### Executing Go Function with Hystrix.Go

Source: https://github.com/afex/hystrix-go/blob/master/README.md

Illustrates the basic usage of `hystrix.Go` to wrap application logic within a Hystrix command. This example shows an asynchronous command execution without a specified fallback function.

```go
hystrix.Go("my_command", func() error {
	// talk to other services
	return nil
}, nil)
```

--------------------------------

### Configuring Hystrix Command Settings

Source: https://github.com/afex/hystrix-go/blob/master/README.md

Provides examples of configuring Hystrix command properties such as timeout, maximum concurrent requests, and error percentage threshold. Settings can be applied to individual commands using `hystrix.ConfigureCommand` or multiple commands via `hystrix.Configure`.

```go
hystrix.ConfigureCommand("my_command", hystrix.CommandConfig{
	Timeout:               1000,
	MaxConcurrentRequests: 100,
	ErrorPercentThreshold: 25,
})
```

```go
hystrix.Configure(map[string]hystrix.CommandConfig{
	"my_command": {
		Timeout: 1000,
		MaxConcurrentRequests: 100,
		ErrorPercentThreshold: 25
	}
})
```

--------------------------------

### Run Hystrix-Go Service with StatsD Integration

Source: https://github.com/afex/hystrix-go/blob/master/loadtest/README.md

This command starts the Hystrix-Go integration service. It specifies the main application file and configures StatsD for metrics collection, directing output to a specified host and port. This allows for monitoring circuit breaker behavior and performance metrics.

```Go
go run service/main.go -statsd mystatsdhost:8125
```

--------------------------------

### Importing Hystrix Go Library

Source: https://github.com/afex/hystrix-go/blob/master/README.md

Demonstrates how to import the `hystrix-go` library into a Go project, making its fault tolerance features available for use.

```go
import "github.com/afex/hystrix-go/hystrix"
```

--------------------------------

### Hystrix Metrics and Plugin Integration

Source: https://github.com/afex/hystrix-go/blob/master/README.md

API documentation for functions related to Hystrix metrics collection and integration with external monitoring systems like the Hystrix Dashboard and Statsd.

```APIDOC
hystrix.NewStreamHandler() *StreamHandler
  - Creates a new HTTP handler for Hystrix event streams.
  - Returns: (*StreamHandler) An HTTP handler that can be registered to serve Hystrix dashboard metrics.
  - Usage: Typically used with `http.ListenAndServe` to expose metrics.

plugins.InitializeStatsdCollector(config *plugins.StatsdCollectorConfig) (*plugins.StatsdCollector, error)
  - Initializes a Statsd collector for Hystrix metrics.
  - Parameters:
    - config: (*plugins.StatsdCollectorConfig) Configuration for the Statsd collector.
      - StatsdAddr: (string) The address of the Statsd server (e.g., "localhost:8125").
      - Prefix: (string) A prefix to add to all Statsd metrics (e.g., "myapp.hystrix").
  - Returns: (*plugins.StatsdCollector, error) The initialized collector and an error if initialization fails.
  - Usage: The returned collector's `NewStatsdCollector` method should be registered with `metricCollector.Registry.Register`.
```

--------------------------------

### Enabling Hystrix Dashboard Metrics Stream

Source: https://github.com/afex/hystrix-go/blob/master/README.md

Shows how to set up an HTTP handler for Hystrix event streams. This allows integration with the Hystrix Dashboard, enabling real-time monitoring and visualization of circuit breaker metrics.

```go
hystrixStreamHandler := hystrix.NewStreamHandler()
hystrixStreamHandler.Start()
go http.ListenAndServe(net.JoinHostPort("", "81"), hystrixStreamHandler)
```

--------------------------------

### Hystrix Command Configuration Functions

Source: https://github.com/afex/hystrix-go/blob/master/README.md

API documentation for `hystrix.ConfigureCommand` and `hystrix.Configure` functions, used to set specific operational parameters for Hystrix commands, such as timeouts, concurrency limits, and error thresholds.

```APIDOC
hystrix.ConfigureCommand(name string, config CommandConfig)
  - Configures settings for a specific Hystrix command.
  - Parameters:
    - name: (string) The name of the command to configure.
    - config: (hystrix.CommandConfig) A struct containing configuration parameters.
      - Timeout: (int) The maximum time in milliseconds a command is allowed to execute.
      - MaxConcurrentRequests: (int) The maximum number of concurrent requests allowed.
      - ErrorPercentThreshold: (int) The error percentage at which the circuit breaker opens.
      - RequestVolumeRejectionThreshold: (int) The minimum number of requests in a rolling window that will trip the circuit.
      - SleepWindow: (int) The amount of time in milliseconds after a circuit opens that it remains in an open state before attempting to close.
      - VolumeThreshold: (int) The minimum number of requests in a rolling window that will trip the circuit.

hystrix.Configure(configs map[string]CommandConfig)
  - Configures settings for multiple Hystrix commands using a map.
  - Parameters:
    - configs: (map[string]hystrix.CommandConfig) A map where keys are command names and values are CommandConfig structs.
```

--------------------------------

### Synchronous Hystrix Command Execution with Hystrix.Do

Source: https://github.com/afex/hystrix-go/blob/master/README.md

Explains the use of `hystrix.Do` for synchronous execution of a Hystrix command. This function simplifies the common pattern of immediately waiting for a command to complete and returns a single error.

```go
err := hystrix.Do("my_command", func() error {
	// talk to other services
	return nil
}, nil)
```

--------------------------------

### Hystrix Command Execution Functions (Go, Do)

Source: https://github.com/afex/hystrix-go/blob/master/README.md

API documentation for `hystrix.Go` and `hystrix.Do` functions, which are used to execute application logic within a Hystrix circuit breaker. `hystrix.Go` provides asynchronous execution with channel-based output, while `hystrix.Do` offers a synchronous, blocking alternative.

```APIDOC
hystrix.Go(name string, run func() error, fallback func(error) error) chan error
  - Executes a function as a Hystrix command asynchronously.
  - Parameters:
    - name: (string) The name of the command.
    - run: (func() error) The primary function to execute.
    - fallback: (func(error) error) Optional fallback function to execute on failure.
  - Returns: (chan error) A channel to receive errors from the command.

hystrix.Do(name string, run func() error, fallback func(error) error) error
  - Executes a function as a Hystrix command synchronously.
  - Parameters:
    - name: (string) The name of the command.
    - run: (func() error) The primary function to execute.
    - fallback: (func(error) error) Optional fallback function to execute on failure.
  - Returns: (error) An error if the command fails, nil otherwise.
```

--------------------------------

### Handling Hystrix.Go Command Output and Errors

Source: https://github.com/afex/hystrix-go/blob/master/README.md

Demonstrates how to use Go channels to asynchronously receive results or errors from a `hystrix.Go` command. This pattern enables non-blocking execution and robust error handling for command outcomes.

```go
output := make(chan bool, 1)
errors := hystrix.Go("my_command", func() error {
	// talk to other services
	output <- true
	return nil
}, nil)

select {
case out := <-output:
	// success
case err := <-errors:
	// failure
}
```

--------------------------------

### Perform Load Test with Apache Bench

Source: https://github.com/afex/hystrix-go/blob/master/loadtest/README.md

This command initiates a load test against the running service using Apache Bench. It sends 10,000,000 requests with a concurrency of 10 to the specified local endpoint. This helps in evaluating the application's performance and circuit breaker resilience under heavy load.

```Shell
ab -n 10000000 -c 10 http://localhost:8888/
```

--------------------------------

### Defining Fallback Behavior with Hystrix.Go

Source: https://github.com/afex/hystrix-go/blob/master/README.md

Shows how to provide a fallback function to `hystrix.Go`. This function executes when the primary command fails or is unable to complete, allowing the application to gracefully handle external service unavailability.

```go
hystrix.Go("my_command", func() error {
	// talk to other services
	return nil
}, func(err error) error {
	// do this when services are down
	return nil
})
```

--------------------------------

### Sending Hystrix Metrics to Statsd

Source: https://github.com/afex/hystrix-go/blob/master/README.md

Illustrates how to configure and register a Statsd collector plugin to send Hystrix circuit breaker metrics to a Statsd server. This enables external aggregation and analysis of performance and health data.

```go
c, err := plugins.InitializeStatsdCollector(&plugins.StatsdCollectorConfig{
	StatsdAddr: "localhost:8125",
	Prefix:     "myapp.hystrix",
})
if err != nil {
	log.Fatalf("could not initialize statsd client: %v", err)
}

metricCollector.Registry.Register(c.NewStatsdCollector)
```

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