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Version: 3.2

Azure Monitor Logs

Cribl LogStream supports sending data to Azure Monitor Logs. This is a streaming Destination type.

Configuring Cribl LogStream to Output to Azure Monitor Logs

In the QuickConnect UI: Click + Add beside Destinations. From the resulting drawer's tiles, select Azure > Monitor Logs. Next, click either + Add New or (if displayed) Select Existing. The resulting drawer will provide the following options and fields.

Or, in the Data Routes UI: From the top nav of a LogStream instance or Group, select Data > Destinations. From the resulting page's tiles or the Destinations left nav, select Azure > Monitor Logs. Next, click + Add New to open a New Destination modal that provides the following options and fields.

General Settings

Output ID: Enter a unique name to identify this Azure Monitor Logs definition.

Workspace ID: Enter the Azure Log Analytics Workspace ID. (In the Azure Dashboard, see Workspace > Advanced settings.)

Workspace key: Enter the Azure Log Analytics Workspace Primary or Secondary Shared Key. (In the Azure Dashboard, see Workspace > Advanced settings.)

Log type: The Record Type of events sent to this LogAnalytics workspace. Defaults to Cribl.

Resource ID: Resource ID of the Azure resource to associate the data with. This populates the _ResourceId property, and allows the data to be included in resource-centric queries. (Optional, but if this field is not specified, the data will not be included in resource-centric queries.)

Backpressure behavior: Whether to block, drop, or queue events when all receivers are exerting backpressure. Defaults to Block.

Persistent Queue Settings

This section is displayed when the Backpressure behavior is set to Persistent Queue.

Max file size: The maximum size to store in each queue file before closing it. Enter a numeral with units of KB, MB, etc. Defaults to 1 MB.

Max queue size: The maximum amount of disk space the queue is allowed to consume. Once this limit is reached, queueing is stopped, and data blocking is applied. Enter a numeral with units of KB, MB, etc.

Queue file path: The location for the persistent queue files. This will be of the form: your/path/here/<worker-id>/<output-id>. Defaults to $CRIBL_HOME/state/queues.

Compression: Codec to use to compress the persisted data, once a file is closed. Defaults to None; Gzip is also available.

Queue-full behavior: Whether to block or drop events when the queue is exerting backpressure (because disk is low or at full capacity). Block is the same behavior as non-PQ blocking, corresponding to the Block option on the Backpressure behavior drop-down. Drop new data throws away incoming data, while leaving the contents of the PQ unchanged.

Processing Settings

Post‑Processing

Pipeline: Pipeline to process data before sending the data out using this output.

System fields: A list of fields to automatically add to events that use this output. By default, includes cribl_pipe (identifying the LogStream Pipeline that processed the event). Supports wildcards. Other options include:

  • cribl_host – LogStream Node that processed the event.
  • cribl_wp – LogStream Worker Process that processed the event.
  • cribl_input – LogStream Source that processed the event.
  • cribl_output – LogStream Destination that processed the event.

Advanced Settings

Validate server certs: Toggle to Yes to reject certificates that are not authorized by a CA in the CA certificate path, nor by another trusted CA (e.g., the system's CA).

Round-robin DNS: Toggle to Yes to use round-robin DNS lookup. When a DNS server returns multiple addresses, this will cause LogStream to cycle through them in the order returned.

Request timeout: Amount of time (in seconds) to wait for a request to complete before aborting it. Defaults to 30.

Request concurrency: Maximum number of concurrent requests before blocking. This is set per Worker Process. Defaults to 5.

Max body size (KB): Maximum size of the request body. Defaults to 4096.

Flush period (sec): Maximum time between requests. Low settings could cause the payload size to be smaller than its configured maximum. Defaults to 1.

Extra HTTP headers: Name/Value pairs to pass as additional HTTP headers.

Environment: If you're using GitOps, optionally use this field to specify a single Git branch on which to enable this configuration. If empty, the config will be enabled everywhere.

Azure Monitor Limitations

The Azure Monitor Logs architecture limits the number of columns per table, characters per column name, and other parameters. For details, see Microsoft's Azure Monitor Service Limits topic.

Azure will drop logs if your data exceeds these limits. To diagnose this, you can search in the Azure Data Explorer console with a query like this:

Operation | summarize count() by Detail

...for error messages of this form:

Data of type <type> was dropped: The number of custom fields <number> is above the limit of 500 fields per data type.

Notes on HTTP-based Outputs

  • Cribl LogStream will attempt to use keepalives to reuse a connection for multiple requests. After 2 minutes of the first use, the connection will be thrown away, and a new one will be reattempted. This is to prevent sticking to a particular Destination when there is a constant flow of events.

  • If keepalives are not supported by the server (or if the server closes a pooled connection while idle), a new connection will be established for the next request.

  • When resolving the Destination's hostname, LogStream will pick the first IP in the list for use in the next connection. Enable Round-robin DNS to better balance distribution of events between destination cluster nodes.