These docs are for Cribl Stream 4.10 and are no longer actively maintained.

See the latest version (4.13).

Splunk Single Instance Destination

This Splunk Destination can stream data to a free Splunk Cloud instance. From the perspective of the receiving Splunk Cloud instance, the data arrives cooked and parsed.

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

Looking for a quick way to switch all of your S2S Destinations to Splunk HEC Destinations? Follow our how-to guide: Switch Cribl Stream Destinations from S2S to Splunk HEC.

Splunk Cloud Platform

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To establish secure connections to Splunk Cloud, you’ll need to configure SSL settings using the private and public keys from the Splunk Cloud Universal Forwarder credentials package.

For details on which Destination to use for Splunk Cloud, see Splunk Cloud Platform and BYOL Integrations. The Splunk HEC Destination is recommended for most use cases.

Configure Cribl Stream to Output to Splunk Destinations

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1. On the top bar, select Products, and then select Cribl Stream. Under Worker Groups, select a Worker Group. Next, you have two options:
   • To configure via QuickConnect, navigate to Routing > QuickConnect (Stream) or Collect (Edge). Select Add Destination and select the Destination you want from the list, choosing either Select Existing or Add New.
   • To configure via the Routes, select Data > Destinations or More > Destinations (Edge). Select the Destination you want. Next, select Add Destination.
2. In the New Destination modal, configure the following under General Settings:
   • Output ID: Enter a unique name to identify this Splunk Single Instance definition. If you clone this Destination, Cribl Stream will add -CLONE to the original Output ID.
   • Description: Optionally, enter a description.
   • Address: Hostname of the Splunk receiver.
   • Port: The port number on the host.
3. Next, you can configure the following Optional Settings:

• Backpressure behavior: Select whether to block, drop, or queue events when all receivers are exerting backpressure. (Causes might include a broken or denied connection, or a rate limiter.) Defaults to Block.
• Tags: Optionally, add tags that you can use to filter and group Destinations on the Destinations page. These tags aren’t added to processed events. Use a tab or hard return between (arbitrary) tag names.

4. Optionally, you can adjust the Persistent Queue, TLS, Processing, Timeout, and Advanced settings outlined in the sections below.
5. Select Save, then Commit & Deploy.

Persistent Queue Settings

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The Persistent Queue Settings tab displays when the Backpressure behavior option in General settings is set to Persistent Queue. Persistent queue buffers and preserves incoming events when a downstream Destination has an outage or experiences backpressure.

Before enabling persistent queue, learn more about persistent queue behavior and how to optimize it with your system:

• About Persistent Queues
• Optimize Destination Persistent Queues (dPQ)
• Destination Backpressure Triggers

On Cribl-managed Cloud Workers (with an Enterprise plan), this tab exposes only the destructive Clear Persistent Queue button (described at the end of this section). A maximum queue size of 1 GB disk space is automatically allocated per PQ‑enabled Destination, per Worker Process. The 1 GB limit is on outbound uncompressed data, and no compression is applied to the queue.

This limit is not configurable. If the queue fills up, Cribl Stream/Edge will block outbound data. To configure the queue size, compression, queue-full fallback behavior, and other options below, use a hybrid Group.

Mode: Use this menu to select when Cribl Stream/Edge engages the persistent queue in response to backpressure events from this Destination. The options are:

If a Worker/Edge Node starts with an invalid Mode setting, it automatically switches to Error mode. This might happen if the Worker/Edge Node is running a version that does not support other modes (older than 4.9.0), or if it encounters a nonexistent value in YAML configuration files.

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 that the queue can consume on each Worker Process. When the queue reaches this limit, the Destination stops queueing data and applies the Queue‑full behavior. Defaults to 5 GB. This field accepts positive numbers with units of KB, MB, GB, and so on. You can set it as high as 1 TB, unless you’ve configured a different Worker Process PQ size limit on the Group Settings/Fleet Settings page.

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

Compression: Set the codec to use when compressing the persisted data after closing a file. Defaults to None. Gzip is also available.

Queue-full behavior: Whether to block or drop events when the queue begins to exert backpressure. A queue begins to exert backpressure when the disk is low or at full capacity. This setting has two options:

• Block: The output will refuse to accept new data until the receiver is ready. The system will return block signals back to the sender.
• Drop new data: Discard all new events until the backpressure event has resolved and the receiver is ready.

Backpressure duration limit: When Mode is set to Backpressure, this setting controls how long to wait during network slowdowns before activating queues. A shorter duration enhances critical data loss prevention, while a longer duration helps avoid unnecessary queue transitions in environments with frequent, brief network fluctuations. The default value is 30 seconds.

Strict ordering: Toggle on (default) to enable FIFO (first in, first out) event forwarding, ensuring Cribl Stream/Edge sends earlier queued events first when receivers recover. The persistent queue flushes every 10 seconds in this mode. Toggle off to prioritize new events over queued events, configure a custom drain rate for the queue, and display this option:

• 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 drain rate can boost the throughput of new and active connections by reserving more resources for them. You can further optimize Worker startup connections and CPU load in the Group Settings/Fleet Settings > Worker Processes settings.

Clear Persistent Queue: For Cloud Enterprise only, click this button if you want to delete the files that are currently queued for delivery to this Destination. If you click this button, a confirmation modal appears. Clearing the queue frees up disk space by permanently deleting the queued data, without delivering it to downstream receivers. This button only appears after you define the Output ID.

Use the Clear Persistent Queue button with caution to avoid data loss. See Steps to Safely Disable and Clear Persistent Queues for more information.

TLS Settings (Client Side)

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Enabled: Defaults to toggled off. When toggled on:

Validate server certs: Reject certificates that are not authorized by a CA in the CA certificate path, or by another trusted CA (for example, the system’s CA). Defaults to toggled on.

Server name (SNI): Server name for the SNI (Server Name Indication) TLS extension. This must be a host name, not an IP address.

Minimum TLS version: Optionally, select the minimum TLS version to use when connecting.

Maximum TLS version: Optionally, select the maximum TLS version to use when connecting.

Certificate name: The name of the predefined certificate.

CA certificate path: Path on client containing CA certificates (in PEM format) to use to verify the server’s cert. Path can reference $ENV_VARS.

Private key path (mutual auth): Path on client containing the private key (in PEM format) to use. Path can reference $ENV_VARS. Use only if mutual auth is required.

Certificate path (mutual auth): Path on client containing certificates in (PEM format) to use. Path can reference $ENV_VARS. Use only if mutual auth is required.

Passphrase: Passphrase to use to decrypt private key. Often the value of the sslPassword or similar parameter in the outputs.conf or server.conf file.

Single .pem File

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If you have a single .pem file containing cacert, key, and cert sections, enter it in all of these fields above: CA certificate path, Private key path (mutual auth), and Certificate path (mutual auth).

Timeout Settings

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Connection timeout: Amount of time (in milliseconds) to wait for the connection to establish, before retrying. Defaults to 10000.

Write timeout: Amount of time (in milliseconds) to wait for a write to complete, before assuming connection is dead. Defaults to 60000.

Processing Settings

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Post‑Processing

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Pipeline: Pipeline or Pack 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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Output multiple metrics: Toggle on to output multiple-measurement metric data points. (Supported in Splunk 8.0 and above, this format enables sending multiple metrics in a single event, improving the efficiency of your Splunk capacity.)

Minimize in-flight data loss: If toggled on (default), Cribl Stream will check whether the indexer is shutting down, and if so, will stop sending data. This helps minimize data loss during shutdown. (Note that Splunk logs will indicate that the Cribl app has set UseAck to true, even though Cribl does not enable full UseAck behavior.) If toggled off, exposes the following alternative option:

Max failed health checks: Displayed (and set to 1 by default) only if Minimize in‑flight data loss is disabled. This option sends periodic requests to Splunk once per minute, to verify that the Splunk endpoint is still alive and can receive data. Its value governs how many failed requests Cribl Stream will allow before closing this connection.

A low threshold value improves connections’ resilience, but by proliferating connections, this can complicate troubleshooting. Set to 0 to disable health checks entirely – here, if the connection to Splunk is forcibly closed, you risk some data loss.

Max S2S version: The highest version of the Splunk-to-Splunk protocol to expose during handshake. Defaults to v4; v3 is also available.

Throttling: Throttle rate, in bytes per second. Defaults to 0, meaning no throttling. Multiple-byte units such as KB, MB, GB, and so forth, are also allowed – for example, 42 MB. When throttling is engaged, your Backpressure behavior selection determines whether Cribl Stream will handle excess data by blocking it, dropping it, or queueing it to disk.

• When used in conjunction with Max connections, the throttling rate is applied per connection. For instance, if Max connections is set to 2 and throttling is set to 3 MB, each of the two connections can send data at a rate of up to 3 MB per second, resulting in a total potential throughput of 6 MB per second across both connections.

Nested field serialization: Specifies how to serialize nested fields into index-time fields. Defaults to None.

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

• Manual: In the resulting Auth token field, enter the shared secret token to use when establishing a connection to a Splunk indexer.

• Secret: This option exposes an Auth token (text secret) drop-down, in which you can select a stored secret that references the auth token described above. A Create link is available to store a new, reusable secret.

Log failed requests to disk: Toggle on to make the payload of the most recently failed request available for inspection. See Inspect Payload to Troubleshoot Closed Connections below.

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.

Inspect Payload to Troubleshoot Closed Connections

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When a downstream receiver closes connections from this Destination (or just stops responding), inspecting the payload of the most recently failed request can help you find the cause. For example:

• Suppose you send an event whose size is larger than the downstream receiver can handle.
• Suppose you send an event that has a number field, but the value exceeds the highest number that the downstream receiver can handle.

When Log failed requests to disk is enabled, you can inspect the last failed request payload. Here is how:

1. In the Destination UI, navigate to the Logs tab.
2. Find a log entry with a connection error message.
3. Expand the log entry.
4. If the message includes the phrase See payload file for more info, note the path in the file field on the next line.

Now you have the path to the directory where Cribl Stream is storing the payload from the last failed request.

Notes about Forwarding to Splunk

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• Data sent to Splunk is not compressed.

• The only ack from indexers that Cribl Stream listens for and acts upon is the shutdown signal described in Minimize in-flight data loss above.

• If events have a Cribl Stream internal field called __criblMetrics, they’ll be forwarded to Splunk as metric events.

• If events do not have a _raw field, they’ll be serialized to JSON prior to sending to Splunk.

• See Splunk’s documentation on editing fields.conf to ensure the visibility of index-time fields sent to Splunk by Cribl Stream.

Troubleshooting

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The Destination’s configuration modal has helpful tabs for troubleshooting:

Live Data: Try capturing live data to see real-time events as they flow through the Destination. On the Live Data tab, click Start Capture to begin viewing real-time data.

Logs: Review and search the logs that provide detailed information about the delivery process, including any errors or warnings that may have occurred.

Test: Ensures that the Destination is correctly set up and reachable. Verify that sample events are sent correctly by clicking Run Test.

You can also view the Monitoring page that provides a comprehensive overview of data volume and rate, helping you identify delivery issues. Analyze the graphs showing events and bytes in/out over time.

Cribl University offers an Advanced Troubleshooting > Destination Integrations: Splunk Cloud 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 select 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.