The Traversal Destination sends OpenTelemetry Protocol (OTLP) log events to a Traversal Processor. Cribl Stream encodes the payload with OTLP 1.3.1 over gRPC or HTTP.

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

The Processor only accepts logs, so this Destination routes log events and drops traces and metrics.

Prerequisites ​

Before you configure the Destination, deploy a Traversal Processor and confirm that Cribl Stream Worker Nodes can reach its ingest listener. For the current Traversal procedure, see Traversal Processor.

• The Processor ingest listener defaults to port 3000. By default it serves plain HTTP. You can enable TLS on the Processor so it serves HTTPS on that same ingest port.
• Include the port in Endpoint. The configuration UI placeholders use http://traversal-processor:3000 for HTTP and traversal-processor:3000 for gRPC. If you omit the port, Cribl Stream defaults to 4317, or to 443 when TLS is enabled or the endpoint is an HTTPS URL.
• Do not send this Destination to the Traversal SaaS API. Send it to the Processor that Traversal deploys in your environment.

Configuring a Traversal Destination ​

In Cribl Stream, set up a Traversal Destination.

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. 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. 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 Destination definition. If you clone this Destination, Cribl Stream will add -CLONE to the original Output ID.

   • Description: Optionally, enter a description.

   • Protocol: Choose the protocol to use when sending data: gRPC (the default), or HTTP. Your selection determines which fields display in Advanced Settings. Selecting HTTP also adds the Retries section.

   • Endpoint: Where to send log events. Enter a URL, hostname, or IP address and port. Supports both IPv4 and IPv6. Enclose IPv6 addresses in square brackets. For HTTP, an example is http://traversal-processor:3000. For gRPC, an example is traversal-processor:3000.

     To proxy outbound HTTP/S requests, see System Proxy Configuration.

   • Logs endpoint override: Displays only when Protocol is HTTP. By default, the Destination sends logs to <endpoint>/v1/logs, where <endpoint> is the Endpoint value. To send logs to a different URL, enter that URL here.

   • Backpressure behavior: Select whether to block, drop, or queue events when all receivers are exerting backpressure. Defaults to Block. When this field is set to persistent queue, see the persistent queue settings for details.

   • 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 tag names.

3. Optionally, adjust the TLS, Authentication, persistent queue, Processing, Retries, and Advanced Settings outlined in the sections below.

4. Select Save, then Commit & Deploy.

5. Use the Test tab in the Destination’s configuration modal to validate the configuration.

TLS Settings (Client Side) ​

TLS is available only when General Settings > Protocol is set to gRPC.

Use TLS: Defaults to toggled off.

Server Validation ​

Configure how this client verifies the remote server’s identity.

Validate server certs: Reject certificates that are not authorized by a CA in the Trusted server CA path, nor by another trusted CA (for example, the system’s CA). Default is toggled on. This setting takes precedence over the Validate server certs setting in Advanced Settings.

Trusted server CA path: Path on the Worker Node containing CA certificates (in PEM format) to use to verify the server’s cert. Path can reference $ENV_VARS. The certificate(s) to trust as the chain root when verifying the server’s identity. This is typically the root CA that anchors the server’s certificate chain.

Mutual Authentication (mTLS) ​

Certificate: Name of the predefined certificate. Selecting a certificate auto-fills the mutual-auth paths below.

Certificate path (mutual auth): Path on the Worker Node containing certificates (in PEM format) to use for client authentication. Path can reference $ENV_VARS.

Private key path (mutual auth): Path on the Worker Node containing the private key (in PEM format) to use for client authentication. Path can reference $ENV_VARS.

Passphrase: Passphrase to use to decrypt private key.

TLS Version ​

Reject connections using TLS versions below or above these thresholds.

Minimum TLS version: Optionally, select the minimum TLS version to accept from connections. Selecting TLSv1 or TLSv1.1 shows a deprecation warning.

Maximum TLS version: Optionally, select the maximum TLS version to accept from connections.

Authentication ​

Select one of the following options for Authentication type.

• None: Don’t use authentication. This is the default.

• Basic (credentials secret): Exposes a Credentials secret field that references HTTP Basic authentication credentials. Choose Select local secret or Select global secret, then pick a stored secret from the drop-down. A Create link is available to store a new, reusable secret. See Create and manage secrets and Global secrets.

• Token (text secret): Exposes a Token (text secret) field that references the bearer token to include in the authorization header. Choose Select local secret or Select global secret, then pick a stored text secret from the drop-down. A Create link is available to store a new, reusable secret. With the gRPC transport, authorization headers are sent as metadata key-value pairs, for example Bearer <your-configured-token>.

• OAuth (text secret): Configure authentication using the OAuth 2.0 Client Credentials flow. Available only when Protocol is set to HTTP. Selecting this option exposes additional fields. See OAuth Authentication.

OAuth Authentication ​

OAuth is available only when Protocol is set to HTTP.

Selecting OAuth (text secret) for Authentication type exposes the following additional fields:

• Login URL: Endpoint for the OAuth token request, which is expected to be a POST call.

• OAuth secret: Select a stored text secret that holds the OAuth client secret parameter value to pass in the token request body. Choose Select local secret or Select global secret, then pick a stored secret from the drop-down. A Create link is available to store a new, reusable secret. See Create and manage secrets and Global secrets.

• OAuth Secret parameter name: Parameter name for the secret value in the token request body.

• Token attribute name: Name of the auth token attribute in the OAuth response. Can be top-level (for example, token) or nested using a period (for example, data.token).

• Authorize expression: JavaScript expression used to compute the Authorization header to pass in requests. Uses ${token} to reference the token obtained from the login POST request. Defaults to `Bearer ${token}`.

• Refresh interval (secs.): How often to refresh the OAuth token. Default 3600 seconds (1 hour). Minimum 1 second. Maximum 300000 seconds (about 83 hours).

• OAuth parameters: Optionally, select Add Parameter for each additional parameter you want to send in the OAuth token request. Cribl Stream will combine the secret with these parameters, and will send the URL-encoded result in a POST request to the endpoint specified in Login URL. Cribl Stream automatically adds the Content-Type header application/x-www-form-urlencoded when sending this request.

  In each row of the resulting table, enter the parameter’s Name. The corresponding Value is a JavaScript expression to compute the parameter’s value. This can also evaluate to a constant. Values not formatted as expressions (for example, id instead of `${id}`) will be evaluated as strings.

• OAuth headers: Optionally, select Add Header for each custom header you want to send in the OAuth token request. Cribl Stream automatically adds the Content-Type header application/x-www-form-urlencoded when sending this request.

  In each row of the resulting table, enter the custom header’s Name. The corresponding Value is a JavaScript expression to compute the header’s value. This can also evaluate to a constant. Values not formatted as expressions (for example, id instead of `${id}`) will be evaluated as strings.

Persistent Queue Settings ​

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
• About Destination Backpressure Triggers

Some of these settings might not appear if you set the persistent queue storage mode to Network filesystem or AWS S3 at the Worker Group level (Worker Group Settings > System > PQ Storage). When using these storage types, this behavior is managed at the Worker Group level. See Worker Group PQ Storage Fields for more information.

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 blocks 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 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.

File size limit: The maximum data volume to store in each queue file before closing it. Enter a numeral with units of KB, MB, and so on. Defaults to 10 MB. When you save the configuration, File size limit must be greater than or equal to Buffer size limit (bytes). Cribl Stream rejects invalid combinations.

Queue size limit: 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 Worker Group/Fleet Settings page.

Queue file path: The location for the persistent queue files. Defaults to $CRIBL_HOME/state/queues. Cribl Stream appends /<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.

Buffer size limit (bytes): The maximum memory to buffer events before flushing them to persistent queue on disk. Enter a value with a unit suffix. For example: 64KB, 1MB, or 10MB. Spaces between the number and unit are allowed (such as 64 KB). Units are case-insensitive. Plain byte values (like 65536) are accepted, but decimals (like 0.5MB) are not. The valid range is 64KB to 10MB. Values outside this range are rounded to the nearest limit. Defaults to 1MB.

Deprecation Notice

The Buffer size limit (bytes) setting replaces the deprecated Max buffer size setting to provide more predictable memory management in version 4.18.0. The Max buffer size setting will be removed in version 4.19.1. For upgraded Worker Groups and Fleets, the new byte-based limit defaults to 1MB. Update your configurations to the new byte-based limit to ensure optimal memory stability.

Strict ordering: Toggle on (default) to enable FIFO (first in, first out) event forwarding, ensuring Cribl Stream 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 Worker Processes settings.

Clear Persistent Queue: For Cloud Enterprise only, select this button if you want to delete the files that are currently queued for delivery to this Destination. If you select 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 How to Safely Disable and Clear Persistent Queues for more information.

Processing Settings ​

Post-Processing ​

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 log events that use this output, as labels. Supports wildcards. By default, includes cribl_pipe (Cribl Stream Pipeline that processed the event). The drop-down offers these options:

• 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_pipe - Cribl Stream Pipeline that processed the event.
• cribl_wp - Cribl Stream Worker Process that processed the event.
• cribl_route - Cribl Stream Route (or QuickConnect) that processed the event.
• cribl_group - Cribl Stream Worker Group of the Node that processed the event.
• cribl_mode - Cribl Stream processing mode.

Retries ​

This tab is displayed when General Settings > Protocol is set to HTTP.

Honor Retry-After header: Toggle on to honor a Retry-After header, provided that the header specifies a delay no longer than 180 seconds. Cribl Stream/Edge limits the delay to 180 seconds even if the Retry-After header specifies a longer delay. Any Retry-After header received takes precedence over all other options configured in the Retries section. Toggle off to ignore all Retry-After headers.

Default Retry Behavior: By default, Cribl Stream/Edge applies predefined retry strategies for certain failed requests to the Destination using an exponential backoff algorithm. You can override these settings by manually configuring the retry behavior for a particular error code.

Destinations created before the 4.16.0 release do not support the default 4xx series retry behavior. If your Destination was created prior to this release and you’d like it to support the behavior, reconfigure the Destination.

To retry requests, Cribl Stream/Edge applies the following rules by default:

By default, any 429 (Too Many Requests) response that is not listed in the retry settings is treated as a non-retryable 4xx error and dropped. If you want 429 responses retried, ensure 429 is included in the Settings for failed HTTP requests.

Settings for failed HTTP requests: You can also manually configure Cribl Stream/Edge to automatically retry requests that receive particular HTTP response status codes.

Upon receiving a response code that’s on the list, Cribl Stream/Edge first waits for a set time interval called the Pre-backoff interval and then begins retrying the request. Time between retries increases based on an exponential backoff algorithm whose base is the Backoff multiplier, until the backoff multiplier reaches the Backoff limit (ms). At that point, Cribl Stream/Edge continues retrying the request without increasing the time between retries any further.

If the sender (which manages the connection to the Destination) is at capacity, it will not accept any incoming events. These incoming events originate internally from a previous stage of the data flow when Destinations send outbound requests to their respective external services, and they include retry requests and new requests. Any events that were already in transit when the sender reached capacity will continue to be processed downstream.

Sender capacity is freed up when an outgoing request succeeds or encounters a non-retryable error. When the sender has available capacity again, it will resume accepting incoming events. This capacity management is influenced by the number of active connections and configured limits, such as concurrency and buffer sizes. If a Pipeline sends events faster than the Destination can process, the buffers may fill up, leading to backpressure and Sender at capacity warnings. This backpressure prevents the sender from accepting additional requests until capacity is restored.

For each response code you want to add to the list, select Add Setting and configure the following settings:

• HTTP status code: A response code that indicates a failed request, for example 429 (Too Many Requests) or 503 (Service Unavailable).
• Pre-backoff interval (ms): The amount of time to wait before beginning retries, in milliseconds. Defaults to 1000 (one second).
• Backoff multiplier: The base for the exponential backoff algorithm. A value of 2 (the default) means that Cribl Stream/Edge will retry after 2 seconds, then 4 seconds, then 8 seconds, and so on.
• Backoff limit (ms): The maximum backoff interval Cribl Stream/Edge should apply for its final retry, in milliseconds. Default (and minimum) is 10,000 (10 seconds); maximum is 180,000 (180 seconds, or 3 minutes).

Retry timed-out HTTP requests: Toggle on to automatically retry requests that have timed out and display the following settings for configuring retry behavior:

• Pre-backoff interval (ms): The amount of time to wait before beginning retries, in milliseconds. Defaults to 1000 (one second).
• Backoff multiplier: The base for the exponential backoff algorithm. A value of 2 (the default) means that Cribl Stream/Edge will retry after 2 seconds, then 4 seconds, then 8 seconds, and so on.
• Backoff limit (ms): The maximum backoff interval Cribl Stream/Edge should apply for its final retry, in milliseconds. Default (and minimum) is 10,000 (10 seconds); maximum is 180,000 (180 seconds, or 3 minutes).

Advanced Settings ​

When General Settings > Protocol is set to gRPC, the UI displays these additional settings:

• Connection timeout: Amount of time (in milliseconds) to wait for the connection to establish before retrying. Defaults to 10000 (10 seconds).

• Keep alive time (seconds): How often the sender should ping the peer to keep the connection alive. Defaults to 30.

• Metadata: Static metadata to send with every gRPC request. Select Add Metadata to add each item as a Key-Value pair. The Value field is a JavaScript expression that is evaluated when the Destination is initialized. If you pass credentials as metadata, Cribl recommends using C.Secret().

• Use dynamic metadata: Toggle on to enable per-event dynamic metadata on outbound gRPC requests. When enabled, Cribl Stream reads metadata key-value pairs from the field specified in Dynamic metadata field on each event. It injects them into the gRPC request metadata and batches events that share the same metadata values. Dynamic metadata entries override any static Metadata entries with matching keys. Defaults to toggled off.

• Dynamic metadata field: The event field that contains the metadata key-value pairs to inject into outbound gRPC request metadata. Displays only when Use dynamic metadata is toggled on. Each key in the object becomes a metadata key. Values must be strings, numbers, booleans, or null. Keys that would override protected values such as content-type are ignored. Events that do not contain this field are grouped into a single shared default batch. No dynamic metadata is injected for these events. Only the static Metadata entries apply. Defaults to __headersOut.

When General Settings > Protocol is set to HTTP, the UI displays these additional settings:

• Validate server certs: Reject certificates that are not authorized by a CA in the CA certificate path, nor by another trusted CA (for example, the system’s CA). Defaults to toggled on. When TLS Settings (Client Side) also sets Validate server certs, that value takes precedence.

• Round-robin DNS: Toggle on to enable round-robin DNS lookup across multiple IPv4 and IPv6 addresses. When a DNS server resolves a Fully Qualified Domain Name (FQDN) to multiple IP addresses, Cribl Stream uses each address in the order the DNS server returns them.

• Keep alive: By default, Cribl Stream sends Keep-Alive headers to the remote server and preserves the connection from the client side. Toggle this off if you want Cribl Stream to close the connection immediately after sending a request.

• Extra HTTP headers: Select Add Header to define additional HTTP headers to pass to all events. Each row is a Name-Value pair. Values will be sent encrypted.

• Safe headers: Add headers here to declare them as safe to log in plaintext. (Sensitive headers such as authorization will always be redacted, even if listed here.) Use a tab or hard return to separate header names.

The following settings display for both protocols:

• Preserve native AnyValue wrappers: Toggle on to serialize values that are already in OTLP AnyValue form (for example, { "string_value": "..." }) directly, instead of wrapping them as key-value maps. When toggled off, Cribl Stream treats those wrappers as plain objects, which can leave wrapper names such as string_value as literal field names in the output. Defaults to toggled on.

If your Pipeline uses the OTLP Logs Function before this Destination, enable Preserve native AnyValue wrappers on both the Function and the Destination. Enabling it on only one side can still leave wrapper names such as string_value as literal field names in the output.

• Compression: Compression type to apply to messages sent to the endpoint. Gzip (the default) and None are available for both protocols. Deflate is available for gRPC only.

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

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

• Body size limit (KB): Maximum size of the request body before compression. Defaults to 4096 KB. The actual request body size might exceed the specified value because the Destination adds bytes when it writes to the downstream receiver. Cribl recommends that you experiment with the Body size limit value until downstream receivers reliably accept all events.

• Max connection reuse (seconds): How long to reuse a keep-alive connection after its first use before forcing it closed. Defaults to 120 seconds. Set to 0 to disable the time-based close and reuse connections for as long as the receiver permits.

• Flush period (sec): Maximum time between requests. Low values could cause the payload size to be smaller than the configured Body size limit. Defaults to 1 second.

• 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.

Troubleshooting ​

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.