SERVER-46686 Explain does not respect maxTimeMS

(cherry picked from commit 8147d05d7038c6bf08a0b523fd69a44c13553cf1)
(cherry picked from commit a221c9d0afcbb52d01bd00d80ca1120efa470a58)

3 files changed, 92 insertions, 3 deletions

diff --git a/jstests/noPassthrough/explain_max_time_ms.js b/jstests/noPassthrough/explain_max_time_ms.js
new file mode 100644
index 00000000000..f9cc72d2da8
--- /dev/null
+++ b/jstests/noPassthrough/explain_max_time_ms.js
@@ -0,0 +1,71 @@
+/**
+ * Tests the explain command with the maxTimeMS option.
+ */
+(function() {
+    "use strict";
+
+    const standalone = MongoRunner.runMongod();
+    assert.neq(null, standalone, "mongod was unable to start up");
+
+    const dbName = "test";
+    const db = standalone.getDB(dbName);
+    const collName = "explain_max_time_ms";
+    const coll = db.getCollection(collName);
+
+    const destCollName = "explain_max_time_ms_dest";
+    const mapFn = function() {
+        emit(this.i, this.j);
+    };
+    const reduceFn = function(key, values) {
+        return Array.sum(values);
+    };
+
+    coll.drop();
+    assert.commandWorked(db.createCollection(collName));
+
+    assert.writeOK(coll.insert({i: 1, j: 1}));
+    assert.writeOK(coll.insert({i: 2, j: 1}));
+    assert.writeOK(coll.insert({i: 2, j: 2}));
+
+    // Set fail point to make sure operations with "maxTimeMS" set will time out.
+    assert.commandWorked(
+        db.adminCommand({configureFailPoint: "maxTimeAlwaysTimeOut", mode: "alwaysOn"}));
+
+    for (let verbosity of["executionStats", "allPlansExecution"]) {
+        // Expect explain to time out if "maxTimeMS" is set on the aggregate command.
+        assert.commandFailedWithCode(assert.throws(function() {
+            coll.explain(verbosity).aggregate([{$match: {i: 1}}], {maxTimeMS: 1});
+        }),
+                                     ErrorCodes.ExceededTimeLimit);
+        // Expect explain to time out if "maxTimeMS" is set on the count command.
+        assert.commandFailedWithCode(assert.throws(function() {
+            coll.explain(verbosity).count({i: 1}, {maxTimeMS: 1});
+        }),
+                                     ErrorCodes.ExceededTimeLimit);
+        // Expect explain to time out if "maxTimeMS" is set on the distinct command.
+        assert.commandFailedWithCode(assert.throws(function() {
+            coll.explain(verbosity).distinct("i", {}, {maxTimeMS: 1});
+        }),
+                                     ErrorCodes.ExceededTimeLimit);
+        // Expect explain to time out if "maxTimeMS" is set on the find command.
+        assert.commandFailedWithCode(assert.throws(function() {
+            coll.find().maxTimeMS(1).explain(verbosity);
+        }),
+                                     ErrorCodes.ExceededTimeLimit);
+        assert.commandFailedWithCode(assert.throws(function() {
+            coll.explain(verbosity).find().maxTimeMS(1).finish();
+        }),
+                                     ErrorCodes.ExceededTimeLimit);
+        // Expect explain to time out if "maxTimeMS" is set on the findAndModify command.
+        assert.commandFailedWithCode(assert.throws(function() {
+            coll.explain(verbosity).findAndModify({update: {$inc: {j: 1}}, maxTimeMS: 1});
+        }),
+                                     ErrorCodes.ExceededTimeLimit);
+    }
+
+    // Disable fail point.
+    assert.commandWorked(
+        db.adminCommand({configureFailPoint: "maxTimeAlwaysTimeOut", mode: "off"}));
+
+    MongoRunner.stopMongod(standalone);
+})();
diff --git a/src/mongo/shell/explain_query.js b/src/mongo/shell/explain_query.js
index 0670734891e..ddf97698984 100644
--- a/src/mongo/shell/explain_query.js
+++ b/src/mongo/shell/explain_query.js
@@ -152,6 +152,11 @@ var DBExplainQuery = (function() {
 
                 var explainCmd = {explain: innerCmd};
                 explainCmd["verbosity"] = this._verbosity;
+                // If "maxTimeMS" is set on innerCmd, it needs to be propagated to the top-level
+                // of explainCmd so that it has the intended effect.
+                if (innerCmd.hasOwnProperty("maxTimeMS")) {
+                    explainCmd.maxTimeMS = innerCmd.maxTimeMS;
+                }
 
                 var explainDb = this._query._db;
 
diff --git a/src/mongo/shell/explainable.js b/src/mongo/shell/explainable.js
index da130b9b13c..ba69f77ce63 100644
--- a/src/mongo/shell/explainable.js
+++ b/src/mongo/shell/explainable.js
@@ -28,6 +28,16 @@ var Explainable = (function() {
         return explainResult;
     };
 
+    var buildExplainCmd = function(innerCmd, verbosity) {
+        var explainCmd = {"explain": innerCmd, "verbosity": verbosity};
+        // If "maxTimeMS" is set on innerCmd, it needs to be propagated to the top-level
+        // of explainCmd so that it has the intended effect.
+        if (innerCmd.hasOwnProperty("maxTimeMS")) {
+            explainCmd.maxTimeMS = innerCmd.maxTimeMS;
+        }
+        return explainCmd;
+    };
+
     function constructor(collection, verbosity) {
         //
         // Private vars.
@@ -110,7 +120,7 @@ var Explainable = (function() {
 
                 let aggCmd = Object.extend(
                     {"aggregate": this._collection.getName(), "pipeline": pipeline}, extraOpts);
-                let explainCmd = {"explain": aggCmd, "verbosity": this._verbosity};
+                let explainCmd = buildExplainCmd(aggCmd, this._verbosity);
                 let explainResult = this._collection.runReadCommand(explainCmd);
                 return throwOrReturn(explainResult);
             }
@@ -133,7 +143,7 @@ var Explainable = (function() {
 
         this.findAndModify = function(params) {
             var famCmd = Object.extend({"findAndModify": this._collection.getName()}, params);
-            var explainCmd = {"explain": famCmd, "verbosity": this._verbosity};
+            var explainCmd = buildExplainCmd(famCmd, this._verbosity);
             var explainResult = this._collection.runReadCommand(explainCmd);
             return throwOrReturn(explainResult);
         };
@@ -156,8 +166,11 @@ var Explainable = (function() {
             if (options && options.hasOwnProperty("collation")) {
                 distinctCmd.collation = options.collation;
             }
+            if (options && options.hasOwnProperty("maxTimeMS")) {
+                distinctCmd.maxTimeMS = options.maxTimeMS;
+            }
 
-            var explainCmd = {explain: distinctCmd, verbosity: this._verbosity};
+            var explainCmd = buildExplainCmd(distinctCmd, this._verbosity);
             var explainResult = this._collection.runReadCommand(explainCmd);
             return throwOrReturn(explainResult);
         };