SERVER-54278 Add feature flag to disable Opportunistic Reads by default

6 files changed, 75 insertions, 2 deletions

diff --git a/buildscripts/resmokeconfig/suites/sharding_opportunistic_secondary_targeting.yml b/buildscripts/resmokeconfig/suites/sharding_opportunistic_secondary_targeting.yml
new file mode 100644
index 00000000000..df51dad2dc0
--- /dev/null
+++ b/buildscripts/resmokeconfig/suites/sharding_opportunistic_secondary_targeting.yml
@@ -0,0 +1,15 @@
+test_kind: js_test
+
+selector:
+  roots:
+  - jstests/sharding/*.js
+
+executor:
+  config:
+    shell_options:
+      nodb: ''
+      readMode: commands
+      global_vars:
+        TestData:
+          setParametersMongos:
+            opportunisticSecondaryTargeting: true
diff --git a/etc/evergreen.yml b/etc/evergreen.yml
index eef959c35fe..6ca4e037eee 100644
--- a/etc/evergreen.yml
+++ b/etc/evergreen.yml
@@ -4688,6 +4688,15 @@ tasks:
       resmoke_args: --storageEngine=wiredTiger
       fallback_num_sub_suites: 4
 
+- name: sharding_opportunistic_secondary_targeting_gen
+  tags: ["sharding", "common"]
+  commands:
+  - func: "generate resmoke tasks"
+    vars:
+      use_large_distro: "true"
+      resmoke_args: --storageEngine=wiredTiger
+      fallback_num_sub_suites: 32
+
 - <<: *task_template
   name: change_streams
   tags: ["change_streams"]
@@ -7434,6 +7443,7 @@ buildvariants:
   - name: sharded_multi_stmt_txn_jscore_passthrough
   - name: .sharding .jscore !.wo_snapshot
   - name: sharding_gen
+  - name: sharding_opportunistic_secondary_targeting_gen
   - name: .stitch
 
 - name: linux-64-duroff
@@ -8344,6 +8354,7 @@ buildvariants:
     - windows-64-vs2017-compile
   - name: session_jscore_passthrough
   - name: sharding_gen
+  - name: sharding_opportunistic_secondary_targeting_gen
   - name: .stitch
 
 - name: enterprise-windows-64-2k8
@@ -8395,6 +8406,7 @@ buildvariants:
   - name: sharding_auth_gen
   - name: sharding_auth_audit_gen
   - name: sharding_ese_gen
+  - name: sharding_opportunistic_secondary_targeting_gen
   - name: snmp
   - name: push
     distros:
@@ -8857,6 +8869,7 @@ buildvariants:
   - name: sharded_multi_stmt_txn_jscore_passthrough
     distros:
     - rhel62-large
+  - name: sharding_opportunistic_secondary_targeting_gen
   - name: snmp
   - name: .stitch
   - name: .updatefuzzer
@@ -10624,6 +10637,35 @@ buildvariants:
   - name: .stitch
   - name: .updatefuzzer
 
+- name: enterprise-ubuntu-sharding-opportunistic-secondary-targeting-1804-64-bit
+  display_name: "~ Enterprise Ubuntu 18.04 (with {opportunisticSecondaryTargeting: true})"
+  batchtime: 1440 # 1 day
+  run_on:
+  - ubuntu1804-test
+  modules:
+  - enterprise
+  expansions:
+    scons_cache_scope: shared
+    compile_flags: MONGO_DISTMOD=ubuntu1804 -j$(grep -c ^processor /proc/cpuinfo) --variables-files=etc/scons/mongodbtoolchain_v3_gcc.vars
+    multiversion_platform: ubuntu1804
+    multiversion_edition: enterprise
+    test_flags: >-
+        --mongosSetParameters="opportunisticSecondaryTargeting: true"
+    large_distro_name: ubuntu1804-build
+  tasks:
+  - name: compile_all_run_unittests_TG
+    distros:
+    - ubuntu1804-build
+  - name: .aggregation !.no_async
+  - name: .sharding .auth
+  - name: .sharding .causally_consistent !.wo_snapshot
+  - name: .concurrency .common !.kill_terminate
+  - name: .integration !.audit
+  - name: .jscore .common
+  - name: .logical_session_cache .one_sec
+  - name: .sharding .jscore !.wo_snapshot !.multi_stmt
+  - name: .sharding .common !.csrs
+
 - name: ubuntu1804-asan
   display_name: ~ ASAN SSL Ubuntu 18.04
   run_on:
diff --git a/src/mongo/executor/SConscript b/src/mongo/executor/SConscript
index 7c015cb39f3..ae3803a1f03 100644
--- a/src/mongo/executor/SConscript
+++ b/src/mongo/executor/SConscript
@@ -45,6 +45,7 @@ env.Library(target='async_multicaster',
 env.Library(target='task_executor_interface',
             source=[
                 'task_executor.cpp',
+                env.Idlc("executor_parameters.idl")[0],
             ],
             LIBDEPS=[
                 '$BUILD_DIR/mongo/base',
@@ -261,7 +262,6 @@ env.Library(
     target='task_executor_pool',
     source=[
         'task_executor_pool.cpp',
-        env.Idlc("task_executor_pool_parameters.idl")[0],
     ],
     LIBDEPS=[
         '$BUILD_DIR/mongo/idl/server_parameter',
diff --git a/src/mongo/executor/task_executor_pool_parameters.idl b/src/mongo/executor/executor_parameters.idl
index 8eba1da54c9..63d1b82231d 100644
--- a/src/mongo/executor/task_executor_pool_parameters.idl
+++ b/src/mongo/executor/executor_parameters.idl
@@ -38,3 +38,12 @@ server_parameters:
     cpp_vartype: "AtomicWord<int>"
     cpp_varname: "taskExecutorPoolSize"
     default: 1
+
+  opportunisticSecondaryTargeting:
+    description: >-
+        Allows attempting to establish connections to multiple secondaries and directing the request 
+        to the first secondary that accepts the connection.
+    set_at: [ startup, runtime ]
+    cpp_vartype: 'AtomicWord<bool>'
+    cpp_varname: 'gOpportunisticSecondaryTargeting'
+    default: false
diff --git a/src/mongo/executor/network_interface_tl.cpp b/src/mongo/executor/network_interface_tl.cpp
index e8cd15f3e60..93abd40fce3 100644
--- a/src/mongo/executor/network_interface_tl.cpp
+++ b/src/mongo/executor/network_interface_tl.cpp
@@ -36,6 +36,7 @@
 #include "mongo/db/commands/test_commands_enabled.h"
 #include "mongo/db/server_options.h"
 #include "mongo/executor/connection_pool_tl.h"
+#include "mongo/executor/executor_parameters_gen.h"
 #include "mongo/transport/transport_layer_manager.h"
 #include "mongo/util/concurrency/idle_thread_block.h"
 #include "mongo/util/log.h"
@@ -271,6 +272,12 @@ Status NetworkInterfaceTL::startCommand(const TaskExecutor::CallbackHandle& cbHa
         request.metadata = newMetadata.obj();
     }
 
+    // If "Opportunistic Secondary Targeting" is disabled, then we target only the first host of the
+    // set we are given.
+    if (request.target.size() > 1 && !gOpportunisticSecondaryTargeting.loadRelaxed()) {
+        request.target.resize(1);
+    }
+
     auto pf = makePromiseFuture<RemoteCommandOnAnyResponse>();
 
     auto cmdState = CommandState::make(this, request, cbHandle, std::move(pf.promise));
diff --git a/src/mongo/executor/task_executor_pool.cpp b/src/mongo/executor/task_executor_pool.cpp
index 2f7bd5d95d8..a56f94580ca 100644
--- a/src/mongo/executor/task_executor_pool.cpp
+++ b/src/mongo/executor/task_executor_pool.cpp
@@ -34,8 +34,8 @@
 #include <algorithm>
 
 #include "mongo/executor/connection_pool_stats.h"
+#include "mongo/executor/executor_parameters_gen.h"
 #include "mongo/executor/task_executor.h"
-#include "mongo/executor/task_executor_pool_parameters_gen.h"
 #include "mongo/util/processinfo.h"
 
 namespace mongo {