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chore: strip out raw HTML from docs (#1414)
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@thisisobate
thisisobate authored Jun 28, 2024
1 parent 5ae6702 commit 09a1763
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172 changes: 98 additions & 74 deletions content/docs/1.4/concepts/external-scalers.md
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Original file line number Diff line number Diff line change
Expand Up @@ -27,11 +27,12 @@ type Scaler interface {
```

The `Scaler` interface defines 4 methods:

- `IsActive` is called on `pollingInterval` defined in the ScaledObject/ScaledJob CRDs and scaling to 1 happens if this returns true.
- `Close` is called to allow the scaler to clean up connections or other resources.
- `GetMetricSpec` returns the target value for the HPA definition for the scaler. For more details refer to [Implementing `GetMetricSpec`](#4-implementing-getmetricspec).
- `GetMetrics` returns the value of the metric referred to from `GetMetricSpec`. For more details refer to [Implementing `GetMetrics`](#5-implementing-getmetrics).
> Refer to the [HPA docs](https://kubernetes.io/docs/tasks/run-application/horizontal-pod-autoscale-walkthrough/) for how HPA calculates replicaCount based on metric value and target value.
> Refer to the [HPA docs](https://kubernetes.io/docs/tasks/run-application/horizontal-pod-autoscale-walkthrough/) for how HPA calculates replicaCount based on metric value and target value.
### External Scaler GRPC interface

Expand All @@ -51,6 +52,7 @@ service ExternalScaler {
- `IsActive` maps to the `IsActive` method on the `Scaler` interface.

Few things to notice:

- `IsActive`, `StreamIsActive`, and `GetMetricsSpec` are called with a `ScaledObjectRef` that contains the scaledObject name/namespace as well as the content of `metadata` defined in the trigger.

For example the following `ScaledObject`:
Expand Down Expand Up @@ -85,6 +87,7 @@ KEDA will attempt a connection to `service-address.svc.local:9090` and calls `Is
}
}
```

## Implementing KEDA external scaler GRPC interface

### Implementing an external scaler:
Expand All @@ -110,6 +113,7 @@ go mod init example.com/external-scaler/sample
mkdir externalscaler
protoc externalscaler.proto --go_out=plugins=grpc:externalscaler
```

{{< /collapsible >}}

{{< collapsible "C#" >}}
Expand Down Expand Up @@ -146,9 +150,8 @@ mkdir Services
```bash
npm install --save grpc request
```
{{< /collapsible >}}

<br />
{{< /collapsible >}}

#### 3. Implementing `IsActive`

Expand Down Expand Up @@ -178,6 +181,7 @@ spec:
Full implementation can be found here: https://github.com/kedacore/external-scaler-samples

`main.go`

```golang
func (e *ExternalScaler) IsActive(ctx context.Context, scaledObject *pb.ScaledObjectRef) (*pb.IsActiveResponse, error) {
// request.Scalermetadata contains the `metadata` defined in the ScaledObject
Expand Down Expand Up @@ -224,12 +228,14 @@ func (e *ExternalScaler) IsActive(ctx context.Context, scaledObject *pb.ScaledOb
}, nil
}
```

{{< /collapsible >}}

{{< collapsible "C#" >}}
Full implementation can be found here: https://github.com/kedacore/external-scaler-samples

`Services/ExternalScalerService.cs`

```csharp
public class ExternalScalerService : ExternalScaler.ExternalScalerBase
{
Expand Down Expand Up @@ -262,79 +268,84 @@ public class ExternalScalerService : ExternalScaler.ExternalScalerBase
}
}
```

{{< /collapsible >}}

{{< collapsible "Javascript" >}}
`index.js`

```js
const grpc = require('grpc')
const request = require('request')
const externalScalerProto = grpc.load('externalscaler.proto')
const grpc = require("grpc");
const request = require("request");
const externalScalerProto = grpc.load("externalscaler.proto");

const server = new grpc.Server()
const server = new grpc.Server();
server.addService(externalScalerProto.externalscaler.ExternalScaler.service, {
isActive: (call, callback) => {
const longitude = call.request.scalerMetadata.longitude
const latitude = call.request.scalerMetadata.latitude
const longitude = call.request.scalerMetadata.longitude;
const latitude = call.request.scalerMetadata.latitude;
if (!longitude || !latitude) {
callback({
code: grpc.status.INVALID_ARGUMENT,
details: 'longitude and latitude must be specified',
})
details: "longitude and latitude must be specified",
});
} else {
const now = new Date()
const yesterday = new Date(new Date().setDate(new Date().getDate()-1));

const startTime = `${yesterday.getUTCFullYear()}-${yesterday.getUTCMonth()}-${yesterday.getUTCDay()}`
const endTime = `${now.getUTCFullYear()}-${now.getUTCMonth()}-${now.getUTCDay()}`
const radiusKm = 500
const query = `format=geojson&starttime=${startTime}&endtime=${endTime}&longitude=${longitude}&latitude=${latitude}&maxradiuskm=${radiusKm}`

request.get({
url: `https://earthquake.usgs.gov/fdsnws/event/1/query?${query}`,
json: true,
}, (err, resp, data) => {
if (err) {
callback({
code: grpc.status.INTERNAL,
details: err,
})
} else if (resp.statusCode !== 200) {
callback({
code: grpc.status.INTERNAL,
details: `expected status 200, got ${resp.statusCode}`
})
} else {
// count how many earthquakes with mag > 1.0
let count = 0
data.features.forEach(i => {
if (i.properties.mag > 1.0) {
count++
}
})
callback(null, {
result: count > 2,
})
const now = new Date();
const yesterday = new Date(new Date().setDate(new Date().getDate() - 1));

const startTime = `${yesterday.getUTCFullYear()}-${yesterday.getUTCMonth()}-${yesterday.getUTCDay()}`;
const endTime = `${now.getUTCFullYear()}-${now.getUTCMonth()}-${now.getUTCDay()}`;
const radiusKm = 500;
const query = `format=geojson&starttime=${startTime}&endtime=${endTime}&longitude=${longitude}&latitude=${latitude}&maxradiuskm=${radiusKm}`;

request.get(
{
url: `https://earthquake.usgs.gov/fdsnws/event/1/query?${query}`,
json: true,
},
(err, resp, data) => {
if (err) {
callback({
code: grpc.status.INTERNAL,
details: err,
});
} else if (resp.statusCode !== 200) {
callback({
code: grpc.status.INTERNAL,
details: `expected status 200, got ${resp.statusCode}`,
});
} else {
// count how many earthquakes with mag > 1.0
let count = 0;
data.features.forEach((i) => {
if (i.properties.mag > 1.0) {
count++;
}
});
callback(null, {
result: count > 2,
});
}
}
})
);
}
}
})
},
});

server.bind('127.0.0.1:9090', grpc.ServerCredentials.createInsecure())
console.log('Server listening on 127.0.0.1:9090')
server.bind("127.0.0.1:9090", grpc.ServerCredentials.createInsecure());
console.log("Server listening on 127.0.0.1:9090");

server.start()
server.start();
```
{{< /collapsible >}}

<br />
{{< /collapsible >}}

#### 4. Implementing `GetMetricSpec`

`GetMetricSpec` returns the `target` value for [the HPA definition for the scaler](https://kubernetes.io/docs/tasks/run-application/horizontal-pod-autoscale-walkthrough/). This scaler will define a static target of 10, but the threshold value is often specified in the metadata for other scalers.

{{< collapsible "Golang" >}}

```golang
func (e *ExternalScaler) GetMetricSpec(context.Context, *pb.ScaledObjectRef) (*pb.GetMetricSpecResponse, error) {
return &pb.GetMetricSpecResponse{
Expand All @@ -345,9 +356,11 @@ func (e *ExternalScaler) GetMetricSpec(context.Context, *pb.ScaledObjectRef) (*p
}, nil
}
```

{{< /collapsible >}}

{{< collapsible "C#" >}}

```csharp
public override async Task<GetMetricSpecResponse> GetMetricSpec(ScaledObjectRef request, ServerCallContext context)
{
Expand All @@ -362,31 +375,35 @@ public override async Task<GetMetricSpecResponse> GetMetricSpec(ScaledObjectRef
return Task.FromResult(resp);
}
```

{{< /collapsible >}}

{{< collapsible "Javascript" >}}

```js
server.addService(externalScalerProto.externalscaler.ExternalScaler.service, {
// ...
getMetricSpec: (call, callback) => {
callback(null, {
metricSpecs: [{
metricName: 'earthquakeThreshold',
targetSize: 10,
}]
})
}
})
metricSpecs: [
{
metricName: "earthquakeThreshold",
targetSize: 10,
},
],
});
},
});
```
{{< /collapsible >}}

<br />
{{< /collapsible >}}

#### 5. Implementing `GetMetrics`

`GetMetrics` returns the value of the metric referred to from `GetMetricSpec`, in this example it's `earthquakeThreshold`.

{{< collapsible "Golang" >}}

```golang
func (e *ExternalScaler) GetMetrics(_ context.Context, metricRequest *pb.GetMetricsRequest) (*pb.GetMetricsResponse, error) {
longitude := metricRequest.ScaledObjectRef.ScalerMetadata["longitude"]
Expand All @@ -409,9 +426,11 @@ func (e *ExternalScaler) GetMetrics(_ context.Context, metricRequest *pb.GetMetr
}, nil
}
```

{{< /collapsible >}}

{{< collapsible "C#" >}}

```csharp
public override async Task<GetMetricsResponse> GetMetrics(GetMetricsRequest request, ServerCallContext context)
{
Expand All @@ -436,38 +455,43 @@ public override async Task<GetMetricsResponse> GetMetrics(GetMetricsRequest requ
return resp;
}
```

{{< /collapsible >}}

{{< collapsible "Javascript" >}}

```js
server.addService(externalScalerProto.externalscaler.ExternalScaler.service, {
// ...
getMetrics: (call, callback) => {
const longitude = call.request.scaledObjectRef.scalerMetadata.longitude
const latitude = call.request.scaledObjectRef.scalerMetadata.latitude
const longitude = call.request.scaledObjectRef.scalerMetadata.longitude;
const latitude = call.request.scaledObjectRef.scalerMetadata.latitude;
if (!longitude || !latitude) {
callback({
code: grpc.status.INVALID_ARGUMENT,
details: 'longitude and latitude must be specified',
})
details: "longitude and latitude must be specified",
});
} else {
getEarthquakeCount((err, count) => {
if (err) {
callback({
code: grpc.status.INTERNAL,
details: err,
})
});
} else {
callback(null, {
metricValues: [{
metricName: 'earthquakeThreshold',
metricValue: count,
}]
})
metricValues: [
{
metricName: "earthquakeThreshold",
metricValue: count,
},
],
});
}
})
});
}
}
})
},
});
```

{{< /collapsible >}}
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