Add constraint package to let us reject invalid assignments.

pkg/constraint/constraint.go

@@ -0,0 +1,27 @@
+/*
+Copyright 2014 Google Inc. All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package constraint
+
+import (
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/api"
+)
+
+// Allowed returns true if manifests is a collection of manifests
+// which can run without conflict on a single minion.
+func Allowed(manifests []api.ContainerManifest) bool {
+	return !PortsConflict(manifests)
+}

pkg/constraint/constraint_test.go

@@ -0,0 +1,98 @@
+/*
+Copyright 2014 Google Inc. All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package constraint
+
+import (
+	"testing"
+
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/api"
+)
+
+func containerWithHostPorts(ports ...int) api.Container {
+	c := api.Container{}
+	for _, p := range ports {
+		c.Ports = append(c.Ports, api.Port{HostPort: p})
+	}
+	return c
+}
+
+func manifestWithContainers(containers ...api.Container) api.ContainerManifest {
+	m := api.ContainerManifest{}
+	for _, c := range containers {
+		m.Containers = append(m.Containers, c)
+	}
+	return m
+}
+
+func TestAllowed(t *testing.T) {
+	table := []struct {
+		allowed   bool
+		manifests []api.ContainerManifest
+	}{
+		{
+			allowed: true,
+			manifests: []api.ContainerManifest{
+				manifestWithContainers(
+					containerWithHostPorts(1, 2, 3),
+					containerWithHostPorts(4, 5, 6),
+				),
+				manifestWithContainers(
+					containerWithHostPorts(7, 8, 9),
+					containerWithHostPorts(10, 11, 12),
+				),
+			},
+		},
+		{
+			allowed: true,
+			manifests: []api.ContainerManifest{
+				manifestWithContainers(
+					containerWithHostPorts(0, 0),
+					containerWithHostPorts(0, 0),
+				),
+				manifestWithContainers(
+					containerWithHostPorts(0, 0),
+					containerWithHostPorts(0, 0),
+				),
+			},
+		},
+		{
+			allowed: false,
+			manifests: []api.ContainerManifest{
+				manifestWithContainers(
+					containerWithHostPorts(3, 3),
+				),
+			},
+		},
+		{
+			allowed: false,
+			manifests: []api.ContainerManifest{
+				manifestWithContainers(
+					containerWithHostPorts(6),
+				),
+				manifestWithContainers(
+					containerWithHostPorts(6),
+				),
+			},
+		},
+	}
+
+	for _, item := range table {
+		if e, a := item.allowed, Allowed(item.manifests); e != a {
+			t.Errorf("Expected %v, got %v: \n%v\v", e, a, item.manifests)
+		}
+	}
+}

pkg/constraint/doc.go

@@ -0,0 +1,23 @@
+/*
+Copyright 2014 Google Inc. All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+// Package constraint has functions for ensuring that collections of
+// containers are allowed to run together on a single host.
+//
+// TODO: Add resource math. Phrase this code in a way that makes it easy
+// to call from schedulers as well as from the feasiblity check that
+// apiserver performs.
+package constraint

pkg/constraint/ports.go

@@ -0,0 +1,41 @@
+/*
+Copyright 2014 Google Inc. All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package constraint
+
+import (
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/api"
+)
+
+// PortsConflict returns true iff two containers attempt to expose
+// the same host port.
+func PortsConflict(manifests []api.ContainerManifest) bool {
+	hostPorts := map[int]struct{}{}
+	for _, manifest := range manifests {
+		for _, container := range manifest.Containers {
+			for _, port := range container.Ports {
+				if port.HostPort == 0 {
+					continue
+				}
+				if _, exists := hostPorts[port.HostPort]; exists {
+					return true
+				}
+				hostPorts[port.HostPort] = struct{}{}
+			}
+		}
+	}
+	return false
+}