Create an OCI Alarm for Compute CPU Utilization

Monitoring is an important part of cloud operations. After deploying compute instances, we need visibility into resource usage such as CPU, memory, disk, and network. CPU utilization is one of the most common metrics monitored for compute instances because high CPU usage may indicate application load, inefficient processes, or capacity limitations. Also high CPU usage will affect the workload performance and it further may create service disruptions.

Oracle Cloud Infrastructure provides the Monitoring service to collect metrics from OCI resources and create alarms when metric values cross defined thresholds. In this article, we will create an OCI alarm for compute CPU utilization. We will also simulate high CPU usage on a compute instance and validate that OCI sends an email notification when the alarm is triggered.

The test case requires OCI services -  OCI Compute, OCI Monitoring, OCI Notifications and Oracle Cloud Agent.  OCI Monitoring collects CPU utilization metrics from the OCI compute instance. An alarm is created on the CpuUtilization metric. When CPU utilization crosses the configured threshold, the alarm moves to firing state and sends a message to an OCI Notifications topic. The email subscription receives the alert.

Prerequisites

Before starting this setup, the following items should be available:  

OCI tenancy access
Required compartment
Running compute instance
Oracle Cloud Agent enabled on the instance
Compute Instance Monitoring plugin enabled
Permission to create alarm
Permission to create notification topic and subscription
Valid email address for receiving notification

Validate Compute Instance Monitoring Plugin

Before creating the alarm, the compute instance should be able to emit monitoring metrics. From the compute instance details page, we can review the Oracle Cloud Agent section and validate that the Compute Instance Monitoring plugin is enabled and running.

If the plugin is disabled, metrics may not appear in OCI Monitoring.

The metric used for this article is: CpuUtilization

Create Notification Topic

First, we will create a Notification topic. The topic will receive the alarm message and forward it to the email subscription.

From OCI Console, navigate to:

Developer Services → Application Integration → Notifications

Create a topic.

Example topic name:

compute-cpu-alarm-topic

After the topic is created, we will add an email subscription.

Create Email Subscription

Open the Notification topic and create a subscription.

Use the protocol:

Email

Provide the email address that should receive the alarm notification.

After creating the subscription, OCI sends a confirmation email. The email subscription must be confirmed before alarm notifications can be received. Oracle’s Notifications documentation explains that Notifications uses topics and subscriptions, and when a message is published to a topic, it sends the message to all subscriptions on that topic.  After confirmation, the subscription status changes to active.

More details are on this topic is available in article

“Send Email Notification When Object Is Uploaded to OCI Object Storage”

Create CPU Utilization Alarm

Now we will create the alarm.

From OCI Console, navigate to:

Observability & Management → Monitoring → Alarm Definitions

Create a new alarm.

Example alarm name:

High CPU Utilization Alarm

Select the metric details:

Metric namespace: oci_computeagent
Metric name: CpuUtilization
Interval: 1 minute
Statistic: Mean

Select the required compartment and compute instance dimension. For the trigger rule, we can use a low threshold for testing.

Example:

CpuUtilization greater than 50%

For a production environment, the threshold can be higher, such as 80% or 85%, based on workload behavior and operational standards.

For notification destination, select the Notification topic:

compute-cpu-alarm-topic

Save the alarm.

Alarm Query Example

The alarm query may look similar to the following:

CpuUtilization[1m].mean() > 50

This means OCI Monitoring evaluates the average CPU utilization over a one-minute interval. If the value is greater than 50, the alarm condition is met.

For testing, a lower threshold makes it easier to trigger the alarm. After validation, the threshold can be adjusted to a production-friendly value.

Simulate High CPU Usage

To validate the alarm, we need to generate CPU load on the compute instance.

Connect to the compute instance using SSH.

For Oracle Linux, we can use the stress tool which is easiest way.

Install stress if it is not already done. We can use yum utility or other available ways to install that.

sudo yum install -y stress

Generate CPU load:

stress --cpu 2 --timeout 300

This command generates CPU load using two CPU workers for 300 seconds.

Wait for Alarm Evaluation

After CPU load is generated, OCI Monitoring needs a few minutes to collect metrics and evaluate the alarm condition.

In the alarm details page, the alarm should move from:

OK

to:

Firing

Once the alarm enters firing state, OCI Notifications sends an email to the confirmed subscription.

A small delay is normal because metrics are collected and evaluated based on the selected interval and alarm configuration.

Validate Email Notification

After the alarm is triggered, check the email inbox.

The notification email should include details such as:

Alarm name
Alarm state
Alarm Type
Alarm Severity
Notification type
Alarm Summary
Body
Time
Query
Number of metrics breaching threshold
Dimensions
Metric values, ordered by dimension

This confirms that the CPU alarm was triggered successfully and the notification flow is working.

Stop CPU Load

After validation, stop the CPU load.

With the stress command, it stops automatically after the timeout

After CPU load stops, CPU utilization should decrease.

After the next alarm evaluation cycle, the alarm should return to:

OK

Depending on the alarm configuration, a notification may also be sent when the alarm clears.

In this article, we created an OCI alarm for compute CPU utilization and connected it with OCI Notifications. We also simulated high CPU usage on the compute instance to validate that the alarm moves to firing state and sends an email notification.

This is a useful monitoring pattern for OCI compute workloads. By using Monitoring alarms and Notifications, we can detect high CPU usage early and improve operational response without using custom scripts or external monitoring tools.