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corherecorhere
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daemon: reload runtimes w/o breaking containers
The existing runtimes reload logic went to great lengths to replace the directory containing runtime wrapper scripts as atomically as possible within the limitations of the Linux filesystem ABI. Trouble is, atomically swapping the wrapper scripts directory solves the wrong problem! The runtime configuration is "locked in" when a container is started, including the path to the runC binary. If a container is started with a runtime which requires a daemon-managed wrapper script and then the daemon is reloaded with a config which no longer requires the wrapper script (i.e. some args -> no args, or the runtime is dropped from the config), that container would become unmanageable. Any attempts to stop, exec or otherwise perform lifecycle management operations on the container are likely to fail due to the wrapper script no longer existing at its original path. Atomically swapping the wrapper scripts is also incompatible with the read-copy-update paradigm for reloading configuration. A handler in the daemon could retain a reference to the pre-reload configuration for an indeterminate amount of time after the daemon configuration has been reloaded and updated. It is possible for the daemon to attempt to start a container using a deleted wrapper script if a request to run a container races a reload. Solve the problem of deleting referenced wrapper scripts by ensuring that all wrapper scripts are *immutable* for the lifetime of the daemon process. Any given runtime wrapper script must always exist with the same contents, no matter how many times the daemon config is reloaded, or what changes are made to the config. This is accomplished by using everyone's favourite design pattern: content-addressable storage. Each wrapper script file name is suffixed with the SHA-256 digest of its contents to (probabilistically) guarantee immutability without needing any concurrency control. Stale runtime wrapper scripts are only cleaned up on the next daemon restart. Split the derived runtimes configuration from the user-supplied configuration to have a place to store derived state without mutating the user-supplied configuration or exposing daemon internals in API struct types. Hold the derived state and the user-supplied configuration in a single struct value so that they can be updated as an atomic unit. Signed-off-by: Cory Snider <[email protected]>
1 parent 0b59246 commit d222bf0

40 files changed

Lines changed: 505 additions & 382 deletions

‎api/types/types.go‎

Lines changed: 0 additions & 11 deletions
Original file line numberDiff line numberDiff line change
@@ -16,7 +16,6 @@ import (
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"github.com/docker/docker/api/types/swarm"
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"github.com/docker/docker/api/types/volume"
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"github.com/docker/go-connections/nat"
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"github.com/opencontainers/runtime-spec/specs-go/features"
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)
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const (
@@ -657,16 +656,6 @@ type Runtime struct {
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658657
Type string `json:"runtimeType,omitempty"`
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Options map[string]interface{} `json:"options,omitempty"`
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// This is exposed here only for internal use
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ShimConfig *ShimConfig `json:"-"`
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Features *features.Features `json:"-"`
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}
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// ShimConfig is used by runtime to configure containerd shims
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type ShimConfig struct {
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Binary string
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Opts interface{}
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}
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672661
// DiskUsageObject represents an object type used for disk usage query filtering.

‎cmd/dockerd/daemon.go‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -268,7 +268,7 @@ func (cli *DaemonCli) start(opts *daemonOptions) (err error) {
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// Restart all autostart containers which has a swarm endpoint
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// and is not yet running now that we have successfully
270270
// initialized the cluster.
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d.RestartSwarmContainers(cli.Config)
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d.RestartSwarmContainers()
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logrus.Info("Daemon has completed initialization")
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‎daemon/config/config_linux.go‎

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Original file line numberDiff line numberDiff line change
@@ -81,15 +81,6 @@ type Config struct {
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Rootless bool `json:"rootless,omitempty"`
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}
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// GetRuntime returns the runtime path and arguments for a given
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// runtime name
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func (conf *Config) GetRuntime(name string) *types.Runtime {
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if rt, ok := conf.Runtimes[name]; ok {
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return &rt
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}
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return nil
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}
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9384
// GetAllRuntimes returns a copy of the runtimes map
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func (conf *Config) GetAllRuntimes() map[string]types.Runtime {
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return conf.Runtimes

‎daemon/config/config_windows.go‎

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Original file line numberDiff line numberDiff line change
@@ -30,12 +30,6 @@ type Config struct {
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// for the Windows daemon.)
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}
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// GetRuntime returns the runtime path and arguments for a given
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// runtime name
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func (conf *Config) GetRuntime(name string) *types.Runtime {
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return nil
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}
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// GetAllRuntimes returns a copy of the runtimes map
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func (conf *Config) GetAllRuntimes() map[string]types.Runtime {
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return map[string]types.Runtime{}

‎daemon/container.go‎

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Original file line numberDiff line numberDiff line change
@@ -235,7 +235,7 @@ func (daemon *Daemon) setHostConfig(container *container.Container, hostConfig *
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// verifyContainerSettings performs validation of the hostconfig and config
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// structures.
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func (daemon *Daemon) verifyContainerSettings(daemonCfg *config.Config, hostConfig *containertypes.HostConfig, config *containertypes.Config, update bool) (warnings []string, err error) {
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func (daemon *Daemon) verifyContainerSettings(daemonCfg *configStore, hostConfig *containertypes.HostConfig, config *containertypes.Config, update bool) (warnings []string, err error) {
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// First perform verification of settings common across all platforms.
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if err = validateContainerConfig(config); err != nil {
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return warnings, err

‎daemon/container_operations.go‎

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Original file line numberDiff line numberDiff line change
@@ -1075,7 +1075,7 @@ func (daemon *Daemon) ConnectToNetwork(container *container.Container, idOrName
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}
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}
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} else {
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if err := daemon.connectToNetwork(daemon.config(), container, idOrName, endpointConfig, true); err != nil {
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if err := daemon.connectToNetwork(&daemon.config().Config, container, idOrName, endpointConfig, true); err != nil {
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return err
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}
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}

‎daemon/container_unix_test.go‎

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Original file line numberDiff line numberDiff line change
@@ -31,11 +31,14 @@ func TestContainerWarningHostAndPublishPorts(t *testing.T) {
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NetworkMode: "host",
3232
PortBindings: tc.ports,
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}
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cs := &config.Config{}
35-
configureRuntimes(cs)
3634
d := &Daemon{}
37-
d.configStore.Store(cs)
38-
wrns, err := d.verifyContainerSettings(cs, hostConfig, &containertypes.Config{}, false)
35+
cfg, err := config.New()
36+
assert.NilError(t, err)
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configureRuntimes(cfg)
38+
runtimes, err := setupRuntimes(cfg)
39+
assert.NilError(t, err)
40+
daemonCfg := &configStore{Config: *cfg, Runtimes: runtimes}
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wrns, err := d.verifyContainerSettings(daemonCfg, hostConfig, &containertypes.Config{}, false)
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assert.NilError(t, err)
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assert.DeepEqual(t, tc.warnings, wrns)
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}

‎daemon/create.go‎

Lines changed: 3 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -57,7 +57,7 @@ func (daemon *Daemon) ContainerCreateIgnoreImagesArgsEscaped(ctx context.Context
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})
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}
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60-
func (daemon *Daemon) containerCreate(ctx context.Context, daemonCfg *config.Config, opts createOpts) (containertypes.CreateResponse, error) {
60+
func (daemon *Daemon) containerCreate(ctx context.Context, daemonCfg *configStore, opts createOpts) (containertypes.CreateResponse, error) {
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start := time.Now()
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if opts.params.Config == nil {
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return containertypes.CreateResponse{}, errdefs.InvalidParameter(errors.New("Config cannot be empty in order to create a container"))
@@ -95,12 +95,12 @@ func (daemon *Daemon) containerCreate(ctx context.Context, daemonCfg *config.Con
9595
if opts.params.HostConfig == nil {
9696
opts.params.HostConfig = &containertypes.HostConfig{}
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}
98-
err = daemon.adaptContainerSettings(daemonCfg, opts.params.HostConfig, opts.params.AdjustCPUShares)
98+
err = daemon.adaptContainerSettings(&daemonCfg.Config, opts.params.HostConfig, opts.params.AdjustCPUShares)
9999
if err != nil {
100100
return containertypes.CreateResponse{Warnings: warnings}, errdefs.InvalidParameter(err)
101101
}
102102

103-
ctr, err := daemon.create(ctx, daemonCfg, opts)
103+
ctr, err := daemon.create(ctx, &daemonCfg.Config, opts)
104104
if err != nil {
105105
return containertypes.CreateResponse{Warnings: warnings}, err
106106
}

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