TCP JSON

Cribl Stream supports sending data over TCP in JSON format.

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

Configuring Cribl Stream to Output Data in TCP JSON Format​

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 TCP JSON. 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 TCP JSON. Next, click Add Destination to open a New Destination modal that provides the options below.

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.

Load balancing: When enabled (default), lets you specify multiple destinations. See Load Balancing Settings below. The following two fields appear only with the No setting.

Address: Hostname of the receiver.

Port: Port number to connect to on the host.

Authentication Settings ​

Use the Authentication method drop-down to select one of these options:

  • Manual: In the resulting Auth token field, you can optionally enter an auth token to use in the connection header.

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

Optional Settings​

Exclude current host IPs: This toggle appears when Load balancing is set to Yes. It determines whether to exclude all IPs of the current host from the list of any resolved hostnames. Defaults to No, which keeps the current host available for load balancing.

Compression: Codec to use to compress the data before sending. Defaults to Gzip.

Throttling: Throttle rate, in bytes per second. Defaults to 0, meaning no throttling. Multiple-byte units such as KB, MB, GB etc. are also allowed, e.g., 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.

Backpressure behavior: Specifies whether to block, drop, or queue events when all receivers are exerting backpressure. Defaults to Block. See Persistent Queue Settings below.

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.

Load Balancing Settings​

Enabling the Load balancing toggle replaces the static General Settings > Address and Port fields with the following controls:

Destinations​

Use the Destinations table to specify a known set of receivers on which to load-balance data. To specify more receivers on new rows, click Add Destination. Each row provides the following fields:

Address: Hostname of the receiver. Optionally, you can paste in a comma-separated list, in <host>:<port> format.

Port: Port number to send data to on this host.

TLS: Whether to inherit TLS configs from group setting, or disable TLS. Defaults to inherit.

TLS servername: Servername to use if establishing a TLS connection. If not specified, defaults to connection host (if not an IP). Otherwise, uses the global TLS settings.

Load weight: Set the relative traffic-handling capability for each connection by assigning a weight (> 0). This column accepts arbitrary values, but for best results, assign weights in the same order of magnitude to all connections. Cribl Stream will attempt to distribute traffic to the connections according to their relative weights.

The final column provides an X button to delete any row from the table.

For details on configuring all these options, see About Load Balancing.

Persistent Queue Settings​

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 destructive Clear Persistent Queue button (described below in 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 will block outbound data. To configure the queue size, compression, queue-full fallback behavior, and other options below, use a hybrid Group.

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 is allowed to consume on each Worker Process. Once this limit is reached, this Destination will stop queueing data and apply the Queue‑full behavior. 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 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 “panic” button if you want to delete the files that are currently queued for delivery to this Destination. A confirmation modal will appear - because this will free up disk space by permanently deleting the queued data, without delivering it to downstream receivers. (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)​

Use TLS defaults to No. When toggled to Yes:

Autofill?: This setting is experimental.

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

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.

Timeout Settings​

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​

Post‑Processing​

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​

Log failed requests to disk: Toggling to Yes makes the payloads of any (future) failed requests available for inspection. See Inspecting Payloads 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.

Setting General Settings > Load balancing to Yes adds the following settings:

DNS resolution period (seconds): Re-resolve any hostnames after each interval of this many seconds, and pick up destinations from A records. Defaults to 600 seconds.

Load balance stats period (seconds): Lookback traffic history period. Defaults to 300 seconds. (Note that If multiple receivers are behind a hostname – i.e., multiple A records – all resolved IPs will inherit the weight of the host, unless each IP is specified separately. In Cribl Stream load balancing, IP settings take priority over those from hostnames.)

Max connections: Constrains the number of concurrent receiver connections, per Worker Process, to limit memory utilization. If set to a number > 0, then on every DNS resolution period, Cribl Stream will randomly select this subset of discovered IPs to connect to. Cribl Stream will rotate IPs in future resolution periods – monitoring weight and historical data, to ensure fair load balancing of events among IPs.

Inspecting Payloads to Troubleshoot Closed Connections​

When a downstream receiver closes connections from this Destination (or just stops responding), inspecting the payloads of the resulting failed requests 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 payloads of failed requests. 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 payloads from failed requests. At the command line, navigate to that directory and inspect any payloads that you think might be relevant.

Format​

TCP JSON events are sent in newline-delimited JSON format, consisting of:

  1. A header line. Can be empty, e.g.: {}. If Auth Token is enabled, the token will be included here as a field called authToken. In addition, if events contain common fields, they will be included here under fields.

  2. A JSON event/record per line.

See an example in our TCP JSON Source topic.