package steward import ( "bytes" "context" "encoding/gob" "fmt" "log" "time" "github.com/nats-io/nats.go" "github.com/prometheus/client_golang/prometheus" ) // processKind are either kindSubscriber or kindPublisher, and are // used to distinguish the kind of process to spawn and to know // the process kind put in the process map. type processKind string const ( processKindSubscriber processKind = "subscriber" processKindPublisher processKind = "publisher" ) // process holds all the logic to handle a message type and it's // method, subscription/publishin messages for a subject, and more. type process struct { messageID int // the subject used for the specific process. One process // can contain only one sender on a message bus, hence // also one subject subject Subject // Put a node here to be able know the node a process is at. // NB: Might not be needed later on. node Node // The processID for the current process processID int // errorCh is the same channel the errorKernel uses to // read incomming errors. By having this channel available // within a process we can send errors to the error kernel, // the EK desided what to do, and sends the action about // what to do back to the process where the error came from. errorCh chan errProcess processKind processKind // Who are we allowed to receive from ? allowedReceivers map[Node]struct{} // methodsAvailable methodsAvailable MethodsAvailable // Helper or service function that can do some kind of work // for the process. // The idea is that this can hold for example the map of the // the hello nodes to limit shared resources in the system as // a whole for sharing a map from the *server level. procFunc procFunc // The channel to send a messages to the procFunc go routine. // This is typically used within the methodHandler. procFuncCh chan Message // copy of the configuration from server configuration *Configuration // The new messages channel copied from *Server toRingbufferCh chan<- []subjectAndMessage // The structure who holds all processes information processes *processes // nats connection natsConn *nats.Conn // natsSubscription returned when calling natsConn.Subscribe natsSubscription *nats.Subscription // context ctx context.Context // context cancelFunc ctxCancel context.CancelFunc // Process name processName processName // startup holds the startup functions for starting up publisher // or subscriber processes startup *startup } // prepareNewProcess will set the the provided values and the default // values for a process. func newProcess(ctx context.Context, metrics *metrics, natsConn *nats.Conn, processes *processes, toRingbufferCh chan<- []subjectAndMessage, configuration *Configuration, subject Subject, errCh chan errProcess, processKind processKind, allowedReceivers []Node, procFunc func() error) process { // create the initial configuration for a sessions communicating with 1 host process. processes.lastProcessID++ // make the slice of allowedReceivers into a map value for easy lookup. m := make(map[Node]struct{}) for _, a := range allowedReceivers { m[a] = struct{}{} } ctx, cancel := context.WithCancel(ctx) var method Method proc := process{ messageID: 0, subject: subject, node: Node(configuration.NodeName), processID: processes.lastProcessID, errorCh: errCh, processKind: processKind, allowedReceivers: m, methodsAvailable: method.GetMethodsAvailable(), toRingbufferCh: toRingbufferCh, configuration: configuration, processes: processes, natsConn: natsConn, ctx: ctx, ctxCancel: cancel, startup: newStartup(metrics), } return proc } // procFunc is a helper function that will do some extra work for // a message received for a process. This allows us to ACK back // to the publisher that the message was received, but we can let // the processFunc keep on working. // This can also be used to wrap in other types which we want to // work with that come from the outside. An example can be handling // of metrics which the message have no notion of, but a procFunc // can have that wrapped in from when it was constructed. type procFunc func(ctx context.Context) error // The purpose of this function is to check if we should start a // publisher or subscriber process, where a process is a go routine // that will handle either sending or receiving messages on one // subject. // // It will give the process the next available ID, and also add the // process to the processes map in the server structure. func (p process) spawnWorker(procs *processes, natsConn *nats.Conn) { // We use the full name of the subject to identify a unique // process. We can do that since a process can only handle // one message queue. var pn processName if p.processKind == processKindPublisher { pn = processNameGet(p.subject.name(), processKindPublisher) } if p.processKind == processKindSubscriber { pn = processNameGet(p.subject.name(), processKindSubscriber) } processName := processNameGet(p.subject.name(), p.processKind) // Add prometheus metrics for the process. p.processes.metrics.promProcessesAllRunning.With(prometheus.Labels{"processName": string(processName)}) // Start a publisher worker, which will start a go routine (process) // That will take care of all the messages for the subject it owns. if p.processKind == processKindPublisher { // If there is a procFunc for the process, start it. if p.procFunc != nil { // Start the procFunc in it's own anonymous func so we are able // to get the return error. go func() { err := p.procFunc(p.ctx) if err != nil { er := fmt.Errorf("error: spawnWorker: procFunc failed: %v", err) sendErrorLogMessage(p.toRingbufferCh, Node(p.node), er) } }() } go p.publishMessages(natsConn) } // Start a subscriber worker, which will start a go routine (process) // That will take care of all the messages for the subject it owns. if p.processKind == processKindSubscriber { // If there is a procFunc for the process, start it. if p.procFunc != nil { // Start the procFunc in it's own anonymous func so we are able // to get the return error. go func() { err := p.procFunc(p.ctx) if err != nil { er := fmt.Errorf("error: spawnWorker: procFunc failed: %v", err) sendErrorLogMessage(p.toRingbufferCh, Node(p.node), er) } }() } p.natsSubscription = p.subscribeMessages() } p.processName = pn // Add information about the new process to the started processes map. idProcMap := make(map[int]process) idProcMap[p.processID] = p procs.mu.Lock() procs.active[pn] = idProcMap procs.mu.Unlock() } // messageDeliverNats will take care of the delivering the message // that is converted to gob format as a nats.Message. It will also // take care of checking timeouts and retries specified for the // message. func (p process) messageDeliverNats(natsConn *nats.Conn, message Message) { retryAttempts := 0 const publishTimer time.Duration = 5 const subscribeSyncTimer time.Duration = 5 for { dataPayload, err := gobEncodeMessage(message) if err != nil { er := fmt.Errorf("error: createDataPayload: %v", err) sendErrorLogMessage(p.toRingbufferCh, Node(p.node), er) continue } msg := &nats.Msg{ Subject: string(p.subject.name()), // Subject: fmt.Sprintf("%s.%s.%s", proc.node, "command", "CLICommandRequest"), // Structure of the reply message are: // ...reply Reply: fmt.Sprintf("%s.reply", p.subject.name()), Data: dataPayload, } // The SubscribeSync used in the subscriber, will get messages that // are sent after it started subscribing. // // Create a subscriber for the reply message. subReply, err := natsConn.SubscribeSync(msg.Reply) if err != nil { er := fmt.Errorf("error: nc.SubscribeSync failed: failed to create reply message: %v", err) // sendErrorLogMessage(p.toRingbufferCh, node(p.node), er) log.Printf("%v, waiting %ds before retrying\n", er, subscribeSyncTimer) time.Sleep(time.Second * subscribeSyncTimer) continue } // Publish message err = natsConn.PublishMsg(msg) if err != nil { er := fmt.Errorf("error: publish failed: %v", err) // sendErrorLogMessage(p.toRingbufferCh, node(p.node), er) log.Printf("%v, waiting %ds before retrying\n", er, publishTimer) time.Sleep(time.Second * publishTimer) continue } // If the message is an ACK type of message we must check that a // reply, and if it is not we don't wait here at all. // fmt.Printf("info: messageDeliverNats: preparing to send message: %v\n", message) if p.subject.CommandOrEvent == CommandACK || p.subject.CommandOrEvent == EventACK { // Wait up until ACKTimeout specified for a reply, // continue and resend if noo reply received, // or exit if max retries for the message reached. msgReply, err := subReply.NextMsg(time.Second * time.Duration(message.ACKTimeout)) if err != nil { er := fmt.Errorf("error: subReply.NextMsg failed for node=%v, subject=%v: %v", p.node, p.subject.name(), err) // sendErrorLogMessage(p.toRingbufferCh, p.node, er) log.Printf(" ** %v\n", er) // did not receive a reply, decide what to do.. retryAttempts++ log.Printf("Retry attempts:%v, retries: %v, ACKTimeout: %v\n", retryAttempts, message.Retries, message.ACKTimeout) switch { case message.Retries == 0: // 0 indicates unlimited retries continue case retryAttempts >= message.Retries: // max retries reached er := fmt.Errorf("info: toNode: %v, fromNode: %v, method: %v: max retries reached, check if node is up and running and if it got a subscriber for the given REQ type", message.ToNode, message.FromNode, message.Method) sendErrorLogMessage(p.toRingbufferCh, p.node, er) return default: // none of the above matched, so we've not reached max retries yet continue } } log.Printf("<--- publisher: received ACK from:%v, for: %v, data: %s\n", message.ToNode, message.Method, msgReply.Data) } return } } // subscriberHandler will deserialize the message when a new message is // received, check the MessageType field in the message to decide what // kind of message it is and then it will check how to handle that message type, // and then call the correct method handler for it. // // This handler function should be started in it's own go routine,so // one individual handler is started per message received so we can keep // the state of the message being processed, and then reply back to the // correct sending process's reply, meaning so we ACK back to the correct // publisher. func (p process) subscriberHandler(natsConn *nats.Conn, thisNode string, msg *nats.Msg) { message := Message{} // Create a buffer to decode the gob encoded binary data back // to it's original structure. buf := bytes.NewBuffer(msg.Data) gobDec := gob.NewDecoder(buf) err := gobDec.Decode(&message) if err != nil { er := fmt.Errorf("error: gob decoding failed: %v", err) sendErrorLogMessage(p.toRingbufferCh, Node(thisNode), er) } // Check if it is an ACK or NACK message, and do the appropriate action accordingly. switch { // Check for ACK type Commands or Event. case p.subject.CommandOrEvent == CommandACK || p.subject.CommandOrEvent == EventACK: mh, ok := p.methodsAvailable.CheckIfExists(message.Method) if !ok { er := fmt.Errorf("error: subscriberHandler: method type not available: %v", p.subject.CommandOrEvent) sendErrorLogMessage(p.toRingbufferCh, Node(thisNode), er) } out := []byte("not allowed from " + message.FromNode) //var err error // Check if we are allowed to receive from that host _, arOK1 := p.allowedReceivers[message.FromNode] _, arOK2 := p.allowedReceivers["*"] if arOK1 || arOK2 { // Start the method handler for that specific subject type. // The handler started here is what actually doing the action // that executed a CLI command, or writes to a log file on // the node who received the message. out, err = mh.handler(p, message, thisNode) if err != nil { er := fmt.Errorf("error: subscriberHandler: handler method failed: %v", err) sendErrorLogMessage(p.toRingbufferCh, Node(thisNode), er) } } else { er := fmt.Errorf("info: we don't allow receiving from: %v, %v", message.FromNode, p.subject) sendErrorLogMessage(p.toRingbufferCh, Node(thisNode), er) } // Send a confirmation message back to the publisher natsConn.Publish(msg.Reply, out) // Check for NACK type Commands or Event. case p.subject.CommandOrEvent == CommandNACK || p.subject.CommandOrEvent == EventNACK: mf, ok := p.methodsAvailable.CheckIfExists(message.Method) if !ok { er := fmt.Errorf("error: subscriberHandler: method type not available: %v", p.subject.CommandOrEvent) sendErrorLogMessage(p.toRingbufferCh, Node(thisNode), er) } // Check if we are allowed to receive from that host _, arOK1 := p.allowedReceivers[message.FromNode] _, arOK2 := p.allowedReceivers["*"] if arOK1 || arOK2 { // Start the method handler for that specific subject type. // The handler started here is what actually doing the action // that executed a CLI command, or writes to a log file on // the node who received the message. // // since we don't send a reply for a NACK message, we don't care about the // out return when calling mf.handler _, err := mf.handler(p, message, thisNode) if err != nil { er := fmt.Errorf("error: subscriberHandler: handler method failed: %v", err) sendErrorLogMessage(p.toRingbufferCh, Node(thisNode), er) } } else { er := fmt.Errorf("info: we don't allow receiving from: %v, %v", message.FromNode, p.subject) sendErrorLogMessage(p.toRingbufferCh, Node(thisNode), er) } default: er := fmt.Errorf("info: did not find that specific type of command: %#v", p.subject.CommandOrEvent) sendErrorLogMessage(p.toRingbufferCh, Node(thisNode), er) } } // SubscribeMessage will register the Nats callback function for the specified // nats subject. This allows us to receive Nats messages for a given subject // on a node. func (p process) subscribeMessages() *nats.Subscription { subject := string(p.subject.name()) natsSubscription, err := p.natsConn.Subscribe(subject, func(msg *nats.Msg) { //_, err := p.natsConn.Subscribe(subject, func(msg *nats.Msg) { // Start up the subscriber handler. go p.subscriberHandler(p.natsConn, p.configuration.NodeName, msg) }) if err != nil { log.Printf("error: Subscribe failed: %v\n", err) return nil } return natsSubscription } // publishMessages will do the publishing of messages for one single // process. func (p process) publishMessages(natsConn *nats.Conn) { for { var err error var m Message // Wait and read the next message on the message channel, or // exit this function if Cancel are received via ctx. select { case m = <-p.subject.messageCh: case <-p.ctx.Done(): er := fmt.Errorf("info: canceling publisher: %v", p.subject.name()) //sendErrorLogMessage(p.toRingbufferCh, Node(p.node), er) log.Printf("%v\n", er) return } // Get the process name so we can look up the process in the // processes map, and increment the message counter. pn := processNameGet(p.subject.name(), processKindPublisher) m.ID = p.messageID p.messageDeliverNats(natsConn, m) // Signaling back to the ringbuffer that we are done with the // current message, and it can remove it from the ringbuffer. m.done <- struct{}{} // Increment the counter for the next message to be sent. p.messageID++ p.processes.mu.Lock() p.processes.active[pn][p.processID] = p p.processes.mu.Unlock() // Handle the error. // // NOTE: None of the processes above generate an error, so the the // if clause will never be triggered. But keeping it here as an example // for now for how to handle errors. if err != nil { // Create an error type which also creates a channel which the // errorKernel will send back the action about what to do. ep := errProcess{ infoText: "process failed", process: p, message: m, errorActionCh: make(chan errorAction), } p.errorCh <- ep // Wait for the response action back from the error kernel, and // decide what to do. Should we continue, quit, or .... ? switch <-ep.errorActionCh { case errActionContinue: // Just log and continue log.Printf("The errAction was continue...so we're continuing\n") case errActionKill: log.Printf("The errAction was kill...so we're killing\n") // .... default: log.Printf("Info: publishMessages: The errAction was not defined, so we're doing nothing\n") } } } }