Merge pull request moby#50327 from Adrien-Atmosphere/50326-wait-for-dependent-containers

Wait for container dependencies upon daemon start up

Author: robmry

daemon/container.go

@@ -1,11 +1,16 @@
+// FIXME(thaJeztah): remove once we are a module; the go:build directive prevents go from downgrading language version to go1.16:
+//go:build go1.23
+
 package daemon
 
 import (
 	"context"
 	"fmt"
+	"maps"
 	"os"
 	"path/filepath"
 	"runtime"
+	"slices"
 	"strings"
 	"time"
 
@@ -196,6 +201,31 @@ func (daemon *Daemon) GetByName(name string) (*container.Container, error) {
 	return e, nil
 }
 
+// GetDependentContainers returns a list of containers that depend on the given container.
+// Dependencies are determined by:
+//   - Network mode dependencies (--network=container:xxx)
+//   - Legacy container links (--link)
+//
+// This is primarily used during daemon startup to determine container startup order,
+// ensuring that dependent containers are started after their dependencies are running.
+// Upon error, it returns the last known dependent containers, which may be empty.
+func (daemon *Daemon) GetDependentContainers(c *container.Container) []*container.Container {
+	var dependentContainers []*container.Container
+
+	if c.HostConfig.NetworkMode.IsContainer() {
+		// If the container is using a network mode that depends on another container,
+		// we need to find that container and add it to the dependency map.
+		dependencyContainer, err := daemon.GetContainer(c.HostConfig.NetworkMode.ConnectedContainer())
+		if err != nil {
+			log.G(context.TODO()).WithError(err).Errorf("Could not find dependent container for %s", c.ID)
+			return dependentContainers
+		}
+		dependentContainers = append(dependentContainers, dependencyContainer)
+	}
+
+	return append(dependentContainers, slices.Collect(maps.Values(daemon.linkIndex.children(c)))...)
+}
+
 func (daemon *Daemon) setSecurityOptions(cfg *config.Config, container *container.Container, hostConfig *containertypes.HostConfig) error {
 	container.Lock()
 	defer container.Unlock()

daemon/daemon.go

@@ -575,8 +575,8 @@ func (daemon *Daemon) restore(cfg *configStore) error {
 			logger.Debug("starting container")
 
 			// ignore errors here as this is a best effort to wait for children
-			// (legacy links) to be running before we try to start the container
-			if children := daemon.linkIndex.children(c); len(children) > 0 {
+			// (legacy links or container network) to be running before we try to start the container
+			if children := daemon.GetDependentContainers(c); len(children) > 0 {
 				timeout := time.NewTimer(5 * time.Second)
 				defer timeout.Stop()