Library: MongoDB
Package: MongoDB
Header: Poco/MongoDB/TopologyDescription.h
Description
Maintains the complete MongoDB replica set topology state.
This class tracks all known servers in a replica set and their current state. It is updated based on 'hello' command responses from MongoDB servers.
The topology type automatically transitions based on server discovery: - Unknown: Initial state, no servers contacted - Single: Single standalone server - ReplicaSetNoPrimary: Replica set without a primary - ReplicaSetWithPrimary: Replica set with a primary - Sharded: Sharded cluster (mongos routers)
THREAD SAFETY: This class is thread-safe. All public methods use internal synchronization to protect the topology state.
Member Summary
Member Functions: addServer, clear, findPrimary, findSecondaries, getServer, hasPrimary, hasServer, markServerUnknown, operator !=, operator =, operator ==, removeServer, serverCount, servers, setName, type, typeToString, updateServer
Enumerations
TopologyType
MongoDB topology type enumeration
Topology not yet determined
Single server (standalone)
Replica set without primary
Replica set with primary
Sharded cluster
Constructors
TopologyDescription
Creates an empty topology description.
TopologyDescription
explicit TopologyDescription(
const std::string & setName
);
Creates a topology description for a replica set with the given name.
TopologyDescription
TopologyDescription(
const TopologyDescription & other
);
Copy constructor.
TopologyDescription
TopologyDescription(
TopologyDescription && other
) noexcept;
Move constructor.
Destructor
~TopologyDescription
Destroys the TopologyDescription.
Member Functions
addServer
void addServer(
const Net::SocketAddress & address
);
Adds a server to the topology in Unknown state. If the server already exists, this is a no-op.
clear
void clear();
Removes all servers and resets to Unknown topology type.
findPrimary
[[nodiscard]]
ServerDescription findPrimary() const;
Finds and returns the primary server. Returns an Unknown server description if no primary exists.
findSecondaries
[[nodiscard]]
std::vector < ServerDescription > findSecondaries() const;
Finds and returns all secondary servers.
getServer
[[nodiscard]]
ServerDescription getServer(
const Net::SocketAddress & address
) const;
Returns the server description for the given address. Returns an Unknown server description if not found.
hasPrimary
[[nodiscard]]
bool hasPrimary() const;
Returns true if a primary server exists in the topology.
hasServer
[[nodiscard]]
bool hasServer(
const Net::SocketAddress & address
) const;
Returns true if the server with the given address is in the topology.
markServerUnknown
void markServerUnknown(
const Net::SocketAddress & address,
const std::string & error = ""
);
Marks a server as Unknown (typically after an error). This may trigger topology type transitions.
operator !=
bool operator != (
const TopologyDescription & other
) const;
Inequality comparison operator.
operator =
TopologyDescription & operator = (
const TopologyDescription & other
);
Assignment operator.
operator =
TopologyDescription & operator = (
TopologyDescription && other
) noexcept;
Move assignment operator.
operator ==
bool operator == (
const TopologyDescription & other
) const;
Equality comparison operator. Compares topology type, set name, and all servers.
removeServer
void removeServer(
const Net::SocketAddress & address
);
Removes a server from the topology. This may trigger topology type transitions.
serverCount
[[nodiscard]]
std::size_t serverCount() const;
Returns the number of servers in the topology.
servers
[[nodiscard]]
std::vector < ServerDescription > servers() const;
Returns a copy of all server descriptions. This is thread-safe but creates a copy.
setName
[[nodiscard]]
std::string setName() const;
Returns the replica set name, or empty string if not a replica set.
setName
void setName(
const std::string & name
);
Sets the replica set name.
type
[[nodiscard]]
TopologyType type() const;
Returns the current topology type.
typeToString 
[[nodiscard]]
static std::string typeToString(
TopologyType type
);
Converts a topology type enum to a human-readable string. Returns "Unknown", "Single Server", "Replica Set (with Primary)", "Replica Set (no Primary)", or "Sharded Cluster".
updateServer
const ServerDescription & updateServer(
const Net::SocketAddress & address,
const Document & helloResponse,
Poco::Int64 rttMicros
);
Updates a server's description from a 'hello' command response. If the server doesn't exist in the topology, it is added. This may also trigger topology type transitions.
Returns a const reference to the updated server description.