SERVER-21522 Make a copy of the $config before running a workload.

Mutating the "threadCount" property in the ThreadManager is now safe
because subsequent executions of a workload group in the schedule will
use fresh $config objects. The proportion of workloads within the group
will be based off the number of threads initially requested, even if a
previous workload needed to be scaled down.

2 files changed, 18 insertions, 13 deletions

diff --git a/jstests/concurrency/fsm_libs/runner.js b/jstests/concurrency/fsm_libs/runner.js
index cfe61369d8a..b19435d8619 100644
--- a/jstests/concurrency/fsm_libs/runner.js
+++ b/jstests/concurrency/fsm_libs/runner.js
@@ -593,8 +593,18 @@ var runner = (function() {
                         throw new IterationEnd(msg);
                     }
 
+                    // Make a deep copy of the $config object for each of the workloads that are
+                    // going to be run to ensure the workload starts with a fresh version of its
+                    // $config.data. This is necessary because $config.data keeps track of
+                    // thread-local state that may be updated during a workload's setup(),
+                    // teardown(), and state functions.
+                    var groupContext = {};
+                    workloads.forEach(function(workload) {
+                        groupContext[workload] = Object.extend({}, context[workload], true);
+                    });
+
                     // Run the next group of workloads in the schedule.
-                    runWorkloadGroup(threadMgr, workloads, context, cluster, clusterOptions,
+                    runWorkloadGroup(threadMgr, workloads, groupContext, cluster, clusterOptions,
                                      executionMode, executionOptions, errors, maxAllowedThreads);
                 });
             } finally {
diff --git a/jstests/concurrency/fsm_libs/thread_mgr.js b/jstests/concurrency/fsm_libs/thread_mgr.js
index 695a4420e7c..d2a1cb99243 100644
--- a/jstests/concurrency/fsm_libs/thread_mgr.js
+++ b/jstests/concurrency/fsm_libs/thread_mgr.js
@@ -42,7 +42,6 @@ var ThreadManager = function(clusterOptions, executionMode) {
 
     var initialized = false;
     var threads = [];
-    var threadCounts = {};
 
     var _workloads, _context;
 
@@ -59,25 +58,21 @@ var ThreadManager = function(clusterOptions, executionMode) {
                 return 0;
             }
             return Array.sum(workloads.map(function(workload) {
-                return threadCounts[workload];
+                return context[workload].config.threadCount;
             }));
         }
 
-        workloads.forEach(function(workload) {
-            var config = context[workload].config;
-            threadCounts[workload] = config.threadCount;
-        });
-
         var requestedNumThreads = computeNumThreads();
         if (requestedNumThreads > maxAllowedThreads) {
             // Scale down the requested '$config.threadCount' values to make
             // them sum to less than 'maxAllowedThreads'
             var factor = maxAllowedThreads / requestedNumThreads;
             workloads.forEach(function(workload) {
-                var threadCount = threadCounts[workload];
+                var config = context[workload].config;
+                var threadCount = config.threadCount;
                 threadCount = Math.floor(factor * threadCount);
                 threadCount = Math.max(1, threadCount); // ensure workload is executed
-                threadCounts[workload] = threadCount;
+                config.threadCount = threadCount;
             });
         }
 
@@ -104,13 +99,14 @@ var ThreadManager = function(clusterOptions, executionMode) {
         var workloadData = {};
         var tid = 0;
         _workloads.forEach(function(workload) {
-            workloadData[workload] = _context[workload].config.data;
+            var config = _context[workload].config;
+            workloadData[workload] = config.data;
             var workloads = [workload]; // worker thread only needs to load 'workload'
             if (executionMode.composed) {
                 workloads = _workloads; // worker thread needs to load all workloads
             }
 
-            for (var i = 0; i < threadCounts[workload]; ++i) {
+            for (var i = 0; i < config.threadCount; ++i) {
                 var args = {
                     tid: tid++,
                     data: workloadData,
@@ -188,7 +184,6 @@ var ThreadManager = function(clusterOptions, executionMode) {
 
         initialized = false;
         threads = [];
-        threadCounts = {};
 
         return errors;
     };