130 lines
4.1 KiB
Go
130 lines
4.1 KiB
Go
// Package executor is used to invoke child processes across various operating
|
|
// systems in a way that provides the following features:
|
|
//
|
|
// - Least privilege
|
|
// - Resource constraints
|
|
// - Process isolation
|
|
//
|
|
// An operating system may be something like "windows" or "linux with systemd".
|
|
// Executors allow drivers like `exec` and `java` to share an implementation
|
|
// for isolation capabilities on a particular operating system.
|
|
//
|
|
// For example:
|
|
//
|
|
// - `exec` and `java` on Linux use a cgroups executor
|
|
// - `exec` and `java` on FreeBSD use a jails executor
|
|
//
|
|
// However, drivers that provide their own isolation should not use executors.
|
|
// For example, using an executor to start QEMU means that the QEMU call is
|
|
// run inside a chroot+cgroup, even though the VM already provides isolation for
|
|
// the task running inside it. This is an extraneous level of indirection.
|
|
package executor
|
|
|
|
import (
|
|
"fmt"
|
|
"os/exec"
|
|
"path/filepath"
|
|
"strings"
|
|
|
|
"github.com/hashicorp/nomad/client/allocdir"
|
|
"github.com/hashicorp/nomad/nomad/structs"
|
|
|
|
cstructs "github.com/hashicorp/nomad/client/driver/structs"
|
|
)
|
|
|
|
var errNoResources = fmt.Errorf("No resources are associated with this task")
|
|
|
|
// If testModeEnvVar is set in a process's environment variables, the
|
|
// LinuxExecutor will detect it and inject the current binary into the chroot.
|
|
// This enables using the test binary in tests to provide portability.
|
|
var testModeEnvVar = "NOMAD_EXECUTOR_TEST_ONLY_13871827980214"
|
|
|
|
// Executor is an interface that any platform- or capability-specific exec
|
|
// wrapper must implement. You should not need to implement a Java executor.
|
|
// Rather, you would implement a cgroups executor that the Java driver will use.
|
|
type Executor interface {
|
|
// Limit must be called before Start and restricts the amount of resources
|
|
// the process can use. Note that an error may be returned ONLY IF the
|
|
// executor implements resource limiting. Otherwise Limit is ignored.
|
|
Limit(*structs.Resources) error
|
|
|
|
// ConfigureTaskDir must be called before Start and ensures that the tasks
|
|
// directory is properly configured.
|
|
ConfigureTaskDir(taskName string, alloc *allocdir.AllocDir) error
|
|
|
|
// Start the process. This may wrap the actual process in another command,
|
|
// depending on the capabilities in this environment. Errors that arise from
|
|
// Limits or Runas may bubble through Start()
|
|
Start() error
|
|
|
|
// Open should be called to restore a previous execution. This might be needed if
|
|
// nomad is restarted.
|
|
Open(string) error
|
|
|
|
// Wait waits till the user's command is completed.
|
|
Wait() *cstructs.WaitResult
|
|
|
|
// Returns a handle that is executor specific for use in reopening.
|
|
ID() (string, error)
|
|
|
|
// Shutdown should use a graceful stop mechanism so the application can
|
|
// perform checkpointing or cleanup, if such a mechanism is available.
|
|
// If such a mechanism is not available, Shutdown() should call ForceStop().
|
|
Shutdown() error
|
|
|
|
// ForceStop will terminate the process without waiting for cleanup. Every
|
|
// implementations must provide this.
|
|
ForceStop() error
|
|
|
|
// Command provides access the underlying Cmd struct in case the Executor
|
|
// interface doesn't expose the functionality you need.
|
|
Command() *exec.Cmd
|
|
}
|
|
|
|
// Command is a mirror of exec.Command that returns a platform-specific Executor
|
|
func Command(name string, args ...string) Executor {
|
|
executor := NewExecutor()
|
|
SetCommand(executor, name, args)
|
|
return executor
|
|
}
|
|
|
|
func SetCommand(e Executor, name string, args []string) {
|
|
cmd := e.Command()
|
|
cmd.Path = name
|
|
cmd.Args = append([]string{name}, args...)
|
|
|
|
if filepath.Base(name) == name {
|
|
if lp, err := exec.LookPath(name); err != nil {
|
|
// cmd.lookPathErr = err
|
|
} else {
|
|
cmd.Path = lp
|
|
}
|
|
}
|
|
}
|
|
|
|
// OpenId is similar to executor.Command but will attempt to reopen with the
|
|
// passed ID.
|
|
func OpenId(id string) (Executor, error) {
|
|
executor := NewExecutor()
|
|
err := executor.Open(id)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
return executor, nil
|
|
}
|
|
|
|
// isTest returns whether the cmd is a test binary.
|
|
func isTest(cmd *exec.Cmd) bool {
|
|
if cmd == nil {
|
|
return false
|
|
}
|
|
|
|
for _, env := range cmd.Env {
|
|
if strings.HasPrefix(env, testModeEnvVar) {
|
|
return true
|
|
}
|
|
}
|
|
|
|
return false
|
|
}
|