WT-5675 Prepare support workgen changes (#5453)

* WT-5675 Prepare support workgen changes
*  Encapsulated timestamps to use epoch time
* Added oldest, stable timestamps to move forward periodically
* Moved irrelevant functions from Workload to WorkloadRunner class
* Renamed _transaction to transaction in all related files

bench/workgen/runner/example_prepare.py

@@ -0,0 +1,78 @@
+#!/usr/bin/env python
+#
+# Public Domain 2014-2020 MongoDB, Inc.
+# Public Domain 2008-2014 WiredTiger, Inc.
+#
+# This is free and unencumbered software released into the public domain.
+#
+# Anyone is free to copy, modify, publish, use, compile, sell, or
+# distribute this software, either in source code form or as a compiled
+# binary, for any purpose, commercial or non-commercial, and by any
+# means.
+#
+# In jurisdictions that recognize copyright laws, the author or authors
+# of this software dedicate any and all copyright interest in the
+# software to the public domain. We make this dedication for the benefit
+# of the public at large and to the detriment of our heirs and
+# successors. We intend this dedication to be an overt act of
+# relinquishment in perpetuity of all present and future rights to this
+# software under copyright law.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+# IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
+# OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+# ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+# OTHER DEALINGS IN THE SOFTWARE.
+#
+
+from runner import *
+from wiredtiger import *
+from workgen import *
+
+conn = wiredtiger_open("WT_TEST", "create,cache_size=500MB")
+s = conn.open_session()
+tname = "table:test"
+config = "key_format=S,value_format=S,"
+s.create(tname, config)
+table = Table(tname)
+table.options.key_size = 20
+table.options.value_size = 10
+
+context = Context()
+op = Operation(Operation.OP_INSERT, table)
+thread = Thread(op * 5000)
+pop_workload = Workload(context, thread)
+print('populate:')
+pop_workload.run(conn)
+
+opread = Operation(Operation.OP_SEARCH, table)
+read_txn = txn(opread * 10, 'read_timestamp')
+# read_timestamp_lag is the lag to the read_timestamp from current time
+read_txn.transaction.read_timestamp_lag = 5
+treader = Thread(read_txn)
+
+opwrite = Operation(Operation.OP_INSERT, table)
+write_txn = txn(opwrite * 10, 'isolation=snapshot')
+# use_prepare_timestamp - Commit the transaction with stable_timestamp.
+write_txn.transaction.use_prepare_timestamp = True
+twriter = Thread(write_txn)
+
+opupdate = Operation(Operation.OP_UPDATE, table)
+update_txn = txn(opupdate * 10, 'isolation=snapshot')
+# use_commit_timestamp - Commit the transaction with commit_timestamp.
+update_txn.transaction.use_commit_timestamp = True
+tupdate = Thread(update_txn)
+
+workload = Workload(context, 10 * twriter + 10 * tupdate + 10 * treader)
+workload.options.run_time = 50
+workload.options.report_interval=500
+# read_timestamp_lag - Number of seconds lag to the oldest_timestamp from current time.
+workload.options.oldest_timestamp_lag=30
+# read_timestamp_lag - Number of seconds lag to the stable_timestamp from current time.
+workload.options.stable_timestamp_lag=10
+# timestamp_advance is the number of seconds to wait before moving oldest and stable timestamp.
+workload.options.timestamp_advance=1
+print('transactional prepare workload:')
+workload.run(conn)

bench/workgen/runner/runner/core.py

@@ -35,7 +35,7 @@
 #   Put the operation (and any suboperations) within a transaction.
 def txn(op, config=None):
     t = Transaction(config)
-    op._transaction = t
+    op.transaction = t
     return op
 
 # sleep --
@@ -301,7 +301,7 @@ def _op_transaction_list(oplist, txn_config):
 def op_group_transaction(ops_arg, ops_per_txn, txn_config):
     if ops_arg != Operation.OP_NONE:
         return txn(ops_arg, txn_config)
-    if ops_arg._transaction != None:
+    if ops_arg.transaction != None:
         raise Exception('nested transactions not supported')
     if ops_arg._repeatgroup != None:
         raise Exception('grouping transactions with multipliers not supported')