Backup DB's on High Availability issue

Question

I have an issue with backing up the DB's from cluster server that have 2 nodes on him.
I have a Cluster server with High Availability (for Active/Active cluster) and I trying to take a full backup from him but it says that :
The selected backup type is not supported on a "Always on secondary replica"...
And sending me to Microsoft webpage :
http://go.microsoft.com/fwlink/?LinkId=208213 
Active Secondary's: Backup on Secondary Replicas.
All I want to do is to backup the primary node with Full Backup type on nightly basis and shrink the log file . (without un-synchronizing every day)
Thank you

Answer 1

Use copy_only for full backup on secondary.
Backup Types Supported on Secondary Replicas
BACKUP DATABASE supports only copy-only full backups of databases, files, or filegroups when
it is executed on secondary replicas. Note that copy-only backups do not impact the log chain or clear the differential bitmap.
Differential backups are not supported on secondary replicas.
BACKUP LOG supports only regular log backups (the COPY_ONLY option is not supported for log
backups on secondary replicas).
A consistent log chain is ensured across log backups taken on any of the replicas (primary or secondary), irrespective of their
availability mode (synchronous-commit or asynchronous-commit).
To back up a secondary database, a secondary replica must be able to communicate with the primary replica and must be SYNCHRONIZED or SYNCHRONIZING.
https://msdn.microsoft.com/en-us/library/hh245119.aspx