The Modules API provides functions that return information about the current operating environment (module, version, and instance).
The Modules API also has functions that retrieve the address of a module, a version, or an instance. This allows an application to send requests from one instance to another, in both the development and production environments.
The following code sample shows how to get the module name and instance id for a request:
import
com.google.appengine.api.modules.ModulesService
;
import
com.google.appengine.api.modules.ModulesServiceFactory
;
ModulesService
modulesApi
=
ModulesServiceFactory
.
getModulesService
();
//
Get
the
service
name
handling
the
current
request
.
String
currentModuleName
=
modulesApi
.
getCurrentModule
();
//
Get
the
instance
handling
the
current
request
.
int
currentInstance
=
modulesApi
.
getCurrentInstance
();
The instance ID of an automatic scaled module will be returned as a unique
base64 encoded value, e.g. e4b565394caa
.
You can communicate between modules in the same app by fetching the hostname of the target module:
The following code sample shows how to get the module name and instance id for a request:
import
com.google.appengine.api.modules.ModulesService
;
import
com.google.appengine.api.modules.ModulesServiceFactory
;
import
java.net.MalformedURLException
;
import
java.net.URL
;
import
java.io.BufferedReader
;
import
java.io.InputStreamReader
;
import
java.io.IOException
;
//
...
ModulesService
modulesApi
=
ModulesServiceFactory
.
getModulesService
();
//
...
try
{
URL
url
=
new
URL
(
"http://"
+
modulesApi
.
getVersionHostname
(
"my-backend-service"
,
"v1"
)
+
"/fetch-stats"
);
BufferedReader
reader
=
new
BufferedReader
(
new
InputStreamReader
(
url
.
openStream
()));
String
line
;
while
((
line
=
reader
.
readLine
())
!=
null
)
{
//
Do
something
...
}
reader
.
close
();
}
catch
(
MalformedURLException
e
)
{
//
...
}
catch
(
IOException
e
)
{
//
...
}
You can also use the URL Fetch service.
