SERVER-49986 Convert isMaster command to hello and keep isMaster, ismaster aliases

15 files changed, 163 insertions, 102 deletions

diff --git a/jstests/core/ismaster.js b/jstests/core/ismaster.js
index a29be88331c..3a0d55324c0 100644
--- a/jstests/core/ismaster.js
+++ b/jstests/core/ismaster.js
@@ -1,45 +1,62 @@
+/**
+ * This test ensures that the hello command and its aliases, ismaster and isMaster, are all
+ * accepted.
+ * @tags: [requires_fcv_47]
+ */
 "use strict";
-var res = db.isMaster();
-// check that the fields that should be there are there and have proper values
-assert(res.maxBsonObjectSize && isNumber(res.maxBsonObjectSize) && res.maxBsonObjectSize > 0,
-       "maxBsonObjectSize possibly missing:" + tojson(res));
-assert(res.maxMessageSizeBytes && isNumber(res.maxMessageSizeBytes) && res.maxBsonObjectSize > 0,
-       "maxMessageSizeBytes possibly missing:" + tojson(res));
-assert(res.maxWriteBatchSize && isNumber(res.maxWriteBatchSize) && res.maxWriteBatchSize > 0,
-       "maxWriteBatchSize possibly missing:" + tojson(res));
-assert.eq("boolean", typeof res.ismaster, "ismaster field is not a boolean" + tojson(res));
-assert(res.ismaster === true, "ismaster field is false" + tojson(res));
-assert(res.localTime, "localTime possibly missing:" + tojson(res));
-assert(res.connectionId, "connectionId missing or false" + tojson(res));
 
-if (!testingReplication) {
-    var badFields = [];
-    var unwantedReplSetFields = [
-        "setName",
-        "setVersion",
-        "secondary",
-        "hosts",
-        "passives",
-        "arbiters",
-        "primary",
-        "aribterOnly",
-        "passive",
-        "slaveDelay",
-        "hidden",
-        "tags",
-        "buildIndexes",
-        "me"
-    ];
-    var field;
-    // check that the fields that shouldn't be there are not there
-    for (field in res) {
-        if (!res.hasOwnProperty(field)) {
-            continue;
-        }
-        if (Array.contains(unwantedReplSetFields, field)) {
-            badFields.push(field);
+function checkResponseFields(commandString) {
+    var res = db.runCommand(commandString);
+    // check that the fields that should be there are there and have proper values
+    assert(res.maxBsonObjectSize && isNumber(res.maxBsonObjectSize) && res.maxBsonObjectSize > 0,
+           "maxBsonObjectSize possibly missing:" + tojson(res));
+    assert(
+        res.maxMessageSizeBytes && isNumber(res.maxMessageSizeBytes) && res.maxBsonObjectSize > 0,
+        "maxMessageSizeBytes possibly missing:" + tojson(res));
+    assert(res.maxWriteBatchSize && isNumber(res.maxWriteBatchSize) && res.maxWriteBatchSize > 0,
+           "maxWriteBatchSize possibly missing:" + tojson(res));
+    assert.eq("boolean", typeof res.ismaster, "ismaster field is not a boolean" + tojson(res));
+
+    // TODO SERVER-49988: Check for res.isWritablePrimary instead of res.ismaster if a hello command
+    // was executed.
+    assert(res.ismaster === true, "ismaster field is false" + tojson(res));
+    assert(res.localTime, "localTime possibly missing:" + tojson(res));
+    assert(res.connectionId, "connectionId missing or false" + tojson(res));
+
+    if (!testingReplication) {
+        var badFields = [];
+        var unwantedReplSetFields = [
+            "setName",
+            "setVersion",
+            "secondary",
+            "hosts",
+            "passives",
+            "arbiters",
+            "primary",
+            "aribterOnly",
+            "passive",
+            "slaveDelay",
+            "hidden",
+            "tags",
+            "buildIndexes",
+            "me"
+        ];
+        var field;
+        // check that the fields that shouldn't be there are not there
+        for (field in res) {
+            if (!res.hasOwnProperty(field)) {
+                continue;
+            }
+            if (Array.contains(unwantedReplSetFields, field)) {
+                badFields.push(field);
+            }
         }
+        assert(
+            badFields.length === 0,
+            "\nthe result:\n" + tojson(res) + "\ncontained fields it shouldn't have: " + badFields);
     }
-    assert(badFields.length === 0,
-           "\nthe result:\n" + tojson(res) + "\ncontained fields it shouldn't have: " + badFields);
 }
+
+checkResponseFields("hello");
+checkResponseFields("ismaster");
+checkResponseFields("isMaster");
diff --git a/jstests/core/list_commands.js b/jstests/core/list_commands.js
index 6e63c179dfb..05c83db2b1f 100644
--- a/jstests/core/list_commands.js
+++ b/jstests/core/list_commands.js
@@ -22,19 +22,19 @@ assert(isSorted(commands));
 
 // Test that result contains basic commands.
 assert(commands.hasOwnProperty("commands"));
-assert(commands["commands"].hasOwnProperty("isMaster"));
+assert(commands["commands"].hasOwnProperty("hello"));
 assert(commands["commands"].hasOwnProperty("insert"));
 assert(commands["commands"].hasOwnProperty("ping"));
 
 // Test that commands listed have required properties
-const isMaster = commands["commands"]["isMaster"];
-assert(isMaster.hasOwnProperty("help"));
-assert(isMaster.hasOwnProperty("slaveOk"));
-assert(isMaster.hasOwnProperty("adminOnly"));
-assert(isMaster.hasOwnProperty("requiresAuth"));
+const hello = commands["commands"]["hello"];
+assert(hello.hasOwnProperty("help"));
+assert(hello.hasOwnProperty("slaveOk"));
+assert(hello.hasOwnProperty("adminOnly"));
+assert(hello.hasOwnProperty("requiresAuth"));
 
 // Test that requiresAuth outputs correct value
 const insert = commands["commands"]["insert"];
-assert(isMaster["requiresAuth"] === false);
+assert(hello["requiresAuth"] === false);
 assert(insert["requiresAuth"] === true);
 })();
diff --git a/jstests/core/views/views_all_commands.js b/jstests/core/views/views_all_commands.js
index 57344485f8c..6623b5b8c0d 100644
--- a/jstests/core/views/views_all_commands.js
+++ b/jstests/core/views/views_all_commands.js
@@ -7,6 +7,7 @@
 //   requires_non_retryable_commands,
 //   requires_non_retryable_writes,
 //   uses_map_reduce_with_temp_collections,
+//   requires_fcv_47,
 // ]
 
 /*
@@ -333,13 +334,13 @@ let viewsCommandTests = {
     grantRolesToRole: {skip: isUnrelated},
     grantRolesToUser: {skip: isUnrelated},
     handshake: {skip: isUnrelated},
+    hello: {skip: isUnrelated},
     hostInfo: {skip: isUnrelated},
     httpClientRequest: {skip: isAnInternalCommand},
     insert: {command: {insert: "view", documents: [{x: 1}]}, expectFailure: true},
     internalRenameIfOptionsAndIndexesMatch: {skip: isAnInternalCommand},
     invalidateUserCache: {skip: isUnrelated},
     isdbgrid: {skip: isUnrelated},
-    isMaster: {skip: isUnrelated},
     killCursors: {
         setup: function(conn) {
             assert.commandWorked(conn.collection.remove({}));
diff --git a/jstests/replsets/db_reads_while_recovering_all_commands.js b/jstests/replsets/db_reads_while_recovering_all_commands.js
index 6670bc1458c..3199178f16b 100644
--- a/jstests/replsets/db_reads_while_recovering_all_commands.js
+++ b/jstests/replsets/db_reads_while_recovering_all_commands.js
@@ -188,12 +188,12 @@ const allCommands = {
     grantPrivilegesToRole: {skip: isPrimaryOnly},
     grantRolesToRole: {skip: isPrimaryOnly},
     grantRolesToUser: {skip: isPrimaryOnly},
+    hello: {skip: isNotAUserDataRead},
     hostInfo: {skip: isNotAUserDataRead},
     httpClientRequest: {skip: isNotAUserDataRead},
     insert: {skip: isPrimaryOnly},
     internalRenameIfOptionsAndIndexesMatch: {skip: isAnInternalCommand},
     invalidateUserCache: {skip: isNotAUserDataRead},
-    isMaster: {skip: isNotAUserDataRead},
     killAllSessions: {skip: isNotAUserDataRead},
     killAllSessionsByPattern: {skip: isNotAUserDataRead},
     killCursors: {skip: isNotAUserDataRead},
diff --git a/jstests/replsets/writes_during_tenant_migration.js b/jstests/replsets/writes_during_tenant_migration.js
index b9a48af39ba..f6dfe5a686c 100644
--- a/jstests/replsets/writes_during_tenant_migration.js
+++ b/jstests/replsets/writes_during_tenant_migration.js
@@ -663,6 +663,7 @@ const testCases = {
     grantPrivilegesToRole: {skip: isAuthCommand},
     grantRolesToRole: {skip: isAuthCommand},
     grantRolesToUser: {skip: isAuthCommand},
+    hello: {skip: isNotRunOnUserDatabase},
     hostInfo: {skip: isNotRunOnUserDatabase},
     httpClientRequest: {skip: isNotRunOnUserDatabase},
     insert: {
@@ -681,7 +682,6 @@ const testCases = {
     },
     internalRenameIfOptionsAndIndexesMatch: {skip: isNotRunOnUserDatabase},
     invalidateUserCache: {skip: isNotRunOnUserDatabase},
-    isMaster: {skip: isNotRunOnUserDatabase},
     killAllSessions: {skip: isNotRunOnUserDatabase},
     killAllSessionsByPattern: {skip: isNotRunOnUserDatabase},
     killCursors: {skip: isNotWriteCommand},
diff --git a/jstests/sharding/database_versioning_all_commands.js b/jstests/sharding/database_versioning_all_commands.js
index bf7fba3a2ca..804da523ba1 100644
--- a/jstests/sharding/database_versioning_all_commands.js
+++ b/jstests/sharding/database_versioning_all_commands.js
@@ -1,6 +1,7 @@
 /**
  * Specifies for each command whether it is expected to send a databaseVersion, and verifies that
  * the commands match the specification.
+ * @tags: [requires_fcv_47]
  */
 (function() {
 'use strict';
@@ -451,6 +452,7 @@ let testCases = {
     grantPrivilegesToRole: {skip: "always targets the config server"},
     grantRolesToRole: {skip: "always targets the config server"},
     grantRolesToUser: {skip: "always targets the config server"},
+    hello: {skip: "executes locally on mongos (not sent to any remote node)"},
     hostInfo: {skip: "executes locally on mongos (not sent to any remote node)"},
     insert: {
         run: {
@@ -462,7 +464,6 @@ let testCases = {
     },
     invalidateUserCache: {skip: "executes locally on mongos (not sent to any remote node)"},
     isdbgrid: {skip: "executes locally on mongos (not sent to any remote node)"},
-    isMaster: {skip: "executes locally on mongos (not sent to any remote node)"},
     killCursors: {skip: "requires a previously established cursor"},
     killAllSessions: {skip: "always broadcast to all hosts in the cluster"},
     killAllSessionsByPattern: {skip: "always broadcast to all hosts in the cluster"},
diff --git a/jstests/sharding/ismaster.js b/jstests/sharding/ismaster.js
index 2d5cea7b586..d1ce254d711 100644
--- a/jstests/sharding/ismaster.js
+++ b/jstests/sharding/ismaster.js
@@ -1,42 +1,63 @@
+/**
+ * This test ensures that the hello command and its aliases, ismaster and isMaster, are all
+ * accepted by mongos.
+ * @tags: [requires_fcv_47]
+ */
 "use strict";
 var st = new ShardingTest({shards: 1, mongos: 1});
-var res = st.s0.getDB("admin").runCommand("ismaster");
-// check that the fields that should be there are there and have proper values
-assert(res.maxBsonObjectSize && isNumber(res.maxBsonObjectSize) && res.maxBsonObjectSize > 0,
-       "maxBsonObjectSize possibly missing:" + tojson(res));
-assert(res.maxMessageSizeBytes && isNumber(res.maxMessageSizeBytes) && res.maxBsonObjectSize > 0,
-       "maxMessageSizeBytes possibly missing:" + tojson(res));
-assert.eq("boolean", typeof res.ismaster, "ismaster field is not a boolean" + tojson(res));
-assert(res.ismaster === true, "ismaster field is false" + tojson(res));
-assert(res.localTime, "localTime possibly missing:" + tojson(res));
-assert(res.msg && res.msg == "isdbgrid", "msg possibly missing or wrong:" + tojson(res));
-var unwantedFields = [
-    "setName",
-    "setVersion",
-    "secondary",
-    "hosts",
-    "passives",
-    "arbiters",
-    "primary",
-    "aribterOnly",
-    "passive",
-    "slaveDelay",
-    "hidden",
-    "tags",
-    "buildIndexes",
-    "me"
-];
-// check that the fields that shouldn't be there are not there
-var badFields = [];
-var field;
-for (field in res) {
-    if (!res.hasOwnProperty(field)) {
-        continue;
-    }
-    if (Array.contains(unwantedFields, field)) {
-        badFields.push(field);
+
+function checkResponseFields(commandString) {
+    jsTestLog("Running the " + commandString + " command");
+    var res = st.s0.getDB("admin").runCommand(commandString);
+
+    // check that the fields that should be there are there and have proper values
+    assert(res.maxBsonObjectSize && isNumber(res.maxBsonObjectSize) && res.maxBsonObjectSize > 0,
+           "maxBsonObjectSize possibly missing:" + tojson(res));
+    assert(
+        res.maxMessageSizeBytes && isNumber(res.maxMessageSizeBytes) && res.maxBsonObjectSize > 0,
+        "maxMessageSizeBytes possibly missing:" + tojson(res));
+
+    // TODO SERVER-49988: Check for res.isWritablePrimary instead of res.ismaster if a hello command
+    // was executed.
+    assert.eq("boolean", typeof res.ismaster, "ismaster field is not a boolean" + tojson(res));
+    assert(res.ismaster === true, "ismaster field is false" + tojson(res));
+
+    assert(res.localTime, "localTime possibly missing:" + tojson(res));
+    assert(res.msg && res.msg == "isdbgrid", "msg possibly missing or wrong:" + tojson(res));
+
+    var unwantedFields = [
+        "setName",
+        "setVersion",
+        "secondary",
+        "hosts",
+        "passives",
+        "arbiters",
+        "primary",
+        "aribterOnly",
+        "passive",
+        "slaveDelay",
+        "hidden",
+        "tags",
+        "buildIndexes",
+        "me"
+    ];
+    // check that the fields that shouldn't be there are not there
+    var badFields = [];
+    var field;
+    for (field in res) {
+        if (!res.hasOwnProperty(field)) {
+            continue;
+        }
+        if (Array.contains(unwantedFields, field)) {
+            badFields.push(field);
+        }
     }
+    assert(badFields.length === 0,
+           "\nthe result:\n" + tojson(res) + "\ncontained fields it shouldn't have: " + badFields);
 }
-assert(badFields.length === 0,
-       "\nthe result:\n" + tojson(res) + "\ncontained fields it shouldn't have: " + badFields);
+
+checkResponseFields("hello");
+checkResponseFields("ismaster");
+checkResponseFields("isMaster");
+
 st.stop();
diff --git a/jstests/sharding/read_write_concern_defaults_application.js b/jstests/sharding/read_write_concern_defaults_application.js
index c45fbc86f43..3f3332ac209 100644
--- a/jstests/sharding/read_write_concern_defaults_application.js
+++ b/jstests/sharding/read_write_concern_defaults_application.js
@@ -26,6 +26,7 @@
  *   requires_majority_read_concern,
  *   requires_profiling,
  *   uses_transactions,
+ *   requires_fcv_47
  * ]
  */
 (function() {
@@ -455,6 +456,7 @@ let testCases = {
         useLogs: true,
     },
     handshake: {skip: "does not accept read or write concern"},
+    hello: {skip: "does not accept read or write concern"},
     hostInfo: {skip: "does not accept read or write concern"},
     httpClientRequest: {skip: "does not accept read or write concern"},
     insert: {
@@ -467,7 +469,6 @@ let testCases = {
     },
     internalRenameIfOptionsAndIndexesMatch: {skip: "internal command"},
     invalidateUserCache: {skip: "does not accept read or write concern"},
-    isMaster: {skip: "does not accept read or write concern"},
     isdbgrid: {skip: "does not accept read or write concern"},
     killAllSessions: {skip: "does not accept read or write concern"},
     killAllSessionsByPattern: {skip: "does not accept read or write concern"},
diff --git a/jstests/sharding/safe_secondary_reads_drop_recreate.js b/jstests/sharding/safe_secondary_reads_drop_recreate.js
index 6a03af25df7..489cdf720e9 100644
--- a/jstests/sharding/safe_secondary_reads_drop_recreate.js
+++ b/jstests/sharding/safe_secondary_reads_drop_recreate.js
@@ -15,6 +15,7 @@
  *                 *when the the collection has been dropped and recreated as empty.*
  * - behavior: Must be "unshardedOnly", or "versioned". Determines what system profiler checks are
  * performed.
+ * @tags: [requires_fcv_47]
  */
 (function() {
 "use strict";
@@ -190,11 +191,11 @@ let testCases = {
     grantRolesToRole: {skip: "primary only"},
     grantRolesToUser: {skip: "primary only"},
     handshake: {skip: "does not return user data"},
+    hello: {skip: "does not return user data"},
     hostInfo: {skip: "does not return user data"},
     insert: {skip: "primary only"},
     invalidateUserCache: {skip: "does not return user data"},
     isdbgrid: {skip: "does not return user data"},
-    isMaster: {skip: "does not return user data"},
     killAllSessions: {skip: "does not return user data"},
     killAllSessionsByPattern: {skip: "does not return user data"},
     killCursors: {skip: "does not return user data"},
diff --git a/jstests/sharding/safe_secondary_reads_single_migration_suspend_range_deletion.js b/jstests/sharding/safe_secondary_reads_single_migration_suspend_range_deletion.js
index 260de634468..1c1797b78dd 100644
--- a/jstests/sharding/safe_secondary_reads_single_migration_suspend_range_deletion.js
+++ b/jstests/sharding/safe_secondary_reads_single_migration_suspend_range_deletion.js
@@ -22,6 +22,7 @@
  *                                     results for the command run with read concern 'available'.
  * - behavior: Must be one of "unshardedOnly", "targetsPrimaryUsesConnectionVersioning" or
  * "versioned". Determines what system profiler checks are performed.
+ * @tags: [requires_fcv_47]
  */
 (function() {
 "use strict";
@@ -224,11 +225,11 @@ let testCases = {
     grantRolesToRole: {skip: "primary only"},
     grantRolesToUser: {skip: "primary only"},
     handshake: {skip: "does not return user data"},
+    hello: {skip: "does not return user data"},
     hostInfo: {skip: "does not return user data"},
     insert: {skip: "primary only"},
     invalidateUserCache: {skip: "does not return user data"},
     isdbgrid: {skip: "does not return user data"},
-    isMaster: {skip: "does not return user data"},
     killCursors: {skip: "does not return user data"},
     killAllSessions: {skip: "does not return user data"},
     killAllSessionsByPattern: {skip: "does not return user data"},
diff --git a/jstests/sharding/safe_secondary_reads_single_migration_waitForDelete.js b/jstests/sharding/safe_secondary_reads_single_migration_waitForDelete.js
index c502137fc03..490b0d0c60a 100644
--- a/jstests/sharding/safe_secondary_reads_single_migration_waitForDelete.js
+++ b/jstests/sharding/safe_secondary_reads_single_migration_waitForDelete.js
@@ -15,6 +15,7 @@
  *                 *when the range has been deleted on the donor.*
  * - behavior: Must be one of "unshardedOnly", "targetsPrimaryUsesConnectionVersioning" or
  * "versioned". Determines what system profiler checks are performed.
+ * @tags: [requires_fcv_47]
  */
 (function() {
 "use strict";
@@ -195,11 +196,11 @@ let testCases = {
     grantRolesToRole: {skip: "primary only"},
     grantRolesToUser: {skip: "primary only"},
     handshake: {skip: "does not return user data"},
+    hello: {skip: "does not return user data"},
     hostInfo: {skip: "does not return user data"},
     insert: {skip: "primary only"},
     invalidateUserCache: {skip: "does not return user data"},
     isdbgrid: {skip: "does not return user data"},
-    isMaster: {skip: "does not return user data"},
     killAllSessions: {skip: "does not return user data"},
     killAllSessionsByPattern: {skip: "does not return user data"},
     killCursors: {skip: "does not return user data"},
diff --git a/src/mongo/db/repl/replication_info.cpp b/src/mongo/db/repl/replication_info.cpp
index a76cefbcce7..5fb4459aea0 100644
--- a/src/mongo/db/repl/replication_info.cpp
+++ b/src/mongo/db/repl/replication_info.cpp
@@ -33,6 +33,7 @@
 #include <list>
 #include <vector>
 
+#include "mongo/base/string_data.h"
 #include "mongo/bson/util/bson_extract.h"
 #include "mongo/client/connpool.h"
 #include "mongo/client/dbclient_connection.h"
@@ -79,6 +80,12 @@ using std::unique_ptr;
 
 namespace repl {
 namespace {
+
+constexpr auto kHelloString = "hello"_sd;
+// Aliases for the hello command in order to provide backwards compatibility.
+constexpr auto kCamelCaseIsMasterString = "isMaster"_sd;
+constexpr auto kLowerCaseIsMasterString = "ismaster"_sd;
+
 /**
  * Appends replication-related fields to the isMaster response. Returns the topology version that
  * was included in the response.
@@ -221,9 +228,11 @@ public:
     }
 } oplogInfoServerStatus;
 
-class CmdIsMaster final : public BasicCommandWithReplyBuilderInterface {
+class CmdHello final : public BasicCommandWithReplyBuilderInterface {
 public:
-    CmdIsMaster() : BasicCommandWithReplyBuilderInterface("isMaster", "ismaster") {}
+    CmdHello()
+        : BasicCommandWithReplyBuilderInterface(
+              kHelloString, {kCamelCaseIsMasterString, kLowerCaseIsMasterString}) {}
 
     const std::set<std::string>& apiVersions() const {
         return kApiVersions1;
@@ -480,7 +489,7 @@ public:
 
         return true;
     }
-} cmdismaster;
+} cmdhello;
 
 OpCounterServerStatusSection replOpCounterServerStatusSection("opcountersRepl", &replOpCounters);
 
diff --git a/src/mongo/db/service_entry_point_common.cpp b/src/mongo/db/service_entry_point_common.cpp
index 6717fc5589d..5b4c5856ee2 100644
--- a/src/mongo/db/service_entry_point_common.cpp
+++ b/src/mongo/db/service_entry_point_common.cpp
@@ -1362,7 +1362,7 @@ DbResponse receivedCommands(OperationContext* opCtx,
 
             const auto session = opCtx->getClient()->session();
             if (session) {
-                if (!opCtx->isExhaust() || c->getName() != "isMaster"_sd) {
+                if (!opCtx->isExhaust() || c->getName() != "hello"_sd) {
                     InExhaustIsMaster::get(session.get())->setInExhaustIsMaster(false);
                 }
             }
@@ -1703,8 +1703,7 @@ Future<DbResponse> ServiceEntryPointCommon::handleRequest(OperationContext* opCt
     if (op == dbMsg || (op == dbQuery && isCommand)) {
         dbresponse = receivedCommands(opCtx, m, behaviors);
         // IsMaster should take kMaxAwaitTimeMs at most, log if it takes twice that.
-        if (auto command = currentOp.getCommand();
-            command && (command->getName() == "ismaster" || command->getName() == "isMaster")) {
+        if (auto command = currentOp.getCommand(); command && (command->getName() == "hello")) {
             slowMsOverride =
                 2 * durationCount<Milliseconds>(SingleServerIsMasterMonitor::kMaxAwaitTime);
         }
diff --git a/src/mongo/s/commands/cluster_is_master_cmd.cpp b/src/mongo/s/commands/cluster_is_master_cmd.cpp
index 5c9a0fdb698..5e864ec3532 100644
--- a/src/mongo/s/commands/cluster_is_master_cmd.cpp
+++ b/src/mongo/s/commands/cluster_is_master_cmd.cpp
@@ -30,6 +30,7 @@
 
 #include "mongo/platform/basic.h"
 
+#include "mongo/base/string_data.h"
 #include "mongo/bson/util/bson_extract.h"
 #include "mongo/db/auth/sasl_mechanism_registry.h"
 #include "mongo/db/client.h"
@@ -55,9 +56,17 @@ MONGO_FAIL_POINT_DEFINE(waitInIsMaster);
 
 namespace {
 
-class CmdIsMaster : public BasicCommandWithReplyBuilderInterface {
+constexpr auto kHelloString = "hello"_sd;
+// Aliases for the hello command in order to provide backwards compatibility.
+constexpr auto kCamelCaseIsMasterString = "isMaster"_sd;
+constexpr auto kLowerCaseIsMasterString = "ismaster"_sd;
+
+
+class CmdHello : public BasicCommandWithReplyBuilderInterface {
 public:
-    CmdIsMaster() : BasicCommandWithReplyBuilderInterface("isMaster", "ismaster") {}
+    CmdHello()
+        : BasicCommandWithReplyBuilderInterface(
+              kHelloString, {kCamelCaseIsMasterString, kLowerCaseIsMasterString}) {}
 
     const std::set<std::string>& apiVersions() const {
         return kApiVersions1;
@@ -228,7 +237,7 @@ public:
         return true;
     }
 
-} isMaster;
+} hello;
 
 }  // namespace
 }  // namespace mongo
diff --git a/src/mongo/s/commands/strategy.cpp b/src/mongo/s/commands/strategy.cpp
index f90d6d1beb6..744fd0008e5 100644
--- a/src/mongo/s/commands/strategy.cpp
+++ b/src/mongo/s/commands/strategy.cpp
@@ -315,7 +315,7 @@ void runCommand(OperationContext* opCtx,
     opCtx->setExhaust(OpMsg::isFlagSet(m, OpMsg::kExhaustSupported));
     const auto session = opCtx->getClient()->session();
     if (session) {
-        if (!opCtx->isExhaust() || command->getName() != "isMaster"_sd) {
+        if (!opCtx->isExhaust() || command->getName() != "hello"_sd) {
             InExhaustIsMaster::get(session.get())->setInExhaustIsMaster(false);
         }
     }