Slow subscribers statistics

    Open EMQX Dashboard, click on the “Module” on the left.

    Then, select the Slow Subscribers Statistics module, and then click Enable

    With this feature enabled, EMQX will start measuring message transmission latency. The measurement always starts when a message is received by EMQX, the end of the measurement is configurable. See more details below in configurations.

    The per clientid-topic latency measurements are then ranked in the table view.

    • top_k_num

      This field determines the upper limit of the number of statistical records in the ranking table

    • expire interval controls the effective time of each ranking record. If the a client-topic has no higher latency inserted for such long time, the record expires. For example if expire interval is 5 minutes, and client1-topic1 had a latency 500ms recorded (ranked top-K) at T1, and for the next 5 minutes, if there is no further measurements greater than 500, the ranking recorded will be deleted shortly after T1+5min

    • stats_type

      The ways to calculate the latency are as follows:

      1. From the time the message arrives at EMQX until the message completes transmission

      2. From the time EMQX starts delivering the message, until the message completes transmission

      1. QoS0

        When EMQX starts to deliver

      2. QoS1

        When EMQX receives puback from the client

      3. Qos2

        When EMQX receives pubcomp from the client

    Note: The open source version is configured in emqx.conf

    image

    Under this tab, the subscriber information will be displayed in descending order according to the time latency. After Clicking Client ID, it will display the subscriber details, where you can analyze and find the problem.