Correctly detect EPERM on crypto/rand.Random.Read failure

Signed-off-by: Stephen J Day <stephen.day@docker.com>
This commit is contained in:
Stephen J Day 2015-06-16 13:06:58 -07:00
parent 020bd0b45f
commit 7e35d16cb6

View file

@ -9,6 +9,7 @@ import (
"fmt"
"io"
"log"
"os"
"syscall"
"time"
)
@ -61,19 +62,15 @@ func Generate() (u UUID) {
_, err := io.ReadFull(rand.Reader, u[:])
if err != nil {
if err == syscall.EPERM {
// EPERM represents an entropy pool exhaustion, a condition under
// which we backoff and retry.
if retries < maxretries {
retries++
Loggerf("error generating version 4 uuid, retrying: %v", err)
continue
}
if retryOnError(err) && retries < maxretries {
retries++
Loggerf("error generating version 4 uuid, retrying: %v", err)
continue
}
// Any other errors represent a system problem. What did someone
// do to /dev/urandom?
panic(fmt.Errorf("error reading random number generator, retried for %v: %v", totalBackoff, err))
panic(fmt.Errorf("error reading random number generator, retried for %v: %v", totalBackoff.String(), err))
}
break
@ -110,3 +107,19 @@ func Parse(s string) (u UUID, err error) {
func (u UUID) String() string {
return fmt.Sprintf(format, u[:4], u[4:6], u[6:8], u[8:10], u[10:])
}
// retryOnError tries to detect whether or not retrying would be fruitful.
func retryOnError(err error) bool {
switch err := err.(type) {
case *os.PathError:
return retryOnError(err.Err) // unpack the target error
case syscall.Errno:
if err == syscall.EPERM {
// EPERM represents an entropy pool exhaustion, a condition under
// which we backoff and retry.
return true
}
}
return false
}