NATS JetStream Connector | OpenMetadata Messaging Services

This section covers how to use the NATS JetStream connector. The connector ingests NATS JetStream streams as OpenMetadata topics. For each stream, the connector collects its state and configuration. The configuration includes subjects, storage type, retention policy, replication factor, and limits on message count and size. The connector can optionally fetch a sample of recent messages and read each stream’s schema from a JetStream key-value (KV) bucket. Configure and schedule NATS JetStream metadata workflows from the OpenMetadata UI:

• Requirements
• Metadata Ingestion
• Troubleshooting

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Requirements

The connector communicates with the NATS JetStream API, so JetStream must be enabled on your NATS server. The connector reads metadata from the JetStream management subjects (for example $JS.API.STREAM.LIST), so the credentials you supply must be allowed to publish to and receive replies from the $JS.API.> subjects. If you want schema ingestion, store your schemas in a JetStream KV bucket and configure the bucket with Schema KV Bucket. To read them, the credentials must also be able to access the underlying KV stream subjects. The only mandatory connection field is NATS Servers. All authentication fields are optional. Leaving them empty connects anonymously.

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Supported Authentication Types

NATS JetStream supports several ways to authenticate. Choose the one that matches your server configuration:

• Anonymous: No credentials. Leave the authentication fields empty. Use this when your NATS server allows unauthenticated access.
• Username and Password: Basic authentication with a NATS user and password.
• Token: A single shared authentication token.
• NKey Seed: NKey-based authentication using the account’s seed (the private key that begins with S).

Any of the above can be combined with Transport Layer Security (TLS) for an encrypted connection. Configure TLS separately with TLS Configuration. Use mutual TLS (mTLS) by supplying a client certificate and key.

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Metadata Ingestion

To ingest metadata from NATS JetStream, you need to create a service connection. The service connects NATS JetStream with OpenMetadata. Once you create a service, OpenMetadata automatically starts ingesting metadata.

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Step 1: Add New Service

1. Navigate to Settings > Services.
2. Click Add New Service.

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Step 2: Select a Service and Connector

From the service type dropdown, select Messaging Services, then click the Nats connector tile.

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Step 3: Add Service Name and Description

• Enter a unique, descriptive Service Name. OpenMetadata identifies services by their service name. Enter a name that distinguishes this deployment from other NATS JetStream services you’re ingesting metadata from.
• Optional: Enter a Description for the service.

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Step 4: Configure Connection Options

Specify your source credentials and verify the connection. The UI displays inline help for each field in the help panel.

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Enter Connection Details

• NATS Servers: NATS server URLs as comma-separated values. Each entry uses the nats://host:port form (the default NATS port is 4222). Example: nats://host1:4222,nats://host2:4222. This is the only required field.
• Authentication Type: The method used to authenticate to NATS. Leave empty for anonymous access, or choose one of the following:
  • Username and Password: Provide a Username and Password for basic authentication.
  • Token: Provide a single Token for token-based authentication.
  • NKey Seed: Provide an NKey Seed (the private key seed beginning with S) for NKey authentication.
• TLS Configuration (Optional): TLS/SSL configuration for secure connections. Provide the CA Certificate used to validate the server. For mutual TLS, also provide the SSL Certificate (client certificate) and SSL Key (the private key for that certificate). Both must be supplied together. For more information, see TLS Configuration.
• Schema KV Bucket (Optional): Name of the JetStream KV bucket where schemas are stored. Keys must match stream names and values should be Avro JSON, Protobuf (.proto), or JSON Schema text. For more information, see Schema KV Bucket.
• Additional NATS Config (Optional): Additional NATS client configuration options passed through to the client. See the NATS Python client documentation. The following connection-managed keys are reserved and can’t be set here: servers, user, password, token, nkeys_seed, nkeys_seed_str, tls, user_credentials, signature_cb, and user_jwt_cb.

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Test Connection

After you add the credentials, click Test Connection, then click Save. The test runs two checks:

• GetTopics: Lists JetStream streams to confirm the connection and JetStream access.
• CheckSchemaKvBucket: Confirms the configured Schema KV bucket is reachable. This check is optional. When no Schema KV Bucket is set, it reports a failure that you can ignore; the overall test still passes.

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Step 5: Configure Ingestion Options

In the What to Ingest step, configure filter rules for the topics (JetStream streams) OpenMetadata ingests.

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How Filter Rules Work

Each rule matches topic names using one of five match types:

• Contains: Matches any name containing the value. For example, orders matches prod_orders and orders_2024.
• Starts with: Matches names beginning with the value. For example, prod_ matches prod_orders and prod_events.
• Ends with: Matches names ending with the value. For example, _raw matches events_raw and logs_raw.
• Is exactly: Matches the exact name only. For example, orders matches only orders.
• Matches regex: Matches names using a regular expression. For example, ^orders_.*_v\d+$ matches orders_eu_v1.

When include and exclusion rules both match a topic, the exclusion rule takes priority.

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Filter Options

The Topic section controls which NATS JetStream streams OpenMetadata ingests. It provides the following controls:

• Scan Mode: Choose one of the following scan modes:
  • Scan all: Ingests every topic the connector can access. This is the default.
  • Only specific: Enables include rules so only topics matching at least one rule are ingested.
• Always exclude: Add permanent exclusion rules (shown in red). Topics matching these rules are never ingested, regardless of include rules.
• Preview: Shows a real-time summary of what will be in scope based on your current rules.
• Include rules: In Only specific mode, click + Add to define a rule. Added rules appear as chips. OpenMetadata includes a topic if it matches any rule.

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Step 6: Create & Deploy

Click Create & Deploy to deploy the agent and start the first metadata ingestion run. OpenMetadata saves the service configuration and immediately begins pulling metadata from the source. To monitor ingestion progress or view the service you just added, go to Settings > Services and select your service.

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Configure Metadata Agent and Schedule Ingestion

The Metadata Agent extracts topics, schemas, and other structural metadata from your source and keeps your OpenMetadata catalog in sync. It powers discovery, lineage, and governance across your data assets. When you click Create & Deploy, OpenMetadata automatically deploys a Metadata Agent for this service and triggers the first ingestion run. View its status and run history from the Agents tab on the service detail page. To configure the additional Metadata Agent and schedule ingestion, follow these steps:

1. Navigate to Settings > Services and select the service type.
2. Click the service you have added.
3. Select the Agents tab and click Add Agent > Metadata. For some services, the dropdown is not available and clicking Add Agent takes you directly to the agent configuration page.
4. On the Configure Ingestion page, do the following and click Next.
   • Name this Ingestion: Enter a unique recognizable name for this ingestion pipeline.
   • Agent Setup: Configure the core parameters for this agent. The following fields are available:

     Field	Default	Description
     Generate Sample Data	Off	Option to turn on/off generating sample data during metadata extraction.
     Mark Deleted Topics	On	Soft-delete topics in OpenMetadata when they are removed from the source. Associated entities like sample data and lineage are also deleted.

     
   • Filter Patterns: Apply include or exclude rules to scope which topics this agent ingests. These follow the same filter options described in Step 5: Configure Ingestion Options.
   • Scope & Behaviour: Control what metadata to include and how to handle deletions. Toggle each option on or off based on your needs:

     Toggle	Default	Description
     Enable Debug Log	Off	Sets the ingestion log level to DEBUG. Useful for troubleshooting.
     Override Metadata	Off	When on, source values overwrite existing descriptions, tags, owners, and display names in OpenMetadata. When off, OpenMetadata only updates fields that have no existing value.

     
5. On the Schedule Interval page, set when the agent runs:
   • Schedule: Choose a preset interval (Hourly, Daily, Weekly, Monthly) or enter a custom cron expression.
   • On-Demand: No automatic schedule; trigger the agent manually when needed.
   
6. Click Add to deploy the agent.

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TLS Configuration

To establish secure connections between OpenMetadata and NATS, configure the TLS Configuration option. Provide the CA Certificate used to validate the NATS server’s certificate. If your server requires mutual TLS (mTLS), also provide the SSL Certificate (the client certificate) and the SSL Key (the private key associated with that certificate). The client certificate and key must always be supplied together. Configuring only one of them results in a connection error.

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Schema KV Bucket

NATS JetStream doesn’t have a built-in schema registry. To ingest topic schemas, store them in a JetStream KV bucket and set the Schema KV Bucket option to that bucket’s name.

• Each key in the bucket must match a stream (topic) name.
• Each value should be schema text in Avro JSON, Protobuf (.proto), or JSON Schema format.

During ingestion, OpenMetadata looks up the latest value for each stream name in the bucket. It then detects the schema type, parses the fields, and attaches the schema to the corresponding topic. Streams without a matching key in the bucket are still ingested, just without a schema.

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Sample Data

When Generate Sample Data is enabled in the ingestion configuration, OpenMetadata fetches up to 10 messages from the last 100 sequences of each stream. The total sample is capped at 1 MB. Only UTF-8 text messages are included. Binary payloads are skipped. Sample data collection also respects the global sample-data storage setting. If sample data storage is disabled server-wide, no sample messages are collected.

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