SERVER-28656 consolidate utility functions for forwarding commands to shards into cluster_commands_common.h

9 files changed, 208 insertions, 281 deletions

diff --git a/src/mongo/s/commands/SConscript b/src/mongo/s/commands/SConscript
index b7af6271a4e..81bae864fae 100644
--- a/src/mongo/s/commands/SConscript
+++ b/src/mongo/s/commands/SConscript
@@ -76,7 +76,6 @@ env.Library(
         'cluster_write.cpp',
         'cluster_write_cmd.cpp',
         'commands_public.cpp',
-        'scatter_gather_from_shards.cpp',
         'sharded_command_processing.cpp',
         'strategy.cpp',
     ],
diff --git a/src/mongo/s/commands/cluster_commands_common.cpp b/src/mongo/s/commands/cluster_commands_common.cpp
index 1e0b13f8fcd..c154029131a 100644
--- a/src/mongo/s/commands/cluster_commands_common.cpp
+++ b/src/mongo/s/commands/cluster_commands_common.cpp
@@ -34,17 +34,182 @@
 
 #include "mongo/db/commands.h"
 #include "mongo/db/query/cursor_response.h"
+#include "mongo/executor/task_executor_pool.h"
+#include "mongo/rpc/get_status_from_command_result.h"
+#include "mongo/rpc/metadata/server_selection_metadata.h"
 #include "mongo/s/catalog/type_collection.h"
 #include "mongo/s/catalog_cache.h"
 #include "mongo/s/client/parallel.h"
 #include "mongo/s/client/shard_connection.h"
+#include "mongo/s/client/shard_registry.h"
 #include "mongo/s/client/version_manager.h"
+#include "mongo/s/commands/sharded_command_processing.h"
 #include "mongo/s/grid.h"
 #include "mongo/s/stale_exception.h"
 #include "mongo/util/log.h"
 
 namespace mongo {
 
+namespace {
+BSONObj appendShardVersion(const BSONObj& cmdObj, ChunkVersion version) {
+    BSONObjBuilder cmdWithVersionBob;
+    cmdWithVersionBob.appendElements(cmdObj);
+    version.appendForCommands(&cmdWithVersionBob);
+    return cmdWithVersionBob.obj();
+}
+}
+
+std::vector<AsyncRequestsSender::Request> buildRequestsForAllShards(OperationContext* opCtx,
+                                                                    const BSONObj& cmdObj) {
+    std::vector<AsyncRequestsSender::Request> requests;
+    std::vector<ShardId> shardIds;
+    Grid::get(opCtx)->shardRegistry()->getAllShardIds(&shardIds);
+    for (auto&& shardId : shardIds) {
+        requests.emplace_back(std::move(shardId), cmdObj);
+    }
+    return requests;
+}
+
+std::vector<AsyncRequestsSender::Request> buildRequestsForTargetedShards(
+    OperationContext* opCtx,
+    const CachedCollectionRoutingInfo& routingInfo,
+    const BSONObj& cmdObj) {
+    std::vector<AsyncRequestsSender::Request> requests;
+    if (routingInfo.cm()) {
+        // The collection is sharded. Target all shards that own data for the collection.
+        std::vector<ShardId> shardIds;
+        Grid::get(opCtx)->shardRegistry()->getAllShardIds(&shardIds);
+        for (const ShardId& shardId : shardIds) {
+            requests.emplace_back(
+                shardId, appendShardVersion(cmdObj, routingInfo.cm()->getVersion(shardId)));
+        }
+    } else {
+        // The collection is unsharded. Target only the primary shard for the database.
+        if (routingInfo.primary()->isConfig()) {
+            // Don't append shard version info when contacting the config servers.
+            requests.emplace_back(routingInfo.primaryId(), cmdObj);
+        } else {
+            requests.emplace_back(routingInfo.primaryId(),
+                                  appendShardVersion(cmdObj, ChunkVersion::UNSHARDED()));
+        }
+    }
+    return requests;
+}
+
+using ShardAndReply = std::tuple<ShardId, BSONObj>;
+
+StatusWith<std::vector<ShardAndReply>> gatherResults(
+    OperationContext* opCtx,
+    const std::string& dbName,
+    const BSONObj& cmdObj,
+    int options,
+    const std::vector<AsyncRequestsSender::Request>& requests,
+    BSONObjBuilder* output) {
+    // Extract the readPreference from the command.
+    rpc::ServerSelectionMetadata ssm;
+    BSONObjBuilder unusedCmdBob;
+    BSONObjBuilder upconvertedMetadataBob;
+    uassertStatusOK(rpc::ServerSelectionMetadata::upconvert(
+        cmdObj, options, &unusedCmdBob, &upconvertedMetadataBob));
+    auto upconvertedMetadata = upconvertedMetadataBob.obj();
+    auto ssmElem = upconvertedMetadata.getField(rpc::ServerSelectionMetadata::fieldName());
+    if (!ssmElem.eoo()) {
+        ssm = uassertStatusOK(rpc::ServerSelectionMetadata::readFromMetadata(ssmElem));
+    }
+    auto readPref = ssm.getReadPreference();
+
+    // Send the requests.
+
+    AsyncRequestsSender ars(
+        opCtx,
+        Grid::get(opCtx)->getExecutorPool()->getArbitraryExecutor(),
+        dbName,
+        requests,
+        readPref ? *readPref : ReadPreferenceSetting(ReadPreference::PrimaryOnly, TagSet()));
+
+    // Get the responses.
+
+    std::vector<ShardAndReply> results;                 // Stores results by ShardId
+    BSONObjBuilder subobj(output->subobjStart("raw"));  // Stores results by ConnectionString
+    BSONObjBuilder errors;                              // Stores errors by ConnectionString
+    int commonErrCode = -1;                             // Stores the overall error code
+
+    BSONElement wcErrorElem;
+    ShardId wcErrorShardId;
+    bool hasWCError = false;
+
+    while (!ars.done()) {
+        auto response = ars.next();
+        const auto swShard = Grid::get(opCtx)->shardRegistry()->getShard(opCtx, response.shardId);
+        if (!swShard.isOK()) {
+            output->resetToEmpty();
+            return swShard.getStatus();
+        }
+        const auto shard = std::move(swShard.getValue());
+
+        auto status = response.swResponse.getStatus();
+        if (status.isOK()) {
+            // We successfully received a response.
+
+            status = getStatusFromCommandResult(response.swResponse.getValue().data);
+            if (ErrorCodes::isStaleShardingError(status.code())) {
+                // Do not report any raw results if we fail to establish a shardVersion.
+                output->resetToEmpty();
+                return status;
+            }
+
+            auto result = std::move(response.swResponse.getValue().data);
+            if (!hasWCError) {
+                if ((wcErrorElem = result["writeConcernError"])) {
+                    wcErrorShardId = response.shardId;
+                    hasWCError = true;
+                }
+            }
+
+            if (status.isOK()) {
+                // The command status was OK.
+                subobj.append(shard->getConnString().toString(), result);
+                results.emplace_back(std::move(response.shardId), std::move(result));
+                continue;
+            }
+        }
+
+        // Either we failed to get a response, or the command had a non-OK status.
+
+        // Convert the error status back into the format of a command result.
+        BSONObjBuilder resultBob;
+        Command::appendCommandStatus(resultBob, status);
+        auto result = resultBob.obj();
+
+        // Update the data structures that store the results.
+        errors.append(shard->getConnString().toString(), status.reason());
+        if (commonErrCode == -1) {
+            commonErrCode = status.code();
+        } else if (commonErrCode != status.code()) {
+            commonErrCode = 0;
+        }
+        subobj.append(shard->getConnString().toString(), result);
+        results.emplace_back(std::move(response.shardId), std::move(result));
+    }
+
+    subobj.done();
+
+    if (hasWCError) {
+        appendWriteConcernErrorToCmdResponse(wcErrorShardId, wcErrorElem, *output);
+    }
+
+    BSONObj errobj = errors.done();
+    if (!errobj.isEmpty()) {
+        // If code for all errors is the same, then report the common error code.
+        if (commonErrCode > 0) {
+            return {ErrorCodes::fromInt(commonErrCode), errobj.toString()};
+        }
+        return {ErrorCodes::OperationFailed, errobj.toString()};
+    }
+
+    return results;
+}
+
 int getUniqueCodeFromCommandResults(const std::vector<Strategy::CommandResult>& results) {
     int commonErrCode = -1;
     for (std::vector<Strategy::CommandResult>::const_iterator it = results.begin();
diff --git a/src/mongo/s/commands/cluster_commands_common.h b/src/mongo/s/commands/cluster_commands_common.h
index 87fd9b7d50c..e9f9cac0b71 100644
--- a/src/mongo/s/commands/cluster_commands_common.h
+++ b/src/mongo/s/commands/cluster_commands_common.h
@@ -32,7 +32,9 @@
 #include <vector>
 
 #include "mongo/base/status.h"
+#include "mongo/base/string_data.h"
 #include "mongo/bson/bsonobj.h"
+#include "mongo/s/async_requests_sender.h"
 #include "mongo/s/commands/strategy.h"
 #include "mongo/stdx/memory.h"
 
@@ -43,6 +45,38 @@ class CachedDatabaseInfo;
 class OperationContext;
 
 /**
+ * Utility function to target all shards for a request that does not have a specific namespace.
+ */
+std::vector<AsyncRequestsSender::Request> buildRequestsForAllShards(OperationContext* opCtx,
+                                                                    const BSONObj& cmdObj);
+
+/**
+ * Utility function to get the set of shards to target for a request on a specific namespace.
+ *
+ * Selects shards to target based on 'routingInfo', and constructs a vector of requests, one per
+ * targeted shard, where the cmdObj to send to each shard has been modified to include the shard's
+ * shardVersion.
+ */
+std::vector<AsyncRequestsSender::Request> buildRequestsForTargetedShards(
+    OperationContext* opCtx, const CachedCollectionRoutingInfo& routingInfo, const BSONObj& cmdObj);
+
+using ShardAndReply = std::tuple<ShardId, BSONObj>;
+
+/**
+ * Logic for commands that simply map out to all shards then fold the results into
+ * a single response.
+ *
+ * All shards are contacted in parallel.
+ */
+StatusWith<std::vector<ShardAndReply>> gatherResults(
+    OperationContext* opCtx,
+    const std::string& dbName,
+    const BSONObj& cmdObj,
+    int options,
+    const std::vector<AsyncRequestsSender::Request>& requests,
+    BSONObjBuilder* output);
+
+/**
  * Utility function to compute a single error code from a vector of command results.
  *
  * @return If there is an error code common to all of the error results, returns that error
diff --git a/src/mongo/s/commands/cluster_current_op.cpp b/src/mongo/s/commands/cluster_current_op.cpp
index ecf1c1fb30b..b704a17a921 100644
--- a/src/mongo/s/commands/cluster_current_op.cpp
+++ b/src/mongo/s/commands/cluster_current_op.cpp
@@ -39,7 +39,7 @@
 #include "mongo/db/commands.h"
 #include "mongo/db/jsobj.h"
 #include "mongo/s/client/shard_registry.h"
-#include "mongo/s/commands/scatter_gather_from_shards.h"
+#include "mongo/s/commands/cluster_commands_common.h"
 #include "mongo/s/commands/strategy.h"
 #include "mongo/s/grid.h"
 #include "mongo/util/log.h"
@@ -88,20 +88,11 @@ public:
              int options,
              std::string& errmsg,
              BSONObjBuilder& output) override {
-
-        // Target all shards.
-        std::vector<AsyncRequestsSender::Request> requests;
-        std::vector<ShardId> shardIds;
-        Grid::get(opCtx)->shardRegistry()->getAllShardIds(&shardIds);
-        for (auto&& shardId : shardIds) {
-            requests.emplace_back(std::move(shardId), cmdObj);
-        }
-
+        auto requests = buildRequestsForAllShards(opCtx, cmdObj);
         auto swResults = gatherResults(opCtx, dbName, cmdObj, options, requests, &output);
         if (!swResults.isOK()) {
             return appendCommandStatus(output, swResults.getStatus());
         }
-
         aggregateResults(std::move(swResults.getValue()), output);
         return true;
     }
diff --git a/src/mongo/s/commands/cluster_db_stats_cmd.cpp b/src/mongo/s/commands/cluster_db_stats_cmd.cpp
index 16151cf0f1c..ea83968a486 100644
--- a/src/mongo/s/commands/cluster_db_stats_cmd.cpp
+++ b/src/mongo/s/commands/cluster_db_stats_cmd.cpp
@@ -30,9 +30,9 @@
 
 #include <vector>
 
-#include "mongo/s/commands/scatter_gather_from_shards.h"
-
+#include "mongo/db/commands.h"
 #include "mongo/s/client/shard_registry.h"
+#include "mongo/s/commands/cluster_commands_common.h"
 #include "mongo/s/grid.h"
 
 namespace mongo {
@@ -71,20 +71,11 @@ public:
              int options,
              std::string& errmsg,
              BSONObjBuilder& output) override {
-
-        // Target all shards.
-        std::vector<AsyncRequestsSender::Request> requests;
-        std::vector<ShardId> shardIds;
-        Grid::get(opCtx)->shardRegistry()->getAllShardIds(&shardIds);
-        for (auto&& shardId : shardIds) {
-            requests.emplace_back(std::move(shardId), cmdObj);
-        }
-
+        auto requests = buildRequestsForAllShards(opCtx, cmdObj);
         auto swResults = gatherResults(opCtx, dbName, cmdObj, options, requests, &output);
         if (!swResults.isOK()) {
             return appendCommandStatus(output, swResults.getStatus());
         }
-
         aggregateResults(std::move(swResults.getValue()), output);
         return true;
     }
diff --git a/src/mongo/s/commands/cluster_repair_database_cmd.cpp b/src/mongo/s/commands/cluster_repair_database_cmd.cpp
index 707d6149846..bd13a094059 100644
--- a/src/mongo/s/commands/cluster_repair_database_cmd.cpp
+++ b/src/mongo/s/commands/cluster_repair_database_cmd.cpp
@@ -28,9 +28,9 @@
 
 #include "mongo/platform/basic.h"
 
-#include "mongo/s/commands/scatter_gather_from_shards.h"
-
+#include "mongo/db/commands.h"
 #include "mongo/s/client/shard_registry.h"
+#include "mongo/s/commands/cluster_commands_common.h"
 #include "mongo/s/grid.h"
 
 namespace mongo {
@@ -65,14 +65,7 @@ public:
              int options,
              std::string& errmsg,
              BSONObjBuilder& output) override {
-        // Target all shards.
-        std::vector<AsyncRequestsSender::Request> requests;
-        std::vector<ShardId> shardIds;
-        Grid::get(opCtx)->shardRegistry()->getAllShardIds(&shardIds);
-        for (auto&& shardId : shardIds) {
-            requests.emplace_back(std::move(shardId), cmdObj);
-        }
-
+        auto requests = buildRequestsForAllShards(opCtx, cmdObj);
         auto swResults = gatherResults(opCtx, dbName, cmdObj, options, requests, &output);
         return appendCommandStatus(output, swResults.getStatus());
     }
diff --git a/src/mongo/s/commands/commands_public.cpp b/src/mongo/s/commands/commands_public.cpp
index 371782d2e4d..032c7a2512c 100644
--- a/src/mongo/s/commands/commands_public.cpp
+++ b/src/mongo/s/commands/commands_public.cpp
@@ -61,7 +61,6 @@
 #include "mongo/s/commands/cluster_aggregate.h"
 #include "mongo/s/commands/cluster_commands_common.h"
 #include "mongo/s/commands/cluster_explain.h"
-#include "mongo/s/commands/scatter_gather_from_shards.h"
 #include "mongo/s/commands/sharded_command_processing.h"
 #include "mongo/s/grid.h"
 #include "mongo/s/query/store_possible_cursor.h"
@@ -253,28 +252,9 @@ protected:
             status = Status::OK();
             output.resetToEmpty();
 
-            // Target only shards that own data for the collection, and append the shardVersion for
-            // the collection to the command.
-            std::vector<AsyncRequestsSender::Request> requests;
             auto routingInfo = uassertStatusOK(
                 Grid::get(opCtx)->catalogCache()->getCollectionRoutingInfo(opCtx, nss));
-            if (routingInfo.cm()) {
-                vector<ShardId> shardIds;
-                Grid::get(opCtx)->shardRegistry()->getAllShardIds(&shardIds);
-                for (const ShardId& shardId : shardIds) {
-                    requests.emplace_back(
-                        std::move(shardId),
-                        appendShardVersion(cmdObj, routingInfo.cm()->getVersion(shardId)));
-                }
-            } else {
-                if (routingInfo.primary()->isConfig()) {
-                    // Don't append shard version info when contacting the config servers.
-                    requests.emplace_back(routingInfo.primaryId(), cmdObj);
-                } else {
-                    requests.emplace_back(routingInfo.primaryId(),
-                                          appendShardVersion(cmdObj, ChunkVersion::UNSHARDED()));
-                }
-            }
+            auto requests = buildRequestsForTargetedShards(opCtx, routingInfo, cmdObj);
 
             auto swResults = gatherResults(opCtx, dbName, cmdObj, options, requests, &output);
             if (ErrorCodes::isStaleShardingError(swResults.getStatus().code())) {
diff --git a/src/mongo/s/commands/scatter_gather_from_shards.cpp b/src/mongo/s/commands/scatter_gather_from_shards.cpp
deleted file mode 100644
index ac331ceaf5d..00000000000
--- a/src/mongo/s/commands/scatter_gather_from_shards.cpp
+++ /dev/null
@@ -1,166 +0,0 @@
-/**
- *    Copyright (C) 2015 MongoDB Inc.
- *
- *    This program is free software: you can redistribute it and/or  modify
- *    it under the terms of the GNU Affero General Public License, version 3,
- *    as published by the Free Software Foundation.
- *
- *    This program is distributed in the hope that it will be useful,
- *    but WITHOUT ANY WARRANTY; without even the implied warranty of
- *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- *    GNU Affero General Public License for more details.
- *
- *    You should have received a copy of the GNU Affero General Public License
- *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
- *
- *    As a special exception, the copyright holders give permission to link the
- *    code of portions of this program with the OpenSSL library under certain
- *    conditions as described in each individual source file and distribute
- *    linked combinations including the program with the OpenSSL library. You
- *    must comply with the GNU Affero General Public License in all respects
- *    for all of the code used other than as permitted herein. If you modify
- *    file(s) with this exception, you may extend this exception to your
- *    version of the file(s), but you are not obligated to do so. If you do not
- *    wish to do so, delete this exception statement from your version. If you
- *    delete this exception statement from all source files in the program,
- *    then also delete it in the license file.
- */
-
-#define MONGO_LOG_DEFAULT_COMPONENT ::mongo::logger::LogComponent::kCommand
-
-#include "mongo/platform/basic.h"
-
-#include "mongo/s/commands/scatter_gather_from_shards.h"
-
-#include <list>
-#include <set>
-
-#include "mongo/db/jsobj.h"
-#include "mongo/executor/task_executor_pool.h"
-#include "mongo/rpc/get_status_from_command_result.h"
-#include "mongo/rpc/metadata/server_selection_metadata.h"
-#include "mongo/s/catalog_cache.h"
-#include "mongo/s/client/shard.h"
-#include "mongo/s/client/shard_registry.h"
-#include "mongo/s/commands/sharded_command_processing.h"
-#include "mongo/s/grid.h"
-#include "mongo/util/log.h"
-
-namespace mongo {
-
-using ShardAndReply = std::tuple<ShardId, BSONObj>;
-
-StatusWith<std::vector<ShardAndReply>> gatherResults(
-    OperationContext* opCtx,
-    const std::string& dbName,
-    const BSONObj& cmdObj,
-    int options,
-    const std::vector<AsyncRequestsSender::Request>& requests,
-    BSONObjBuilder* output) {
-    // Extract the readPreference from the command.
-
-    rpc::ServerSelectionMetadata ssm;
-    BSONObjBuilder unusedCmdBob;
-    BSONObjBuilder upconvertedMetadataBob;
-    uassertStatusOK(rpc::ServerSelectionMetadata::upconvert(
-        cmdObj, options, &unusedCmdBob, &upconvertedMetadataBob));
-    auto upconvertedMetadata = upconvertedMetadataBob.obj();
-    auto ssmElem = upconvertedMetadata.getField(rpc::ServerSelectionMetadata::fieldName());
-    if (!ssmElem.eoo()) {
-        ssm = uassertStatusOK(rpc::ServerSelectionMetadata::readFromMetadata(ssmElem));
-    }
-    auto readPref = ssm.getReadPreference();
-
-    // Send the requests.
-
-    AsyncRequestsSender ars(
-        opCtx,
-        Grid::get(opCtx)->getExecutorPool()->getArbitraryExecutor(),
-        dbName,
-        requests,
-        readPref ? *readPref : ReadPreferenceSetting(ReadPreference::PrimaryOnly, TagSet()));
-
-    // Get the responses.
-
-    std::vector<ShardAndReply> results;                 // Stores results by ShardId
-    BSONObjBuilder subobj(output->subobjStart("raw"));  // Stores results by ConnectionString
-    BSONObjBuilder errors;                              // Stores errors by ConnectionString
-    int commonErrCode = -1;                             // Stores the overall error code
-
-    BSONElement wcErrorElem;
-    ShardId wcErrorShardId;
-    bool hasWCError = false;
-
-    while (!ars.done()) {
-        auto response = ars.next();
-        const auto swShard = Grid::get(opCtx)->shardRegistry()->getShard(opCtx, response.shardId);
-        if (!swShard.isOK()) {
-            output->resetToEmpty();
-            return swShard.getStatus();
-        }
-        const auto shard = std::move(swShard.getValue());
-
-        auto status = response.swResponse.getStatus();
-        if (status.isOK()) {
-            // We successfully received a response.
-
-            status = getStatusFromCommandResult(response.swResponse.getValue().data);
-            if (ErrorCodes::isStaleShardingError(status.code())) {
-                // Do not report any raw results if we fail to establish a shardVersion.
-                output->resetToEmpty();
-                return status;
-            }
-
-            auto result = std::move(response.swResponse.getValue().data);
-            if (!hasWCError) {
-                if ((wcErrorElem = result["writeConcernError"])) {
-                    wcErrorShardId = response.shardId;
-                    hasWCError = true;
-                }
-            }
-
-            if (status.isOK()) {
-                // The command status was OK.
-                subobj.append(shard->getConnString().toString(), result);
-                results.emplace_back(std::move(response.shardId), std::move(result));
-                continue;
-            }
-        }
-
-        // Either we failed to get a response, or the command had a non-OK status.
-
-        // Convert the error status back into the format of a command result.
-        BSONObjBuilder resultBob;
-        Command::appendCommandStatus(resultBob, status);
-        auto result = resultBob.obj();
-
-        // Update the data structures that store the results.
-        errors.append(shard->getConnString().toString(), status.reason());
-        if (commonErrCode == -1) {
-            commonErrCode = status.code();
-        } else if (commonErrCode != status.code()) {
-            commonErrCode = 0;
-        }
-        subobj.append(shard->getConnString().toString(), result);
-        results.emplace_back(std::move(response.shardId), std::move(result));
-    }
-
-    subobj.done();
-
-    if (hasWCError) {
-        appendWriteConcernErrorToCmdResponse(wcErrorShardId, wcErrorElem, *output);
-    }
-
-    BSONObj errobj = errors.done();
-    if (!errobj.isEmpty()) {
-        // If code for all errors is the same, then report the common error code.
-        if (commonErrCode > 0) {
-            return {ErrorCodes::fromInt(commonErrCode), errobj.toString()};
-        }
-        return {ErrorCodes::OperationFailed, errobj.toString()};
-    }
-
-    return results;
-}
-
-}  // namespace mongo
diff --git a/src/mongo/s/commands/scatter_gather_from_shards.h b/src/mongo/s/commands/scatter_gather_from_shards.h
deleted file mode 100644
index ebca85f01a3..00000000000
--- a/src/mongo/s/commands/scatter_gather_from_shards.h
+++ /dev/null
@@ -1,60 +0,0 @@
-/**
-*    Copyright (C) 2015 10gen Inc.
-*
-*    This program is free software: you can redistribute it and/or  modify
-*    it under the terms of the GNU Affero General Public License, version 3,
-*    as published by the Free Software Foundation.
-*
-*    This program is distributed in the hope that it will be useful,
-*    but WITHOUT ANY WARRANTY; without even the implied warranty of
-*    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-*    GNU Affero General Public License for more details.
-*
-*    You should have received a copy of the GNU Affero General Public License
-*    along with this program.  If not, see <http://www.gnu.org/licenses/>.
-*
-*    As a special exception, the copyright holders give permission to link the
-*    code of portions of this program with the OpenSSL library under certain
-*    conditions as described in each individual source file and distribute
-*    linked combinations including the program with the OpenSSL library. You
-*    must comply with the GNU Affero General Public License in all respects
-*    for all of the code used other than as permitted herein. If you modify
-*    file(s) with this exception, you may extend this exception to your
-*    version of the file(s), but you are not obligated to do so. If you do not
-*    wish to do so, delete this exception statement from your version. If you
-*    delete this exception statement from all source files in the program,
-*    then also delete it in the license file.
-*/
-
-#include <string>
-#include <tuple>
-#include <vector>
-
-#include "mongo/base/string_data.h"
-#include "mongo/db/commands.h"
-#include "mongo/s/async_requests_sender.h"
-#include "mongo/s/client/shard.h"
-
-namespace mongo {
-
-class BSONObj;
-class BSONObjBuilder;
-class OperationContext;
-
-using ShardAndReply = std::tuple<ShardId, BSONObj>;
-
-/**
- * Logic for commands that simply map out to all shards then fold the results into
- * a single response.
- *
- * All shards are contacted in parallel.
- */
-StatusWith<std::vector<ShardAndReply>> gatherResults(
-    OperationContext* opCtx,
-    const std::string& dbName,
-    const BSONObj& cmdObj,
-    int options,
-    const std::vector<AsyncRequestsSender::Request>& requests,
-    BSONObjBuilder* output);
-
-}  // namespace mongo