Switch MySQL-db to PyMySQL: CentOS 8.0 doesn't have MySQLdb-python package available and some MTR tests need it, so I'm switching to PyMySQL (python2-pymysql). Fortunately PyMySQL has a MySQL-db compatible-mode so switching is relatively easy. I've already added necessary packages in sandcastle so that's why the tests are passing there
3. Catch InternalError for ER_DEADLOCK instead of OperationalError: This is a behavioral difference between PyMySQL and MySQL-db. This appears to be fixed in latest PyMySQL but in the current version in CentOS 8.0 it still has that bug and throws InternalError. I've changed the code to expect both.
4. Reduce contention and iterations in certain test cases as PyMySQL is slower
5. Avoid sending super long queries as it'll get truncated in PyMySQL
6. Update CR.* to CR.CR_* as the prefix for CR codes in PyMySQL is CR_ while MySQLdb has no prefix

Porting notes:

Should fix individual tests on the next rebase.

Differential Revision: D20578783

mysql-test/suite/innodb_stress/include/innodb_stress.inc

@@ -39,7 +39,7 @@ if ($do_checksum)
 {
     # populate the table and store its checksum before any load.
     let $exec =
-$PYTHON $MYSQL_TEST_DIR/suite/innodb_stress/t/load_generator.py $pid_file $kill_db_after
+/usr/bin/python3 $MYSQL_TEST_DIR/suite/innodb_stress/t/load_generator.py $pid_file $kill_db_after
 $num_records 0 0 $user $master_host $MASTER_MYPORT
 $table 0 $max_rows $MYSQL_TMP_DIR/load_generator 0 0 0;
     exec $exec >> $MYSQL_TMP_DIR/load_generator/errors.log;
@@ -68,14 +68,14 @@ while ($num_crashes)
   if ($use_blob)
   {
     let $exec =
-$PYTHON $MYSQL_TEST_DIR/suite/innodb_stress/t/load_generator.py $pid_file $kill_db_after
+/usr/bin/python3 $MYSQL_TEST_DIR/suite/innodb_stress/t/load_generator.py $pid_file $kill_db_after
 $num_records  $num_workers $num_transactions $user $master_host $MASTER_MYPORT
 $table 1 $max_rows $MYSQL_TMP_DIR/load_generator 0 $checksum $secondary_index_checks;
   }
   if (!$use_blob)
   {
     let $exec =
-$PYTHON $MYSQL_TEST_DIR/suite/innodb_stress/t/load_generator.py $pid_file $kill_db_after
+/usr/bin/python3 $MYSQL_TEST_DIR/suite/innodb_stress/t/load_generator.py $pid_file $kill_db_after
 $num_records  $num_workers $num_transactions $user $master_host $MASTER_MYPORT
 $table 0 $max_rows $MYSQL_TMP_DIR/load_generator 0 $checksum $secondary_index_checks;
   }
@@ -106,7 +106,7 @@ $table 0 $max_rows $MYSQL_TMP_DIR/load_generator 0 $checksum $secondary_index_ch
     --echo applying fake updates to the slave
     let $slave_pid_file = `SELECT @@pid_file`;
     let $slave_exec =
-$PYTHON $MYSQL_TEST_DIR/suite/innodb_stress/t/load_generator.py $slave_pid_file $kill_db_after
+/usr/bin/python3 $MYSQL_TEST_DIR/suite/innodb_stress/t/load_generator.py $slave_pid_file $kill_db_after
 0  $num_workers $num_transactions $user $master_host $SLAVE_MYPORT
 $table 0 $max_rows $MYSQL_TMP_DIR/load_generator_slave 1 $checksum $secondary_index_checks;
     exec $slave_exec >> $MYSQL_TMP_DIR/load_generator/errors.log;

mysql-test/suite/innodb_stress/t/load_generator.py

@@ -97,6 +97,7 @@ def populate_table(con, num_records_before, do_blob, log):
 
   for i in range(start_id, num_records_before):
       msg = get_msg(do_blob, i)
+      # print("length is %d, complen is %d" % (len(msg), len(zlib.compress(msg, 6))), file=log)
       stmt = """
 INSERT INTO t1(id,msg_prefix,msg,msg_length,msg_checksum) VALUES (%d,'%s','%s',%d,'%s')
 """ % (i+1, msg[0:255], msg, len(msg), sha1(msg))
@@ -223,6 +224,8 @@ def validate_msg(self, msg_prefix, msg, msg_length, msg_checksum, idx):
     prefix_match = msg_prefix == msg[0:255]
 
     checksum = sha1(msg)
+    if type(msg_checksum) == bytes:
+      msg_checksum = msg_checksum.decode('ascii')
     checksum_match = checksum == msg_checksum
 
     len_match = len(msg) == msg_length
@@ -363,6 +366,7 @@ def runme(self):
       except mysql.connector.Error as e:
         if e.args[0] in [2006, 2013, 2055]:  # server is killed
           print("mysqld down, transaction %d" % self.xid)
+          print("mysqld down, transaction %d" % self.xid, file=self.log)
           return
         elif e.args[0] in [1213, 1205]:    # deadlock or lock wait timeout, ignore
           return
@@ -403,7 +407,7 @@ def runme(self):
   server_pid = int(open(pid_file).read())
   log = open('%s/main.log' % LG_TMP_DIR, 'a')
 
-#  print  "kill_db_after = ",kill_db_after," num_records_before = ", \
+#  print( "kill_db_after = ",kill_db_after," num_records_before = ", \)
 #num_records_before, " num_workers= ",num_workers, "num_xactions_per_worker =",\
 #num_xactions_per_worker, "user = ",user, "host =", host,"port = ",port,\
 #" db = ", db, " server_pid = ", server_pid

mysql-test/t/admission_control_multi_query.py

@@ -1,6 +1,7 @@
 import time
 import sys
 import MySQLdb
+from MySQLdb.constants import *
 import argparse
 import random
 import threading

mysql-test/t/admission_control_multi_query.test

@@ -8,7 +8,7 @@ grant all on test.* to test_user@localhost;
 use test_db;
 create table t1 (a int primary key, b int) engine=InnoDB;
 
-let $exec = python $MYSQL_TEST_DIR/t/admission_control_multi_query.py --user='test_user' --host=127.0.0.1 --port=$MASTER_MYPORT --database='test_db';
+let $exec = /usr/bin/python3 $MYSQL_TEST_DIR/t/admission_control_multi_query.py --user='test_user' --host=127.0.0.1 --port=$MASTER_MYPORT --database='test_db';
 exec $exec > $MYSQLTEST_VARDIR/tmp/admission_control_multi_query.output;
 
 drop database test_db;

mysql-test/t/admission_control_multi_query_weighted.test

@@ -8,7 +8,7 @@ grant all on test.* to test_user@localhost;
 use test_db;
 create table t1 (a int primary key, b int) engine=InnoDB;
 
-let $exec = python $MYSQL_TEST_DIR/t/admission_control_multi_query.py --user='test_user' --host=127.0.0.1 --port=$MASTER_MYPORT --database='test_db' --weighted-queues;
+let $exec = /usr/bin/python3 $MYSQL_TEST_DIR/t/admission_control_multi_query.py --user='test_user' --host=127.0.0.1 --port=$MASTER_MYPORT --database='test_db' --weighted-queues;
 exec $exec > $MYSQLTEST_VARDIR/tmp/admission_control_multi_query.output;
 
 drop database test_db;

mysql-test/t/slocket_listen.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/python3
 from socket import socket, AF_UNIX, SOCK_DGRAM
 from select import select
 from os import unlink, getcwd, stat