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package correlation
import (
"crypto/rand"
"io"
"sync"
"time"
"github.com/oklog/ulid/v2"
)
// Replaceable for testing purposes.
var ulidEntropySource io.Reader = &safeMonotonicReader{
delegate: ulid.Monotonic(rand.Reader, 0),
}
func generatePseudorandomCorrelationID() string {
return "E:" + encodeReverseBase62(time.Now().UnixNano())
}
// generateRandomCorrelationID will attempt to generate a correlationid randomly
// if this fails, will log a message and fallback to a pseudorandom approach.
func generateRandomCorrelationIDWithFallback() string {
uid, err := ulid.New(ulid.Timestamp(time.Now()), ulidEntropySource)
if err != nil {
// Swallow the error and return a pseudorandom correlation_id.
// Operators can determine that an error occurred by the shape of the
// correlation_id, which will be prefixed with a `E:`
return generatePseudorandomCorrelationID()
}
return uid.String()
}
// RandomID generates a random correlation ID.
// Deprecated: use SafeRandomID instead.
// Note, that this method will not return an error, it is here for compatibility reasons only.
func RandomID() (string, error) { return generateRandomCorrelationIDWithFallback(), nil }
// SafeRandomID generates a random correlation ID.
func SafeRandomID() string { return generateRandomCorrelationIDWithFallback() }
// safeMonotonicReader is a thread-safe wrapper around a ulid.Monotonic instance, which is not safe for concurrent use by itself.
// See https://godoc.org/github.com/oklog/ulid#Monotonic.
type safeMonotonicReader struct {
mtx sync.Mutex
delegate ulid.MonotonicReader
}
var _ ulid.MonotonicReader = &safeMonotonicReader{}
func (r *safeMonotonicReader) MonotonicRead(ms uint64, p []byte) error {
r.mtx.Lock()
defer r.mtx.Unlock()
return r.delegate.MonotonicRead(ms, p)
}
func (r *safeMonotonicReader) Read(p []byte) (int, error) {
r.mtx.Lock()
defer r.mtx.Unlock()
return r.delegate.Read(p)
}
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