Library Version 18.1.40

DbEnv::repmgr_msg_dispatch()
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## DbEnv::repmgr_msg_dispatch()

    #include <db_cxx.h>

    int
    DbEnv::repmgr_msg_dispatch(
            void (*msg_dispatch_fcn) (DbEnv *env, DbChannel *channel,
                                      Dbt *request, u_int32_t nrequest,
                                      u_int32_t cb_flags),
            u_int32_t flags);

Sets the message dispatch function. This function is responsible for receiving messages sent from remote sites using either the DbChannel::send_msg() or DbChannel::send_request() methods. If the message received by this function was sent using the DbChannel::send_msg() method then no response is required. If the message was sent using the DbChannel::send_request() method, then this function must send a response using the DbChannel::send_msg() method.

For best results, the `DbEnv::repmgr_msg_dispatch()` method should be called before the Replication Manager has been started.

The `DbEnv::repmgr_msg_dispatch()` method either returns a non-zero error value or throws an exception that encapsulates a non-zero error value on failure, and returns 0 on success.

### Parameters

#### msg_dispatch_fcn

This parameter is the application-specific function used to handle messages sent over Replication Manager message channels. It takes four parameters:

- `channel`

  Provides the DbChannel to be used to send a response back to the originator of the message. If the message was sent by the remote site using DbChannel::send_request() then this function should send a response back to the originator using the channel provided on this parameter. The message should be sent by calling DbChannel::send_msg() exactly once.

  This channel is valid only during the current invocation of the dispatch function; it is destroyed when the dispatch function returns. The application may not save a copy of the pointer and use it later elsewhere. Methods that do not make sense in the context of a message dispatch function (such as DbChannel::send_request() and DbChannel::close() ) will be rejected with `EINVAL`.

- `request`

  Array of Dbts containing the message received from the remote site.

- `nrequest`

  Specifies the number of elements in the `request` array.

- `cb_flags`

  This flag is `DB_REPMGR_NEED_RESPONSE` if the message requires a response. Otherwise, it is `0`.

This function does not return a value. If the function encounters an error, you can reflect the error back to the originator of the message by formatting an error message of your own design into the response.

#### flags

This parameter is currently unused, and must be set to 0.

### Errors

The `DbEnv::repmgr_msg_dispatch()` method may fail and throw a DbException exception, encapsulating one of the following non-zero errors, or return one of the following non-zero errors:

#### EINVAL

If this method is called from a Base API application, or if an invalid flag value or parameter was specified.

### Class

DbEnv

### See Also

Replication and Related Methods

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