NatsConnection

NATS connection using the default driver.

Description

The NatsConnection class is used to define NATS connections using the default driver.

Important points

  • By defining a connection and sharing it through multiple message queues, you can reduce the number of used database connections.

Configuration parameters

  • client_id: (optional) name of the client id
  • connection(s):
    • discovery_key: (optional) key to retrieve the connection from IDiscovery
    • host: host name or IP address
    • port: port number (default: 27017)
    • uri: resource URI or connection string with all parameters in it
  • credential(s):
    • store_key: (optional) key to retrieve the credentials from ICredentialStore
    • username: username
    • password: user’s password
  • options:
    • retry_connect: (optional) turns on/off automated reconnect when the connection is lost (default: true)
    • max_reconnect: (optional) maximum number of reconnection attempts (default: 3)
    • reconnect_timeout: (optional) number of milliseconds to wait on each reconnection attempt (default: 3000)
    • flush_timeout: (optional) number of milliseconds to wait on flushing messages (default: 3000)

References

  • *:logger:*:*:1.0 - (optional) ILogger components to pass log messages
  • *:discovery:*:*:1.0 - (optional) IDiscovery services
  • *:credential-store:*:*:1.0 (optional) credential stores to resolve credentials

Constructors

NewNatsConnection

Creates a new instance of the connection component.

NewNatsConnection() *NatsConnection

Fields

Connection

NATS connection pool object.

Connection: *nats.Conn

ConnectionResolver

Connection resolver.

ConnectionResolver: *NatsConnectionResolver

flushTimeout

Number of milliseconds to wait on flushing messages (default: 3000)

flushTimeout: int

Logger

Logger

Logger: *CompositeLogger

maxReconnect

Maximum number of reconnection attempts (default: 3)

maxReconnect: int

Options

Connection options

Options: *ConfigParams

reconnectTimeout

Number of milliseconds to wait on each reconnection attempt (default: 3000)

reconnectTimeout: int

retryConnect

Retry to connect option

retryConnect: bool

subscriptions

Topic subscriptions

subscriptions: []*NatsSubscription

Methods

checkOpen

Checks if the connection is open.
Raises an error if the connection is closed.

(c *NatsConnection) checkOpen() error

  • returns: error - error or nil if no errors occurred.

Close

Closes a component and frees used resources.

(c *NatsConnection) Close(ctx context.Context, correlationId string) error

  • ctx: context.Context - operation context.
  • correlationId: string - (optional) transaction id used to trace execution through the call chain.
  • returns: error - error or nil if no errors occurred.

Configure

Configures the component by passing its configuration parameters.

(c *NatsConnection) Configure(ctx context.Context, config *ConfigParams)

  • ctx: context.Context - operation context.
  • config: *ConfigParams - configuration parameters to be set.

CreateQueue

Creates a message queue. If the connection doesn’t support this function, it exists without error.

(c *NatsConnection) CreateQueue() error

  • name: string - name of the queue to be created.
  • returns: error - error or nil if no errors occurred.

DeleteQueue

Deletes a message queue. If the connection doesn’t support this function, it exists without error.

(c *NatsConnection) DeleteQueue() error

  • name: string - name of the queue to be deleted.
  • returns: error - error or nil if no errors occurred.

GetConnection

Gets the connection.

(c *NatsConnection) GetConnection() *nats.Conn

  • returns: *nats.Conn - connection to NATS

IsOpen

Checks if the component is open.

(c *NatsConnection) IsOpen() bool

  • returns: bool - true if the component is open and false otherwise.

Open

Opens the component.

(c *NatsConnection) Open(ctx context.Context, correlationId string) error

  • ctx: context.Context - operation context.
  • correlationId: string - (optional) transaction id used to trace execution through the call chain.
  • returns: error - error or nil if no errors occurred.

Publish

Publishes a message to a specified topic.

(c *NatsConnection) Publish(ctx context.Context, subject string, message *nats.Msg) error

  • ctx: context.Context - operation context.
  • subject: string - subject(topic) where the message will be placed
  • message: *nats.Msg - message to be published
  • returns: error - error or nil if no errors occurred.

ReadQueueNames

Reads a list of registered queue names. If the connection doesn’t support this function, it returns an empty list.

(c *NatsConnection) ReadQueueNames() ([]string, error)

  • returns: ([]string, error) - queue names.

SetReferences

Sets references to dependent components.

(c *NatsConnection) SetReferences(ctx context.Context, references IReferences)

  • ctx: context.Context - operation context.
  • references: IReferences - references to locate the component’s dependencies.

Subscribe

Subscribes to a topic.

(c *NatsConnection) Subscribe(ctx context.Context, subject string, queue string, listener INatsMessageListener) error

  • ctx: context.Context - operation context.
  • subject: string - subject(topic) name
  • options: string - subscription options
  • listener: INatsMessageListener - message listener
  • returns: error - error or nil if no errors occurred.

Unsubscribe

Unsubscribes from a previously subscribed topic.

(c *NatsConnection) Unsubscribe(ctx context.Context, subject string, queue string, listener INatsMessageListener) error

  • ctx: context.Context - operation context.
  • subject: string - subject(topic) name
  • listener: INatsMessageListener - message listener
  • returns: error - error or nil no errors occured.