What causes "socket address is too long: %s" in docker/compose?

Shorten the socket path: create sockets in /tmp, $XDG_RUNTIME_DIR root, or another shallow directory.

socket address is too long: %s

Error message

socket address is too long: %s

What it means

Before dialing a Unix socket, memnet validates that the path fits in sockaddr_un.Path (108 bytes on Linux, ~104 on macOS) — the kernel hard limit for Unix socket addresses. A longer path cannot be represented in the sockaddr, so dial would fail with a cryptic EINVAL/ENAMETOOLONG; validateSocketPath fails fast with the offending path instead.

Source

Thrown at internal/memnet/conn_unix.go:36

package memnet

import (
	"context"
	"fmt"
	"net"
	"syscall"
)

const maxUnixSocketPathSize = len(syscall.RawSockaddrUnix{}.Path)

func dialNamedPipe(_ context.Context, _ string) (net.Conn, error) {
	return nil, fmt.Errorf("named pipes are only available on Windows")
}

func validateSocketPath(addr string) error {
	if len(addr) > maxUnixSocketPathSize {
		return fmt.Errorf("socket address is too long: %s", addr)
	}
	return nil
}

View on GitHub (pinned to ddc4b044b6)

Solutions

Shorten the socket path: create sockets in /tmp, $XDG_RUNTIME_DIR root, or another shallow directory.
Compute and assert path length before creating/dialing: len(path) < 108 on Linux (104 on macOS).
Use abstract Unix sockets only if the API supports them (this path-based API does not).
Move long-running CI workloads to a shorter checkout directory (e.g. /w or /srv) if the path comes from the workspace.

Example fix

# before: socket path too long
unix:///home/user/work/very/long/nested/path/runtime/dir/docker-api-proxy.sock

# after
unix:///tmp/dd-proxy.sock

Defensive patterns

Strategy: validation

Validate before calling

const maxUnixPath = 104 // conservative across linux(108)/macOS(104)
func socketPathFits(p string) bool { return len(p) <= maxUnixPath }
if !socketPathFits(path) { /* pick a shorter dir */ }

Try / catch

conn, err := memnet.Dial(ctx, "unix", addr)
if err != nil {
    if len(addr) > 104 {
        err = fmt.Errorf("socket path too long (%d bytes); move socket to a shallow dir: %w", len(addr), err)
    }
    return nil, err
}

Prevention

Create sockets under /tmp, /run, or $XDG_RUNTIME_DIR, not deep project trees.
Assert path length before bind/dial in tests.
Shorten long CI checkout paths.

When it happens

Trigger: Calling memnet.Dial/DialEndpoint with a unix:// address whose path exceeds the platform sockaddr_un.Path size — e.g. sockets created deep under long project directories (common with testcontainers, tmpdirs nested in $PWD, or XDG_RUNTIME_DIR with long usernames).

Common situations: CI checkout paths like /home/runner/work/very-long-repo-and-branch-name/... plus nested temp dirs pushing the socket path past ~104 chars; Docker contexts whose socket lives under a deeply nested runtime dir; tests generating sockets under t.TempDir() inside long absolute paths.

Related errors

AI-assisted analysis of docker/compose@ddc4b044b6 (2026-08-15). Data as JSON: /api/errors/9c078e966106d995. Report an issue: GitHub.