SERVER-22178 Always retry sorted findAndModify upon write conflict.

Previously, if there was a WriteConflictException while actually doing
the update or delete, we would retry the findAndModify, but if the
update or delete stage detected that the document was already deleted
or that it no longer matched the predicate, it would not retry. This
patch ensures the findAndModify will be retried in either of those
scenarios.

jstests/concurrency/fsm_all_sharded_replication.js

@@ -45,9 +45,13 @@ var blacklist = [
     'compact_simultaneous_padding_bytes.js',  // compact can only be run against a mongod
     'convert_to_capped_collection.js',        // convertToCapped can't be run on mongos processes
     'convert_to_capped_collection_index.js',  // convertToCapped can't be run on mongos processes
-    'findAndModify_remove_queue.js',          // remove cannot be {} for findAndModify
-    'findAndModify_update_collscan.js',       // findAndModify requires a shard key
-    'findAndModify_update_queue.js',          // findAndModify requires a shard key
+    'findAndModify_mixed_queue.js',           // findAndModify requires a shard key
+    'findAndModify_mixed_queue_unindexed.js',   // findAndModify requires a shard key
+    'findAndModify_remove_queue.js',            // remove cannot be {} for findAndModify
+    'findAndModify_remove_queue_unindexed.js',  // findAndModify requires a shard key
+    'findAndModify_update_collscan.js',         // findAndModify requires a shard key
+    'findAndModify_update_queue.js',            // findAndModify requires a shard key
+    'findAndModify_update_queue_unindexed.js',  // findAndModify requires a shard key
     'group.js',                // the group command cannot be issued against a sharded cluster
     'group_cond.js',           // the group command cannot be issued against a sharded cluster
     'indexed_insert_eval.js',  // eval doesn't work with sharded collections

jstests/concurrency/fsm_all_sharded_replication_with_balancer.js

@@ -50,9 +50,13 @@ var blacklist = [
     'compact_simultaneous_padding_bytes.js',  // compact can only be run against a mongod
     'convert_to_capped_collection.js',        // convertToCapped can't be run on mongos processes
     'convert_to_capped_collection_index.js',  // convertToCapped can't be run on mongos processes
-    'findAndModify_remove_queue.js',          // remove cannot be {} for findAndModify
-    'findAndModify_update_collscan.js',       // findAndModify requires a shard key
-    'findAndModify_update_queue.js',          // findAndModify requires a shard key
+    'findAndModify_mixed_queue.js',           // findAndModify requires a shard key
+    'findAndModify_mixed_queue_unindexed.js',   // findAndModify requires a shard key
+    'findAndModify_remove_queue.js',            // remove cannot be {} for findAndModify
+    'findAndModify_remove_queue_unindexed.js',  // findAndModify requires a shard key
+    'findAndModify_update_collscan.js',         // findAndModify requires a shard key
+    'findAndModify_update_queue.js',            // findAndModify requires a shard key
+    'findAndModify_update_queue_unindexed.js',  // findAndModify requires a shard key
     'group.js',                // the group command cannot be issued against a sharded cluster
     'group_cond.js',           // the group command cannot be issued against a sharded cluster
     'indexed_insert_eval.js',  // eval doesn't work with sharded collections

jstests/concurrency/fsm_workloads/findAndModify_mixed_queue_unindexed.js

@@ -0,0 +1,96 @@
+'use strict';
+
+/**
+ * findAndModify_mixed_queue_unindexed.js
+ *
+ * This workload is a combination of findAndModify_remove_queue_unindexed.js and
+ * findAndModify_update_queue_unindexed.js.
+ *
+ * Each thread contends on the same document as one another by randomly performing either a
+ * findAndModify update operation or a findAndModify remove operation. The lack of an index that
+ * could satisfy the sort forces the findAndModify operations to scan all the matching documents in
+ * order to find the relevant document. This increases the amount of work each findAndModify
+ * operation has to do before getting to the matching document, and thus increases the chance of a
+ * write conflict because each is trying to update or remove the same document.
+ *
+ * This workload was designed to reproduce SERVER-21434.
+ */
+load('jstests/concurrency/fsm_libs/extend_workload.js');                  // for extendWorkload
+load('jstests/concurrency/fsm_workloads/findAndModify_remove_queue.js');  // for $config
+load('jstests/concurrency/fsm_workload_helpers/server_types.js');         // for isMMAPv1
+
+var $config = extendWorkload(
+    $config,
+    function($config, $super) {
+
+        // Use the workload name as the database name, since the workload name is assumed to be
+        // unique.
+        $config.data.uniqueDBName = 'findAndModify_mixed_queue_unindexed';
+
+        $config.data.newDocForInsert = function newDocForInsert(i) {
+            return {
+                _id: i,
+                rand: Random.rand(),
+                counter: 0
+            };
+        };
+
+        $config.data.getIndexSpecs = function getIndexSpecs() {
+            return [];
+        };
+
+        $config.data.opName = 'modified';
+
+        $config.data.validateResult = function validateResult(db, collName, res) {
+            assertAlways.commandWorked(res);
+
+            var doc = res.value;
+            if (isMongod(db) && !isMMAPv1(db)) {
+                // MMAPv1 does not automatically retry if there was a conflict, so it is expected
+                // that it may return null in the case of a conflict. All other storage engines
+                // should automatically retry the operation, and thus should never return null.
+                assertWhenOwnColl.neq(
+                    doc, null, 'findAndModify should have found a matching document');
+            }
+            if (doc !== null) {
+                this.saveDocId(db, collName, doc._id);
+            }
+        };
+
+        $config.states = (function() {
+            // Avoid removing documents that were already updated.
+            function remove(db, collName) {
+                var res = db.runCommand({
+                    findAndModify: db[collName].getName(),
+                    query: {counter: 0},
+                    sort: {rand: -1},
+                    remove: true
+                });
+                this.validateResult(db, collName, res);
+            }
+
+            function update(db, collName) {
+                // Update the counter field to avoid matching the same document again.
+                var res = db.runCommand({
+                    findAndModify: db[collName].getName(),
+                    query: {counter: 0},
+                    sort: {rand: -1},
+                    update: {$inc: {counter: 1}}, new: false
+                });
+                this.validateResult(db, collName, res);
+            }
+
+            return {
+                remove: remove,
+                update: update,
+            };
+
+        })();
+
+        $config.transitions = {
+            remove: {remove: 0.5, update: 0.5},
+            update: {remove: 0.5, update: 0.5},
+        };
+
+        return $config;
+    });

jstests/concurrency/fsm_workloads/findAndModify_remove_queue.js

@@ -26,10 +26,8 @@ var $config = (function() {
             };
         },
 
-        getIndexSpec: function getIndexSpec() {
-            return {
-                rand: 1
-            };
+        getIndexSpecs: function getIndexSpecs() {
+            return [{rand: 1}];
         },
 
         opName: 'removed',
@@ -114,7 +112,9 @@ var $config = (function() {
         assertAlways.writeOK(res);
         assertAlways.eq(this.numDocs, res.nInserted);
 
-        assertAlways.commandWorked(db[collName].ensureIndex(this.getIndexSpec()));
+        this.getIndexSpecs().forEach(function ensureIndex(indexSpec) {
+            assertAlways.commandWorked(db[collName].ensureIndex(indexSpec));
+        });
     }
 
     function teardown(db, collName, cluster) {
@@ -133,7 +133,7 @@ var $config = (function() {
             }
         }
 
-        assertWhenOwnColl(function() {
+        assertWhenOwnColl(() => {
             var docs = ownedDB[collName].find().toArray();
             var ids = [];
 
@@ -142,7 +142,7 @@ var $config = (function() {
             }
 
             checkForDuplicateIds(ids, this.opName);
-        }.bind(this));
+        });
 
         var res = ownedDB.dropDatabase();
         assertAlways.commandWorked(res);

jstests/concurrency/fsm_workloads/findAndModify_remove_queue_unindexed.js

@@ -0,0 +1,31 @@
+'use strict';
+
+/**
+ * findAndModify_remove_queue_unindexed.js
+ *
+ * This is the same workload as findAndModify_remove_queue.js, but without the relevant index.
+ *
+ * The lack of an index that could satisfy the sort forces the findAndModify operations to scan all
+ * the matching documents in order to find the relevant document. This increases the amount of work
+ * each findAndModify operation has to do before getting to the matching document, and thus
+ * increases the chance of a write conflict because each concurrent findAndModify operation is
+ * trying to remove the same document from the queue.
+ *
+ * This workload was designed to reproduce SERVER-21434.
+ */
+load('jstests/concurrency/fsm_libs/extend_workload.js');                  // for extendWorkload
+load('jstests/concurrency/fsm_workloads/findAndModify_remove_queue.js');  // for $config
+
+var $config = extendWorkload($config,
+                             function($config, $super) {
+
+                                 // Use the workload name as the database name, since the workload
+                                 // name is assumed to be unique.
+                                 $config.data.uniqueDBName = 'findAndModify_remove_queue_unindexed';
+
+                                 $config.data.getIndexSpecs = function getIndexSpecs() {
+                                     return [];
+                                 };
+
+                                 return $config;
+                             });

jstests/concurrency/fsm_workloads/findAndModify_update_queue.js

@@ -31,11 +31,8 @@ var $config = extendWorkload(
             };
         };
 
-        $config.data.getIndexSpec = function getIndexSpec() {
-            return {
-                counter: 1,
-                rand: -1
-            };
+        $config.data.getIndexSpecs = function getIndexSpecs() {
+            return [{counter: 1, rand: -1}];
         };
 
         $config.data.opName = 'updated';

jstests/concurrency/fsm_workloads/findAndModify_update_queue_unindexed.js

@@ -0,0 +1,31 @@
+'use strict';
+
+/**
+ * findAndModify_update_queue_unindexed.js
+ *
+ * This is the same workload as findAndModify_update_queue.js, but without the relevant index.
+ *
+ * The lack of an index that could satisfy the sort forces the findAndModify operations to scan all
+ * the matching documents in order to find the relevant document. This increases the amount of work
+ * each findAndModify operation has to do before getting to the matching document, and thus
+ * increases the chance of a write conflict because each concurrent findAndModify operation is
+ * trying to update the same document from the queue.
+ *
+ * This workload was designed to reproduce SERVER-21434.
+ */
+load('jstests/concurrency/fsm_libs/extend_workload.js');                  // for extendWorkload
+load('jstests/concurrency/fsm_workloads/findAndModify_update_queue.js');  // for $config
+
+var $config = extendWorkload($config,
+                             function($config, $super) {
+
+                                 // Use the workload name as the database name, since the workload
+                                 // name is assumed to be unique.
+                                 $config.data.uniqueDBName = 'findAndModify_update_queue_unindexed';
+
+                                 $config.data.getIndexSpecs = function getIndexSpecs() {
+                                     return [];
+                                 };
+
+                                 return $config;
+                             });

src/mongo/db/exec/SConscript

@@ -77,6 +77,7 @@ env.Library(
         "text_or.cpp",
         "update.cpp",
         "working_set_common.cpp",
+        "write_stage_common.cpp",
     ],
     LIBDEPS = [
         "scoped_timer",