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Azure Event Hubs

Cribl Stream supports sending data to Azure Event Hubs.

Type: Streaming | TLS Support: Configurable | PQ Support: Yes

Azure Event Hubs uses a binary protocol over TCP. It does not support HTTP proxies, so Cribl Stream must send events directly to receivers. You might need to adjust your firewall rules to allow this traffic.

See Microsoft’s Compare Azure Event Hubs Tiers topic to configure tiers whose features and quotas match your desired data volume and throughput.

Configuring Cribl Stream to Output to Azure Event Hubs
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From the top nav, click Manage, then select a Worker Group to configure. Next, you have two options:

To configure via the graphical QuickConnect UI, click Routing > QuickConnect (Stream) or Collect (Edge). Next, click Add Destination at right. From the resulting drawer’s tiles, select Azure > Events Hub. Next, click either Add Destination or (if displayed) Select Existing. The resulting drawer will provide the options below.

Or, to configure via the Routing UI, click Data > Destinations (Stream) or More > Destinations (Edge). From the resulting page’s tiles or the Destinations left nav, select Azure > Events Hub. Next, click Add Destination to open a New Destination modal that provides the options below.

General Settings
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Output ID: Enter a unique name to identify this Azure Event Hubs definition.

Brokers: List of Event Hub Kafka brokers to connect to. (For example, yourdomain.servicebus.windows.net:9093.) Find the hostname in Shared Access Policies, in the host portion of the primary or secondary connection string.

Event Hub name: The name of the Event Hub (a.k.a., Kafka Topic) on which to publish events. Can be overwritten using the __topicOut field.

Optional Settings
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** Acknowledgments**: Control the number of required acknowledgments. Defaults to Leader.

Record data format: Format to use to serialize events before writing to the Event Hub Kafka brokers. Defaults to JSON.

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

Tags: Optionally, add tags that you can use to filter and group Destinations in Cribl Stream’s Manage Destinations page. These tags aren’t added to processed events. Use a tab or hard return between (arbitrary) tag names.

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

On Cribl-managed Cribl.Cloud Workers (with an Enterprise plan), this tab exposes only the Clear Persistent Queue button. A maximum queue size of 1 GB disk space is automatically allocated per Worker Process. If the queue fills up, Cribl Stream will block outbound data.

Max file size: The maximum data volume 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, Cribl Stream stops queueing and applies the fallback Queue‑full behavior. Enter a numeral with units of KB, MB, etc.

Queue file path: The location for the persistent queue files. Defaults to $CRIBL_HOME/state/queues. To this value, Cribl Stream will append /<worker‑id>/<output‑id>.

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.

Clear persistent queue: Click this button if you want to flush out files that are currently queued for delivery to this Destination. A confirmation modal will appear. (Appears only after Output ID has been defined.)

Strict ordering: The default Yes position enables FIFO (first in, first out) event forwarding. When receivers recover, Cribl Stream will send earlier queued events before forwarding newly arrived events. To instead prioritize new events before draining the queue, toggle this off. Doing so will expose this additional control:

  • Drain rate limit (EPS): Optionally, set a throttling rate (in events per second) on writing from the queue to receivers. (The default 0 value disables throttling.) Throttling the queue’s drain rate can boost the throughput of new/active connections, by reserving more resources for them. You can further optimize Workers’ startup connections and CPU load at Group Settings > Worker Processes.

TLS Settings (Client Side)
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Enabled Defaults to Yes.

Validate server certs: Defaults to Yes.

Authentication
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Authentication parameters to use when connecting to brokers. Using TLS is highly recommended.

Enabled: With the default Yes setting, this section’s remaining settings are displayed, and all are required settings.

SASL mechanism: SASL (Simple Authentication and Security Layer) authentication mechanism to use with Kafka brokers. Defaults to PLAIN, which exposes Basic Authentication options that rely on Azure Event Hubs connection strings. Select OAUTHBEARER to enable OAuth Authentication via a different set of options.

Basic Authentication
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Selecting the PLAIN SASL mechanism provides the options listed in this section.

Username: The username for authentication. For Event Hubs, this should always be $ConnectionString.

Authentication method: Use the buttons to select one of these options:

  • Manual: Use this default option to enter your Event Hubs connection string’s primary or secondary key from the Event Hubs workspace. Exposes a Password field for this purpose.
  • Secret: This option exposes a Password (text secret) drop-down, in which you can select a stored secret that references an Event Hubs connection string. The secret can reside in Cribl Stream’s internal secrets manager or (if enabled) in an external KMS. A Create link is available if you need a new secret.
Connection String Format
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Either authentication method above uses an Azure Event Hubs connection string in this format:

Endpoint=sb://<FQDN>/;SharedAccessKeyName=<your‑shared-access‑key-name>;SharedAccessKey=<your‑shared-access‑key-value>

A fictitious example is:

Endpoint=sb://dummynamespace.servicebus.windows.net/;SharedAccessKeyName=DummyAccessKeyName;SharedAccessKey=5dOntTRytoC24opYThisAsit3is2B+OGY1US/fuL3ly=

OAuth Authentication
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Selecting the OAUTHBEARER SASL mechanism provides the options listed in this section.

Microsoft Entra ID authentication endpoint: Specifies the Azure Active Directory endpoint from which to acquire authentication tokens. Defaults to https://login.microsoftonline.com. You can instead select https://login.microsoftonline.us or https://login.partner.microsoftonline.cn.

Client ID: Enter the client_id to pass in the OAuth request parameter.

Tenant identifier: Enter your Azure Active Directory subscription’s directory ID (tenant ID).

Scope: Enter the scope to pass in the OAuth request parameter. This will be of the form: https://<Event‑Hubs‑Namespace-Host-name>/.default. (For example, for an Event Hubs Namespace > Host name: goatyoga.servicebus.windows.net, Scope: https://goatyoga.servicebus.windows.net/.default.)

Authentication method: Use the buttons to select one of these options:

  • Manual: This default option exposes a Client secret field, in which to directly enter the client_secret to pass in the OAuth request parameter.
  • Secret: Exposes a Client secret (text secret) drop-down, in which you can select a stored secret that references the client_secret. A Create link is available to define a new secret.
  • Certificate: Exposes a Certificate name drop-down, in which you can select a stored certificate. A Create link is available to define a new cert.

Processing Settings
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Post‑Processing
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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 Cribl Stream Pipeline that processed the event). Supports wildcards. Other options include:

  • cribl_host – Cribl Stream Node that processed the event.
  • cribl_input – Cribl Stream Source that processed the event.
  • cribl_output – Cribl Stream Destination that processed the event.
  • cribl_route – Cribl Stream Route (or QuickConnect) that processed the event.
  • cribl_wp – Cribl Stream Worker Process that processed the event.

Advanced Settings
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Max record size (KB, uncompressed): Maximum size (KB) of each record batch before compression. Setting should be < message.max.bytes settings in Kafka brokers. Defaults to 768.

Max events per batch: Maximum number of events in a batch before forcing a flush. Defaults to 1000.

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

Connection timeout (ms): Maximum time to wait for a successful connection. Defaults to 10000 ms (10 seconds). Valid range is 1000 to 3600000 ms (1 second to 1 hour).

Request timeout (ms): Maximum time to wait for a successful request. Defaults to 60000 ms (1 minute).

Max retries: Maximum number of times to retry a failed request before the message fails. Defaults to 5; enter 0 to not retry at all.

Authentication timeout (ms): Maximum time to wait for Kafka to respond to an authentication request. Defaults to 1000 (1 second).

Reauthentication threshold (ms): If the broker requires periodic reauthentication, this setting defines how long before the reauthentication timeout Cribl Stream initiates the reauthentication. Defaults to 10000 (10 seconds).

A small value for this setting, combined with high network latency, might prevent the Destination from reauthenticating before the Kafka broker closes the connection.

A large value might cause the Destination to send reauthentication messages too soon, wasting bandwidth.

The Kafka setting connections.max.reauth.ms controls the reuthentication threshold on the Kafka side.

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.

Internal Fields
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Cribl Stream uses a set of internal fields to assist in forwarding data to a Destination.

Fields for this Destination:

  • __topicOut
  • __key
  • __headers
  • __keySchemaIdOut
  • __valueSchemaIdOut

Troubleshooting Resources
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Cribl University offers an Advanced Troubleshooting > Destination Integrations: Azure Event Hubs short course. To follow the direct course link, first log into your Cribl University account. (To create an account, select the Sign up link. You’ll need to click through a short Terms & Conditions presentation, with chill music, before proceeding to courses – but Cribl’s training is always free of charge.) Once logged in, check out other useful Advanced Troubleshooting short courses and Troubleshooting Criblets.