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// Package emf implements an EMF metrics publisher.
//
// This package is designated as private and is intended for use only by the
// smithy client runtime. The exported API therein is not considered stable and
// is subject to breaking changes without notice.
package emf
import (
"github.com/aws/aws-sdk-go-v2/aws/middleware/private/metrics"
"github.com/aws/aws-sdk-go-v2/internal/sdk"
)
const (
emfIdentifier = "_aws"
timestampKey = "Timestamp"
cloudWatchMetricsKey = "CloudWatchMetrics"
namespaceKey = "Namespace"
dimensionsKey = "Dimensions"
metricsKey = "Metrics"
)
// Entry represents a log entry in the EMF format.
type Entry struct {
namespace string
serializer metrics.Serializer
metrics []metric
dimensions [][]string
fields map[string]interface{}
}
type metric struct {
Name string
}
// NewEntry creates a new Entry with the specified namespace and serializer.
func NewEntry(namespace string, serializer metrics.Serializer) Entry {
return Entry{
namespace: namespace,
serializer: serializer,
metrics: []metric{},
dimensions: [][]string{{}},
fields: map[string]interface{}{},
}
}
// Build constructs the EMF log entry as a JSON string.
func (e *Entry) Build() (string, error) {
entry := map[string]interface{}{}
entry[emfIdentifier] = map[string]interface{}{
timestampKey: sdk.NowTime().UnixNano() / 1e6,
cloudWatchMetricsKey: []map[string]interface{}{
{
namespaceKey: e.namespace,
dimensionsKey: e.dimensions,
metricsKey: e.metrics,
},
},
}
for k, v := range e.fields {
entry[k] = v
}
jsonEntry, err := e.serializer.Serialize(entry)
if err != nil {
return "", err
}
return jsonEntry, nil
}
// AddDimension adds a CW Dimension to the EMF entry.
func (e *Entry) AddDimension(key string, value string) {
// Dimensions are a list of lists. We only support a single list.
e.dimensions[0] = append(e.dimensions[0], key)
e.fields[key] = value
}
// AddMetric adds a CW Metric to the EMF entry.
func (e *Entry) AddMetric(key string, value float64) {
e.metrics = append(e.metrics, metric{key})
e.fields[key] = value
}
// AddProperty adds a CW Property to the EMF entry.
// Properties are not published as metrics, but they are available in logs and in CW insights.
func (e *Entry) AddProperty(key string, value interface{}) {
e.fields[key] = value
}
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