Client Status Events

The AMPS engine will publish client status events to the internal /AMPS/ClientStatus topic whenever a client connects, issues a logon command, disconnects, enters or removes a subscription, queries a SOW or issues a sow_delete. AMPS sends a message if a client fails authentication. In addition, upon a disconnect, a client status message will be published for each subscription that the client had registered at the time of the disconnect. This mechanism allows any client to monitor what other clients are doing and is especially useful for publishers to determine when clients subscribe to a topic of interest.

To help identify clients, it is recommended that clients send a logon command to the AMPS engine and specify a meaningful client name. This client name is used to identify the client within client status event messages, logging output and information on clients within the monitoring console. The client name must be unique if a transaction log is configured for the AMPS instance.

Each message published to the client status topic will contain an event and a client_name. Depending on the event type, the message will contain other relevant fields.

For example, the following JSON document demonstrates the message for a SOW query:

{
 "ClientStatus":{
    "timestamp":"20160509T171919.976304Z",
    "event":"sow",
    "client_name":"test_client",
    "connection_name":"AMPS-Sample-any-tcp-9-242891694350073019",
    "correlation_id":null,
    "query_id":"1",
    "topic":"order",
    "filter":"/item/qty > 50",
    "options":"send_empties",
    "sub_id":"1",
    "auth_id":null,
    "entitlement_filter":null
 }
}

The table below defines the header fields which may be returned as part of the subscription messages to the /AMPS/ClientStatus topic.

FIX	XML	JSON/BSON/MsgPack	Description
20062	Reason	reason	Reason for the event (if applicable). This is present on client disconnect events to record the reason that the client disconnected.
20065	Timestamp	timestamp	Timestamp at which AMPS processed the message.
20066	Event	event	Command executed by the client.
20067	ClientName	client_name	Client Name
20068	Tpc	topic	Topic for the event (if applicable).
20069	Filter	filter	Filter (if applicable).
20070	SubId	sub_id	Subscription ID (if applicable).
20071	ConnName	connection_name	Internal AMPS connection name.
20072	Options	options	The options for the subscription (if applicable).
20073	QId	query_id	The identifier for the query (if applicable).
20074	CorrelationID	correlation_id	The correlation ID of the command (if applicable).
20080	ClientAddr	client_address	The remote address of the client.
20081	AuthId	auth_id	The authenticated identity of the client (if applicable).
20082	EntitlementFilter	entitlement_filter	The entitlement filter for the command (if applicable).

Since the client status messages must be able to be serialized based on data in AMPS, the /AMPS/ClientStatus topic is not available for message types that rely on a fixed schema, such as protobuf or struct, and is not available for messages that have no fixed serialization such as binary or composite message types.