Adjust disallowed CpuShares in /containers/create

Previous versions of libcontainer allowed CpuShares that were greater
than the maximum or less than the minimum supported by the kernel, and
relied on the kernel to do the right thing. Newer libcontainer fails
after creating the container if the requested CpuShares is different
from what was actually created by the kernel, which breaks compatibility
with earlier Docker Remote API versions. This change explicitly adjusts
the requested CpuShares in API versions < 1.20.

Signed-off-by: Samuel Karp <skarp@amazon.com>

api/server/server.go

@@ -894,6 +894,7 @@ func (s *Server) postContainersCreate(version version.Version, w http.ResponseWr
 	if err != nil {
 		return err
 	}
+	adjustCpuShares(version, hostConfig)
 
 	containerId, warnings, err := s.daemon.ContainerCreate(name, config, hostConfig)
 	if err != nil {

api/server/server_linux.go

@@ -8,12 +8,21 @@ import (
 	"net/http"
 	"strconv"
 
+	"github.com/Sirupsen/logrus"
 	"github.com/docker/docker/daemon"
 	"github.com/docker/docker/pkg/sockets"
 	"github.com/docker/docker/pkg/systemd"
+	"github.com/docker/docker/pkg/version"
+	"github.com/docker/docker/runconfig"
 	"github.com/docker/libnetwork/portallocator"
 )
 
+const (
+	// See http://git.kernel.org/cgit/linux/kernel/git/tip/tip.git/tree/kernel/sched/sched.h?id=8cd9234c64c584432f6992fe944ca9e46ca8ea76#n269
+	linuxMinCpuShares = 2
+	linuxMaxCpuShares = 262144
+)
+
 // newServer sets up the required serverClosers and does protocol specific checking.
 func (s *Server) newServer(proto, addr string) ([]serverCloser, error) {
 	var (
@@ -96,3 +105,18 @@ func allocateDaemonPort(addr string) error {
 	}
 	return nil
 }
+
+func adjustCpuShares(version version.Version, hostConfig *runconfig.HostConfig) {
+	if version.LessThan("1.19") {
+		if hostConfig.CpuShares > 0 {
+			// Handle unsupported CpuShares
+			if hostConfig.CpuShares < linuxMinCpuShares {
+				logrus.Warnf("Changing requested CpuShares of %d to minimum allowed of %d", hostConfig.CpuShares, linuxMinCpuShares)
+				hostConfig.CpuShares = linuxMinCpuShares
+			} else if hostConfig.CpuShares > linuxMaxCpuShares {
+				logrus.Warnf("Changing requested CpuShares of %d to maximum allowed of %d", hostConfig.CpuShares, linuxMaxCpuShares)
+				hostConfig.CpuShares = linuxMaxCpuShares
+			}
+		}
+	}
+}

api/server/server_linux_test.go

@@ -0,0 +1,68 @@
+// +build linux
+
+package server
+
+import (
+	"testing"
+
+	"github.com/docker/docker/pkg/version"
+	"github.com/docker/docker/runconfig"
+)
+
+func TestAdjustCpuSharesOldApi(t *testing.T) {
+	apiVersion := version.Version("1.18")
+	hostConfig := &runconfig.HostConfig{
+		CpuShares: linuxMinCpuShares - 1,
+	}
+	adjustCpuShares(apiVersion, hostConfig)
+	if hostConfig.CpuShares != linuxMinCpuShares {
+		t.Errorf("Expected CpuShares to be %d", linuxMinCpuShares)
+	}
+
+	hostConfig.CpuShares = linuxMaxCpuShares + 1
+	adjustCpuShares(apiVersion, hostConfig)
+	if hostConfig.CpuShares != linuxMaxCpuShares {
+		t.Errorf("Expected CpuShares to be %d", linuxMaxCpuShares)
+	}
+
+	hostConfig.CpuShares = 0
+	adjustCpuShares(apiVersion, hostConfig)
+	if hostConfig.CpuShares != 0 {
+		t.Error("Expected CpuShares to be unchanged")
+	}
+
+	hostConfig.CpuShares = 1024
+	adjustCpuShares(apiVersion, hostConfig)
+	if hostConfig.CpuShares != 1024 {
+		t.Error("Expected CpuShares to be unchanged")
+	}
+}
+
+func TestAdjustCpuSharesNoAdjustment(t *testing.T) {
+	apiVersion := version.Version("1.19")
+	hostConfig := &runconfig.HostConfig{
+		CpuShares: linuxMinCpuShares - 1,
+	}
+	adjustCpuShares(apiVersion, hostConfig)
+	if hostConfig.CpuShares != linuxMinCpuShares-1 {
+		t.Errorf("Expected CpuShares to be %d", linuxMinCpuShares-1)
+	}
+
+	hostConfig.CpuShares = linuxMaxCpuShares + 1
+	adjustCpuShares(apiVersion, hostConfig)
+	if hostConfig.CpuShares != linuxMaxCpuShares+1 {
+		t.Errorf("Expected CpuShares to be %d", linuxMaxCpuShares+1)
+	}
+
+	hostConfig.CpuShares = 0
+	adjustCpuShares(apiVersion, hostConfig)
+	if hostConfig.CpuShares != 0 {
+		t.Error("Expected CpuShares to be unchanged")
+	}
+
+	hostConfig.CpuShares = 1024
+	adjustCpuShares(apiVersion, hostConfig)
+	if hostConfig.CpuShares != 1024 {
+		t.Error("Expected CpuShares to be unchanged")
+	}
+}

api/server/server_windows.go

@@ -54,3 +54,6 @@ func (s *Server) AcceptConnections(d *daemon.Daemon) {
 func allocateDaemonPort(addr string) error {
 	return nil
 }
+
+func adjustCpuShares(version version.Version, hostConfig *runconfig.HostConfig) {
+}