# IT operations

Every minute, a web service reports its error count and its CPU load. A further Channel reports deployments; it is a Pulse Channel, so its value exists only in the Sample that carries it, here at minute 10. An error spike soon after a deployment is probably caused by it.

Parameters (in the page address as ?errors=…):

- Error spike above (`errors`): 0 to 15 errors/min in steps of 1, default 5
- Error spike for (`spikeMinutes`): 0 to 10 min in steps of 1, default 2
- Regression within (`window`): 5 to 90 min in steps of 5, default 30
- High CPU above (`cpu`): 50 to 100 % in steps of 5, default 90
- High CPU for (`cpuMinutes`): 1 to 15 min in steps of 1, default 5

The site cannot run the default parameters: (JavaScript) TypeError: Cannot read properties of undefined (reading 'length')

Java source at the default parameters:

```java
import static io.github.romanhaendler.rbed.Conditions.*;

import io.github.romanhaendler.rbed.*;
import java.time.Duration;
import java.util.HashMap;
import java.util.Map;

Channel cpu = Channel.named("cpu");
Channel deploy = Channel.pulse("deploy");
Channel errors = Channel.named("errors");

Rule deployment = Rule.named("Deployment").when(deploy.above(0.5));
Rule errorSpike = Rule.named("ErrorSpike")
    .when(errors.above(5)).forDuration(Duration.ofMinutes(2));
Rule regression = Rule.named("Regression")
    .when(after(deployment).within(Duration.ofMinutes(30)).and(errors.above(5)))
    .forDuration(Duration.ofMinutes(2));
Rule highCpu = Rule.named("HighCpu")
    .when(cpu.above(90)).forDuration(Duration.ofMinutes(5));
Detector detector = Detector.builder()
    .rules(deployment, errorSpike, regression, highCpu)
    .build();

for (int m = 0; m < 120; m++) {   // every minute
  Map<Channel, Double> values = new HashMap<>();
  values.put(errors, m >= 25 && m < 35 ? 12.0 : m >= 80 && m < 85 ? 9.0 : 1.0);
  values.put(cpu, m >= 90 && m < 100 ? 95.0 : 50.0);
  if (m == 10) values.put(deploy, 1.0);   // a deployment, in this Sample only
  detector.push(m * 60_000L, values);
}
detector.close();
```

## The Rules

- **Deployment**: a deployment is reported. It Ends with the next Sample, which carries no deployment.
- **ErrorSpike**: more than 5 errors per minute for 2 minutes.
- **Regression**: more than 5 errors per minute for 2 minutes, all within 30 minutes after a Deployment Ended.
- **HighCpu**: the CPU above 90 % for 5 minutes.

At the defaults, the deployment at minute 10 is a `Deployment` from minute 10 to 11. The errors are above 5 per minute from minute 25 to 35 and from 80 to 85, an `ErrorSpike` each, Confirmed after 2 minutes. The spike at minute 25 starts 14 minutes after the Deployment Ended, so it is a `Regression` as well; the one at minute 80 is too long after it. The CPU is above 90 % from minute 90 to 100, and `HighCpu` is Confirmed at minute 95.

### Things to try

- Narrow *Regression within* to 15 minutes: the spike at minute 25 starts inside the window, but its 2 minutes are not reached before the window closes at minute 26, so the Pending `Regression` is Discarded.

## Reference

The example is [DeploymentRegressionExample](https://github.com/romanhaendler/rbed/blob/main/src/test/java/io/github/romanhaendler/rbed/examples/DeploymentRegressionExample.java), a test with its expected Events, listed in the README's [Examples](https://github.com/romanhaendler/rbed#examples).

Methods used: [`Channel.named`](https://romanhaendler.github.io/rbed/api/io.github.romanhaendler.rbed/io/github/romanhaendler/rbed/Channel.html#named%28java.lang.String%29), [`Channel.pulse`](https://romanhaendler.github.io/rbed/api/io.github.romanhaendler.rbed/io/github/romanhaendler/rbed/Channel.html#pulse%28java.lang.String%29), [`Rule.named`](https://romanhaendler.github.io/rbed/api/io.github.romanhaendler.rbed/io/github/romanhaendler/rbed/Rule.html#named%28java.lang.String%29), [`Rule.when`](https://romanhaendler.github.io/rbed/api/io.github.romanhaendler.rbed/io/github/romanhaendler/rbed/Rule.html#when%28io.github.romanhaendler.rbed.Condition%29), [`Expression.above`](https://romanhaendler.github.io/rbed/api/io.github.romanhaendler.rbed/io/github/romanhaendler/rbed/Expression.html#above%28double%29), [`Rule.forDuration`](https://romanhaendler.github.io/rbed/api/io.github.romanhaendler.rbed/io/github/romanhaendler/rbed/Rule.html#forDuration%28java.time.Duration%29), [`Conditions.after`](https://romanhaendler.github.io/rbed/api/io.github.romanhaendler.rbed/io/github/romanhaendler/rbed/Conditions.html#after%28io.github.romanhaendler.rbed.Rule%29), [`After.within`](https://romanhaendler.github.io/rbed/api/io.github.romanhaendler.rbed/io/github/romanhaendler/rbed/After.html#within%28java.time.Duration%29), [`Condition.and`](https://romanhaendler.github.io/rbed/api/io.github.romanhaendler.rbed/io/github/romanhaendler/rbed/Condition.html#and%28io.github.romanhaendler.rbed.Condition%29), [`Detector.builder`](https://romanhaendler.github.io/rbed/api/io.github.romanhaendler.rbed/io/github/romanhaendler/rbed/Detector.html#builder%28%29), [`Detector.Builder.rules`](https://romanhaendler.github.io/rbed/api/io.github.romanhaendler.rbed/io/github/romanhaendler/rbed/Detector.Builder.html#rules%28io.github.romanhaendler.rbed.Rule...%29), [`Detector.Builder.build`](https://romanhaendler.github.io/rbed/api/io.github.romanhaendler.rbed/io/github/romanhaendler/rbed/Detector.Builder.html#build%28%29), [`Detector.push`](https://romanhaendler.github.io/rbed/api/io.github.romanhaendler.rbed/io/github/romanhaendler/rbed/Detector.html#push%28long,java.util.Map%29), [`Detector.close`](https://romanhaendler.github.io/rbed/api/io.github.romanhaendler.rbed/io/github/romanhaendler/rbed/Detector.html#close%28%29).

The concepts at work, each on a page of its own: [Pulse Channels](https://romanhaendler.github.io/rbed/pulse-channels/), [After another Event](https://romanhaendler.github.io/rbed/after/).