mirror of
https://github.com/postmannen/ctrl.git
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468 lines
16 KiB
Go
468 lines
16 KiB
Go
// Notes:
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package steward
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import (
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"bytes"
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"encoding/gob"
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"fmt"
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"log"
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"os/exec"
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"sync"
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"time"
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"github.com/nats-io/nats.go"
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)
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// CommandOrEvent describes on the message level if this is
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// an event or command kind of message in the Subject name.
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// This field is mainly used to be able to spawn up different
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// worker processes based on the Subject name so we can have
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// one process for handling event kind, and another for
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// handling command kind of messages.
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// This type is used in both building the subject name, and
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// also inside the Message type to describe if it is a Command
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// or Event.
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type CommandOrEvent string
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// TODO: Figure it makes sense to have these types at all.
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// It might make more sense to implement these as two
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// individual subjects.
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const (
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// shellCommand, command that will just wait for an
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// ack, and nothing of the output of the command are
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// delivered back in the reply ack message.
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// The message should contain the unique ID of the
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// command.
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Command CommandOrEvent = "command"
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// shellCommand, wait for and return the output
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// of the command in the ACK message. This means
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// that the command should be executed immediately
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// and that we should get the confirmation that it
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// was successful or not.
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Event CommandOrEvent = "event"
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// eventCommand, just wait for the ACK that the
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// message is received. What action happens on the
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// receiving side is up to the received to decide.
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)
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type Message struct {
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// The Unique ID of the message
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ID int `json:"id" yaml:"id"`
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// The actual data in the message
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// TODO: Change this to a slice instead...or maybe use an
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// interface type here to handle several data types ?
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Data []string `json:"data" yaml:"data"`
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// The type of the message being sent
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CommandOrEvent CommandOrEvent `json:"commandOrEvent" yaml:"commandOrEvent"`
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FromNode node
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}
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// server is the structure that will hold the state about spawned
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// processes on a local instance.
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type server struct {
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natsConn *nats.Conn
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// TODO: sessions should probably hold a slice/map of processes ?
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processes map[subjectName]process
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// The last processID created
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lastProcessID int
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// The name of the node
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nodeName string
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mu sync.Mutex
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// The channel where we receive new messages from the outside to
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// insert into the system for being processed
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newMessagesCh chan []jsonFromFile
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// errorCh is used to report errors from a process
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// NB: Implementing this as an int to report for testing
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errorCh chan errProcess
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// errorKernel
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errorKernel *errorKernel
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// TODO: replace this with some structure to hold the logCh value
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logCh chan []byte
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}
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// newServer will prepare and return a server type
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func NewServer(brokerAddress string, nodeName string) (*server, error) {
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conn, err := nats.Connect(brokerAddress, nil)
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if err != nil {
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log.Printf("error: nats.Connect failed: %v\n", err)
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}
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s := &server{
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nodeName: nodeName,
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natsConn: conn,
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processes: make(map[subjectName]process),
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newMessagesCh: make(chan []jsonFromFile),
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errorCh: make(chan errProcess, 2),
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logCh: make(chan []byte),
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}
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// Start the error kernel that will do all the error handling
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// not done within a process.
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s.errorKernel = newErrorKernel()
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s.errorKernel.startErrorKernel(s.errorCh)
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return s, nil
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}
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// Start will spawn up all the defined subscriber processes.
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// Spawning of publisher processes is done on the fly by checking
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// if there is publisher process for a given message subject. This
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// checking is also started here in Start by calling handleMessagesToPublish.
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func (s *server) Start() {
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// Start the checking the input file for new messages from operator.
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go s.getMessagesFromFile("./", "inmsg.txt", s.newMessagesCh)
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// Start the textlogging service that will run on the subscribers
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// TODO: Figure out how to structure event services like these
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go s.startTextLogging(s.logCh)
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// Start a subscriber for shellCommand messages
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{
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fmt.Printf("nodeName: %#v\n", s.nodeName)
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sub := newSubject(s.nodeName, "command", "shellcommand")
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proc := s.processPrepareNew(sub, s.errorCh, processKindSubscriber)
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// fmt.Printf("*** %#v\n", proc)
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go s.processSpawnWorker(proc)
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}
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// Start a subscriber for textLogging messages
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{
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fmt.Printf("nodeName: %#v\n", s.nodeName)
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sub := newSubject(s.nodeName, "event", "textlogging")
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proc := s.processPrepareNew(sub, s.errorCh, processKindSubscriber)
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// fmt.Printf("*** %#v\n", proc)
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go s.processSpawnWorker(proc)
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}
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time.Sleep(time.Second * 2)
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s.printProcessesMap()
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s.handleMessagesToPublish()
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select {}
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}
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func (s *server) printProcessesMap() {
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fmt.Println("--------------------------------------------------------------------------------------------")
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fmt.Printf("*** Output of processes map :\n")
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for _, v := range s.processes {
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fmt.Printf("*** - : %v\n", v)
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}
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fmt.Println("--------------------------------------------------------------------------------------------")
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}
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// handleNewOperatorMessages will handle all the new operator messages
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// given to the system, and route them to the correct subject queue.
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func (s *server) handleMessagesToPublish() {
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// Process the messages that have been received on the incomming
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// message pipe. Check and send if there are a specific subject
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// for it, and no subject exist throw an error.
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//
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// TODO: Later on the only thing that should be checked here is
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// that there is a node for the specific message, and the super-
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// visor should create the process with the wanted subject on both
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// the publishing and the receiving node. If there is no such node
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// an error should be generated and processed by the error-kernel.
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go func() {
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for v := range s.newMessagesCh {
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for i, vv := range v {
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// Adding a label here so we are able to redo the sending
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// of the last message if a process with specified subject
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// is not present.
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redo:
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m := vv.Message
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subjName := vv.Subject.name()
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fmt.Printf("** handleNewOperatorMessages: message: %v, ** subject: %#v\n", m, vv.Subject)
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_, ok := s.processes[subjName]
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if ok {
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log.Printf("info: found the specific subject: %v\n", subjName)
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// Put the message on the correct process's messageCh
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s.processes[subjName].subject.messageCh <- m
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} else {
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// If a publisher do not exist for the given subject, create it.
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log.Printf("info: did not find that specific subject, starting new process for subject: %v\n", subjName)
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sub := newSubject(v[i].Subject.Node, v[i].Subject.CommandOrEvent, v[i].Subject.Method)
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proc := s.processPrepareNew(sub, s.errorCh, processKindPublisher)
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// fmt.Printf("*** %#v\n", proc)
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go s.processSpawnWorker(proc)
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time.Sleep(time.Millisecond * 500)
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s.printProcessesMap()
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goto redo
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}
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}
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}
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}()
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}
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type node string
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// subject contains the representation of a subject to be used with one
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// specific process
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type Subject struct {
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// node, the name of the node
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Node string `json:"node" yaml:"node"`
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// messageType, command/event
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CommandOrEvent CommandOrEvent `json:"commandOrEvent" yaml:"commandOrEvent"`
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// method, what is this message doing, etc. shellcommand, syslog, etc.
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Method string `json:"method" yaml:"method"`
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// messageCh is the channel for receiving new content to be sent
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messageCh chan Message
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}
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// newSubject will return a new variable of the type subject, and insert
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// all the values given as arguments. It will also create the channel
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// to receive new messages on the specific subject.
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func newSubject(node string, commandOrEvent CommandOrEvent, method string) Subject {
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return Subject{
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Node: node,
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CommandOrEvent: commandOrEvent,
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Method: method,
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messageCh: make(chan Message),
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}
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}
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// subjectName is the complete representation of a subject
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type subjectName string
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func (s Subject) name() subjectName {
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return subjectName(fmt.Sprintf("%s.%s.%s", s.Node, s.CommandOrEvent, s.Method))
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}
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// processKind are either kindSubscriber or kindPublisher, and are
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// used to distinguish the kind of process to spawn and to know
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// the process kind put in the process map.
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type processKind string
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const (
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processKindSubscriber processKind = "subscriber"
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processKindPublisher processKind = "publisher"
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)
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// process are represent the communication to one individual host
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type process struct {
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messageID int
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// the subject used for the specific process. One process
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// can contain only one sender on a message bus, hence
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// also one subject
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subject Subject
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// Put a node here to be able know the node a process is at.
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// NB: Might not be needed later on.
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node node
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// The processID for the current process
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processID int
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// errorCh is used to report errors from a process
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// NB: Implementing this as an int to report for testing
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errorCh chan errProcess
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processKind processKind
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}
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// prepareNewProcess will set the the provided values and the default
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// values for a process.
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func (s *server) processPrepareNew(subject Subject, errCh chan errProcess, processKind processKind) process {
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// create the initial configuration for a sessions communicating with 1 host process.
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s.lastProcessID++
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proc := process{
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messageID: 0,
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subject: subject,
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node: node(subject.Node),
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processID: s.lastProcessID,
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errorCh: errCh,
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processKind: processKind,
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//messageCh: make(chan Message),
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}
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return proc
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}
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// spawnProcess will spawn a new process. It will give the process
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// the next available ID, and also add the process to the processes
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// map.
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func (s *server) processSpawnWorker(proc process) {
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s.mu.Lock()
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// We use the full name of the subject to identify a unique
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// process. We can do that since a process can only handle
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// one message queue.
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s.processes[proc.subject.name()] = proc
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s.mu.Unlock()
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// TODO: I think it makes most sense that the messages would come to
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// here from some other message-pickup-process, and that process will
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// give the message to the correct publisher process. A channel that
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// is listened on in the for loop below could be used to receive the
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// messages from the message-pickup-process.
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//
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// Handle publisher workers
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if proc.processKind == processKindPublisher {
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for {
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// Wait and read the next message on the message channel
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m := <-proc.subject.messageCh
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m.ID = s.processes[proc.subject.name()].messageID
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messageDeliver(proc, m, s.natsConn)
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// Increment the counter for the next message to be sent.
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proc.messageID++
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s.processes[proc.subject.name()] = proc
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time.Sleep(time.Second * 1)
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// NB: simulate that we get an error, and that we can send that
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// out of the process and receive it in another thread.
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ep := errProcess{
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infoText: "process failed",
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process: proc,
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message: m,
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errorActionCh: make(chan errorAction),
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}
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s.errorCh <- ep
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// Wait for the response action back from the error kernel, and
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// decide what to do. Should we continue, quit, or .... ?
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switch <-ep.errorActionCh {
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case errActionContinue:
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log.Printf("The errAction was continue...so we're continuing\n")
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}
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}
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}
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// handle subscriber workers
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if proc.processKind == processKindSubscriber {
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//subject := fmt.Sprintf("%s.%s.%s", s.nodeName, "command", "shellcommand")
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subject := string(proc.subject.name())
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// Subscribe will start up a Go routine under the hood calling the
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// callback function specified when a new message is received.
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_, err := s.natsConn.Subscribe(subject, func(msg *nats.Msg) {
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// We start one handler per message received by using go routines here.
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// This is for being able to reply back the current publisher who sent
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// the message.
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go s.subscriberHandler(s.natsConn, s.nodeName, msg)
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})
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if err != nil {
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log.Printf("error: Subscribe failed: %v\n", err)
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}
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}
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}
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func messageDeliver(proc process, message Message, natsConn *nats.Conn) {
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for {
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dataPayload, err := gobEncodePayload(message)
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if err != nil {
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log.Printf("error: createDataPayload: %v\n", err)
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}
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msg := &nats.Msg{
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Subject: string(proc.subject.name()),
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// Subject: fmt.Sprintf("%s.%s.%s", proc.node, "command", "shellcommand"),
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// Structure of the reply message are:
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// reply.<nodename>.<message type>.<method>
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Reply: fmt.Sprintf("reply.%s", proc.subject.name()),
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Data: dataPayload,
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}
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// The SubscribeSync used in the subscriber, will get messages that
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// are sent after it started subscribing, so we start a publisher
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// that sends out a message every second.
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//
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// Create a subscriber for the reply message.
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subReply, err := natsConn.SubscribeSync(msg.Reply)
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if err != nil {
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log.Printf("error: nc.SubscribeSync failed: %v\n", err)
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continue
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}
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// Publish message
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err = natsConn.PublishMsg(msg)
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if err != nil {
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log.Printf("error: publish failed: %v\n", err)
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continue
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}
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// Wait up until 10 seconds for a reply,
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// continue and resend if to reply received.
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msgReply, err := subReply.NextMsg(time.Second * 10)
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if err != nil {
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log.Printf("error: subRepl.NextMsg failed for node=%v, subject=%v: %v\n", proc.node, proc.subject.name(), err)
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// did not receive a reply, continuing from top again
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continue
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}
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log.Printf("publisher: received ACK: %s\n", msgReply.Data)
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return
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}
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}
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// gobEncodePayload will encode the message structure along with its
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// valued in gob binary format.
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// TODO: Check if it adds value to compress with gzip.
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func gobEncodePayload(m Message) ([]byte, error) {
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var buf bytes.Buffer
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gobEnc := gob.NewEncoder(&buf)
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err := gobEnc.Encode(m)
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if err != nil {
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return nil, fmt.Errorf("error: gob.Enode failed: %v", err)
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}
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return buf.Bytes(), nil
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}
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// handler will deserialize the message when a new message is received,
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// check the MessageType field in the message to decide what kind of
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// message it is and then it will check how to handle that message type,
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// and handle it.
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// This handler function should be started in it's own go routine,so
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// one individual handler is started per message received so we can keep
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// the state of the message being processed, and then reply back to the
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// correct sending process's reply, meaning so we ACK back to the correct
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// publisher.
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func (s *server) subscriberHandler(natsConn *nats.Conn, node string, msg *nats.Msg) {
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message := Message{}
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// Create a buffer to decode the gob encoded binary data back
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// to it's original structure.
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buf := bytes.NewBuffer(msg.Data)
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gobDec := gob.NewDecoder(buf)
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err := gobDec.Decode(&message)
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if err != nil {
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log.Printf("error: gob decoding failed: %v\n", err)
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}
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//fmt.Printf("%v\n", msg)
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// TODO: Maybe the handling of the errors within the subscriber
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// should also involve the error-kernel to report back centrally
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// that there was a problem like missing method to handle a specific
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// method etc.
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switch {
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case message.CommandOrEvent == "Command":
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// Since the command to execute is at the first position in the
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// slice we need to slice it out. The arguments are at the
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// remaining positions.
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c := message.Data[0]
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a := message.Data[1:]
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cmd := exec.Command(c, a...)
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//cmd.Stdout = os.Stdout
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out, err := cmd.CombinedOutput()
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if err != nil {
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log.Printf("error: execution of command failed: %v\n", err)
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}
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fmt.Printf("%s", out)
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// Send a confirmation message back to the publisher
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natsConn.Publish(msg.Reply, []byte("confirmed from: "+node+": "+fmt.Sprintf("%v\n%s", message.ID, out)))
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case message.CommandOrEvent == "Event":
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fmt.Printf("info: sending over the message %#v\n", message)
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for _, d := range message.Data {
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s.logCh <- []byte(d)
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}
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// Send a confirmation message back to the publisher
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natsConn.Publish(msg.Reply, []byte("confirmed from: "+node+": "+fmt.Sprint(message.ID)))
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default:
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log.Printf("info: did not find that specific type of command: %#v\n", message.CommandOrEvent)
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}
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}
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