Files
tiny-forge/internal/deployer/deployer.go
T
alexei.dolgolyov be6ad15efc fix: comprehensive security, performance, and quality hardening
Security: apply AdminOnly middleware to mutating routes, require
ENCRYPTION_KEY and ADMIN_PASSWORD (no insecure defaults), restrict
CORS to same-origin, fix OIDC token delivery via cookie instead of
URL query param, add rate limiting on login, add MaxBytesReader,
validate volume paths against traversal, add security headers,
validate user roles, add Secure flag to OIDC cookie.

Performance: set SQLite MaxOpenConns(1) to prevent SQLITE_BUSY,
add FK indexes on 8 columns, track notifier goroutines with
WaitGroup for graceful shutdown, use GetRegistryByName instead of
GetAllRegistries in deployer, pass basePath param to avoid redundant
settings query, return empty slices from store to remove reflection.

Quality: refactor TriggerDeploy to delegate to runDeploy (~100 lines
removed), consolidate duplicated utilities (extractPort, boolToInt,
now, isTerminalStatus) into shared exports, migrate all log.Printf
to slog structured logging, use consistent webhook response envelope,
remove dead code (parseEnvVars, duplicate auth types).

UX: clean up NPM proxy on instance removal via API, add README with
quickstart guide, add .env.example, require ADMIN_PASSWORD in
docker-compose, document staging-net prerequisite.
2026-03-29 12:49:24 +03:00

692 lines
22 KiB
Go

package deployer
import (
"context"
"encoding/json"
"fmt"
"log/slog"
"path/filepath"
"sort"
"sync"
"sync/atomic"
"github.com/alexei/docker-watcher/internal/crypto"
"github.com/alexei/docker-watcher/internal/docker"
"github.com/alexei/docker-watcher/internal/events"
"github.com/alexei/docker-watcher/internal/health"
"github.com/alexei/docker-watcher/internal/notify"
"github.com/alexei/docker-watcher/internal/npm"
"github.com/alexei/docker-watcher/internal/store"
"github.com/moby/moby/api/types/mount"
"github.com/google/uuid"
)
// Deployer orchestrates the full deployment flow: pull image, create container,
// start, configure proxy, health check, and handle rollback on failure.
// It implements both webhook.DeployTriggerer and registry.DeployTriggerer.
type Deployer struct {
docker *docker.Client
npm *npm.Client
store *store.Store
health *health.Checker
notifier *notify.Notifier
eventBus EventPublisher
encKey [32]byte
// Graceful shutdown: tracks in-progress deploys.
activeWg sync.WaitGroup
shuttingDown atomic.Bool
}
// EventPublisher is the interface for publishing events to the event bus.
type EventPublisher interface {
Publish(evt events.Event)
}
// New creates a new Deployer with all required dependencies.
func New(
dockerClient *docker.Client,
npmClient *npm.Client,
st *store.Store,
checker *health.Checker,
notifier *notify.Notifier,
eventBus EventPublisher,
encKey [32]byte,
) *Deployer {
return &Deployer{
docker: dockerClient,
npm: npmClient,
store: st,
health: checker,
notifier: notifier,
eventBus: eventBus,
encKey: encKey,
}
}
// Drain waits for all in-progress deploys to complete. Call this during graceful shutdown.
func (d *Deployer) Drain() {
d.shuttingDown.Store(true)
slog.Info("deployer: draining in-progress deploys")
d.activeWg.Wait()
slog.Info("deployer: all deploys drained")
}
// AsyncTriggerDeploy creates a deploy record and returns the deploy ID immediately,
// then runs the full deploy pipeline in a background goroutine. Use this from HTTP handlers
// to avoid blocking the request. Progress is streamed via SSE.
func (d *Deployer) AsyncTriggerDeploy(ctx context.Context, projectID, stageID, imageTag string) (string, error) {
if d.shuttingDown.Load() {
return "", fmt.Errorf("deployer is shutting down, rejecting new deploy")
}
// Validate inputs synchronously so the caller gets immediate feedback.
project, err := d.store.GetProjectByID(projectID)
if err != nil {
return "", fmt.Errorf("get project: %w", err)
}
stage, err := d.store.GetStageByID(stageID)
if err != nil {
return "", fmt.Errorf("get stage: %w", err)
}
if err := d.validatePromoteFrom(stage, imageTag); err != nil {
return "", fmt.Errorf("promote validation: %w", err)
}
// Create deploy record synchronously so caller gets the ID.
deploy, err := d.store.CreateDeploy(store.Deploy{
ProjectID: projectID,
StageID: stageID,
ImageTag: imageTag,
Status: "pending",
})
if err != nil {
return "", fmt.Errorf("create deploy record: %w", err)
}
// Run the actual deploy in the background.
d.activeWg.Add(1)
go func() {
defer d.activeWg.Done()
// Use a detached context so client disconnect doesn't abort the deploy.
bgCtx := context.Background()
if err := d.runDeploy(bgCtx, project, stage, deploy.ID, imageTag); err != nil {
slog.Error("async deploy failed", "deploy_id", deploy.ID, "error", err)
}
}()
return deploy.ID, nil
}
// runDeploy is the internal deploy pipeline used by AsyncTriggerDeploy.
// It assumes the deploy record already exists and project/stage are validated.
func (d *Deployer) runDeploy(ctx context.Context, project store.Project, stage store.Stage, deployID string, imageTag string) error {
settings, err := d.store.GetSettings()
if err != nil {
if updateErr := d.store.UpdateDeployStatus(deployID, "failed", err.Error()); updateErr != nil {
slog.Warn("update deploy status", "error", updateErr)
}
return fmt.Errorf("get settings: %w", err)
}
slog.Info("starting deploy",
"deploy_id", deployID,
"project", project.Name,
"stage", stage.Name,
"tag", imageTag,
)
d.logDeploy(deployID, fmt.Sprintf("Starting deploy of %s:%s for project %s, stage %s", project.Image, imageTag, project.Name, stage.Name), "info")
// Enforce max_instances before deploying.
if err := d.enforceMaxInstances(ctx, stage, deployID, settings); err != nil {
d.logDeploy(deployID, fmt.Sprintf("Failed to enforce max instances: %v", err), "error")
}
var containerID string
var npmProxyID int
var instanceID string
var deployErr error
if stage.MaxInstances == 1 {
containerID, npmProxyID, instanceID, deployErr = d.blueGreenDeploy(ctx, project, stage, settings, deployID, imageTag)
} else {
containerID, npmProxyID, instanceID, deployErr = d.executeDeploy(ctx, project, stage, settings, deployID, imageTag)
}
if deployErr != nil {
d.logDeploy(deployID, fmt.Sprintf("Deploy failed: %v", deployErr), "error")
d.publishDeployStatus(deployID, project.ID, stage.ID, imageTag, "failed", deployErr.Error())
d.rollback(ctx, deployID, containerID, npmProxyID, instanceID)
d.notifier.Send(settings.NotificationURL, notify.Event{
Type: "deploy_failure",
Project: project.Name,
Stage: stage.Name,
ImageTag: imageTag,
Error: deployErr.Error(),
})
return fmt.Errorf("deploy failed: %w", deployErr)
}
if err := d.store.UpdateDeployStatus(deployID, "success", ""); err != nil {
slog.Warn("update deploy status to success", "error", err)
}
d.publishDeployStatus(deployID, project.ID, stage.ID, imageTag, "success", "")
subdomain := d.buildSubdomain(project, stage, settings, imageTag)
fullURL := fmt.Sprintf("https://%s.%s", subdomain, settings.Domain)
d.logDeploy(deployID, fmt.Sprintf("Deploy successful: %s", fullURL), "info")
d.notifier.Send(settings.NotificationURL, notify.Event{
Type: "deploy_success",
Project: project.Name,
Stage: stage.Name,
ImageTag: imageTag,
Subdomain: subdomain,
URL: fullURL,
})
return nil
}
// TriggerDeploy is the synchronous entry point for deployments (used by poller and webhook).
// It validates inputs, creates a deploy record, and delegates to runDeploy.
func (d *Deployer) TriggerDeploy(ctx context.Context, projectID, stageID, imageTag string) error {
if d.shuttingDown.Load() {
return fmt.Errorf("deployer is shutting down, rejecting new deploy")
}
d.activeWg.Add(1)
defer d.activeWg.Done()
project, err := d.store.GetProjectByID(projectID)
if err != nil {
return fmt.Errorf("get project: %w", err)
}
stage, err := d.store.GetStageByID(stageID)
if err != nil {
return fmt.Errorf("get stage: %w", err)
}
if err := d.validatePromoteFrom(stage, imageTag); err != nil {
return fmt.Errorf("promote validation: %w", err)
}
deploy, err := d.store.CreateDeploy(store.Deploy{
ProjectID: projectID,
StageID: stageID,
ImageTag: imageTag,
Status: "pending",
})
if err != nil {
return fmt.Errorf("create deploy record: %w", err)
}
if err := d.runDeploy(ctx, project, stage, deploy.ID, imageTag); err != nil {
return err
}
return nil
}
// executeDeploy runs the deploy pipeline steps and returns rollback-relevant state.
// It returns (containerID, npmProxyID, instanceID, error).
func (d *Deployer) executeDeploy(
ctx context.Context,
project store.Project,
stage store.Stage,
settings store.Settings,
deployID string,
imageTag string,
) (string, int, string, error) {
var containerID string
var npmProxyID int
var instanceID string
// Step 1: Pull image.
if err := d.store.UpdateDeployStatus(deployID, "pulling", ""); err != nil {
slog.Warn("update deploy status", "error", err)
}
d.publishDeployStatus(deployID, project.ID, stage.ID, imageTag, "pulling", "")
d.logDeploy(deployID, fmt.Sprintf("Pulling image %s:%s", project.Image, imageTag), "info")
authConfig, err := d.buildRegistryAuth(project)
if err != nil {
return containerID, npmProxyID, instanceID, fmt.Errorf("build registry auth: %w", err)
}
if err := d.docker.PullImage(ctx, project.Image, imageTag, authConfig); err != nil {
return containerID, npmProxyID, instanceID, fmt.Errorf("pull image: %w", err)
}
d.logDeploy(deployID, "Image pulled successfully", "info")
// Step 2: Ensure network exists.
networkID, err := d.docker.EnsureNetwork(ctx, settings.Network)
if err != nil {
return containerID, npmProxyID, instanceID, fmt.Errorf("ensure network: %w", err)
}
d.logDeploy(deployID, fmt.Sprintf("Network %s ready (ID: %s)", settings.Network, truncateID(networkID)), "info")
// Step 3: Create and start container.
if err := d.store.UpdateDeployStatus(deployID, "starting", ""); err != nil {
slog.Warn("update deploy status", "error", err)
}
d.publishDeployStatus(deployID, project.ID, stage.ID, imageTag, "starting", "")
// Pre-generate instance ID so it can be set as a container label.
instanceID = uuid.New().String()
subdomain := d.buildSubdomain(project, stage, settings, imageTag)
containerName := docker.ContainerName(project.Name, stage.Name, imageTag)
portStr := fmt.Sprintf("%d/tcp", project.Port)
envVars := d.mergeEnvVars(project, stage.ID)
mounts := d.computeVolumeMounts(project.ID, stage.Name, imageTag, settings.BaseVolumePath)
containerCfg := docker.ContainerConfig{
Name: containerName,
Image: project.Image + ":" + imageTag,
Env: envVars,
ExposedPorts: []string{portStr},
NetworkName: settings.Network,
NetworkID: networkID,
Project: project.Name,
Stage: stage.Name,
InstanceID: instanceID,
Mounts: mounts,
}
d.logDeploy(deployID, fmt.Sprintf("Creating container %s", containerName), "info")
containerID, err = d.docker.CreateContainer(ctx, containerCfg)
if err != nil {
return containerID, npmProxyID, instanceID, fmt.Errorf("create container: %w", err)
}
d.logDeploy(deployID, fmt.Sprintf("Container created (ID: %s)", truncateID(containerID)), "info")
// Create instance record in store with the pre-generated ID.
inst, err := d.store.CreateInstanceWithID(store.Instance{
ID: instanceID,
StageID: stage.ID,
ProjectID: project.ID,
ContainerID: containerID,
ImageTag: imageTag,
Subdomain: subdomain,
Status: "stopped",
Port: project.Port,
})
if err != nil {
return containerID, npmProxyID, instanceID, fmt.Errorf("create instance record: %w", err)
}
instanceID = inst.ID
// Link deploy to instance.
if err := d.store.SetDeployInstanceID(deployID, instanceID); err != nil {
slog.Warn("link deploy to instance", "error", err)
}
d.logDeploy(deployID, fmt.Sprintf("Starting container %s", containerName), "info")
if err := d.docker.StartContainer(ctx, containerID); err != nil {
return containerID, npmProxyID, instanceID, fmt.Errorf("start container: %w", err)
}
if err := d.store.UpdateInstanceStatus(instanceID, "running"); err != nil {
slog.Warn("update instance status to running", "error", err)
}
d.publishInstanceStatus(instanceID, project.ID, stage.ID, "running")
d.logDeploy(deployID, "Container started", "info")
// Step 4: Configure NPM proxy.
if err := d.store.UpdateDeployStatus(deployID, "configuring_proxy", ""); err != nil {
slog.Warn("update deploy status", "error", err)
}
d.publishDeployStatus(deployID, project.ID, stage.ID, imageTag, "configuring_proxy", "")
npmProxyID, err = d.configureProxy(ctx, deployID, settings, containerName, project.Port, subdomain)
if err != nil {
return containerID, npmProxyID, instanceID, fmt.Errorf("configure proxy: %w", err)
}
// Update instance with NPM proxy ID.
inst.NpmProxyID = npmProxyID
inst.Subdomain = subdomain
if err := d.store.UpdateInstance(inst); err != nil {
slog.Warn("update instance with proxy ID", "error", err)
}
// Step 5: Health check.
if project.Healthcheck != "" {
if err := d.store.UpdateDeployStatus(deployID, "health_checking", ""); err != nil {
slog.Warn("update deploy status", "error", err)
}
d.publishDeployStatus(deployID, project.ID, stage.ID, imageTag, "health_checking", "")
healthURL := fmt.Sprintf("http://%s:%d%s", containerName, project.Port, project.Healthcheck)
d.logDeploy(deployID, fmt.Sprintf("Running health check: %s", healthURL), "info")
if err := d.health.Check(ctx, healthURL); err != nil {
return containerID, npmProxyID, instanceID, fmt.Errorf("health check: %w", err)
}
d.logDeploy(deployID, "Health check passed", "info")
} else {
d.logDeploy(deployID, "No health check configured, skipping", "info")
}
return containerID, npmProxyID, instanceID, nil
}
// configureProxy creates or updates an NPM proxy host for the deployed container.
// It authenticates to NPM using credentials from settings, then creates the proxy.
// Returns the NPM proxy host ID.
func (d *Deployer) configureProxy(
ctx context.Context,
deployID string,
settings store.Settings,
containerName string,
containerPort int,
subdomain string,
) (int, error) {
// Authenticate to NPM.
npmPassword, err := d.decryptNpmPassword(settings.NpmPassword)
if err != nil {
return 0, fmt.Errorf("decrypt npm password: %w", err)
}
if err := d.npm.Authenticate(ctx, settings.NpmEmail, npmPassword); err != nil {
return 0, fmt.Errorf("authenticate to npm: %w", err)
}
fqdn := subdomain + "." + settings.Domain
d.logDeploy(deployID, fmt.Sprintf("Configuring proxy: %s -> %s:%d", fqdn, containerName, containerPort), "info")
// Check if a proxy host already exists for this domain.
existing, found, err := d.npm.FindProxyHostByDomain(ctx, fqdn)
if err != nil {
return 0, fmt.Errorf("find existing proxy host: %w", err)
}
proxyConfig := npm.ProxyHostConfig{
DomainNames: []string{fqdn},
ForwardScheme: "http",
ForwardHost: containerName,
ForwardPort: containerPort,
BlockExploits: true,
AllowWebsocket: true,
HTTP2Support: true,
Meta: npm.Meta{},
Locations: []any{},
}
if found {
d.logDeploy(deployID, fmt.Sprintf("Updating existing proxy host %d for %s", existing.ID, fqdn), "info")
host, err := d.npm.UpdateProxyHost(ctx, existing.ID, proxyConfig)
if err != nil {
return 0, fmt.Errorf("update proxy host: %w", err)
}
d.logDeploy(deployID, "Proxy host updated", "info")
return host.ID, nil
}
d.logDeploy(deployID, fmt.Sprintf("Creating new proxy host for %s", fqdn), "info")
host, err := d.npm.CreateProxyHost(ctx, proxyConfig)
if err != nil {
return 0, fmt.Errorf("create proxy host: %w", err)
}
d.logDeploy(deployID, fmt.Sprintf("Proxy host created (ID: %d)", host.ID), "info")
return host.ID, nil
}
// enforceMaxInstances removes the oldest instances when the stage has reached its limit.
// This makes room for the new deployment.
func (d *Deployer) enforceMaxInstances(ctx context.Context, stage store.Stage, deployID string, settings store.Settings) error {
if stage.MaxInstances <= 0 {
return nil
}
instances, err := d.store.GetInstancesByStageID(stage.ID)
if err != nil {
return fmt.Errorf("get instances for stage: %w", err)
}
// Filter to running/stopped instances (not already failed/removing).
var active []store.Instance
for _, inst := range instances {
if inst.Status == "running" || inst.Status == "stopped" {
active = append(active, inst)
}
}
// We need room for one more instance, so remove oldest when at limit.
removeCount := len(active) - stage.MaxInstances + 1
if removeCount <= 0 {
return nil
}
// Sort by created_at ascending (oldest first).
sort.Slice(active, func(i, j int) bool {
return active[i].CreatedAt < active[j].CreatedAt
})
for i := 0; i < removeCount && i < len(active); i++ {
inst := active[i]
d.logDeploy(deployID, fmt.Sprintf("Removing oldest instance %s (tag: %s) to enforce max_instances=%d", inst.ID, inst.ImageTag, stage.MaxInstances), "info")
if err := d.removeInstance(ctx, inst, settings); err != nil {
d.logDeploy(deployID, fmt.Sprintf("Failed to remove instance %s: %v", inst.ID, err), "warn")
continue
}
d.logDeploy(deployID, fmt.Sprintf("Removed instance %s", inst.ID), "info")
}
return nil
}
// removeInstance stops and removes a container, deletes its NPM proxy host,
// and removes the instance record from the store.
func (d *Deployer) removeInstance(ctx context.Context, inst store.Instance, settings store.Settings) error {
// Mark as removing.
if err := d.store.UpdateInstanceStatus(inst.ID, "removing"); err != nil {
slog.Warn("update instance status to removing", "instance_id", inst.ID, "error", err)
}
// Remove Docker container.
if inst.ContainerID != "" {
if err := d.docker.RemoveContainer(ctx, inst.ContainerID, true); err != nil {
slog.Warn("remove container", "container_id", inst.ContainerID, "error", err)
}
}
// Delete NPM proxy host.
if inst.NpmProxyID > 0 {
npmPassword, err := d.decryptNpmPassword(settings.NpmPassword)
if err != nil {
slog.Warn("decrypt npm password for proxy cleanup", "error", err)
} else if authErr := d.npm.Authenticate(ctx, settings.NpmEmail, npmPassword); authErr != nil {
slog.Warn("authenticate npm for proxy cleanup", "error", authErr)
} else if delErr := d.npm.DeleteProxyHost(ctx, inst.NpmProxyID); delErr != nil {
slog.Warn("delete proxy host", "proxy_id", inst.NpmProxyID, "error", delErr)
}
}
// Delete instance record.
if err := d.store.DeleteInstance(inst.ID); err != nil {
return fmt.Errorf("delete instance record: %w", err)
}
return nil
}
// buildSubdomain generates the subdomain for an instance based on settings and stage config.
func (d *Deployer) buildSubdomain(project store.Project, stage store.Stage, settings store.Settings, imageTag string) string {
return GenerateTaggedSubdomain(settings.SubdomainPattern, project.Name, stage.Name, imageTag, stage.Subdomain)
}
// buildRegistryAuth constructs the Docker registry auth string for pulling images.
// If the project has a registry configured, it looks up the registry token.
func (d *Deployer) buildRegistryAuth(project store.Project) (string, error) {
if project.Registry == "" {
return "", nil
}
reg, err := d.store.GetRegistryByName(project.Registry)
if err != nil {
return "", fmt.Errorf("get registry %s: %w", project.Registry, err)
}
if reg.Token != "" {
decrypted, err := crypto.Decrypt(d.encKey, reg.Token)
if err != nil {
return "", fmt.Errorf("decrypt registry token: %w", err)
}
return docker.EncodeRegistryAuth(decrypted, decrypted, reg.URL)
}
return "", nil
}
// decryptNpmPassword decrypts the NPM password from settings.
// Returns empty string if the encrypted password is empty.
func (d *Deployer) decryptNpmPassword(encryptedPassword string) (string, error) {
if encryptedPassword == "" {
return "", nil
}
return crypto.Decrypt(d.encKey, encryptedPassword)
}
// mergeEnvVars builds the final environment variable list for a container:
// 1. Parse project-level env JSON
// 2. Overlay with stage-level env overrides (stage wins on key conflict)
// 3. Decrypt any encrypted (secret) values
// Returns a []string of KEY=VALUE pairs.
func (d *Deployer) mergeEnvVars(project store.Project, stageID string) []string {
// Step 1: Parse project-level env.
envMap := make(map[string]string)
if project.Env != "" && project.Env != "{}" {
var projectEnv map[string]string
if err := json.Unmarshal([]byte(project.Env), &projectEnv); err != nil {
slog.Warn("parse project env vars", "error", err)
} else {
for k, v := range projectEnv {
envMap[k] = v
}
}
}
// Step 2: Overlay with stage-level overrides.
stageEnvs, err := d.store.GetStageEnvByStageID(stageID)
if err != nil {
slog.Warn("get stage env overrides", "stage_id", stageID, "error", err)
} else {
for _, se := range stageEnvs {
value := se.Value
if se.Encrypted {
// Step 3: Decrypt secret values.
decrypted, err := crypto.Decrypt(d.encKey, se.Value)
if err != nil {
slog.Warn("decrypt stage env value", "key", se.Key, "error", err)
continue
}
value = decrypted
}
envMap[se.Key] = value
}
}
vars := make([]string, 0, len(envMap))
for k, v := range envMap {
vars = append(vars, k+"="+v)
}
return vars
}
// computeVolumeMounts builds Docker mount specifications from the project's volume config.
// For shared mode, source is used as-is.
// For isolated mode, source gets /{stage}-{tag}/ appended.
func (d *Deployer) computeVolumeMounts(projectID, stageName, imageTag, basePath string) []mount.Mount {
vols, err := d.store.GetVolumesByProjectID(projectID)
if err != nil {
slog.Warn("get project volumes", "project_id", projectID, "error", err)
return nil
}
if len(vols) == 0 {
return nil
}
mounts := make([]mount.Mount, 0, len(vols))
for _, vol := range vols {
source := vol.Source
// Prepend base path if source is relative (doesn't start with /).
if basePath != "" && !filepath.IsAbs(source) {
source = filepath.Join(basePath, source)
}
if vol.Mode == "isolated" {
source = filepath.Join(source, fmt.Sprintf("%s-%s", stageName, imageTag))
}
mounts = append(mounts, mount.Mount{
Type: mount.TypeBind,
Source: source,
Target: vol.Target,
})
}
return mounts
}
// logDeploy appends a log entry for a deploy and publishes it on the event bus.
// Errors are logged to stderr but not propagated.
func (d *Deployer) logDeploy(deployID, message, level string) {
if err := d.store.AppendDeployLog(deployID, message, level); err != nil {
slog.Warn("append deploy log", "error", err)
}
if d.eventBus != nil {
d.eventBus.Publish(events.Event{
Type: events.EventDeployLog,
Payload: events.DeployLogPayload{
DeployID: deployID,
Message: message,
Level: level,
},
})
}
}
// publishDeployStatus publishes a deploy status change event on the bus.
func (d *Deployer) publishDeployStatus(deployID, projectID, stageID, imageTag, status, deployErr string) {
if d.eventBus != nil {
d.eventBus.Publish(events.Event{
Type: events.EventDeployStatus,
Payload: events.DeployStatusPayload{
DeployID: deployID,
ProjectID: projectID,
StageID: stageID,
ImageTag: imageTag,
Status: status,
Error: deployErr,
},
})
}
}
// publishInstanceStatus publishes an instance status change event on the bus.
func (d *Deployer) publishInstanceStatus(instanceID, projectID, stageID, status string) {
if d.eventBus != nil {
d.eventBus.Publish(events.Event{
Type: events.EventInstanceStatus,
Payload: events.InstanceStatusPayload{
InstanceID: instanceID,
ProjectID: projectID,
StageID: stageID,
Status: status,
},
})
}
}
// truncateID safely truncates a Docker ID to 12 characters for display.
func truncateID(id string) string {
if len(id) > 12 {
return id[:12]
}
return id
}