Schedule Snapshot Design

The scheduled snapshot feature will utilize the existing architecture of VMPR. In terms of functionality, scheduled snapshot is basically VMPR without its archiving capability.

Introduction

• Schedule snapshot will be a new object in xapi as VMSS.
• A pool can have multiple VMSS.
• Multiple VMs can be a part of VMSS but a VM cannot be a part of multiple VMSS.
• A VMSS takes VMs snapshot with type [snapshot, checkpoint, snapshot_with_quiesce].
• VMSS takes snapshot of VMs on configured intervals:
  • hourly -> On everyday, Each hour, Mins [0;15;30;45]
  • daily -> On everyday, Hour [0 to 23], Mins [0;15;30;45]
  • weekly -> Days [Monday,Tuesday,Wednesday,Thursday,Friday,Saturday,Sunday], Hour[0 to 23], Mins [0;15;30;45]
• VMSS will have a limit on retaining number of VM snapshots in range [1 to 10].

Datapath Design

• There will be a cron job for VMSS.
• VMSS plugin will go through all the scheduled snapshot policies in the pool and check if any of them are due.
• If a snapshot is due then : Go through all the VM objects in XAPI associated with this scheduled snapshot policy and create a new snapshot.
• If the snapshot operation fails, create a notification alert for the event and move to the next VM.
• Check if an older snapshot now needs to be deleted to comply with the retained snapshots defined in the scheduled policy.
• If we need to delete any existing snapshots, delete the oldest snapshot created via scheduled policy.
• Set the last-run timestamp in the scheduled policy.

Xapi Changes

There is a new record for VM Scheduled Snapshot with new fields.

New fields:

• name-label type String : Name label for VMSS.
• name-description type String : Name description for VMSS.
• enabled type Bool : Enable/Disable VMSS to take snapshot.
• type type Enum [snapshot; checkpoint; snapshot_with_quiesce] : Type of snapshot VMSS takes.
• retained-snapshots type Int64 : Number of snapshots limit for a VM, max limit is 10 and default is 7.
• frequency type Enum [hourly; daily; weekly] : Frequency of taking snapshot of VMs.
• schedule type Map(String,String) with (key, value) pair:
  • hour : 0 to 23
  • min : [0;15;30;45]
  • days : [Monday,Tuesday,Wednesday,Thursday,Friday,Saturday,Sunday]
• last-run-time type Date : DateTime of last execution of VMSS.
• VMs type VM refs : List of VMs part of VMSS.

New fields to VM record:

• scheduled-snapshot type VMSS ref : VM part of VMSS.
• is-vmss-snapshot type Bool : If snapshot created from VMSS.

New APIs

• vmss_snapshot_now (Ref vmss, Pool_Operater) -> String : This call executes the scheduled snapshot immediately.
• vmss_set_retained_snapshots (Ref vmss, Int value, Pool_Operater) -> unit : Set the value of vmss retained snapshots, max is 10.
• vmss_set_frequency (Ref vmss, String “value”, Pool_Operater) -> unit : Set the value of the vmss frequency field.
• vmss_set_type (Ref vmss, String “value”, Pool_Operater) -> unit : Set the snapshot type of the vmss type field.
• vmss_set_scheduled (Ref vmss, Map(String,String) “value”, Pool_Operater) -> unit : Set the vmss scheduled to take snapshot.
• vmss_add_to_schedule (Ref vmss, String “key”, String “value”, Pool_Operater) -> unit : Add key value pair to VMSS schedule.
• vmss_remove_from_schedule (Ref vmss, String “key”, Pool_Operater) -> unit : Remove key from VMSS schedule.
• vmss_set_last_run_time (Ref vmss, DateTime “value”, Local_Root) -> unit : Set the last run time for VMSS.
• task_set_status (Ref task, status_type “value”, READ_ONLY) -> unit : Set the status of task owned by same user, Pool_Operator can set status for any tasks.

New CLIs

• vmss-create (required : “name-label”;“type”;“frequency”, optional : “name-description”;“enabled”;“schedule:”;“retained-snapshots”) -> unit : Creates VM scheduled snapshot.
• vmss-destroy (required : uuid) -> unit : Destroys a VM scheduled snapshot.