SUSE/saptune

package system

import (
    "fmt"
    "io/ioutil"
    "os"
    "strconv"
    "syscall"
)

// saptune lock file
var stLockFile = "/run/.saptune.lock"

// map of 'realm command' combinations to set the lock or not
var lockCommands = map[string]bool{"daemon start": true, "daemon status": false, "daemon stop": true, "service apply": true, "service start": true, "service status": false, "service stop": true, "service restart": true, "service revert": true, "service reload": true, "service takeover": true, "service enable": false, "service disable": false, "service enablestart": true, "service disablestop": true, "note list": false, "note revertall": true, "note enabled": false, "note applied": false, "note apply": true, "note simulate": false, "note customise": true, "note create": true, "note edit": true, "note revert": true, "note show": false, "note delete": true, "note verify": false, "note rename": true, "solution list": false, "solution verify": false, "solution enabled": false, "solution applied": false, "solution apply": true, "solution change": true, "solution simulate": false, "solution customise": true, "solution create": true, "solution edit": true, "solution revert": true, "solution show": false, "solution delete": true, "solution rename": true, "staging status": true, "staging enable": true, "staging disable": true, "staging is-enabled": true, "staging list": true, "staging diff": true, "staging analysis": true, "staging release": true, "revert all": true, "lock remove": false, "check": false, "status": false, "version": false, "help": false}

// isOwnLock return true, if lock file is from the current running process
// pid inside the lock file is the pid of current running saptune instance
func isOwnLock() bool {
    if !saptuneIsLocked() {
        // no lock file found, return false
        return false
    }
    p, err := ioutil.ReadFile(stLockFile)
    if err != nil {
        ErrorLog("problems during reading the lock file - '%v'", err)
        ReleaseSaptuneLock()
        OSExit(99)
    }
    // file exists, check if empty or if pid inside is from a dead process
    // if yes, remove file and return false
    pid, _ := strconv.Atoi(string(p))
    return pid == os.Getpid()
}

// SaptuneLock creates the saptune lock file
func SaptuneLock() {
    // check for saptune lock file
    if saptuneIsLocked() {
        ErrorExit("saptune currently in use, try later ...", 11)
    }
    lcmd := realmAndCmd()
    setLock := false
    if _, ok := lockCommands[lcmd]; !ok {
        // not a valid combination of 'realm command'
        ErrLog("not a valid combination of 'realm command' discovered - %s\n", lcmd)
        setLock = true
    } else {
        setLock = lockCommands[lcmd]
    }
    if setLock {
        stLock, err := os.OpenFile(stLockFile, os.O_CREATE|os.O_RDWR|os.O_EXCL, 0600)
        if err != nil {
            ErrorExit("problems setting lock", 12)
        } else {
            fmt.Fprintf(stLock, "%d", os.Getpid())
        }
        stLock.Close()
    } else {
        InfoLog("no lock set for '%s'\n", lcmd)
    }
}

// saptuneIsLocked checks, if the lock file for saptune exists
func saptuneIsLocked() bool {
    f, err := os.Stat(stLockFile)
    if os.IsNotExist(err) {
        return false
    }
    // file is empty, remove file and return false
    if f.Size() == 0 {
        ReleaseSaptuneLock()
        return false
    }
    // file exists, read content
    p, err := ioutil.ReadFile(stLockFile)
    if err != nil {
        ErrorLog("problems during reading the lock file - '%v'", err)
        ReleaseSaptuneLock()
        OSExit(99)
    }
    // file contains a pid. Check, if process is still alive
    // if not (dead process) remove file and return false
    // TODO - check, if p is really a pid
    pid, _ := strconv.Atoi(string(p))
    if err := syscall.Kill(pid, syscall.Signal(0)); err == nil {
        // process exists, must not be the same process, which
        // created the lock file. Will be checked in ErrorExit
        return true
    }
    // process does not exists
    ReleaseSaptuneLock()
    return false
}

// ReleaseSaptuneLock removes the saptune lock file
func ReleaseSaptuneLock() {
    if err := os.Remove(stLockFile); os.IsNotExist(err) {
        // no lock file available, nothing to do
    } else if err != nil {
        ErrorLog("problems removing lock. Please remove lock file '%s' manually before the next start of saptune.\n", stLockFile)
    }
}