Broker Info

5 min

The Broker Info page reports the operational state of the MQTT broker in Litmus Unify. It shows which protocol limits and optional features are in effect, how many clients are connected, and how many messages the broker has handled.

To access the Broker Info page:

Navigate to MQTT > Broker Info.

Metrics reference

The page includes two kinds of value. Protocol limits and Server capabilities are broker configurations. They tell you what the broker accepts. Clients and Messages are counters that change as traffic flows.

Protocol limits

Metric	Description
Maximum Message Expiry Interval	Longest time (in seconds) that the broker holds an undelivered message before discarding it
Maximum Session Expiry Interval	Longest time (in seconds) that the broker keeps a disconnected client's session state, including its subscriptions and queued messages
Maximum Client Writes Pending	Number of outbound writes the broker queues for a single client before it refuses further writes to that client
Maximum Packet Size	Largest MQTT packet (in bytes) that the broker accepts. The broker rejects larger packets
Receive Maximum	Number of QoS messages a client can have in flight before it waits for acknowledgment
Topic Alias Maximum	Highest topic alias value a client can use. A topic alias replaces a full topic string with a short integer to reduce packet size

Server capabilities

Metric	Description
Maximum QoS	Highest quality of service level the broker accepts: 0, 1, or 2
Retain Available	Whether the broker stores retained messages and delivers them to new subscribers. 1 is true and 0 is false.
Wildcard Sub Available	Whether clients can subscribe using the + and # wildcards. 1 is true and 0 is false.
Sub Id Available	Whether clients can attach a subscription identifier to a subscription and receive it back on matching messages. 1 is true and 0 is false.
Shared Sub Available	Whether clients can share a subscription so that the broker distributes messages across a group instead of sending to every member. 1 is true and 0 is false.

Clients

Metric	Description
Clients Connected	Clients with an active connection to the broker
Clients Disconnected	Clients with a persistent session that are not currently connected
Clients Max	Maximum number of clients that can connect to the broker
Clients Total	Cumulative total number of clients
Subscriptions	Active subscriptions across all clients

Messages

Metric	Description
Messages Sent	Messages the broker has delivered to clients
Messages Received	Messages the broker has accepted from clients
Messages Dropped	Messages the broker discarded without delivering

MQTT