From 979b0567a605826906d22ad5e0a1d79f9d4ab946 Mon Sep 17 00:00:00 2001
From: Christian Pointner <equinox@helsinki.at>
Date: Tue, 22 Dec 2015 23:01:47 +0100
Subject: session is now safe to be used even if it is about to be removed


diff --git a/src/helsinki.at/rhimport/session.go b/src/helsinki.at/rhimport/session.go
index 864aac6..8843c81 100644
--- a/src/helsinki.at/rhimport/session.go
+++ b/src/helsinki.at/rhimport/session.go
@@ -25,6 +25,7 @@
 package rhimport
 
 import (
+	"fmt"
 	"net/http"
 )
 
@@ -132,15 +133,23 @@ func (self *Session) run() {
 }
 
 func (self *SessionChan) Run() {
-	self.runChan <- true
+	select {
+	case self.runChan <- true:
+	default: // command is already pending or session is about to be closed/removed
+	}
 }
 
 func (self *SessionChan) Cancel() {
-	self.cancelChan <- true
+	select {
+	case self.cancelChan <- true:
+	default: // cancel is already pending or session is about to be closed/removed
+	}
 }
 
 func (self *Session) addProgressHandler(userdata interface{}, cb ImportProgressCB) (resp sessionAddProgressHandlerResponse) {
-	rhdl.Printf("Session: addProgressHandler called with: %+v", userdata)
+	if self.state != SESSION_NEW && self.state != SESSION_RUNNING {
+		resp.err = fmt.Errorf("session is already done/canceled")
+	}
 	self.progressCBs = append(self.progressCBs, &SessionProgressCB{cb, userdata})
 	return
 }
@@ -151,14 +160,20 @@ func (self *SessionChan) AddProgressHandler(userdata interface{}, cb ImportProgr
 	req.userdata = userdata
 	req.callback = cb
 	req.response = res_ch
-	self.addProgressChan <- req
+	select {
+	case self.addProgressChan <- req:
+	default:
+		return fmt.Errorf("session is about to be closed/removed")
+	}
 
 	res := <-res_ch
 	return res.err
 }
 
 func (self *Session) addDoneHandler(userdata interface{}, cb func(ImportResult, interface{}) bool) (resp sessionAddDoneHandlerResponse) {
-	rhdl.Printf("Session: addDoneHandler called with: %+v", userdata)
+	if self.state == SESSION_NEW && self.state != SESSION_RUNNING {
+		resp.err = fmt.Errorf("session is already done/canceled")
+	}
 	self.doneCBs = append(self.doneCBs, &SessionDoneCB{cb, userdata})
 	return
 }
@@ -169,12 +184,36 @@ func (self *SessionChan) AddDoneHandler(userdata interface{}, cb func(ImportResu
 	req.userdata = userdata
 	req.callback = cb
 	req.response = res_ch
-	self.addDoneChan <- req
+	select {
+	case self.addDoneChan <- req:
+	default:
+		return fmt.Errorf("session is about to be closed/removed")
+	}
 
 	res := <-res_ch
 	return res.err
 }
 
+func (self *Session) callProgressHandler(p *ProgressData) {
+	for _, cb := range self.progressCBs {
+		if cb.cb != nil {
+			if keep := cb.cb(p.step, p.step_name, p.progress, cb.userdata); !keep {
+				cb.cb = nil
+			}
+		}
+	}
+}
+
+func (self *Session) callDoneHandler(r *ImportResult) {
+	for _, cb := range self.doneCBs {
+		if cb.cb != nil {
+			if keep := cb.cb(*r, cb.userdata); !keep {
+				cb.cb = nil
+			}
+		}
+	}
+}
+
 func (self *Session) dispatchRequests() {
 	defer func() { self.done <- true }()
 	for {
@@ -188,8 +227,9 @@ func (self *Session) dispatchRequests() {
 				rhdl.Println("Session: canceling running import")
 				select {
 				case self.cancelIntChan <- true:
-				default: // session got canceled already
+				default: // session got canceled already??
 				}
+				self.state = SESSION_CANCELED
 			} else {
 				return
 			}
@@ -198,22 +238,10 @@ func (self *Session) dispatchRequests() {
 		case req := <-self.addDoneChan:
 			req.response <- self.addDoneHandler(req.userdata, req.callback)
 		case p := <-self.progressIntChan:
-			for _, cb := range self.progressCBs {
-				if cb.cb != nil {
-					if keep := cb.cb(p.step, p.step_name, p.progress, cb.userdata); !keep {
-						cb.cb = nil
-					}
-				}
-			}
+			self.callProgressHandler(&p)
 		case r := <-self.doneIntChan:
 			self.state = SESSION_DONE
-			for _, cb := range self.doneCBs {
-				if cb.cb != nil {
-					if keep := cb.cb(r, cb.userdata); !keep {
-						cb.cb = nil
-					}
-				}
-			}
+			self.callDoneHandler(&r)
 		}
 	}
 }
@@ -234,10 +262,12 @@ func (self *Session) Cleanup() {
 	close(self.done)
 	close(self.progressIntChan)
 	close(self.doneIntChan)
-	close(self.runChan)
-	close(self.cancelChan)
-	close(self.addProgressChan)
-	close(self.addDoneChan)
+	//   don't close the channels we give out because this might lead to a panic if
+	//   somebody wites to an already removed session
+	// close(self.runChan)
+	// close(self.cancelChan)
+	// close(self.addProgressChan)
+	// close(self.addDoneChan)
 	rhdl.Printf("session is now cleaned up")
 }
 
@@ -247,12 +277,12 @@ func NewSession(ctx *ImportContext) (session *Session) {
 	session.ctx = *ctx
 	session.done = make(chan bool)
 	session.cancelIntChan = make(chan bool, 1)
-	session.progressIntChan = make(chan ProgressData)
-	session.doneIntChan = make(chan ImportResult)
-	session.runChan = make(chan bool)
-	session.cancelChan = make(chan bool)
-	session.addProgressChan = make(chan sessionAddProgressHandlerRequest)
-	session.addDoneChan = make(chan sessionAddDoneHandlerRequest)
+	session.progressIntChan = make(chan ProgressData, 10)
+	session.doneIntChan = make(chan ImportResult, 1)
+	session.runChan = make(chan bool, 1)
+	session.cancelChan = make(chan bool, 1)
+	session.addProgressChan = make(chan sessionAddProgressHandlerRequest, 10)
+	session.addDoneChan = make(chan sessionAddDoneHandlerRequest, 10)
 	go session.dispatchRequests()
 	return
 }
-- 
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