Monitoring data usage in Hermes

  • Release version: Xanadu
  • Updated April 28, 2025
  • 2 minutes to read
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    Summary of Monitoring data usage in Hermes

    ServiceNow customers can monitor the volume of data produced to the Hermes messaging cluster over time using the Hermes Usage Dashboard. Data usage is calculated by aggregating the combined size of message keys and message payloads sent to the cluster. This monitoring enables insight into data inflow measured in megabytes, helping track performance and usage trends across topics and applications.

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    Key Features

    • Hermes Usage Dashboard: Visualizes data usage trends over time for all topics or individual topics within Hermes.
    • Data Aggregation: Usage data is collected hourly and aggregated daily or monthly depending on the selected date range, supporting analysis up to 12 months.
    • Role-Based Access: Access requires either the hermesadmin or admin role.
    • Flexible Views: Compare topics within a single application or across all applications you own to identify spikes, drops, or trends in data production.
    • Data Source: Metrics are sourced from the hermesusagemetrics table, which stores usage data points reflecting the latest hourly values.

    Practical Use Cases

    • Monitor if an application’s data production to Hermes is increasing, decreasing, or stable over time.
    • Identify unusual usage patterns such as sudden spikes or drops to troubleshoot potential issues or validate system changes.
    • Assess whether data being produced aligns with Hermes support capabilities by detecting consistent decreases in usage.
    • Compare usage among multiple topics within an application to optimize resource allocation and messaging strategies.

    Important Details

    • The dashboard shows overall trends rather than moment-to-moment traffic to provide meaningful long-term insights.
    • Data is summarized monthly for date ranges exceeding 60 days and daily for shorter ranges.
    • Each message’s usage size includes both the key size (if present) and the message payload size to ensure accurate accounting.
    • Relevant related tasks include checking Hermes Kafka cluster status and viewing Hermes service logs for deeper troubleshooting.

    Monitor data usage in Hermes over time.

    Monitor the amount of data that is produced to the Hermes cluster over time in the Hermes Usage Dashboard.

    Usage data is calculated by aggregating the size of all messages sent to the cluster. The size for each message is determined by combining the key size, if present, and the actual size of the message sent to the Hermes cluster. For example, if a 100 MB message is sent to the cluster with a 2 MB key size, 102 MB usage is recorded for the message.

    Key benefits

    • Monitor Hermes performance with insights into data inflow in megabytes for a specified time period.
    • Visualize data usage over time for all topics or a single topic.
    • Compare data usage for topics that belong to an application.
    Figure 1. Hermes Usage Dashboard
    Hermes Metrics Dashboard.

    Required roles

    Either the hermes_admin or admin role is required to view the Hermes Usage Dashboard.

    Accessing the Hermes Usage Dashboard

    View usage by navigating to All > Hermes Messaging Service > Usage Dashboard.

    Use cases

    • Monitor data usage for an application. Determine if usage has increased or decreased over time.
    • View data usage for a specific topic. Determine if usage patterns changed by looking for spikes or drops in usage.
    • Look for decreased usage over time to determine if your application is producing data that isn't supported by Hermes.
    • Compare data usage for topics in a single application or all applications that belong to you.

    Reports

    Data displayed in the Hermes Metrics Dashboard is collected from the Hermes usage metrics [hermes_usage_metrics] table.
    • Metric data is captured hourly, with each collection point reflecting the latest value recorded within that hour.
    • Metric data is aggregated and displayed over time. This means the dashboard enables you to view an overall trend rather than precise moment-to-moment traffic.
    • Metric data displayed on the dashboard is initially aggregated daily. Depending on the date range you select, the dashboard dynamically adjusts its view. For example, for ranges greater than 60 days, it presents the data in monthly summaries. For ranges less than 60 days, it displays daily summaries.
    • Metric data is retained for 12 months.
    Title Type Source table Description
    Total Megabytes In Single score Hermes usage metrics [hermes_usage_metrics] table View the aggregated total of data produced to Hermes in megabytes.
    Usage trends Trend Hermes usage metrics [hermes_usage_metrics] table Monitor data usage in terms of bytes in for selected topics over time.
    Topic Usage Data Bar Hermes usage metrics [hermes_usage_metrics] table Compare data usage for each topic over time.