Determine docker host via env then context (#2444)

* Determine docker host via env then context

Previously always used the system default (eg /var/run/docker.sock) which would fail if the default docker socket was not installed, no longer symlinked to the home directory socket, or pointed to a daemon that wasn't running. This can happen when docker desktop and orbstack are running togehter on the same system.

Now cog will try to find the daemon socket by looking at the following in order
1. the DOCKER_HOST env variable
2. the docker context specified by DOCKER_CONTEXT
3. the current docker context set in the docker config
4. the system default

* remove unused code

Author: michaeldwan

go.mod

@@ -9,7 +9,7 @@ require (
 	github.com/aws/aws-sdk-go-v2/credentials v1.17.67
 	github.com/aws/aws-sdk-go-v2/service/s3 v1.79.3
 	github.com/creack/pty v1.1.24
-	github.com/docker/cli v28.1.1+incompatible
+	github.com/docker/cli v28.3.0+incompatible
 	github.com/docker/docker v28.1.1+incompatible
 	github.com/docker/go-connections v0.5.0
 	github.com/getkin/kin-openapi v0.128.0
@@ -126,6 +126,7 @@ require (
 	github.com/felixge/httpsnoop v1.0.4 // indirect
 	github.com/firefart/nonamedreturns v1.0.5 // indirect
 	github.com/fsnotify/fsnotify v1.9.0 // indirect
+	github.com/fvbommel/sortorder v1.1.0 // indirect
 	github.com/fzipp/gocyclo v0.6.0 // indirect
 	github.com/ghostiam/protogetter v0.3.9 // indirect
 	github.com/go-critic/go-critic v0.12.0 // indirect
@@ -205,6 +206,7 @@ require (
 	github.com/moby/go-archive v0.1.0 // indirect
 	github.com/moby/locker v1.0.1 // indirect
 	github.com/moby/patternmatcher v0.6.0 // indirect
+	github.com/moby/sys/atomicwriter v0.1.0 // indirect
 	github.com/moby/sys/sequential v0.6.0 // indirect
 	github.com/moby/sys/signal v0.7.1 // indirect
 	github.com/moby/sys/user v0.4.0 // indirect

go.sum

@@ -177,6 +177,8 @@ github.com/dnephin/pflag v1.0.7 h1:oxONGlWxhmUct0YzKTgrpQv9AUA1wtPBn7zuSjJqptk=
 github.com/dnephin/pflag v1.0.7/go.mod h1:uxE91IoWURlOiTUIA8Mq5ZZkAv3dPUfZNaT80Zm7OQE=
 github.com/docker/cli v28.1.1+incompatible h1:eyUemzeI45DY7eDPuwUcmDyDj1pM98oD5MdSpiItp8k=
 github.com/docker/cli v28.1.1+incompatible/go.mod h1:JLrzqnKDaYBop7H2jaqPtU4hHvMKP+vjCwu2uszcLI8=
+github.com/docker/cli v28.3.0+incompatible h1:s+ttruVLhB5ayeuf2BciwDVxYdKi+RoUlxmwNHV3Vfo=
+github.com/docker/cli v28.3.0+incompatible/go.mod h1:JLrzqnKDaYBop7H2jaqPtU4hHvMKP+vjCwu2uszcLI8=
 github.com/docker/distribution v2.8.3+incompatible h1:AtKxIZ36LoNK51+Z6RpzLpddBirtxJnzDrHLEKxTAYk=
 github.com/docker/distribution v2.8.3+incompatible/go.mod h1:J2gT2udsDAN96Uj4KfcMRqY0/ypR+oyYUYmja8H+y+w=
 github.com/docker/docker v28.1.1+incompatible h1:49M11BFLsVO1gxY9UX9p/zwkE/rswggs8AdFmXQw51I=
@@ -203,6 +205,8 @@ github.com/frankban/quicktest v1.14.6 h1:7Xjx+VpznH+oBnejlPUj8oUpdxnVs4f8XU8WnHk
 github.com/frankban/quicktest v1.14.6/go.mod h1:4ptaffx2x8+WTWXmUCuVU6aPUX1/Mz7zb5vbUoiM6w0=
 github.com/fsnotify/fsnotify v1.9.0 h1:2Ml+OJNzbYCTzsxtv8vKSFD9PbJjmhYF14k/jKC7S9k=
 github.com/fsnotify/fsnotify v1.9.0/go.mod h1:8jBTzvmWwFyi3Pb8djgCCO5IBqzKJ/Jwo8TRcHyHii0=
+github.com/fvbommel/sortorder v1.1.0 h1:fUmoe+HLsBTctBDoaBwpQo5N+nrCp8g/BjKb/6ZQmYw=
+github.com/fvbommel/sortorder v1.1.0/go.mod h1:uk88iVf1ovNn1iLfgUVU2F9o5eO30ui720w+kxuqRs0=
 github.com/fzipp/gocyclo v0.6.0 h1:lsblElZG7d3ALtGMx9fmxeTKZaLLpU8mET09yN4BBLo=
 github.com/fzipp/gocyclo v0.6.0/go.mod h1:rXPyn8fnlpa0R2csP/31uerbiVBugk5whMdlyaLkLoA=
 github.com/getkin/kin-openapi v0.128.0 h1:jqq3D9vC9pPq1dGcOCv7yOp1DaEe7c/T1vzcLbITSp4=

pkg/docker/api_client.go

@@ -1,15 +1,12 @@
 package docker
 
 import (
-	"bytes"
 	"context"
-	"encoding/json"
 	"errors"
 	"fmt"
 	"io"
 	"net"
 	"os"
-	"os/exec"
 	"strconv"
 	"strings"
 
@@ -45,25 +42,26 @@ func NewAPIClient(ctx context.Context, opts ...Option) (*apiClient, error) {
 		opt(clientOptions)
 	}
 
-	// Check to see if we need to override docker host
-	host := os.Getenv("DOCKER_HOST")
-	if host == "" {
-		inspects, err := findDockerHost()
-		if err == nil {
-			for _, inspect := range inspects {
-				endpoint, ok := inspect.Endpoints["docker"]
-				if ok {
-					os.Setenv("DOCKER_HOST", endpoint.Host)
-					break
-				}
-			}
+	if clientOptions.host == "" {
+		host, err := determineDockerHost()
+		if err != nil {
+			return nil, fmt.Errorf("error determining docker host: %w", err)
 		}
+		clientOptions.host = host
 	}
 
 	// TODO[md]: we create a client at the top of each cli invocation, the sdk client hits an api which
 	// adds (a tiny biy of) overead. swap this with a handle that'll lazily initialize a client and ping for health.
 	// ditto for fetching registry credentials.
-	client, err := dc.NewClientWithOpts(dc.FromEnv, dc.WithAPIVersionNegotiation())
+
+	dockerClientOpts := []dc.Opt{
+		dc.WithTLSClientConfigFromEnv(),
+		dc.WithVersionFromEnv(),
+		dc.WithAPIVersionNegotiation(),
+		dc.WithHost(clientOptions.host),
+	}
+
+	client, err := dc.NewClientWithOpts(dockerClientOpts...)
 	if err != nil {
 		return nil, fmt.Errorf("error creating docker client: %w", err)
 	}
@@ -628,25 +626,3 @@ func shouldAttachStdin(stdin io.Reader) (attach bool, tty bool) {
 	// the container to attach stdin and keep open
 	return true, true
 }
-
-func findDockerHost() ([]command.ContextInspect, error) {
-	dockerCmd := DockerCommandFromEnvironment()
-	cmd := exec.Command(dockerCmd, "context", "inspect")
-
-	// Create a buffer to capture the standard output
-	var out bytes.Buffer
-	cmd.Stdout = &out
-
-	// Run the command
-	err := cmd.Run()
-	if err != nil {
-		return nil, err
-	}
-
-	var resp []command.ContextInspect
-	if err := json.Unmarshal(out.Bytes(), &resp); err != nil {
-		return nil, fmt.Errorf("error unmarshaling inspect response: %w", err)
-	}
-
-	return resp, nil
-}

pkg/docker/command/context_inspect.go

@@ -0,0 +1,71 @@
+package docker
+
+import (
+	"fmt"
+	"os"
+
+	dconfig "github.com/docker/cli/cli/config"
+	dctxdocker "github.com/docker/cli/cli/context/docker"
+	dctxstore "github.com/docker/cli/cli/context/store"
+
+	"github.com/replicate/cog/pkg/util/console"
+)
+
+// determineDockerHost returns the host to use for the docker client.
+// It first checks the DOCKER_HOST environment variable, then the docker context, and finally the system default.
+func determineDockerHost() (string, error) {
+	// 1) if DOCKER_HOST is set, use it
+	if host := os.Getenv("DOCKER_HOST"); host != "" {
+		return host, nil
+	}
+
+	// 2) try to get a host from the docker context. Use DOCKER_CONTEXT if set, otherwise check the current context
+	if host, err := dockerHostFromContext(os.Getenv("DOCKER_CONTEXT")); err != nil {
+		console.Warnf("error finding docker host from context: %v", err)
+
+		// if DOCKER_CONTEXT was explicitly set, return an error since the user probably expects that context to be used
+		if os.Getenv("DOCKER_CONTEXT") != "" {
+			return "", err
+		}
+	} else if host != "" {
+		return host, nil
+	}
+
+	// 3) if we couldn't get a host from env or context, fallback to the system default
+	return defaultDockerHost, nil
+}
+
+func dockerHostFromContext(contextName string) (string, error) {
+	if contextName == "" {
+		cf, err := dconfig.Load(dconfig.Dir())
+		if err != nil {
+			return "", err
+		}
+		contextName = cf.CurrentContext
+	}
+
+	typeGetter := func() any { return &dctxdocker.EndpointMeta{} }
+	storeConfig := dctxstore.NewConfig(typeGetter, dctxstore.EndpointTypeGetter(dctxdocker.DockerEndpoint, typeGetter))
+
+	store := dctxstore.New(dconfig.ContextStoreDir(), storeConfig)
+	meta, err := store.GetMetadata(contextName)
+	if err != nil {
+		return "", err
+	}
+
+	endpoint, ok := meta.Endpoints[dctxdocker.DockerEndpoint]
+	if !ok {
+		return "", fmt.Errorf("no docker endpoints found for context %s", contextName)
+	}
+
+	dockerEPMeta, ok := endpoint.(dctxdocker.EndpointMeta)
+	if !ok {
+		return "", fmt.Errorf("invalid context config: %v", endpoint)
+	}
+
+	if dockerEPMeta.Host == "" {
+		return "", fmt.Errorf("no host found for context %s", contextName)
+	}
+
+	return dockerEPMeta.Host, nil
+}

pkg/docker/host.go

@@ -0,0 +1,7 @@
+//go:build !windows
+
+package docker
+
+const (
+	defaultDockerHost = "unix:///var/run/docker.sock"
+)

pkg/docker/host_unix.go

@@ -0,0 +1,5 @@
+package docker
+
+const (
+	defaultDockerHost = "npipe:////.pipe/docker_engine"
+)

pkg/docker/host_windows.go

@@ -4,6 +4,7 @@ import "github.com/docker/docker/api/types/registry"
 
 type clientOptions struct {
 	authConfigs map[string]registry.AuthConfig
+	host        string
 }
 
 type Option func(*clientOptions)
@@ -13,3 +14,9 @@ func WithAuthConfig(authConfig registry.AuthConfig) Option {
 		o.authConfigs[authConfig.ServerAddress] = authConfig
 	}
 }
+
+func WithHost(host string) Option {
+	return func(o *clientOptions) {
+		o.host = host
+	}
+}