Automatic Reconnections

    The client will try to re-connect to one of the servers it knows about, either through the URLs provided in the call or the URLs provided by the NATS system during earlier connects. This feature allows NATS applications and the NATS system itself to self-heal and reconfigure itself with no additional configuration or intervention.

    Your application can register callbacks (in the connection options) to be notified about the following connection events:

    • ClosedCB ConnHandler

    The ClosedCB handler is called when a client will no longer be connected.

    • DisconnectedCB ConnHandler

    The DisconnectedCB handler is called whenever the connection is disconnected. It will not be called if DisconnectedErrCB is set DEPRECATED: Use DisconnectedErrCB instead which passes error that caused the disconnect event.

    • DisconnectedErrCB ConnErrHandler

    The DisconnectedErrCB handler is called whenever the connection is disconnected. Disconnected error could be nil, for instance when user explicitly closes the connection. NOTE: DisconnectedCB will not be called if DisconnectedErrCB is set

    The ReconnectedCB handler is called whenever the connection is successfully reconnected.

    • DiscoveredServersCB ConnHandler
    • AsyncErrorCB ErrHandler

    The AsyncErrorCB handler is called whenever asynchronous connection errors happen (e.g. slow consumer errors)

    • Timeout time.Duration

    Timeout sets the timeout for a Dial operation on a connection. Default is 2 * time.Second

    PingInterval is the period at which the client will be sending ping commands to the server, disabled if 0 or negative. Default is 2 * time.Minute

    • MaxPingsOut int

    MaxPingsOut is the maximum number of pending ping commands that can be awaiting a response before raising an ErrStaleConnection error. Default is 2

    Besides the error and advisory callbacks mentioned above you can also set a few reconnection attributes in the connection options:

    • AllowReconnect bool

    AllowReconnect enables reconnection logic to be used when we encounter a disconnect from the current server. Default is true

    • ReconnectWait time.Duration

    ReconnectWait sets the time to backoff after attempting to (and failing to) reconnect. Default is

    • CustomReconnectDelayCB ReconnectDelayHandler

    CustomReconnectDelayCB is invoked after the library tried every URL in the server list and failed to reconnect. It passes to the user the current number of attempts. This function returns the amount of time the library will sleep before attempting to reconnect again. It is strongly recommended that this value contains some jitter to prevent all connections to attempt reconnecting at the same time.

    • ReconnectJitter time.Duration

    ReconnectJitter sets the upper bound for a random delay added to ReconnectWait during a reconnect when no TLS is used. Note that any jitter is capped with ReconnectJitterMax. Default is 100 * time.Millisecond

    • ReconnectJitterTLS time.Duration

    ReconnectJitterTLS sets the upper bound for a random delay added to ReconnectWait during a reconnect when TLS is used. Note that any jitter is capped with ReconnectJitterMax. Default is 1 * time.Second

    • ReconnectBufSize int

    ReconnectBufSize is the size of the backing bufio during reconnect. Once this has been exhausted publish operations will return an error. Default is 8 * 1024 * 1024

    • RetryOnFailedConnect bool

    RetryOnFailedConnect sets the connection in reconnecting state right away if it can’t connect to a server in the initial set. The MaxReconnect and ReconnectWait options are used for this process, similarly to when an established connection is disconnected. If a ReconnectHandler is set, it will be invoked when the connection is established, and if a ClosedHandler is set, it will be invoked if it fails to connect (after exhausting the MaxReconnect attempts). Default is