hashicorp/nomad · error

panic(err)

Error message

panic(err)

What it means

logmon resolves its own plugin binary path at package init time via os.Executable(); the package-level `var bin = getBin()` runs during process startup. If the OS cannot determine the executable path, the error is unrecoverable for the plugin and is panicked.

Source

Thrown at client/logmon/plugin.go:23

import (
	"context"
	"os"
	"os/exec"

	"github.com/hashicorp/go-hclog"
	"github.com/hashicorp/go-plugin"
	"github.com/hashicorp/nomad/client/logmon/proto"
	"github.com/hashicorp/nomad/plugins/base"
	"google.golang.org/grpc"
)

var bin = getBin()

func getBin() string {
	b, err := os.Executable()
	if err != nil {
		panic(err)
	}
	return b
}

// LaunchLogMon launches a new logmon or reattaches to an existing one.
// TODO: Integrate with base plugin loader
func LaunchLogMon(logger hclog.Logger, reattachConfig *plugin.ReattachConfig) (LogMon, *plugin.Client, error) {
	logger = logger.Named("logmon")
	conf := &plugin.ClientConfig{
		HandshakeConfig: base.Handshake,
		Plugins: map[string]plugin.Plugin{
			"logmon": &Plugin{},
		},
		AllowedProtocols: []plugin.Protocol{
			plugin.ProtocolGRPC,
		},
		Logger: logger,
	}

View on GitHub (pinned to 482b49bf1a)

Solutions

1. Ensure the Nomad executable file still exists on disk while the process runs; don't delete/replace the binary in place during upgrades
2. Upgrade via unlink+replace of a new file rather than truncating/moving the running binary path
3. Check the underlying err in the panic to identify the OS-level cause (permission, missing /proc, deleted file)
4. Restart the agent from a valid, existing binary path

Example fix

// before
var bin = getBin() // panics at init on error
// after
var bin = func() string {
    b, err := os.Executable()
    if err != nil {
        b = os.Args[0] // fallback instead of panicking
    }
    return b
}()

// package init cannot be recovered from inside the package; wrap usage
func initLogmon() (err error) {
    defer func() {
        if r := recover(); r != nil {
            err = fmt.Errorf("logmon init failed: %v", r)
        }
    }()
    _ = logmon.Plugin // triggers bin resolution
    return nil
}

When it happens

Trigger: Package initialization of client/logmon when os.Executable() fails — e.g. the executable file was deleted/replaced after start, /proc is unavailable, or the process was launched in a way the OS cannot trace back to a binary path.

Common situations: Binary deleted or upgraded (moved) while the agent process is running; running in minimal containers with odd /proc mounts; exec'ing the Nomad binary from a temp file that was removed; unusual embedding environments where os.Executable returns an error.

Related errors

• Failed to determine the nomad executable: %v
• rpc.dial_timeout must be greater than or equal to zero
• client_introduction.enforcement must be set
• No addresses found, please configure one.
• invalid acl policy: %v

AI-assisted analysis of hashicorp/nomad@482b49bf1a (2026-09-04). Data as JSON: /api/errors/3a3a24e9f8425c7a. Report an issue: GitHub.