Kafka Lag Monitor is a VS Code extension for inspecting Apache Kafka clusters from the Explorer sidebar. It shows topics, consumer groups, lag totals, partition lag, topic metadata, recent messages, and a simple producer panel for test messages.

Plugin address

Azure DevOps: https://dev.azure.com/fattahpour/kafka-lag-monitor/_git/kafka-lag-monitor
GitHub: https://github.com/fattahpour/kafka-lag-monitor
VSIX package: kafka-lag-monitor-0.0.1.vsix

The extension is not published to the VS Code Marketplace yet. Install it from the VSIX package in this repository.

Install the extension

Open VS Code.
Open the Command Palette.
Run Extensions: Install from VSIX....
Select kafka-lag-monitor-0.0.1.vsix.
Reload VS Code if prompted.

For development, open this repository in VS Code and press F5 to launch the Extension Development Host.

How to use

Open the Explorer sidebar in VS Code.
Find the Kafka Lag Monitor view.
Click the + icon in the view title bar, or run Kafka: Add Connection from the Command Palette.
Enter a connection name and Kafka brokers, for example localhost:9092 or broker1:9093,broker2:9093.
Choose the connection security mode: no SSL, SSL, mTLS, or SASL.
Expand the connection in Kafka Lag Monitor.
Expand Topics to inspect topic names and partition counts.
Click a topic to open its metadata.
Right-click a topic and choose Kafka: Browse Messages to inspect recent records.
Right-click a topic and choose Kafka: Produce Message to send a test record.
Expand Consumer Groups to see total lag by group.
Click a consumer group to open the Lag Dashboard.

Connection passwords and mTLS key passphrases are stored in VS Code SecretStorage. They are not written to connection files.

Main features

Explorer tree for Kafka connections, topics, and consumer groups.
Topic metadata view with partitions, leaders, replicas, ISR, and configs.
Lag Dashboard with total lag and per-topic/per-partition breakdown.
Message Browser with partition selection and Earliest, Prev, Next, Latest, and Refresh navigation.
Produce Message panel with partition, key, value, and headers fields.
Connection wizard for plain Kafka, SSL, mTLS, and SASL.
Connection edit, remove, reconnect, and refresh commands.

Commands

Kafka: Add Connection - create a new Kafka connection profile.
Kafka: Edit Connection - update an existing connection profile.
Kafka: Remove Connection - remove a connection and its stored secrets.
Kafka: Reconnect - reconnect after changing brokers or credentials.
Kafka: Browse Messages - open a topic message browser.
Kafka: Produce Message - open a topic producer panel.
Kafka Lag Monitor: Refresh - reload the Explorer tree.

Configuration

The recommended setup path is Kafka: Add Connection. It prompts for brokers, SSL/mTLS settings, SASL mechanism, username, and password.

Connection profiles are stored in the first workspace folder at:

.vscode/kafka-lag-monitor.connections.json

If that file does not exist yet, the extension uses a default local profile for localhost:9092. You can also inspect or hand-edit non-secret connection settings in the workspace file:

{
  "connections": [
    {
      "name": "local-cluster",
      "brokers": ["localhost:9092"],
      "sasl": null,
      "ssl": false,
      "clientId": "kafka-lag-monitor"
    },
    {
      "name": "secure-cluster",
      "brokers": ["broker1:9093"],
      "sasl": { "mechanism": "scram-sha-512" },
      "ssl": true,
      "clientId": "kafka-lag-monitor"
    },
    {
      "name": "mtls-cluster",
      "brokers": ["broker1:9093"],
      "sasl": null,
      "ssl": {
        "ca": "/etc/kafka/ca.pem",
        "cert": "/etc/kafka/client-cert.pem",
        "key": "/etc/kafka/client-key.pem"
      },
      "clientId": "kafka-lag-monitor"
    }
  ]
}

Lag thresholds and dashboard polling remain VS Code settings:

"kafkaLagMonitor.lagWarningThreshold": 100,
"kafkaLagMonitor.lagCriticalThreshold": 1000,
"kafkaLagMonitor.pollIntervalSeconds": 10

Build and package

Install dependencies, compile, and run tests:

npm install
npm run compile
npm test

Build the VSIX package:

npx @vscode/vsce package --allow-missing-repository

The package output is:

kafka-lag-monitor-0.0.1.vsix

Local integration test

With Kafka running locally, create a topic and some lag:

kafka-topics.sh --bootstrap-server localhost:9092 --create --topic orders.events --partitions 3 --replication-factor 1
for i in 1 2 3 4 5; do echo "order-$i"; done | kafka-console-producer.sh --bootstrap-server localhost:9092 --topic orders.events
kafka-console-consumer.sh --bootstrap-server localhost:9092 --topic orders.events --group order-service --max-messages 2

Then run the extension with F5, add a localhost:9092 connection, expand the connection, and check: