SERVER-28814 Attach ServerSelectionMetadata to OpCtx in mongos

This eliminates the need to pass it in to Command::explain()

18 files changed, 22 insertions, 43 deletions

diff --git a/src/mongo/db/commands.cpp b/src/mongo/db/commands.cpp
index f82b97562a3..e6eba884659 100644
--- a/src/mongo/db/commands.cpp
+++ b/src/mongo/db/commands.cpp
@@ -167,7 +167,6 @@ Status Command::explain(OperationContext* opCtx,
                         const string& dbname,
                         const BSONObj& cmdObj,
                         ExplainOptions::Verbosity verbosity,
-                        const rpc::ServerSelectionMetadata& serverSelectionMetadata,
                         BSONObjBuilder* out) const {
     return {ErrorCodes::IllegalOperation, str::stream() << "Cannot explain cmd: " << getName()};
 }
diff --git a/src/mongo/db/commands.h b/src/mongo/db/commands.h
index 05493e2c444..a6a53116bac 100644
--- a/src/mongo/db/commands.h
+++ b/src/mongo/db/commands.h
@@ -210,17 +210,11 @@ public:
      *
      *   2) Calling Explain::explainStages(...) on the PlanExecutor. This is the function
      *   which knows how to convert an execution stage tree into explain output.
-     *
-     * TODO: Remove the 'serverSelectionMetadata' parameter in favor of reading the
-     * ServerSelectionMetadata off 'opCtx'. Once OP_COMMAND is implemented in mongos, this metadata
-     * will be parsed and attached as a decoration on the OperationContext, as is already done on
-     * the mongod side.
      */
     virtual Status explain(OperationContext* opCtx,
                            const std::string& dbname,
                            const BSONObj& cmdObj,
                            ExplainOptions::Verbosity verbosity,
-                           const rpc::ServerSelectionMetadata& serverSelectionMetadata,
                            BSONObjBuilder* out) const;
 
     /**
diff --git a/src/mongo/db/commands/count_cmd.cpp b/src/mongo/db/commands/count_cmd.cpp
index 8ca762e2022..2af91e01876 100644
--- a/src/mongo/db/commands/count_cmd.cpp
+++ b/src/mongo/db/commands/count_cmd.cpp
@@ -104,7 +104,6 @@ public:
                            const std::string& dbname,
                            const BSONObj& cmdObj,
                            ExplainOptions::Verbosity verbosity,
-                           const rpc::ServerSelectionMetadata&,
                            BSONObjBuilder* out) const {
         const bool isExplain = true;
         auto request = CountRequest::parseFromBSON(dbname, cmdObj, isExplain);
diff --git a/src/mongo/db/commands/distinct.cpp b/src/mongo/db/commands/distinct.cpp
index 6b67bd840c1..6c2bef4012a 100644
--- a/src/mongo/db/commands/distinct.cpp
+++ b/src/mongo/db/commands/distinct.cpp
@@ -116,7 +116,6 @@ public:
                            const std::string& dbname,
                            const BSONObj& cmdObj,
                            ExplainOptions::Verbosity verbosity,
-                           const rpc::ServerSelectionMetadata&,
                            BSONObjBuilder* out) const {
         const NamespaceString nss(parseNsCollectionRequired(dbname, cmdObj));
 
diff --git a/src/mongo/db/commands/explain_cmd.cpp b/src/mongo/db/commands/explain_cmd.cpp
index 9f49c8b38e7..59004e87e12 100644
--- a/src/mongo/db/commands/explain_cmd.cpp
+++ b/src/mongo/db/commands/explain_cmd.cpp
@@ -165,12 +165,8 @@ public:
         }
 
         // Actually call the nested command's explain(...) method.
-        Status explainStatus = commToExplain->explain(opCtx,
-                                                      dbname,
-                                                      explainObj,
-                                                      verbosity.getValue(),
-                                                      rpc::ServerSelectionMetadata::get(opCtx),
-                                                      &result);
+        Status explainStatus =
+            commToExplain->explain(opCtx, dbname, explainObj, verbosity.getValue(), &result);
         if (!explainStatus.isOK()) {
             return appendCommandStatus(result, explainStatus);
         }
diff --git a/src/mongo/db/commands/find_and_modify.cpp b/src/mongo/db/commands/find_and_modify.cpp
index 05eedc835a8..ce8abf5ab8c 100644
--- a/src/mongo/db/commands/find_and_modify.cpp
+++ b/src/mongo/db/commands/find_and_modify.cpp
@@ -252,7 +252,6 @@ public:
                    const std::string& dbName,
                    const BSONObj& cmdObj,
                    ExplainOptions::Verbosity verbosity,
-                   const rpc::ServerSelectionMetadata&,
                    BSONObjBuilder* out) const override {
         const NamespaceString fullNs = parseNsCollectionRequired(dbName, cmdObj);
         Status allowedWriteStatus = userAllowedWriteNS(fullNs.ns());
diff --git a/src/mongo/db/commands/find_cmd.cpp b/src/mongo/db/commands/find_cmd.cpp
index b874eecaa99..dc6640989f9 100644
--- a/src/mongo/db/commands/find_cmd.cpp
+++ b/src/mongo/db/commands/find_cmd.cpp
@@ -134,7 +134,6 @@ public:
                    const std::string& dbname,
                    const BSONObj& cmdObj,
                    ExplainOptions::Verbosity verbosity,
-                   const rpc::ServerSelectionMetadata&,
                    BSONObjBuilder* out) const override {
         const NamespaceString nss(parseNs(dbname, cmdObj));
         if (!nss.isValid()) {
diff --git a/src/mongo/db/commands/group_cmd.cpp b/src/mongo/db/commands/group_cmd.cpp
index c7f0b70c6ba..ac17916ef31 100644
--- a/src/mongo/db/commands/group_cmd.cpp
+++ b/src/mongo/db/commands/group_cmd.cpp
@@ -124,7 +124,6 @@ private:
                            const std::string& dbname,
                            const BSONObj& cmdObj,
                            ExplainOptions::Verbosity verbosity,
-                           const rpc::ServerSelectionMetadata&,
                            BSONObjBuilder* out) const {
         GroupRequest groupRequest;
         Status parseRequestStatus = _parseRequest(dbname, cmdObj, &groupRequest);
diff --git a/src/mongo/db/commands/pipeline_command.cpp b/src/mongo/db/commands/pipeline_command.cpp
index a28bc7ae9c5..8a133a7185c 100644
--- a/src/mongo/db/commands/pipeline_command.cpp
+++ b/src/mongo/db/commands/pipeline_command.cpp
@@ -94,7 +94,6 @@ public:
                    const std::string& dbname,
                    const BSONObj& cmdObj,
                    ExplainOptions::Verbosity verbosity,
-                   const rpc::ServerSelectionMetadata& serverSelectionMetadata,
                    BSONObjBuilder* out) const override {
         return _runAggCommand(opCtx, dbname, cmdObj, verbosity, out);
     }
diff --git a/src/mongo/db/commands/write_commands/write_commands.cpp b/src/mongo/db/commands/write_commands/write_commands.cpp
index 905a93f0eb6..a3ecd02b36a 100644
--- a/src/mongo/db/commands/write_commands/write_commands.cpp
+++ b/src/mongo/db/commands/write_commands/write_commands.cpp
@@ -304,7 +304,6 @@ public:
                    const std::string& dbname,
                    const BSONObj& cmdObj,
                    ExplainOptions::Verbosity verbosity,
-                   const rpc::ServerSelectionMetadata&,
                    BSONObjBuilder* out) const final {
         const auto batch = parseUpdateCommand(dbname, cmdObj);
         uassert(ErrorCodes::InvalidLength,
@@ -375,7 +374,6 @@ public:
                    const std::string& dbname,
                    const BSONObj& cmdObj,
                    ExplainOptions::Verbosity verbosity,
-                   const rpc::ServerSelectionMetadata&,
                    BSONObjBuilder* out) const final {
         const auto batch = parseDeleteCommand(dbname, cmdObj);
         uassert(ErrorCodes::InvalidLength,
diff --git a/src/mongo/s/commands/cluster_count_cmd.cpp b/src/mongo/s/commands/cluster_count_cmd.cpp
index 2389a7c9b97..ea66e57fef8 100644
--- a/src/mongo/s/commands/cluster_count_cmd.cpp
+++ b/src/mongo/s/commands/cluster_count_cmd.cpp
@@ -241,7 +241,6 @@ public:
                    const std::string& dbname,
                    const BSONObj& cmdObj,
                    ExplainOptions::Verbosity verbosity,
-                   const rpc::ServerSelectionMetadata& ssm,
                    BSONObjBuilder* out) const override {
         const NamespaceString nss(parseNs(dbname, cmdObj));
         uassert(ErrorCodes::InvalidNamespace,
diff --git a/src/mongo/s/commands/cluster_explain_cmd.cpp b/src/mongo/s/commands/cluster_explain_cmd.cpp
index db053de01a0..6f03cecb53b 100644
--- a/src/mongo/s/commands/cluster_explain_cmd.cpp
+++ b/src/mongo/s/commands/cluster_explain_cmd.cpp
@@ -143,16 +143,9 @@ public:
                        str::stream() << "Explain failed due to unknown command: " << cmdName});
         }
 
-        auto readPref = ClusterFind::extractUnwrappedReadPref(cmdObj);
-        if (!readPref.isOK()) {
-            return appendCommandStatus(result, readPref.getStatus());
-        }
-        const bool secondaryOk = (readPref.getValue().pref != ReadPreference::PrimaryOnly);
-        rpc::ServerSelectionMetadata metadata(secondaryOk, readPref.getValue());
-
         // Actually call the nested command's explain(...) method.
-        Status explainStatus = commToExplain->explain(
-            opCtx, dbName, explainObj, verbosity.getValue(), metadata, &result);
+        Status explainStatus =
+            commToExplain->explain(opCtx, dbName, explainObj, verbosity.getValue(), &result);
         if (!explainStatus.isOK()) {
             return appendCommandStatus(result, explainStatus);
         }
diff --git a/src/mongo/s/commands/cluster_find_and_modify_cmd.cpp b/src/mongo/s/commands/cluster_find_and_modify_cmd.cpp
index f16c508ca59..ee23438a2fb 100644
--- a/src/mongo/s/commands/cluster_find_and_modify_cmd.cpp
+++ b/src/mongo/s/commands/cluster_find_and_modify_cmd.cpp
@@ -84,7 +84,6 @@ public:
                    const std::string& dbName,
                    const BSONObj& cmdObj,
                    ExplainOptions::Verbosity verbosity,
-                   const rpc::ServerSelectionMetadata& serverSelectionMetadata,
                    BSONObjBuilder* out) const override {
         const NamespaceString nss(parseNsCollectionRequired(dbName, cmdObj));
 
diff --git a/src/mongo/s/commands/cluster_find_cmd.cpp b/src/mongo/s/commands/cluster_find_cmd.cpp
index a09a839a94a..83598d92401 100644
--- a/src/mongo/s/commands/cluster_find_cmd.cpp
+++ b/src/mongo/s/commands/cluster_find_cmd.cpp
@@ -38,6 +38,7 @@
 #include "mongo/db/stats/counters.h"
 #include "mongo/db/views/resolved_view.h"
 #include "mongo/rpc/get_status_from_command_result.h"
+#include "mongo/rpc/metadata/server_selection_metadata.h"
 #include "mongo/s/commands/cluster_aggregate.h"
 #include "mongo/s/commands/strategy.h"
 #include "mongo/s/query/cluster_find.h"
@@ -105,7 +106,6 @@ public:
                    const std::string& dbname,
                    const BSONObj& cmdObj,
                    ExplainOptions::Verbosity verbosity,
-                   const rpc::ServerSelectionMetadata& serverSelectionMetadata,
                    BSONObjBuilder* out) const final {
         const NamespaceString nss(parseNsCollectionRequired(dbname, cmdObj));
         // Parse the command BSON to a QueryRequest.
@@ -115,8 +115,12 @@ public:
             return qr.getStatus();
         }
 
-        auto result = Strategy::explainFind(
-            opCtx, cmdObj, *qr.getValue(), verbosity, serverSelectionMetadata, out);
+        auto result = Strategy::explainFind(opCtx,
+                                            cmdObj,
+                                            *qr.getValue(),
+                                            verbosity,
+                                            rpc::ServerSelectionMetadata::get(opCtx),
+                                            out);
 
         if (result == ErrorCodes::CommandOnShardedViewNotSupportedOnMongod) {
             auto resolvedView = ResolvedView::fromBSON(out->asTempObj());
diff --git a/src/mongo/s/commands/cluster_pipeline_cmd.cpp b/src/mongo/s/commands/cluster_pipeline_cmd.cpp
index dca24de659e..9841f87d6a4 100644
--- a/src/mongo/s/commands/cluster_pipeline_cmd.cpp
+++ b/src/mongo/s/commands/cluster_pipeline_cmd.cpp
@@ -80,13 +80,12 @@ public:
                    const std::string& dbname,
                    const BSONObj& cmdObj,
                    ExplainOptions::Verbosity verbosity,
-                   const rpc::ServerSelectionMetadata& serverSelectionMetadata,
                    BSONObjBuilder* out) const override {
         // Add the server selection metadata to the aggregate command in the "unwrapped" format that
         // runAggregate() expects: {aggregate: ..., $queryOptions: {$readPreference: ...}}.
         BSONObjBuilder aggCmdBuilder;
         aggCmdBuilder.appendElements(cmdObj);
-        if (auto readPref = serverSelectionMetadata.getReadPreference()) {
+        if (auto readPref = rpc::ServerSelectionMetadata::get(opCtx).getReadPreference()) {
             aggCmdBuilder.append(QueryRequest::kUnwrappedReadPrefField,
                                  BSON("$readPreference" << readPref->toBSON()));
         }
diff --git a/src/mongo/s/commands/cluster_write_cmd.cpp b/src/mongo/s/commands/cluster_write_cmd.cpp
index dc9ab0c27b9..96d40270a32 100644
--- a/src/mongo/s/commands/cluster_write_cmd.cpp
+++ b/src/mongo/s/commands/cluster_write_cmd.cpp
@@ -96,7 +96,6 @@ public:
                            const std::string& dbname,
                            const BSONObj& cmdObj,
                            ExplainOptions::Verbosity verbosity,
-                           const rpc::ServerSelectionMetadata& serverSelectionMetadata,
                            BSONObjBuilder* out) const {
         BatchedCommandRequest request(_writeType);
 
diff --git a/src/mongo/s/commands/commands_public.cpp b/src/mongo/s/commands/commands_public.cpp
index 208539821b9..80fbf479a93 100644
--- a/src/mongo/s/commands/commands_public.cpp
+++ b/src/mongo/s/commands/commands_public.cpp
@@ -888,7 +888,6 @@ public:
                    const std::string& dbname,
                    const BSONObj& cmdObj,
                    ExplainOptions::Verbosity verbosity,
-                   const rpc::ServerSelectionMetadata& serverSelectionMetadata,
                    BSONObjBuilder* out) const override {
         // We will time how long it takes to run the commands on the shards.
         Timer timer;
@@ -1116,7 +1115,6 @@ public:
                    const std::string& dbname,
                    const BSONObj& cmdObj,
                    ExplainOptions::Verbosity verbosity,
-                   const rpc::ServerSelectionMetadata& ssm,
                    BSONObjBuilder* out) const {
         const NamespaceString nss(parseNsCollectionRequired(dbname, cmdObj));
 
diff --git a/src/mongo/s/commands/strategy.cpp b/src/mongo/s/commands/strategy.cpp
index 707b728efe4..59f899a88b1 100644
--- a/src/mongo/s/commands/strategy.cpp
+++ b/src/mongo/s/commands/strategy.cpp
@@ -353,15 +353,20 @@ DbResponse Strategy::clientCommandOp(OperationContext* opCtx,
         if (e.type() == Object && (e.fieldName()[0] == '$' ? str::equals("query", e.fieldName() + 1)
                                                            : str::equals("query", e.fieldName()))) {
             // Extract the embedded query object.
-            if (cmdObj.hasField(Query::ReadPrefField.name())) {
+            if (auto readPrefElem = cmdObj[Query::ReadPrefField.name()]) {
                 // The command has a read preference setting. We don't want to lose this information
-                // so we copy this to a new field called $queryOptions.$readPreference
+                // so we put it on the OperationContext and copy it to a new field called
+                // $queryOptions.$readPreference
+                auto readPref =
+                    uassertStatusOK(ReadPreferenceSetting::fromBSON(readPrefElem.Obj()));
+                rpc::ServerSelectionMetadata::get(opCtx) = rpc::ServerSelectionMetadata(
+                    readPref.pref != ReadPreference::PrimaryOnly, readPref);
                 haveReadPref = true;
                 BSONObjBuilder finalCmdObjBuilder;
                 finalCmdObjBuilder.appendElements(e.embeddedObject());
 
                 BSONObjBuilder queryOptionsBuilder(finalCmdObjBuilder.subobjStart("$queryOptions"));
-                queryOptionsBuilder.append(cmdObj[Query::ReadPrefField.name()]);
+                queryOptionsBuilder.append(readPrefElem);
                 queryOptionsBuilder.done();
 
                 cmdObj = finalCmdObjBuilder.obj();
@@ -373,6 +378,8 @@ DbResponse Strategy::clientCommandOp(OperationContext* opCtx,
         if (!haveReadPref && q.queryOptions & QueryOption_SlaveOk) {
             // If the slaveOK bit is set, behave as-if read preference secondary-preferred was
             // specified.
+            rpc::ServerSelectionMetadata::get(opCtx) = rpc::ServerSelectionMetadata(
+                true, ReadPreferenceSetting(ReadPreference::SecondaryPreferred));
             BSONObjBuilder finalCmdObjBuilder;
             finalCmdObjBuilder.appendElements(cmdObj);