These docs are for Cribl Stream 4.8 and are no longer actively maintained.

See the latest version (4.13).

OpenTelemetry (OTel) Source

Cribl Stream supports receiving trace, metric, and log events from OTLP-compliant senders. Cribl Stream supports log events beginning in v.4.7.

Type: Push | TLS Support: YES | Event Breaker Support: No

Supported and Unsupported Input Data

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In Cribl Stream 4.0.3 and later, the Open Telemetry Source supports receiving compressed inbound data (with DEFLATE or gzip compression), as well as uncompressed data.

In Cribl Stream 4.1 and later, this Source supports receiving telemetry data over either of the transports that the OpenTelemetry Protocol (OTLP) describes: gRPC or HTTP. OTLP defines Protocol buffer (Protobuf) schemas for its payloads (requests and responses). With the HTTP transport, this Source supports Binary Protobuf payload encoding, but currently does not support JSON Protobuf.

The OpenTelemetry Project’s Signals documentation provides these hierarchical definitions of Cribl Stream’s supported trace and metric event types:

• A trace tracks the progression of a single request.
  • Each trace is a tree of spans.
  • A span object represents the work being done by the individual services, or components, involved in a request as that request flows through a system.
• A metric provides aggreggated statistical information.
  • A metric contains individual measurements called data points.
• A log provides a recording of an event.
  • See the OTLP Logs Function topic for an explanation of OTLP logs structure.

Breaking Changes Between OTLP 0.19.0 and 1.3.1

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With version 0.19.0, the OTLP Protobuf spec introduced breaking changes in its field names. This means that if you created Routes or Pipelines that work with OTLP version 0.10.0, they may break when you use them with OTLP 1.3.1.

To use Routes or Pipelines created before Cribl Stream 4.7 with OTLP 1.3.1, you must check their filters and logic for any use of obsolete field names, and modify them accordingly,

Configuring an OTel Source

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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 Source at left. From the resulting drawer’s tiles, select [Push > ] OpenTelemetry. 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 > Sources (Stream) or More > Sources (Edge). From the resulting page’s tiles or left nav, select [Push > ] OpenTelemetry. Next, click New Source to open a New Source modal that provides the options below.

The sections described below are spread across several tabs. Click the tab links at left, or the Next and Prev buttons, to navigate among tabs. Click Save when you’ve configured your Source.

General Settings

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Input ID: Unique ID for this Source. For example, OTel042.

Address: Enter the hostname/IP to listen on. Defaults to 0.0.0.0 (all addresses, IPv4 format).

Port: By default, OTel applications send output to port 4317 when using the gRPC protocol, and port 4318 when using HTTP. This setting defaults to 4317 – you must change it if you set Protocol (below) to HTTP, or you want Cribl Stream to collect data from an OTel application that is using a different port.

Optional Settings

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Protocol: Use the drop-down to choose the protocol matching the data you will ingest: gRPC (the default), or HTTP.

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

Authentication

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Select one of the following options for authentication:

• None: Don’t use authentication.

• Auth token: Enter the bearer token that must be included in the authorization header.

• Auth token (text secret): Provide an HTTP token referenced by a secret. Select a stored text secret in the resulting drop-down, or click Create to configure a new secret.

• Basic: Displays Username and Password fields for you to enter HTTP Basic authentication credentials.

• Basic (credentials secret): Provide username and password credentials referenced by a secret. Select a stored text secret in the resulting Credentials secret drop-down, or click Create to configure a new secret.

TLS Settings (Server Side)

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In OTel terminology, your Cribl Stream OTel Source will receive OTel data from a Collector running on a local agent. In Cribl Stream’s terminology, the Collector is the client and the OTel Source is the server. This is why this Source’s UI identifies the Source’s TLS Settings as “server-side.”

For more about this client-server relationship, see the TLS Configuration Example below.

Enabled defaults to No. When toggled to Yes:

Certificate name: Name of the predefined certificate.

Private key path: Server path containing the private key (in PEM format) to use. Path can reference $ENV_VARS.

Certificate path: Server path containing certificates (in PEM format) to use. Path can reference $ENV_VARS.

CA certificate path: Server path containing CA certificates (in PEM format) to use. Path can reference $ENV_VARS.

Authenticate client (mutual auth): Require clients to present their certificates. Used to perform mutual authentication using SSL certs (mTLS). Defaults to No. When toggled to Yes:

• Validate client 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 Yes.

• Common Name: Regex that a peer certificate’s subject attribute must match in order to connect. Defaults to .*. Matches on the substring after CN=. As needed, escape regex tokens to match literal characters. (For example, to match the subject CN=worker.cribl.local, you would enter: worker\.cribl\.local.) If the subject attribute contains Subject Alternative Name (SAN) entries, the Source will check the regex against all of those but ignore the Common Name (CN) entry (if any). If the certificate has no SAN extension, the Source will check the regex against the single name in the CN.

Minimum TLS version: Defines the oldest TLS version allowed for incoming connections. Connections using an earlier version will be rejected. Use this setting to enforce a baseline for secure communication.

Maximum TLS version: Defines the newest TLS version that can be negotiated during a connection. Use this setting to restrict connections to tested and supported TLS versions.

Persistent Queue Settings

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In this section, you can optionally specify persistent queue storage, using the following controls. This will buffer and preserve incoming events when a downstream Destination is down, or exhibiting backpressure.

On Cribl-managed Cribl.Cloud Workers (with an Enterprise plan), this tab exposes only the Enable Persistent Queue toggle. If enabled, PQ is automatically configured in Always On mode, with a maximum queue size of 1 GB disk space allocated per PQ-enabled Source, per Worker Process.

The 1 GB limit is on uncompressed inbound data, and no compression is applied to the queue. This limit is not configurable. For configurable queue size, compression, mode, and other options below, use a hybrid Group.

Enable Persistent Queue: Defaults to No. When toggled to Yes:

Mode: Select a condition for engaging persistent queues.

• Always On: This default option will always write events to the persistent queue, before forwarding them to Cribl Stream’s data processing engine.
• Smart: This option will engage PQ only when the Source detects backpressure from Cribl Stream’s data processing engine.

Max buffer size: The maximum number of events to hold in memory before reporting backpressure to the sender and writing the queue to disk. Defaults to 1000. (This buffer is per connection, not just per Worker Process – and this can dramatically expand memory usage.)

Commit frequency: The number of events to send downstream before committing that Stream has read them. Defaults to 42.

Max file size: The maximum data volume to store in each queue file before closing it and (optionally) applying the configured Compression. Enter a numeral with units of KB, MB, etc. If not specified, Cribl Stream applies the default 1 MB.

Max queue size: The maximum amount of disk space that the queue is allowed to consume on each Worker Process. Once this limit is reached, this Source will stop queueing data and block incoming data. Required, and defaults to 5 GB. Accepts positive numbers with units of KB, MB, GB, etc. Can be set as high as 1 TB, unless you’ve configured a different Max PQ size per Worker Process in Group Settings.

Queue file path: The location for the persistent queue files. Defaults to $CRIBL_HOME/state/queues. To this field’s specified path, Cribl Stream will append /<worker-id>/inputs/<input-id>.

Compression: Optional codec to compress the persisted data after a file is closed. Defaults to None; Gzip is also available.

In Cribl Stream 4.1 and later, Source-side PQ’s default Mode is Always on, to best ensure events’ delivery. For details on optimizing this selection, see Always On versus Smart Mode.

You can optimize Workers’ startup connections and CPU load at Group Settings > Worker Processes.

Processing Settings

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Fields

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In this section, you can add Fields to each event, using Eval-like functionality.

Name: Field name.

Value: JavaScript expression to compute field’s value, enclosed in quotes or backticks. (Can evaluate to a constant.)

Pre-Processing

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In this section’s Pipeline drop-down list, you can select a single existing Pipeline to process data from this input before the data is sent through the Routes.

Advanced Settings

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Advanced Settings always displays OTLP version, Extract spans, Extract metrics, and Environment. When OTLP version is set to 1.3.1, the UI also displays Extract logs.

The Extract spans, Extract metrics, and Extract logs settings are unique to OTel. Their default No settings allow Cribl Stream to essentially function as a bump on the wire, generating a single event for each incoming OTel event. This can be useful when, for example, you want to send whole OTel events to persistent storage.

• OTLP version: The drop-down offers 0.10.0 (default) and 1.3.1.

• Extract spans: Toggle to Yes if you want Cribl Stream to generate an individual event for each span. (Recall that traces contain multiple spans.)

• Extract metrics: Toggle to Yes if you want Cribl Stream to generate an individual event for each data point. (Recall that OTel metric events contain multiple data points.)

• Extract logs: Available only when OTLP version is set to 1.3.1. Toggle to Yes if you want Cribl Stream to generate an individual event for each log record. Cribl recommends doing this to make it easier to transform and manipulate logs.

• Environment: Optionally, specify a single Git branch on which to enable this configuration. If this field is empty, the config will be enabled everywhere.

When General Settings > Protocol is set to gRPC, the UI displays one additional setting:

• Max active connections: Maximum number of active connections allowed per Worker Process. Defaults to 1000. Set a lower value if connection storms are causing the Source to hang. Set 0 for unlimited connections.

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

• Health check endpoint: Toggle to Yes to enable a health check endpoint specific to this Source, http(s)://<host>:<port>/cribl_health. A 200 HTTP response code is returned when the Source is healthy. Otherwise, two errors you could receive are:

  • ECONNRESET where the Source failed to initialize due to not having listeners on the port.
  • 503 or Server is busy, max active connections reached indicate there are too many connections per Worker Process.

• Max active requests: Maximum number of active requests allowed for this Source, per Worker Process. Defaults to 256. Enter 0 for unlimited.

• Max requests per socket: The maximum number of requests Cribl Stream should allow on one socket before instructing the client to close the connection. Defaults to 0 (unlimited). See Balancing Connection Reuse Against Request Distribution below.

• Socket timeout (seconds): How long Cribl Stream should wait before assuming that an inactive socket has timed out. The default 0 value means wait forever.

• Request timeout (seconds): How long to wait for an incoming request to complete before aborting it. The default 0 value means wait indefinitely.

• Keep-alive timeout (seconds): After the last response is sent, Cribl Stream will wait this long for additional data before closing the socket connection. Defaults to 5 seconds; minimum is 1 second; maximum is 600 seconds (10 minutes).

• IP allowlist regex: Grants access to requests originating from specific IP addresses that match a defined pattern. Unmatched requests are rejected with a 403 (Forbidden) status code. Defaults to .* (allow all).

• IP denylist regex: Blocks requests originating from specific IP addresses that match a defined pattern, even if they would be allowed by default. Rejected requests receive a 403 (Forbidden) status code. Defaults to ^$ (allow all).

Balancing Connection Reuse Against Request Distribution

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Max requests per socket allows you to limit the number of HTTP requests an upstream client can send on one network connection. Once the limit is reached, Cribl Stream uses HTTP headers to inform the client that it must establish a new connection to send any more requests. (Specifically, Cribl Stream sets the HTTP Connection header to close.) After that, if the client disregards what Cribl Stream has asked it to do and tries to send another HTTP request over the existing connection, Cribl Stream will respond with an HTTP status code of 503 Service Unavailable.

Use this setting to strike a balance between connection reuse by the client, and distribution of requests among one or more Worker Node processes by Cribl Stream:

• When a client sends a sequence of requests on the same connection, that is called connection reuse. Because connection reuse benefits client performance by avoiding the overhead of creating new connections, clients have an incentive to maximize connection reuse.

• Meanwhile, a single process on that Worker Node will handle all the requests of a single network connection, for the lifetime of the connection. When receiving a large overall set of data, Cribl Stream performs better when the workload is distributed across multiple Worker Node processes. In that situation, it makes sense to limit connection reuse.

There is no one-size-fits-all solution, because of variation in the size of the payload a client sends with a request and in the number of requests a client wants to send in one sequence. Start by estimating how long connections will stay open. To do this, multiply the typical time that requests take to process (based on payload size) times the number of requests the client typically wants to send.

If the result is 60 seconds or longer, set Max requests per socket to force the client to create a new connection sooner. This way, more data can be spread over more Worker Node processes within a given unit of time.

For example: Suppose a client tries to send thousands of requests over a very few connections that stay open for hours on end. By setting a relatively low Max requests per socket, you can ensure that the same work is done over more, shorter-lived connections distributed between more Worker Node processes, yielding better performance from Cribl Stream.

A final point to consider is that one Cribl Stream Source can receive requests from more than one client, making it more complicated to determine an optimal value for Max requests per socket.

Connected Destinations

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Select Send to Routes to enable conditional routing, filtering, and cloning of this Source’s data via the Routing table.

Select QuickConnect to send this Source’s data to one or more Destinations via independent, direct connections.

Internal Fields

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OTel internal fields are metadata fields added to events processed by the OTel Source. These fields provide essential context about the event’s origin and processing details and can be referenced in filters, Routes, and Pipelines to apply specific logic based on the event’s metadata. These fields are not included in the final output unless explicitly configured at the Pipeline or Destination stage.

Fields for this Source:

• __otlp.version – The OTLP version used to parse the event. For example, 0.10.0 or 1.3.1. This helps ensure compatibility with upstream systems and configurations.
• __otlp.type – The type of telemetry data. For example, logs, metrics, or traces. This is crucial for distinguishing between different signal types in Pipelines.
• __otlp.extracted – A boolean flag that denotes whether individual records were extracted from a batch event. If true, the event represents an extracted record. This behavior is directly governed by the Extract spans, Extract metrics, and Extract logs general settings of the OTel Source.

TLS Configuration Example

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Here’s a simple example for using TLS to secure the communication between an OpenTelemetry client and your Cribl Stream OTel Source.

1. Choose or generate a certificate and key. If you need to generate a certificate/key pair, you can adapt the following OpenSSL command:

   openssl req -nodes -new -x509 -newkey rsa:2048 -keyout myKey.pem -out myCert.pem -days 420

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   This example command will generate both a self-signed cert named myCert.pem (certified for 420 days), and an unencrypted, 2048-bit RSA private key named myKey.pem.

2. Configure the TLS Settings (Server Side). Toggle Enabled to Yes, then:

   • Enter the appropriate values in the Certificate name, Private key path, and Certificate path fields. A Create link is available if you need a new certificate, and Certificate name also works as a drop-down to allow you to choose from any existing certificates.
   • Leave the CA certificate path field empty.
   • Leave Authenticate client (mutual auth) toggled to No.

3. Configure the OTel client. See the OTel Collector TLS Configuration Settings README for an explanation of the relevant settings. The config file might be named otel-config.yaml, otel-local-config.yaml, or just config.yaml, depending on your environment. This YAML file will have an exporters section, which you must edit to include an otlp sub-section, as follows:

   • Add an endpoint whose value is the IP address of either (a) the Cribl Stream Worker Node on which your OTel Source is running, or (b) the IP address of the load balancer for the relevant Worker Group. In the example snippet below, this is the <Cribl_IP_address>. Specify the port on which Cribl Stream’s OTel Source is listening; port 4317 is the default.
   • Set tls > insecure to false. This matches your setting TLS Settings (Server Side) > Enabled to Yes on the Cribl Stream OTel Source.
   • Set tls > insecure_skip_verify to true. This matches your setting TLS Settings (Server Side) > Authenticate client (mutual auth) to No on the Cribl Stream OTel Source. Setting insecure_skip_verify to true is also required if you’re using a self-signed certificate.

   Here’s how the section you edited should look:

   exporters:
     otlp:
       endpoint: "https://<Cribl_IP_address>:4317"
       tls:
         insecure: false
         insecure_skip_verify: true

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Troubleshooting

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

Live Data: Try capturing live data to see real-time events as they are ingested. 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 ingestion process, including any errors or warnings that may have occurred.

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

Common Issue

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When your upstream sender is the OpenTelemetry Collector and its logs show the error Exporting failed. Will retry the request after interval, try increasing the duration specified in Advanced Settings > Keep-alive timeout (seconds). Choose a duration that aligns with your OpenTelemetry Collector configuration, such that the OpenTelemetry Collector has enough time to send its events before the keep-alive timeout elapses.