Merge pull request #185 from sharady/schedule-snapshot-design

CP-15502: Schedule Snapshot Design

Author: johnelse

xapi/design/schedule-snapshot.md

@@ -0,0 +1,77 @@
+---
+title: Schedule Snapshot Design
+layout: default
+design_doc: true
+revision: 1
+status: proposed
+---
+
+The scheduled snapshot feature will utilize the existing architecture of VMPR. In terms of functionality, schedule 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 and each VMSS will be configured to take snapshot of type disk, checkpoint or quiesce for the VMs as part of VMSS, on configured intervals.
+
+Datapath Design
+---------------
+
+* There will be a cron job for VMSS.
+* VMSS plugin will go through all the schedule 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 schedule 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.
+* Flag the snapshot to have been created by the schedule service, using either other-config for the VM object or another parameter added for this purpose.
+* Check if an older snapshot now needs to be deleted to comply with the retention value defined in the schedule policy.
+* If we need to delete any existing snapshots, delete the oldest snapshot created via schedule policy.
+* Set the last-run timestamp in the schedule 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.
+* "is-schedule-snapshot-enabled" type Bool : Enable/Disable VMSS to take snapshot.
+* "schedule-snapshot-type" type [DiskSnapshot; Checkpoint; Quiesce] : Type of snapshot policy takes.
+* "schedule-snapshot-retention-value" type Int64 : Number of snapshots limit for a VM, max limit is 10.
+* "schedule-snapshot-frequency" type [hourly; daily; weekly] : Frequency of taking snapshot of VMs.
+* "snapshot-schedule" type (hour: DateTime, min: DateTime, days: string list) : Time Hour, Min of interval  of 15mins and Days of a week. 
+* "is-schedule-snapshot-running" type Bool : If VMSS is in progress of taking snapshot.
+* "schedule-snapshot-last-run-time" type Date : DateTime of last execution of VMSS.
+* "is-alarm-enabled" type Bool : Alarm enable/disable for VMSS.
+* "alarm-config" : type (is_alarm_enabled,["email_address", ((String), "");"smtp_server", ((String), "");"smtp_port", ((IntRange(1,65535)), "25")] : Sets the alarm config field for VMSS.
+* "VMs" type VM refs : List of VMs part of VMSS.
+
+New fields to VM record:
+
+* "schedule-snapshot" type VMSS ref : VM part of VMSS.
+* "is-snapshot-from-vmss" type Bool : If snapshot created from VMSS.
+
+New APIs
+--------
+
+* vmss_snapshot_now (Ref vmss, Pool_Operater) -> String : This call executes the schedule snapshot immediately.
+* vmss_create_alert (Ref _vmss, String "name", Int "priority", String "body", String "data", Local_Root) -> unit : This call creates an alert for schedule snapshot.
+* vmss_get_alerts (Ref vmss, Int "hours_from_now", Pool_Operater) -> Set String : This call fetches a history of alerts for a given schedule snapshot
+* vmss_set_snapshot_retention_value (Ref vmss, Int value, Pool_Operater) -> unit : Set the value of the_schedule_snapshot_retention value max is 10.
+* vmss_set_is_schedule_snapshot_running (Ref vmss, Bool value, Local_Root) -> unit : Set the value of the is_schedule_snapshot_running field
+* vmss_set_snapshot_frequency (Ref vmss, String "value", Pool_Operater) -> unit : Set the value of the snapshot_frequency field
+* vmss_set_snapshot_schedule (Ref vmss, Map(String,String) "value", Pool_Operater) -> unit : Set the schedule to take snapshot.
+* vmss_set_is_alarm_enabled (Ref vmss, Bool "value", Pool_Operater) -> unit : Set the value of the is_alarm_enabled field
+* vmss_set_alarm_config (Ref vmss, Map(String,String) "value", Pool_Operater) -> unit : Set the alarm_config
+* vmss_add_to_snapshot_schedule (Ref vmss, String "key", String "value", Pool_Operater) -> unit : Add key value pair to VMSS
+* vmss_add_to_alarm_config (Ref vmss, String "key", String "value", Pool_Operater) -> unit : Add key value pair to alarm_config field.
+* vmss_remove_from_snapshot_schedule (Ref vmss, String "key", Pool_Operater) -> unit : Remove key from VMSS.
+* vmss_remove_from_alarm_config (Ref vmss, String "key", Pool_Operater) -> unit : Remove key from alarm_config field.
+* vmss_set_schedule_snapshot_last_run_time (Ref vmss, DateTime "value", Local_Root) -> unit : Set the last run time for VMSS.
+
+New CLIs
+--------
+
+* vmss-create (required : "name-label";"schedule-snapshot-type";"schedule-snapshot-frequency", optional : "name-description";"is-schedule-snapshot-enabled";"snapshot-schedule:";"snapshot-retention-value";"is-alarm-enabled";"alarm-config:") -> unit : Creates VM schedule snapshot.
+* vmss-destroy (required : uuid) -> unit : Destroys a VM schedule snapshot.
+