events: autogenerate fieldpath filters

To ensure consistent fieldpath matching for events, we generate the
fieldpath matching using protobuf definitions. This is done through a
plugin called "fieldpath" that defines a `Field` method for each type
with the plugin enabled. Generated code handles top-level envelope
fields, as well as deferred serialization for matching any types.

In practice, this means that we can cheaply match events on `topic` and
`namespace`. If we want to match on attributes within the event, we can
use the `event` prefix to address these fields. For example, the
following will match all envelopes that have a field named
`container_id` that has the value `testing`:

```
ctr events "event.container_id==testing"
```

The above will decode the underlying event and check that particular
field. Accordingly, if only `topic` or `namespace` is used, the event
will not be decoded and only match on the envelope.

Signed-off-by: Stephen J Day <stephen.day@docker.com>

api/services/events/v1/container.pb.go

@@ -50,6 +50,9 @@ import fmt "fmt"
 import math "math"
 import _ "github.com/gogo/protobuf/gogoproto"
 import google_protobuf1 "github.com/gogo/protobuf/types"
+import _ "github.com/containerd/containerd/protobuf/plugin"
+
+import github_com_containerd_containerd_typeurl "github.com/containerd/containerd/typeurl"
 
 import strings "strings"
 import reflect "reflect"
@@ -114,6 +117,101 @@ func init() {
 	proto.RegisterType((*ContainerUpdate)(nil), "containerd.services.events.v1.ContainerUpdate")
 	proto.RegisterType((*ContainerDelete)(nil), "containerd.services.events.v1.ContainerDelete")
 }
+
+// Field returns the value for the given fieldpath as a string, if defined.
+// If the value is not defined, the second value will be false.
+func (m *ContainerCreate) Field(fieldpath []string) (string, bool) {
+	if len(fieldpath) == 0 {
+		return "", false
+	}
+
+	switch fieldpath[0] {
+	case "id":
+		return string(m.ID), len(m.ID) > 0
+	case "image":
+		return string(m.Image), len(m.Image) > 0
+	case "runtime":
+		// NOTE(stevvooe): This is probably not correct in many cases.
+		// We assume that the target message also implements the Field
+		// method, which isn't likely true in a lot of cases.
+		//
+		// If you have a broken build and have found this comment,
+		// you may be closer to a solution.
+		if m.Runtime == nil {
+			return "", false
+		}
+
+		return m.Runtime.Field(fieldpath[1:])
+	}
+	return "", false
+}
+
+// Field returns the value for the given fieldpath as a string, if defined.
+// If the value is not defined, the second value will be false.
+func (m *ContainerCreate_Runtime) Field(fieldpath []string) (string, bool) {
+	if len(fieldpath) == 0 {
+		return "", false
+	}
+
+	switch fieldpath[0] {
+	case "name":
+		return string(m.Name), len(m.Name) > 0
+	case "options":
+		decoded, err := github_com_containerd_containerd_typeurl.UnmarshalAny(m.Options)
+		if err != nil {
+			return "", false
+		}
+
+		adaptor, ok := decoded.(interface {
+			Field([]string) (string, bool)
+		})
+		if !ok {
+			return "", false
+		}
+		return adaptor.Field(fieldpath[1:])
+	}
+	return "", false
+}
+
+// Field returns the value for the given fieldpath as a string, if defined.
+// If the value is not defined, the second value will be false.
+func (m *ContainerUpdate) Field(fieldpath []string) (string, bool) {
+	if len(fieldpath) == 0 {
+		return "", false
+	}
+
+	switch fieldpath[0] {
+	case "id":
+		return string(m.ID), len(m.ID) > 0
+	case "image":
+		return string(m.Image), len(m.Image) > 0
+	case "labels":
+		// Labels fields have been special-cased by name. If this breaks,
+		// add better special casing to fieldpath plugin.
+		if len(m.Labels) == 0 {
+			return "", false
+		}
+		value, ok := m.Labels[strings.Join(fieldpath[1:], ".")]
+		return value, ok
+	case "rootfs":
+		return string(m.RootFS), len(m.RootFS) > 0
+	}
+	return "", false
+}
+
+// Field returns the value for the given fieldpath as a string, if defined.
+// If the value is not defined, the second value will be false.
+func (m *ContainerDelete) Field(fieldpath []string) (string, bool) {
+	if len(fieldpath) == 0 {
+		return "", false
+	}
+
+	switch fieldpath[0] {
+	case "id":
+		return string(m.ID), len(m.ID) > 0
+	}
+	return "", false
+}
 func (m *ContainerCreate) Marshal() (dAtA []byte, err error) {
 	size := m.Size()
 	dAtA = make([]byte, size)
@@ -1132,31 +1230,32 @@ func init() {
 }
 
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