# Alert Reference Use this reference to map each alert to its identifier, category, instance field, and severity. | Alert | Alert Identifier | Description | Category | Instance | Severity | | ----------------------------------------------------- | ---------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | -------------- | ------------------ | -------------------------- | | Kafka Broker is down | 1000 | Raised when the Kafka broker is not part of the cluster for at least 1 minute. Example: `host-1`, `host-2`. | Infrastructure | `brokerID` | `INFO`, `CRITICAL` | | Zookeeper Node is down | 1001 | Raised when the Zookeeper node is not reachable. This information is based on Zookeeper JMX. If it responds to JMX queries, it is considered to be running. | Infrastructure | `service name` | `INFO`, `CRITICAL` | | Connect Worker is down | 1002 | Raised when the Kafka Connect worker is not responding to the `/connectors` API call for more than 1 minute. | Infrastructure | `worker URL` | `MEDIUM` | | Schema Registry is down | 1003 | Raised when the Schema Registry node is not responding to the root API call for more than 1 minute. | Infrastructure | `service URL` | `HIGH`, `INFO` | | Under replicated partitions | 1005 | Raised when there are topic partitions not meeting the configured replication factor. | Infrastructure | `partitions` | `HIGH`, `INFO` | | Partitions offline | 1006 | Raised when there are partitions without an active leader. These partitions are not readable or writable. | Infrastructure | `brokers` | `HIGH`, `INFO` | | Active Controllers | 1007 | Raised when the number of active controllers is not `1`. Each cluster should have exactly one controller. | Infrastructure | `brokers` | `HIGH`, `INFO` | | Multiple Broker Versions | 1008 | Raised when brokers in the cluster are running different Kafka versions. | Infrastructure | `brokers versions` | `HIGH`, `INFO` | | File-open descriptors high capacity on Brokers | 1009 | Raised when a broker has too many open file descriptors. | Infrastructure | `brokerID` | `HIGH`, `INFO`, `CRITICAL` | | Average % the request handler is idle | 1010 | Raised when the average fraction of time the request handler threads are idle falls below the threshold. When the value is smaller than `0.02`, the alert level is `CRITICAL`. When the value is smaller than `0.1`, the alert level is `HIGH`. | Infrastructure | `brokerID` | `HIGH`, `INFO`, `CRITICAL` | | Fetch requests failure | 1011 | Raised when the failed Fetch request rate per second is greater than a threshold. If the value is greater than `0.1`, the alert level is `CRITICAL`. Otherwise, it is `HIGH`. | Infrastructure | `brokerID` | `HIGH`, `INFO`, `CRITICAL` | | Produce requests failure | 1012 | Raised when the failed Produce request rate per second is greater than a threshold. If the value is greater than `0.1`, the alert level is `CRITICAL`. Otherwise, it is `HIGH`. | Infrastructure | `brokerID` | `HIGH`, `INFO`, `CRITICAL` | | Broker disk usage is greater than the cluster average | 1013 | Raised when a Kafka broker's disk usage is greater than the cluster average. The default threshold is `1 GB` of disk usage. | Infrastructure | `brokerID` | `MEDIUM`, `INFO` | | Leader Imbalance | 1014 | Raised when a Kafka broker has more leader replicas than the cluster average. | Infrastructure | `brokerID` | `INFO` | | Consumer Lag exceeded | 2000 | Raises an alert when consumer lag exceeds the threshold on any partition. | Consumers | `topic` | `HIGH`, `INFO` | | Connector deleted | 3000 | Raised when a connector was deleted. | Kafka Connect | `connector name` | `INFO` | | Topic has been created | 4000 | Raised when a new topic was added. | Topics | `topic` | `INFO` | | Topic has been deleted | 4001 | Raised when a topic was deleted. | Topics | `topic` | `INFO` | | Topic data has been deleted | 4002 | Raised when records from a topic were deleted. | Topics | `topic` | `INFO` | | Data Produced | 5000 | Raises an alert when the data produced on a topic does not match the expected threshold. | Data Produced | `topic` | `LOW`, `INFO` | | Connector Failed | 6000 | Raises an alert when a connector, or any worker in a connector, is down. | Apps | `connector` | `LOW`, `INFO` | --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.lenses.io/latest/user-guide/using/alerting-and-monitoring/alert-reference.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.