Configuring Cribl Stream to Receive Loki Logs Data

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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 > ] Amazon > Loki. 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 > ] Amazon > Loki. Next, click New Source to open a New Source modal that provides the options below.

General Settings

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Input ID: Enter a unique name to identify this Source definition.

Address: Enter the hostname/IP to listen to. Defaults to 0.0.0.0.

Port: Enter the port number to listen on.

Logs API endpoint: Absolute path on which to listen for Loki logs requests. Defaults to /loki/api/v1/push, which will (in this example) expand as: http://<your‑upstream‑URL>:<your‑port>/loki/api/v1/push.

Optional Settings

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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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Use the Authentication type drop-down to specify how Loki’s Promtail agent will authenticate against Cribl Stream:

• None: Don’t use authentication.

• Auth token: Use HTTP token authentication. In the resulting Token field, enter the bearer token that must be included in the HTTP 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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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.

Passphrase: Passphrase to use to decrypt private key.

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. Defaults to No. When toggled to Yes:

• 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).

• Common name: Regex matching subject common names in peer certificates allowed to connect. Defaults to .*. Matches on the substring after CN=. As needed, escape regex tokens to match literal characters. E.g., to match the subject CN=worker.cribl.local, you would enter: worker\.cribl\.local.

Minimum TLS version: Optionally, select the minimum TLS version to accept from connections.

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

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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Enable proxy protocol: Toggle to Yes if the connection is proxied by a device that supports Proxy Protocol v1 or v2. This setting affects how the Source handles the __srcIpPort field.

Capture request headers: Toggle this to Yes to add request headers to events, in the __headers field.

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

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.

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).

The longer the Keep‑alive timeout, the more Cribl Stream will reuse connections. The shorter the timeout, the closer Cribl Stream gets to creating a new connection for every request. When request frequency is high, you can use longer timeouts to reduce the number of connections created, which mitigates the associated cost.

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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Cribl Stream uses a set of internal fields to assist in handling of data. These “meta” fields are not part of an event, but they are accessible, and Functions can use them to make processing decisions.

Fields for this Source:

• __final
• __headers – Added only when Advanced Settings > Capture request headers is set to Yes.
• __inputId
• __labels – Will contain all the labels found in each event’s corresponding Loki stream.
• __srcIpPort – See details below.
• _time

Overriding __srcIpPort with Client IP/Port

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The __srcIpPort field’s value contains the IP address and (optionally) port of the Loki client sending data to this Source.

When any proxies (including load balancers) lie between the Loki client and the Source, the last proxy adds an X‑Forwarded‑For header whose value is the IP/port of the original client. With multiple proxies, this header’s value will be an array, whose first item is the original client IP/port.

If X‑Forwarded‑For is present, and Advanced Settings > Enable proxy protocol is set to No, the original client IP/port in this header will override the value of __srcIpPort.

If Enable proxy protocol is set to Yes, the X‑Forwarded‑For header’s contents will not override the __srcIpPort value. (Here, the upstream proxy can convey the client IP/port without using this header.)