Hedging options should only be available on `mongos`

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    • Type: Bug
    • Resolution: Won't Fix
    • Priority: Major - P3
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    • Affects Version/s: None
    • Component/s: Internal Code
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    • Service Arch
    • ALL
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      Try running the following against a mongod server:

      db.adminCommand( { getParameter : 1, "readHedgingMode" : 1 } );
      Show
      Try running the following against a mongod server: db.adminCommand( { getParameter : 1, "readHedgingMode" : 1 } );
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      Hedging is controlled by the following server parameter, settable at both startup and runtime:

      server_parameters:
  readHedgingMode:
    description: >-
        Enables hedged reads.
    set_at: [ startup, runtime ]
    cpp_class:
      name: HedgingModeServerParameter

      The parameter is mapped to a global atomic, defined here and initialized to enabled:

      AtomicWord<ReadHedgingMode> gReadHedgingMode{ReadHedgingMode::kOn};

      This server parameter, along with other mongos-specific parameters (e.g., loadBalancerPort), is packed with async_requests_sender:

      env.Library(
    target='async_requests_sender',
    source=[
        'async_requests_sender.cpp',
    ],
    LIBDEPS=[
        ...
        'mongos_server_parameters',
    ],
    LIBDEPS_PRIVATE=[
        '$BUILD_DIR/mongo/executor/hedge_options_util',
    ],
)

      However, there are non-mongos compilation units that link against this target. For example, the following makes hedging and other mongos-specific behavior available for mongod servers:

      env.Library(
    target='sharded_agg_helpers',
    ...
    LIBDEPS=[
        ...
        '$BUILD_DIR/mongo/s/async_requests_sender',
        ...
    ],
)

            Assignee:
            [DO NOT USE] Backlog - Service Architecture
            Reporter:
            Amirsaman Memaripour
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              Created:
              Updated:
              Resolved: