[minor/hack] whitelist regexes, take 2

doc/configuration.rst

@@ -289,6 +289,17 @@ add agents to the whitelist manually.
 
 	Dec 17 23:39:10 ip-172-30-200-53 mig-scheduler[9181]: - - - [warning] getHeartbeats(): Agent 'linux.somehost.example.net.4vjs8ubqo0100' is not authorized
 
+For environments that are particularly dynamic, it is possible to use regexes
+in the whitelist. This is done by prepending `re:` to the whitelist entry.
+
+.. code::
+
+	re:linux.server[0-9]{1,4}.example.net.[a-z0-9]{13}
+
+Keep the list of regexes short. Until MIG implements a better agent validation
+mechanisms, the whitelist is reread for every registration, and regexes are
+recompiled every time. On a busy platform, this can be done hundreds of times
+per second and induce heavy cpu usage.
 
 Database creation
 ~~~~~~~~~~~~~~~~~

doc/configuration.rst.html

@@ -210,6 +210,9 @@ sudo chown mig-user /var/cache/mig -R</code></pre>
 windows.db4.sub.example.com.56b2andxmyb00</code></pre>
             <p>If the scheduler receives a heartbeat from an agent that is not present in the whitelist, it will log an error message. An operator can process the logs and add agents to the whitelist manually.</p>
             <pre><code class="">Dec 17 23:39:10 ip-172-30-200-53 mig-scheduler[9181]: - - - [warning] getHeartbeats(): Agent 'linux.somehost.example.net.4vjs8ubqo0100' is not authorized</code></pre>
+            <p>For environments that are particularly dynamic, it is possible to use regexes in the whitelist. This is done by prepending <cite>re:</cite> to the whitelist entry.</p>
+            <pre><code class="">re:linux.server[0-9]{1,4}.example.net.[a-z0-9]{13}</code></pre>
+            <p>Keep the list of regexes short. Until MIG implements a better agent validation mechanisms, the whitelist is reread for every registration, and regexes are recompiled every time. On a busy platform, this can be done hundreds of times per second and induce heavy cpu usage.</p>
         </section>
         <section id="database-creation">
             <h3>4.3   Database creation</h3>

src/mig/scheduler/authorization.go

@@ -39,14 +39,22 @@ func isAgentAuthorized(agentQueueLoc string, ctx Context) (ok bool, err error) {
 		if err := scanner.Err(); err != nil {
 			panic(err)
 		}
-		re, err = regexp.Compile("^" + scanner.Text() + "$")
-		if err != nil {
-			panic(err)
-		}
-		if re.MatchString(agentQueueLoc) {
-			ctx.Channels.Log <- mig.Log{OpID: ctx.OpID, Desc: fmt.Sprintf("Agent '%s' is authorized", agentQueueLoc)}.Debug()
-			ok = true
-			return
+		if len(scanner.Text()) > 4 && scanner.Text()[0:3] == "re:" {
+			re, err = regexp.Compile("^" + scanner.Text()[3:] + "$")
+			if err != nil {
+				panic(err)
+			}
+			if re.MatchString(agentQueueLoc) {
+				ctx.Channels.Log <- mig.Log{OpID: ctx.OpID, Desc: fmt.Sprintf("Agent '%s' is authorized", agentQueueLoc)}.Debug()
+				ok = true
+				return
+			}
+		} else {
+			if scanner.Text() == agentQueueLoc {
+				ctx.Channels.Log <- mig.Log{OpID: ctx.OpID, Desc: fmt.Sprintf("Agent '%s' is authorized", agentQueueLoc)}.Debug()
+				ok = true
+				return
+			}
 		}
 	}
 	// whitelist check failed, agent isn't authorized