Add `--cpus` flag to control cpu resources

This fix tries to address the proposal raised in 27921 and add
`--cpus` flag for `docker run/create`.

Basically, `--cpus` will allow user to specify a number (possibly partial)
about how many CPUs the container will use. For example, on a 2-CPU system
`--cpus 1.5` means the container will take 75% (1.5/2) of the CPU share.

This fix adds a `NanoCPUs` field to `HostConfig` since swarmkit alreay
have a concept of NanoCPUs for tasks. The `--cpus` flag will translate
the number into reused `NanoCPUs` to be consistent.

This fix adds integration tests to cover the changes.

Related docs (`docker run` and Remote APIs) have been updated.

This fix fixes 27921.

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

command/service/opts.go

@@ -2,7 +2,6 @@ package service
 
 import (
 	"fmt"
-	"math/big"
 	"strconv"
 	"strings"
 	"time"
@@ -40,33 +39,6 @@ func (m *memBytes) Value() int64 {
 	return int64(*m)
 }
 
-type nanoCPUs int64
-
-func (c *nanoCPUs) String() string {
-	return big.NewRat(c.Value(), 1e9).FloatString(3)
-}
-
-func (c *nanoCPUs) Set(value string) error {
-	cpu, ok := new(big.Rat).SetString(value)
-	if !ok {
-		return fmt.Errorf("Failed to parse %v as a rational number", value)
-	}
-	nano := cpu.Mul(cpu, big.NewRat(1e9, 1))
-	if !nano.IsInt() {
-		return fmt.Errorf("value is too precise")
-	}
-	*c = nanoCPUs(nano.Num().Int64())
-	return nil
-}
-
-func (c *nanoCPUs) Type() string {
-	return "NanoCPUs"
-}
-
-func (c *nanoCPUs) Value() int64 {
-	return int64(*c)
-}
-
 // PositiveDurationOpt is an option type for time.Duration that uses a pointer.
 // It bahave similarly to DurationOpt but only allows positive duration values.
 type PositiveDurationOpt struct {
@@ -156,9 +128,9 @@ type updateOptions struct {
 }
 
 type resourceOptions struct {
-	limitCPU      nanoCPUs
+	limitCPU      opts.NanoCPUs
 	limitMemBytes memBytes
-	resCPU        nanoCPUs
+	resCPU        opts.NanoCPUs
 	resMemBytes   memBytes
 }
 

command/service/opts_test.go

@@ -6,6 +6,7 @@ import (
 	"time"
 
 	"github.com/docker/docker/api/types/container"
+	"github.com/docker/docker/opts"
 	"github.com/docker/docker/pkg/testutil/assert"
 )
 
@@ -21,12 +22,12 @@ func TestMemBytesSetAndValue(t *testing.T) {
 }
 
 func TestNanoCPUsString(t *testing.T) {
-	var cpus nanoCPUs = 6100000000
+	var cpus opts.NanoCPUs = 6100000000
 	assert.Equal(t, cpus.String(), "6.100")
 }
 
 func TestNanoCPUsSetAndValue(t *testing.T) {
-	var cpus nanoCPUs
+	var cpus opts.NanoCPUs
 	assert.NilError(t, cpus.Set("0.35"))
 	assert.Equal(t, cpus.Value(), int64(350000000))
 }