use systemd Upholds with depends_on

By default, systemd does not start a service if its dependencies started
succesfully after failing. Upholds (reverse: UpheldBy) will handle
starting dependent containers for us to mimic Compose behavior.

README.md

@@ -184,30 +184,31 @@ If a feature is missing, please feel free to [create an issue](https://github.co
 
 #### [`services`](https://docs.docker.com/compose/compose-file/05-services/)
 
-|   |     |
-|---|:---:|
-| [`image`](https://docs.docker.com/compose/compose-file/05-services/#image) | ✅ |
-| [`container_name`](https://docs.docker.com/compose/compose-file/05-services/#container_name) | ✅ |
-| [`environment`](https://docs.docker.com/compose/compose-file/05-services/#environment) | ✅ |
-| [`volumes`](https://docs.docker.com/compose/compose-file/05-services/#volumes) | ✅ |
-| [`labels`](https://docs.docker.com/compose/compose-file/05-services/#labels) | ✅ |
-| [`ports`](https://docs.docker.com/compose/compose-file/05-services/#ports) | ✅ |
-| [`dns`](https://docs.docker.com/compose/compose-file/05-services/#dns) | ✅ |
-| [`cap_add/cap_drop`](https://docs.docker.com/compose/compose-file/05-services/#cap_add) | ✅ |
-| [`logging`](https://docs.docker.com/compose/compose-file/05-services/#logging) | ✅ |
-| [`restart`](https://docs.docker.com/compose/compose-file/05-services/#restart) | ✅ |
-| [`deploy.restart_policy`](https://docs.docker.com/compose/compose-file/deploy/#restart_policy) | ✅ |
-| [`devices`](https://docs.docker.com/compose/compose-file/05-services/#devices) | ✅ |
-| [`networks.aliases`](https://docs.docker.com/compose/compose-file/05-services/#aliases) | ✅ |
-| [`network_mode`](https://docs.docker.com/compose/compose-file/05-services/#network_mode) | ✅ |
-| [`privileged`](https://docs.docker.com/compose/compose-file/05-services/#privileged) | ✅ |
-| [`extra_hosts`](https://docs.docker.com/compose/compose-file/05-services/#extra_hosts) | ✅ |
-| [`sysctls`](https://docs.docker.com/compose/compose-file/05-services/#sysctls) | ✅ |
-| [`shm_size`](https://docs.docker.com/compose/compose-file/05-services/#shm_size) | ✅ |
-| [`runtime`](https://docs.docker.com/compose/compose-file/05-services/#runtime) | ✅ |
-| [`security_opt`](https://docs.docker.com/compose/compose-file/05-services/#security_opt) | ✅ |
-| [`command`](https://docs.docker.com/compose/compose-file/05-services/#command) | ✅ |
-| [`healthcheck`](https://docs.docker.com/compose/compose-file/05-services/#healthcheck) | ✅ |
+|   |     | Notes |
+|---|:---:|-------|
+| [`image`](https://docs.docker.com/compose/compose-file/05-services/#image) | ✅ | |
+| [`container_name`](https://docs.docker.com/compose/compose-file/05-services/#container_name) | ✅ | |
+| [`environment`](https://docs.docker.com/compose/compose-file/05-services/#environment) | ✅ | |
+| [`volumes`](https://docs.docker.com/compose/compose-file/05-services/#volumes) | ✅ | |
+| [`labels`](https://docs.docker.com/compose/compose-file/05-services/#labels) | ✅ | |
+| [`ports`](https://docs.docker.com/compose/compose-file/05-services/#ports) | ✅ | |
+| [`dns`](https://docs.docker.com/compose/compose-file/05-services/#dns) | ✅ | |
+| [`cap_add/cap_drop`](https://docs.docker.com/compose/compose-file/05-services/#cap_add) | ✅ | |
+| [`logging`](https://docs.docker.com/compose/compose-file/05-services/#logging) | ✅ | |
+| [`depends_on`](https://docs.docker.com/compose/compose-file/05-services/#depends_on) | ⚠️ | Only short syntax is supported. |
+| [`restart`](https://docs.docker.com/compose/compose-file/05-services/#restart) | ✅ | |
+| [`deploy.restart_policy`](https://docs.docker.com/compose/compose-file/deploy/#restart_policy) | ✅ | |
+| [`devices`](https://docs.docker.com/compose/compose-file/05-services/#devices) | ✅ | |
+| [`networks.aliases`](https://docs.docker.com/compose/compose-file/05-services/#aliases) | ✅ | |
+| [`network_mode`](https://docs.docker.com/compose/compose-file/05-services/#network_mode) | ✅ | |
+| [`privileged`](https://docs.docker.com/compose/compose-file/05-services/#privileged) | ✅ | |
+| [`extra_hosts`](https://docs.docker.com/compose/compose-file/05-services/#extra_hosts) | ✅ | |
+| [`sysctls`](https://docs.docker.com/compose/compose-file/05-services/#sysctls) | ✅ | |
+| [`shm_size`](https://docs.docker.com/compose/compose-file/05-services/#shm_size) | ✅ | |
+| [`runtime`](https://docs.docker.com/compose/compose-file/05-services/#runtime) | ✅ | |
+| [`security_opt`](https://docs.docker.com/compose/compose-file/05-services/#security_opt) | ✅ | |
+| [`command`](https://docs.docker.com/compose/compose-file/05-services/#command) | ✅ | |
+| [`healthcheck`](https://docs.docker.com/compose/compose-file/05-services/#healthcheck) | ✅ | |
 
 #### [`networks`](https://docs.docker.com/compose/compose-file/06-networks/)
 

compose.go

@@ -266,6 +266,9 @@ func (g *Generator) buildNixContainer(service types.ServiceConfig) (*NixContaine
 	}
 
 	// Figure out explicit dependencies for this container.
+	//
+	// TODO(aksiksi): Support the long syntax.
+	// https://docs.docker.com/compose/compose-file/05-services/#long-syntax-1
 	for _, s := range service.GetDependencies() {
 		targetContainerName, ok := g.serviceToContainerName[s]
 		if !ok {
@@ -429,17 +432,6 @@ func (g *Generator) buildNixContainer(service types.ServiceConfig) (*NixContaine
 		c.ExtraOptions = append(c.ExtraOptions, mapToRepeatedKeyValFlag("--log-opt", logging.Options)...)
 	}
 
-	// Add systemd dependencies on network(s).
-	for _, networkName := range c.Networks {
-		c.SystemdConfig.Unit.After = append(c.SystemdConfig.Unit.After, g.networkNameToService(networkName))
-		c.SystemdConfig.Unit.Requires = append(c.SystemdConfig.Unit.Requires, g.networkNameToService(networkName))
-	}
-	// Add systemd dependency on root target.
-	if !g.NoCreateRootTarget {
-		c.SystemdConfig.Unit.PartOf = append(c.SystemdConfig.Unit.PartOf, fmt.Sprintf("%s.target", rootTarget(g.Runtime, g.Project)))
-		c.SystemdConfig.Unit.WantedBy = append(c.SystemdConfig.Unit.WantedBy, fmt.Sprintf("%s.target", rootTarget(g.Runtime, g.Project)))
-	}
-
 	// Health check.
 	// https://docs.docker.com/compose/compose-file/05-services/#healthcheck
 	if healthCheck := service.HealthCheck; healthCheck != nil {
@@ -489,6 +481,30 @@ func (g *Generator) buildNixContainer(service types.ServiceConfig) (*NixContaine
 	slices.Sort(c.ExtraOptions)
 	slices.Sort(c.Networks)
 
+	// Add systemd dependencies on network(s).
+	for _, networkName := range c.Networks {
+		c.SystemdConfig.Unit.After = append(c.SystemdConfig.Unit.After, g.networkNameToService(networkName))
+		c.SystemdConfig.Unit.Requires = append(c.SystemdConfig.Unit.Requires, g.networkNameToService(networkName))
+	}
+	// Add systemd dependency on root target.
+	if !g.NoCreateRootTarget {
+		c.SystemdConfig.Unit.PartOf = append(c.SystemdConfig.Unit.PartOf, fmt.Sprintf("%s.target", rootTarget(g.Runtime, g.Project)))
+		c.SystemdConfig.Unit.WantedBy = append(c.SystemdConfig.Unit.WantedBy, fmt.Sprintf("%s.target", rootTarget(g.Runtime, g.Project)))
+	}
+
+	// Set UpheldBy for this service's dependencies. This ensures that, when the dependency comes up,
+	// this container will also be started - and continuously restarted with backoff - until it comes up.
+	// See: https://www.freedesktop.org/software/systemd/man/latest/systemd.unit.html#Upholds=
+	//
+	// Why do we need to do this? Because, by default, systemd does not attempt to start failed dependent units
+	// when the parent (dependency) comes up. See: https://github.com/systemd/systemd/issues/1312.
+	//
+	// Note 2: Upholds is supported in version 249+. NixOS 23.05 uses 253.6, so this should always be supported.
+	// See: https://github.com/NixOS/nixpkgs/blob/nixos-23.05/pkgs/os-specific/linux/systemd/default.nix#L148.
+	for _, containerName := range c.DependsOn {
+		c.SystemdConfig.Unit.UpheldBy = append(c.SystemdConfig.Unit.UpheldBy, fmt.Sprintf("%s-%s.service", g.Runtime, containerName))
+	}
+
 	return c, nil
 }
 

nixos-test/docker-compose.nix

@@ -57,6 +57,9 @@
       "/var/volumes/radarr:/config:rw"
       "storage:/storage:rw"
     ];
+    dependsOn = [
+      "myproject-sabnzbd"
+    ];
     log-driver = "journald";
     extraOptions = [
       "--network-alias=radarr"
@@ -78,6 +81,9 @@
     partOf = [
       "docker-compose-myproject-root.target"
     ];
+    unitConfig.UpheldBy = [
+      "docker-myproject-sabnzbd.service"
+    ];
     wantedBy = [
       "docker-compose-myproject-root.target"
     ];

nixos-test/docker-compose.yml

@@ -20,6 +20,8 @@ services:
     volumes:
       - /var/volumes/radarr:/config
       - storage:/storage
+    depends_on:
+      - sabnzbd
     restart: unless-stopped
 
 networks:

nixos-test/podman-compose.nix

@@ -60,6 +60,9 @@
       "/mnt/media:/storage:rw"
       "/var/volumes/radarr:/config:rw"
     ];
+    dependsOn = [
+      "myproject-sabnzbd"
+    ];
     log-driver = "journald";
     extraOptions = [
       "--network-alias=radarr"
@@ -79,6 +82,9 @@
     partOf = [
       "podman-compose-myproject-root.target"
     ];
+    unitConfig.UpheldBy = [
+      "podman-myproject-sabnzbd.service"
+    ];
     wantedBy = [
       "podman-compose-myproject-root.target"
     ];

systemd.go

@@ -70,6 +70,7 @@ type UnitConfig struct {
 	After    []string
 	Requires []string
 	PartOf   []string
+	UpheldBy []string
 	WantedBy []string
 	// Map for generic options.
 	Options map[string]any
@@ -86,6 +87,8 @@ func (u *UnitConfig) Set(key string, value any) {
 		u.Requires = append(u.Requires, value.(string))
 	case "PartOf":
 		u.PartOf = append(u.PartOf, value.(string))
+	case "UpheldBy":
+		u.UpheldBy = append(u.UpheldBy, value.(string))
 	case "WantedBy":
 		u.WantedBy = append(u.WantedBy, value.(string))
 	default:

templates/container.nix.tmpl

@@ -116,6 +116,13 @@ systemd.services."{{.Runtime}}-{{.Name}}" = {
     {{- end}}
   ];
   {{- end}}
+  {{- if .SystemdConfig.Unit.UpheldBy}}
+  unitConfig.UpheldBy = [
+    {{- range .SystemdConfig.Unit.UpheldBy}}
+    "{{.}}"
+    {{- end}}
+  ];
+  {{- end}}
   {{- if .SystemdConfig.Unit.WantedBy}}
   wantedBy = [
     {{- range .SystemdConfig.Unit.WantedBy}}

testdata/TestDocker_EnvFilesOnly_out.nix

@@ -55,6 +55,9 @@
     partOf = [
       "docker-compose-myproject-root.target"
     ];
+    unitConfig.UpheldBy = [
+      "docker-myproject-sabnzbd.service"
+    ];
     wantedBy = [
       "docker-compose-myproject-root.target"
     ];
@@ -211,6 +214,9 @@
     partOf = [
       "docker-compose-myproject-root.target"
     ];
+    unitConfig.UpheldBy = [
+      "docker-myproject-sabnzbd.service"
+    ];
     wantedBy = [
       "docker-compose-myproject-root.target"
     ];
@@ -260,6 +266,9 @@
     partOf = [
       "docker-compose-myproject-root.target"
     ];
+    unitConfig.UpheldBy = [
+      "docker-sabnzbd.service"
+    ];
     wantedBy = [
       "docker-compose-myproject-root.target"
     ];

testdata/TestDocker_RemoveVolumes_out.nix

@@ -57,6 +57,9 @@
     partOf = [
       "docker-compose-myproject-root.target"
     ];
+    unitConfig.UpheldBy = [
+      "docker-myproject-sabnzbd.service"
+    ];
     wantedBy = [
       "docker-compose-myproject-root.target"
     ];
@@ -236,6 +239,9 @@
     partOf = [
       "docker-compose-myproject-root.target"
     ];
+    unitConfig.UpheldBy = [
+      "docker-myproject-sabnzbd.service"
+    ];
     wantedBy = [
       "docker-compose-myproject-root.target"
     ];
@@ -286,6 +292,9 @@
     partOf = [
       "docker-compose-myproject-root.target"
     ];
+    unitConfig.UpheldBy = [
+      "docker-sabnzbd.service"
+    ];
     wantedBy = [
       "docker-compose-myproject-root.target"
     ];

testdata/TestDocker_SystemdMount_out.nix

@@ -59,6 +59,9 @@
     partOf = [
       "docker-compose-myproject-root.target"
     ];
+    unitConfig.UpheldBy = [
+      "docker-myproject-sabnzbd.service"
+    ];
     wantedBy = [
       "docker-compose-myproject-root.target"
     ];
@@ -244,6 +247,9 @@
     partOf = [
       "docker-compose-myproject-root.target"
     ];
+    unitConfig.UpheldBy = [
+      "docker-myproject-sabnzbd.service"
+    ];
     wantedBy = [
       "docker-compose-myproject-root.target"
     ];
@@ -294,6 +300,9 @@
     partOf = [
       "docker-compose-myproject-root.target"
     ];
+    unitConfig.UpheldBy = [
+      "docker-sabnzbd.service"
+    ];
     wantedBy = [
       "docker-compose-myproject-root.target"
     ];

testdata/TestDocker_WithProject_out.nix

@@ -57,6 +57,9 @@
     partOf = [
       "docker-compose-myproject-root.target"
     ];
+    unitConfig.UpheldBy = [
+      "docker-myproject-sabnzbd.service"
+    ];
     wantedBy = [
       "docker-compose-myproject-root.target"
     ];
@@ -236,6 +239,9 @@
     partOf = [
       "docker-compose-myproject-root.target"
     ];
+    unitConfig.UpheldBy = [
+      "docker-myproject-sabnzbd.service"
+    ];
     wantedBy = [
       "docker-compose-myproject-root.target"
     ];
@@ -286,6 +292,9 @@
     partOf = [
       "docker-compose-myproject-root.target"
     ];
+    unitConfig.UpheldBy = [
+      "docker-sabnzbd.service"
+    ];
     wantedBy = [
       "docker-compose-myproject-root.target"
     ];

testdata/TestDocker_out.nix

@@ -56,6 +56,9 @@
     partOf = [
       "docker-compose-myproject-root.target"
     ];
+    unitConfig.UpheldBy = [
+      "docker-myproject-sabnzbd.service"
+    ];
     wantedBy = [
       "docker-compose-myproject-root.target"
     ];
@@ -232,6 +235,9 @@
     partOf = [
       "docker-compose-myproject-root.target"
     ];
+    unitConfig.UpheldBy = [
+      "docker-myproject-sabnzbd.service"
+    ];
     wantedBy = [
       "docker-compose-myproject-root.target"
     ];
@@ -281,6 +287,9 @@
     partOf = [
       "docker-compose-myproject-root.target"
     ];
+    unitConfig.UpheldBy = [
+      "docker-sabnzbd.service"
+    ];
     wantedBy = [
       "docker-compose-myproject-root.target"
     ];

testdata/TestPodman_WithProject_out.nix

@@ -56,6 +56,9 @@
     partOf = [
       "podman-compose-myproject-root.target"
     ];
+    unitConfig.UpheldBy = [
+      "podman-myproject-sabnzbd.service"
+    ];
     wantedBy = [
       "podman-compose-myproject-root.target"
     ];
@@ -225,6 +228,9 @@
     partOf = [
       "podman-compose-myproject-root.target"
     ];
+    unitConfig.UpheldBy = [
+      "podman-myproject-sabnzbd.service"
+    ];
     wantedBy = [
       "podman-compose-myproject-root.target"
     ];
@@ -275,6 +281,9 @@
     partOf = [
       "podman-compose-myproject-root.target"
     ];
+    unitConfig.UpheldBy = [
+      "podman-sabnzbd.service"
+    ];
     wantedBy = [
       "podman-compose-myproject-root.target"
     ];