httpprocprobed/prog/processlist.go

/*
	httpprocwatchd provides HTTP interface to a list of process' statuses
	formatted as JSON.
	Copyright (c) 2021 Alexander "Arav" Andreev <me@arav.top>

	This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <https://www.gnu.org/licenses/>.
*/

package prog

import (
	"encoding/xml"
	"os/exec"
	"strconv"
	"strings"
)

// ProcessList is a map of processes' statuses.
type ProcessList map[string]bool

// NewProcessList returns a ProcessList with initialised map.
func NewProcessList() *ProcessList {
	pl := make(ProcessList)
	return &pl
}

// AddProcess appends a process to a ProcessList
func (pl *ProcessList) AddProcess(name string, isup bool) {
	(*pl)[name] = isup
}

// ProcessXMLEntry is a XML representation of a process stored in ProcessList.
type ProcessXMLEntry struct {
	XMLName xml.Name
	Name    string `xml:"name,attr"`
	IsUp    bool   `xml:",chardata"`
}

// MarshalXML implements Marshaler interface for a ProcessList.
func (l ProcessList) MarshalXML(e *xml.Encoder, start xml.StartElement) error {
	if len(l) == 0 {
		return nil
	}

	if err := e.EncodeToken(start); err != nil {
		return err
	}

	for key, val := range l {
		e.Encode(ProcessXMLEntry{
			XMLName: xml.Name{Local: "Process"},
			Name:    key,
			IsUp:    val})
	}

	return e.EncodeToken(start.End())
}

// IsProcessUp returns true if process is up, and a list of PIDs for
// that process name. Uses pgrep to get PID of a process and if
// a process is not working, then pgrep returns nothing.
func IsProcessUp(name string) (bool, []int, error) {
	out, err := exec.Command("pgrep", "-f", name).Output()
	if err != nil || len(out) < 2 {
		return false, nil, err
	}

	spids := strings.Split(string(out[:len(out)-1]), "\n")
	pids := make([]int, len(spids))
	for i, v := range spids {
		pids[i], err = strconv.Atoi(v)
		if err != nil {
			return false, nil, nil
		}
	}

	return true, pids, nil
}