Google Cloud Messaging dont return Canonical ID - google-cloud-messaging

Question

I have deliberately registered my app several times to GCM to test the canonical id concept, but the cloud doesnt return it to me. See my server log below, its the same device and I can see in the Android log that it received the message four times. But I never get a canonical id in return from Google, what is it I misunderstand?
[INFO com.bipper.filters.PushUpdatesFilter] method: POST childId: 13 has pending updates: true url: /mybipperapi/do/parents/1/children/13/usagelimits
[INFO com.bipper.services.gcm.GcmSenderService] registrationId: APA91bHQIWguRXvpVrg7Xh1nOsUqqbephClS9KkuuFf0eg3fkfgjkmvi1o-0WaSwWWdWwqXw9e3X80OsZwdINr1ufBjEXQJ5om48lL6q8bH3Vrlaf5U11FbyzQdVvzGy-3QBqahc_nMh9FeiL2sBzU0KPGG3y9xtYg
[INFO com.bipper.services.gcm.GcmSenderService] Sent message to one device: [ messageId=0:1349650679774901%d3cfcce76e2555b5 ]
[INFO com.bipper.services.gcm.GcmSenderService] registrationId: APA91bE9Vl_qijVdpFTqlJXA2OHyaF2cjKaCi8ZvNrD5r2woNs_TSuJgVuxn7RIF3pef6vdtd2MMV1TrWnusbGPXy4uWT4KJBhuAoAYgCjbXJduv-oz13_xICIKYOZTAFH2OpuC8E1Hw65KN6N4QukxG0W4Zor8jSg
[INFO com.bipper.services.gcm.GcmSenderService] Sent message to one device: [ messageId=0:1349650679857971%d3cfcce76e2555b5 ]
[INFO com.bipper.services.gcm.GcmSenderService] registrationId: APA91bEzQag9HBPbrR0wtaSuR3HA5NV795ZuDzxwQJVnQfc2r1lDv0gUXxc6GikUJDWMiUSge-b0BS1Tz2yIr8flpBqmAdpgQnatvP19PVm9zd8PopE51T-NJkfqqX65oPfKkx93Os7qS8_-IokjbyNIOK5FDCsrAQ
[INFO com.bipper.services.gcm.GcmSenderService] Sent message to one device: [ messageId=0:1349650679940798%d3cfcce76e2555b5 ]
[INFO com.bipper.services.gcm.GcmSenderService] registrationId: APA91bG_nVU-8VM9JSbTlxjAuseJ4LZG75BOoP5kd85garpcW698w4uwGWCy3dkUt3pXiXWhAV-KLPuEr-vw4_yARwjma2U46KXjmEoBwkTaVNi9t5M4sKRtqaKGZTcsaoa_Ng4EenVw41QFTi2At75946WR3Qu7jQ
[INFO com.bipper.services.gcm.GcmSenderService] Sent message to one device: [ messageId=0:1349650680044947%d3cfcce76e2555b5 ]
[WARN com.bipper.filters.PushUpdatesFilter] results has size 4, this is fishy
[INFO com.bipper.filters.PushUpdatesFilter] [ messageId=0:1349650679774901%d3cfcce76e2555b5 ]
[INFO com.bipper.filters.PushUpdatesFilter] [ messageId=0:1349650679857971%d3cfcce76e2555b5 ]
[INFO com.bipper.filters.PushUpdatesFilter] [ messageId=0:1349650679940798%d3cfcce76e2555b5 ]
[INFO com.bipper.filters.PushUpdatesFilter] [ messageId=0:1349650680044947%d3cfcce76e2555b5 ]
The documentation(link) says:
Canonical IDs
On the server side, as long as the application is behaving well,
everything should work normally. However, if a bug in the application
triggers multiple registrations for the same device, it can be hard to
reconcile state and you might end up with duplicate messages.
GCM provides a facility called "canonical registration IDs" to easily
recover from these situations. A canonical registration ID is defined
to be the ID of the last registration requested by your application.
This is the ID that the server should use when sending messages to the
device.
If later on you try to send a message using a different registration
ID, GCM will process the request as usual, but it will include the
canonical registration ID in the registration_id field of the
response. Make sure to replace the registration ID stored in your
server with this canonical ID, as eventually the ID you're using will
stop working.

Answer 1

When you parse the results from GCM, you have to manually check if it returns you a canonicalId.
String canonicalRegId = result.getCanonicalRegistrationId();
You then have to make sure this new id is used to push to the device.

Answer 2

As per Google docs,
When a plain-text request is successful (HTTP status code 200), the
response body contains 1 or 2 lines in the form of key/value pairs.
The first line is always available and its content is either id=ID of
sent message or Error=GCM error code. The second line, if available,
has the format of registration_id=canonical ID. The second line(containing canonical id) is
optional, and it can only be sent if the first line is not an error.
If there is a canonical id present, pgratton is right, you will have to parse the result and get it using result.getCanonicalRegistrationId();
Even after receiving a success response after pushing, canonical id can be null. In most cases, it will be null which means the token with which you pushed is OK and there is no need to replace it. When there is a change in the token (eg. in the case where Google refreshes the tokens) and if we still push with our old token, i guess you would then receive the canonical id in your response with which you must replace the old token.
If your push returns a failure response also, canonical id won't be present in the response.