# Alert Rules

You can set up Alert rules on:

1. Consumers
2. Producers
3. Infrastructure

{% hint style="info" %}
Alerts are always stored in Lenses even if you don't send them out to an external alerting system.
{% endhint %}

## Consumer Alert Rules

Consumer alert rules are rules set on a consumer groups for specific topics. They allow you defined a consumer lag per partition for the topic overall and optionally send them to an channel for routing to your external alerting system.

Select the `Environments & Topics` option from the left sidebar, expand the environment node you are interested in and select the `Alerts` node, this will open the listing of alerts.

Select consumer rules to see a list of existing consumer groups rules, you can then either edit one or create a new rule.

<figure><img src="/files/z2iq25Ih7jwmBLgZB7Kg" alt=""><figcaption></figcaption></figure>

## Producer Alert Rules

Producer alert rules allow you set alerts when the number of messages produced to a topic meets certain criteria:

1. Less, equals or greater than a specified amount
2. Over a time period, e.g every 1 minute, hour etc.

<figure><img src="/files/lgETyy38C1cPw9JCdmEi" alt=""><figcaption></figcaption></figure>

To create an producer alert for an environment, select the topics and environment on the left main panel, then expand the environment node you are interested in and select Alerts. You can also acces this via the context menus on the environment dashboard view.

Select consumer rules to see a list of existing producer rules, you can then either edit one or create a new rule.

## Infrastructure Alert Rules

Infrastructure alerts are built in to Lenses. You can toggle them on or off and send them to alert channels.

| Alert                                 | Description                                                                                                                                                                    |
| ------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| Lenses License                        | The Lenses license is invalid.                                                                                                                                                 |
| Kafka broker is down                  | A Kafka broker in the cluster is not healthy.                                                                                                                                  |
| Zookeeper node is down                | A Zookeeper node is not healthy.                                                                                                                                               |
| Connect Worker is down                | A Kafka Connect worker node is not healthy.                                                                                                                                    |
| Schema Registry is down               | A Schema Registry instance is not healthy.                                                                                                                                     |
| Under replicated partitions           | The Kafka cluster has one or more under-replicated partitions.                                                                                                                 |
| Partitions offline                    | The Kafka cluster has one or more partitions offline, with no active leader.                                                                                                   |
| Active Controller                     | The Kafka cluster has zero, or more than one, active controller.                                                                                                               |
| Multiple Broker versions              | The Kafka cluster is under a version upgrade and not all brokers have been upgraded.                                                                                           |
| File-open descriptors on Brokers      | A Kafka broker has an alarming number of open file descriptors. This alert triggers when the operating system exceeds 90% of the available open file descriptors.              |
| Average % the request handler is idle | The average fraction of time the request handler threads are idle is dangerously low. The alert is **HIGH** when the value is below 10%, and **CRITICAL** when it is below 2%. |
| Fetch requests failure                | Fetch requests are failing. If the failure rate per second is greater than 10%, the alert level is **CRITICAL**. Otherwise, it is **HIGH**.                                    |
| Produce requests failure              | Produce requests are failing. If the failure rate per second is greater than 10%, the alert level is **CRITICAL**. Otherwise, it is **HIGH**.                                  |
| Broker disk usage                     | A Kafka broker’s disk usage is greater than the cluster average. The built-in threshold is 1 GByte.                                                                            |
| Leader imbalance                      | A Kafka broker has more leader replicas than the average broker in the cluster.                                                                                                |


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