Wrapper around Connection that selects a replica set server by read preference and re-sends a failed request when that is safe. The connection is opened on first use and reused while it stays open; a failed attempt drops it, so the next attempt selects a server again. Safe reads are re-sent after a network error, a timeout or a listed error reply; getMore and killCursors are never re-sent; every other command only after a not-primary reply, which means it was not executed. MongoDB/README-ReplicaSet.md lists the commands and replies.

Usage example:

ReplicaSet rs(config);
ReplicaSetConnection::Ptr conn = new ReplicaSetConnection(rs, ReadPreference::Primary);

OpMsgMessage request("mydb", "mycollection");
request.setCommandName(OpMsgMessage::CMD_FIND);
request.body().add("filter", filterDoc);

OpMsgMessage response;
conn->sendRequest(request, response);  // find is re-sent after a network error

THREAD SAFETY: This class is NOT thread-safe, just like Connection. Each thread must have its own ReplicaSetConnection instance, or use connection pooling with external synchronization.

For multi-threaded applications, use ReplicaSetPoolableConnectionFactory with Poco::ObjectPool.

Creates a ReplicaSetConnection for the given replica set and read preference. Timeouts and the wait for an available server come from the ReplicaSet configuration. Connects on first use.

Creates a ReplicaSetConnection with explicit timeouts for its own connections; topology refreshes keep the configured ones. socketTimeout 0 (the default) means the ReplicaSet's configured socket timeout; set Config::socketTimeoutSeconds to 0 for no timeout. Connects on first use.

Destroys the ReplicaSetConnection.

Returns the address of the currently connected server. Throws Poco::NullPointerException if not connected.

Returns a reference to the underlying Connection. Throws Poco::NullPointerException if not connected.

Returns true if currently connected to a server.

Returns true if the currently connected server still matches the read preference. Returns false if not connected or if the server no longer satisfies the read preference. This is useful for connection pool validation to detect when a server role has changed (e.g., primary became secondary).

Reads a response for a previously sent request.

Throws Poco::IOException if the connection that carries the reply is gone; no other connection can continue it.

Forces reconnection by selecting a new server from the replica set. Useful if you detect an error and want to send the request again.

Sends a request and reads the response, re-sending as described above. Makes at most max(number of servers in the topology, 5) attempts; a failed connect counts as one. An error reply not listed in MongoDB/README-ReplicaSet.md is returned in response. Throws Poco::IOException or Poco::TimeoutException when a network failure is not re-sent or the last attempt fails; IOException("MongoDB server error: ...") for a listed reply that is not re-sent or ends the last attempt, which response holds; IOException("No suitable server found in replica set"), with the previous failure, if any, nested; DataFormatException or NotImplementedException for a malformed reply or an unsupported BSON element type.

Sends a one-way request (fire-and-forget). Sets MSG_MORE_TO_COME flag and acknowledged=false.

Note: One-way requests are not re-sent on failure.