package once

import (
	"context"
	"sync"
	"sync/atomic"
)

// Inspired from Golang sync.Once but it is only marked
// initialized when the provided function returns nil.

// Init represents the structure.
type Init struct {
	done uint32
	m    sync.Mutex
}

// Do is similar to sync.Once.Do - makes one successful
// call to the function. ie, it invokes the function

- Once object lock configuration is set to a bucket
  - New objects inherit the retention settings of the bucket object lock configuration automatically
  - Retention headers can be optionally set while uploading objects
  - Once objects are uploaded PutObjectRetention API can be called to change retention settings

	"path/filepath"
	"strings"
	"syscall"
	"time"

	"github.com/minio/minio/internal/event"
	xhttp "github.com/minio/minio/internal/http"
	"github.com/minio/minio/internal/logger"
	"github.com/minio/minio/internal/once"
	"github.com/minio/minio/internal/store"
	"github.com/minio/pkg/v2/certs"
	xnet "github.com/minio/pkg/v2/net"
)

// Webhook constants
const (
	WebhookEndpoint   = "endpoint"
	WebhookAuthToken  = "auth_token"

Once the **patch** is successfully applied, developer must run tests to validate the fix that was backported by running following tests, locally.

Unit tests

```
λ make test
```

	CreateKey(ctx context.Context, keyID string) error

	// DeleteKey deletes a key at the KMS with the given key ID.
	// Please note that is a dangerous operation.
	// Once a key has been deleted all data that has been encrypted with it cannot be decrypted
	// anymore, and therefore, is lost.
	DeleteKey(ctx context.Context, keyID string) error

	// ListKeys lists all key names.

```

#### 3.2 Public Prometheus config

If Prometheus endpoint authentication type is set to `public`. Following prometheus config is sufficient to start scraping metrics data from MinIO.
This can be collected from any server once per collection.

##### Cluster

```yaml
scrape_configs:
- job_name: minio-job
  metrics_path: /minio/v2/metrics/cluster
  scheme: http
  static_configs:
  - targets: ['localhost:9000']
```

Context timeouts are propagated, and a default timeout of 1 minute is added if none is specified.

There is no cancellation propagation for single payload requests.
When the context is canceled, the request will return at once with an appropriate error. 
However, the remote call will not see the cancellation - as can be seen from the 'missing' context on the handler.
The result will be discarded.

### Typed handlers

	// If an error is returned the cached value is not set.
	// Only one caller will call this function at any time, others will be blocking.
	// The returned value can no longer be modified once returned.
	// Should be set before calling Get().
	updateFn func() (T, error)

	// ttl for a cached value.
	ttl time.Duration

	opts Opts

	// Once can be used to initialize values for lazy initialization.

	"sync"
)

// PipeWriter is similar to io.PipeWriter with wait group
type PipeWriter struct {
	*io.PipeWriter
	once sync.Once
	done func()
}

// CloseWithError close with supplied error the writer end.
func (w *PipeWriter) CloseWithError(err error) error {
	err = w.PipeWriter.CloseWithError(err)
	w.once.Do(func() {
		w.done()
	})
	return err
}

// PipeReader is similar to io.PipeReader with wait group

## Implementation

ILM tiering takes place when a object placed in the bucket meets lifecycle transition rules and becomes eligible for tiering. MinIO scanner (which runs at one minute intervals, each time scanning one sixteenth of the namespace), picks up the object for tiering. The data is moved to the remote tier in entirety, leaving only the object metadata on MinIO.