First cut at a Proposal #3

Client-server-discovery-lifecycle.md

@@ -72,3 +72,47 @@ The sbt launcher provides a locking facility.
        fail: port = start new process; write(f, port)
    }
 ```
+
+
+## Proposal 3: A combination of the above.
+
+Here's a more concrete proposal of how launching a server would work.  However, first, let's make some assumptions that are potentially contentious that lead to the following proposal:
+
+1. the sbt launcher's locking mechanism is sufficient for us to find a means to avoid double-server-startup.
+2. We want clients to have *one* means of attempting to fork the sbt server process.
+*TODO - more here*
+
+We create a new interface for the sbt launcher, called `xsbt.ServerMain`:
+
+```java
+package xsbti;
+
+public interface ServerMain {
+  public ServerPort[] start(AppConfiguration configuration);
+  public boolean isAlive(ServerPort[] ports);
+}
+```
+
+The interface has two methods.  One responsible for starting the Server, and another which can be used to check whether or not another server is alive, based on a given set of server port connections.  The sbt launcher is responsible for:
+
+1. Obtaining the lock file for the CWD + AppConfiguratoin-hash pairing.  (That is there can only be one server of a given configuration (organization + module id) in any working directory).
+2. Reading the ServerPorts from the active configuration.
+3. Checking to see if the old server is alive.  If so, report these ports to the client (TODO - how?)
+4. If the old server was not alive, start up a new server (fork + detach?).  Write the new server bindings to the lock file.
+
+
+Port bindings come in triples of `Address`, `Port` and `Protocol` mappings:
+
+```java
+package xsbti;
+
+interface ServerPort {
+  public java.net.INetAddress address();  // Can be IPv6 or IPv4
+  public int port();
+  public String protocol();  // A string-based definition of protocol, i.e. http, https 
+                             // or even custom, like sbt
+}
+```
+
+Clients should be able to be notified of all open ServerPort bindings created by a server.
+