drivers: make internal DisableLogCollection capability public

The `DisableLogCollection` capability was introduced as an experimental
interface for the Docker driver in 0.10.4. The interface has been stable and
allowing third-party task drivers the same capability would be useful for those
drivers that don't need the additional overhead of logmon.

This PR only makes the capability public. It doesn't yet add it to the
configuration options for the other internal drivers.

Fixes: #14636 #15686

.changelog/17196.txt

@@ -0,0 +1,3 @@
+```release-note:improvement
+drivers: Add `DisableLogCollection` to task driver capabilities interface
+```

client/allocrunner/taskrunner/logmon_hook.go

@@ -19,7 +19,6 @@ import (
 	"github.com/hashicorp/nomad/helper/uuid"
 	"github.com/hashicorp/nomad/nomad/structs"
 	bstructs "github.com/hashicorp/nomad/plugins/base/structs"
-	"github.com/hashicorp/nomad/plugins/drivers"
 	pstructs "github.com/hashicorp/nomad/plugins/shared/structs"
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/codes"
@@ -157,16 +156,8 @@ func (h *logmonHook) isLoggingDisabled() bool {
 		return true
 	}
 
-	// internal plugins have access to a capability to disable logging and
-	// metrics via a private interface; this is an "experimental" interface and
-	// currently only the docker driver exposes this to users.
-	ic, ok := h.runner.driver.(drivers.InternalCapabilitiesDriver)
-	if !ok {
-		return false
-	}
-
-	caps := ic.InternalCapabilities()
-	if caps.DisableLogCollection {
+	caps := h.runner.driverCapabilities
+	if caps != nil && caps.DisableLogCollection {
 		h.logger.Debug("log collection is disabled by driver")
 		return true
 	}

drivers/docker/config.go

@@ -793,13 +793,6 @@ func (d *Driver) TaskConfigSchema() (*hclspec.Spec, error) {
 // Capabilities is returned by the Capabilities RPC and indicates what optional
 // features this driver supports.
 func (d *Driver) Capabilities() (*drivers.Capabilities, error) {
+	driverCapabilities.DisableLogCollection = d.config != nil && d.config.DisableLogCollection
 	return driverCapabilities, nil
 }
-
-var _ drivers.InternalCapabilitiesDriver = (*Driver)(nil)
-
-func (d *Driver) InternalCapabilities() drivers.InternalCapabilities {
-	return drivers.InternalCapabilities{
-		DisableLogCollection: d.config != nil && d.config.DisableLogCollection,
-	}
-}

drivers/docker/config_test.go

@@ -9,6 +9,7 @@ import (
 	"github.com/hashicorp/nomad/ci"
 	"github.com/hashicorp/nomad/helper/pluginutils/hclutils"
 	"github.com/hashicorp/nomad/plugins/drivers"
+	"github.com/shoenig/test/must"
 	"github.com/stretchr/testify/require"
 )
 
@@ -621,28 +622,55 @@ func TestConfig_DriverConfig_GC(t *testing.T) {
 	}
 }
 
-func TestConfig_InternalCapabilities(t *testing.T) {
+func TestConfig_Capabilities(t *testing.T) {
 	ci.Parallel(t)
 
 	cases := []struct {
 		name     string
 		config   string
-		expected drivers.InternalCapabilities
+		expected *drivers.Capabilities
 	}{
 		{
-			name:     "pure default",
-			config:   `{}`,
-			expected: drivers.InternalCapabilities{},
+			name:   "pure default",
+			config: `{}`,
+			expected: &drivers.Capabilities{
+				SendSignals:          true,
+				Exec:                 true,
+				FSIsolation:          "image",
+				NetIsolationModes:    []drivers.NetIsolationMode{"host", "group", "task"},
+				MustInitiateNetwork:  true,
+				MountConfigs:         0,
+				RemoteTasks:          false,
+				DisableLogCollection: false,
+			},
 		},
 		{
-			name:     "disabled",
-			config:   `{ disable_log_collection = true }`,
-			expected: drivers.InternalCapabilities{DisableLogCollection: true},
+			name:   "disabled",
+			config: `{ disable_log_collection = true }`,
+			expected: &drivers.Capabilities{
+				SendSignals:          true,
+				Exec:                 true,
+				FSIsolation:          "image",
+				NetIsolationModes:    []drivers.NetIsolationMode{"host", "group", "task"},
+				MustInitiateNetwork:  true,
+				MountConfigs:         0,
+				RemoteTasks:          false,
+				DisableLogCollection: true,
+			},
 		},
 		{
-			name:     "enabled explicitly",
-			config:   `{ disable_log_collection = false }`,
-			expected: drivers.InternalCapabilities{},
+			name:   "enabled explicitly",
+			config: `{ disable_log_collection = false }`,
+			expected: &drivers.Capabilities{
+				SendSignals:          true,
+				Exec:                 true,
+				FSIsolation:          "image",
+				NetIsolationModes:    []drivers.NetIsolationMode{"host", "group", "task"},
+				MustInitiateNetwork:  true,
+				MountConfigs:         0,
+				RemoteTasks:          false,
+				DisableLogCollection: false,
+			},
 		},
 	}
 
@@ -652,7 +680,9 @@ func TestConfig_InternalCapabilities(t *testing.T) {
 			hclutils.NewConfigParser(configSpec).ParseHCL(t, "config "+c.config, &tc)
 
 			d := &Driver{config: &tc}
-			require.Equal(t, c.expected, d.InternalCapabilities())
+			caps, err := d.Capabilities()
+			must.NoError(t, err)
+			must.Eq(t, c.expected, caps)
 		})
 	}
 }

plugins/drivers/client.go

@@ -77,6 +77,7 @@ func (d *driverPluginClient) Capabilities() (*Capabilities, error) {
 
 		caps.MountConfigs = MountConfigSupport(resp.Capabilities.MountConfigs)
 		caps.RemoteTasks = resp.Capabilities.RemoteTasks
+		caps.DisableLogCollection = resp.Capabilities.DisableLogCollection
 	}
 
 	return caps, nil

plugins/drivers/driver.go

@@ -174,6 +174,10 @@ type Capabilities struct {
 	// adjust behavior such as propogating task handles between allocations
 	// to avoid downtime when a client is lost.
 	RemoteTasks bool
+
+	// DisableLogCollection indicates this driver has disabled log collection
+	// and the client should not start a logmon process.
+	DisableLogCollection bool
 }
 
 func (c *Capabilities) HasNetIsolationMode(m NetIsolationMode) bool {