gmondump

gmondump [OPTIONS]

-h, --help
    Displays a help message showing all available options and exits.

-V, --version
    Prints the version information of gmondump and exits.

-d RRD_DIR, --dir=RRD_DIR
    Specifies the root directory where Ganglia RRD (Round Robin Database) files are stored. This is typically the directory managed by gmetad.

-o OUTPUT_FILE, --output=OUTPUT_FILE
    Redirects the XML output to the specified file. If this option is not provided, gmondump writes the output to standard output (stdout).

-c CLUSTER_NAME, --cluster=CLUSTER_NAME
    Filters the output to include data only from the specified Ganglia cluster. This is useful in environments with multiple monitored clusters.

-H HOST_NAME, --host=HOST_NAME
    Filters the output to include data only from the specified host. This allows targeting specific machine data within a cluster.

-m METRIC_NAME, --metric=METRIC_NAME
    Filters the output to include data only for the specified metric name (e.g., 'cpu_idle', 'mem_free').

-a, --all-data
    Dumps all historical data points available in the RRD files for the selected metrics, rather than just the latest recorded value. Using this option can lead to very large output files.

-v, --verbose
    Enables verbose output, providing more detailed information about the dumping process, including which files are being processed.

gmondump is a utility included with the Ganglia distributed monitoring system. Its primary function is to extract historical performance metrics stored in Ganglia's RRD (Round Robin Database) files. The command reads these highly efficient time-series databases, which contain collected data from various hosts and clusters, and typically outputs the information in a structured XML format.

This tool is invaluable for a variety of tasks, including migrating Ganglia data to new servers, performing offline analysis of historical performance trends, debugging issues with RRD files, or integrating Ganglia data with external systems. By default, gmondump outputs only the latest recorded value for each metric. However, it can be instructed to dump all historical data points, which can generate very large output files depending on the scale of the monitoring environment.

• Requires Ganglia RRD Files: gmondump relies on the RRD file structure created by gmetad or gmond. It will not function correctly without a valid and accessible Ganglia RRD directory.
• Large Output with --all-data: When using the --all-data (-a) option, the generated XML output can be extremely large, especially in large-scale deployments or with long data retention periods. This can consume significant disk space and may require substantial time to process.
• XML Parsing Required: The primary output format is XML, which necessitates appropriate XML parsers or scripting tools for further processing, analysis, or integration into other systems.
• Resource Intensive: Dumping large datasets can be I/O intensive on the host system, potentially impacting disk performance during the operation.

• Data Migration: Facilitates moving existing Ganglia RRD data from one server to another, or upgrading Ganglia installations while preserving historical metrics.
• Offline Analysis: Enables exporting comprehensive historical data for detailed post-mortem analysis using external analytical tools, custom scripts, or data visualization platforms.
• Debugging and Troubleshooting: Provides a way to inspect the raw content of RRD files and verify data integrity, which is invaluable when diagnosing data collection or storage issues within Ganglia.
• Integration with Other Systems: Offers a structured data source (XML) for integrating Ganglia metrics into other monitoring dashboards, data warehouses, custom reporting tools, or third-party applications.

The XML output generated by gmondump follows a hierarchical structure, typically rooted by a <GANGLIA_RRD> element. Within this, data is organized into <CLUSTER>, <HOST>, and <METRIC> tags, mirroring Ganglia's internal data model. Each metric entry usually includes attributes such as 'name', 'val' (for the current value), and, if the --all-data option is used, time-series data points with their corresponding timestamps. Users intending to process this output should have familiarity with XML parsing techniques.

gmondump emerged as a vital utility within the Ganglia distributed monitoring system, an open-source project initiated at the University of California, Berkeley, in the early 2000s. From its inception, Ganglia leveraged RRDtool for the efficient storage and retrieval of time-series performance data. As the adoption and complexity of Ganglia deployments grew, so did the need for robust mechanisms to extract this valuable historical data for purposes such as migration, in-depth analysis, or integration with external systems.

gmondump was developed to meet this demand, providing a structured, typically XML, export of the collected performance metrics. It has remained a stable and essential component of the Ganglia distribution, underscoring the project's commitment to data accessibility and interoperability. Its core functionality of exporting RRD data has largely remained consistent throughout its development history.

gmond(8), gmetad(8), rrdtool(1), ganglia-web(8)