Update Local Development documents (#1159)

document state changing feature of local SDK server.

site/content/en/docs/Guides/Client SDKs/local.md

@@ -17,7 +17,7 @@ Therefore, when developing locally, we also need a process for the SDK to connec
 
 To do this, we can run the same binary that runs inside Agones, but pass in a flag
 to run it in "local mode". Local mode means that the sidecar binary
-won't try and connect to anything, and will just send logs messages to stdout so 
+will not try to connect to anything, and will just send log messages to stdout and persist local state in memory so 
 that you can see exactly what the SDK in your game server is doing, and can
 confirm everything works.
 
@@ -62,9 +62,35 @@ happen when live as well.
 For example:
 
 ```console
-$ ./sdk-server.linux.amd64 --local -f ../../../examples/simple-udp/gameserver.yaml
-{"ctlConf":{"Address":"localhost","IsLocal":true,"LocalFile":"../../../examples/simple-udp/gameserver.yaml"},"grpcPort":59357,"httpPort":59358,"level":"info","msg":"Starting sdk sidecar","source":"main","time":"2018-08-25T17:56:39-07:00","version":"0.4.0-b44960a8"}
+$ export AGONES_PATH=/home/go/src/agones.dev/agones
+$ ./sdk-server.linux.amd64 --local -f ${AGONES_PATH}/examples/simple-udp/gameserver.yaml
+{"ctlConf":{"Address":"localhost","IsLocal":true,"LocalFile":"/home/go/src/agones.dev/agones/examples/simple-udp/gameserver.yaml"},"grpcPort":59357,"httpPort":59358,"level":"info","msg":"Starting sdk sidecar","source":"main","time":"2018-08-25T17:56:39-07:00","version":"0.4.0-b44960a8"}
 {"level":"info","msg":"Reading GameServer configuration","path":"/home/user/workspace/agones/src/agones.dev/agones/examples/simple-udp/gameserver.yaml","source":"main","time":"2018-08-25T17:56:39-07:00"}
 {"level":"info","msg":"Starting SDKServer grpc service...","source":"main","time":"2018-08-25T17:56:39-07:00"}
 {"level":"info","msg":"Starting SDKServer grpc-gateway...","source":"main","time":"2018-08-25T17:56:39-07:00"}
-```
+```
+
+### Changing State of a Local GameServer
+
+Some SDK calls would change the GameServer state according to [GameServer State Diagram]({{< ref "../../Reference/gameserver.md#gameserver-state-diagram" >}}). Also local SDK server would persist labels and annotations updates.
+
+Here is a complete list of these commands: ready, allocate, setlabel, setannotation, shutdown, reserve.
+
+For example call to Reserve() for 30 seconds would change the GameServer state to Reserve and if no call to Allocate() occurs it would return back to Ready state after this period.
+
+{{< alert title="Note" color="info">}}
+All state transitions are supported for local SDK server, however not all of them are valid in the real scenario. For instance, you cannot make a transition of a GameServer from Shutdown to a Ready state, but can do using local SDK server.
+{{< /alert >}}
+
+All changes to the GameServer state could be observed and retrieved using Watch() or GameServer() methods using GameServer SDK.
+
+Example of using HTTP gateway locally:
+```console
+$ curl -X POST "http://localhost:59358/ready" -H "accept: application/json" -H "Content-Type: application/json" -d "{}"
+{}
+$ curl -GET "http://localhost:59358/gameserver" -H "accept: application/json"
+{"object_meta":{"creation_timestamp":"-62135596800"},"spec":{"health":{}},"status":{"state":"Ready"}}
+$ curl -X PUT "http://localhost:59358/metadata/label" -H "accept: application/json" -H "Content-Type: application/json" -d "{ \"key\": \"foo\", \"value\": \"bar\"}"
+$ curl -GET "http://localhost:59358/gameserver" -H "accept: application/json"}"
+{"object_meta":{"creation_timestamp":"-62135596800","labels":{"agones.dev/sdk-foo":"bar"}},"spec":{"health":{}},"status":{"state":"Ready"}}
+```