Add data lifcycle docs (apache#516)

docs/interacting/data-lifecycle.md

@@ -0,0 +1,102 @@
+# Data Lifecycle
+
+## [Measures](../concept/data-model.md#measures) and [Streams](../concept/data-model.md#streams)
+
+Due to the design of BanyanDB, the data in the `Measures and Streams` can not be deleted directly.
+The data will be deleted automatically based on the [Groups](../concept/data-model.md#groups) `TTL` setting.
+
+The TTL means the `time to live` of the data in the group. 
+Each group has an internal trigger which is triggered by writing events. If there is no further data, the expired data can’t get removed.
+
+For example, the following command will create a group with a TTL of 7 days:
+```shell
+bydbctl group create -f - <<EOF
+metadata:
+  name: sw_metric
+catalog: CATALOG_MEASURE
+resource_opts:
+  shard_num: 2
+  segment_interval:
+    unit: UNIT_DAY
+    num: 1
+  ttl:
+    unit: UNIT_DAY
+    num: 7
+EOF
+```
+The data in this group will keep 7 days.
+
+If you want to change the `TTL` of the data in this group to be 1 day, use the command:
+
+```shell
+bydbctl group update -f - <<EOF
+metadata:
+  name: sw_metric
+catalog: CATALOG_MEASURE
+resource_opts:
+  shard_num: 2
+  segment_interval:
+    unit: UNIT_DAY
+    num: 1
+  ttl:
+    unit: UNIT_DAY
+    num: 1
+EOF
+```
+
+More ttl units can be found in the [IntervalRule.Unit](../api-reference.md#intervalruleunit).
+
+You can also manage the Group by other clients such as [Web-UI](./web-ui/schema/group.md) or [Java-Client](java-client.md).
+
+## [Property](../concept/data-model.md#properties)
+
+`Property` data provides both [CRUD](./bydbctl/property.md) operations and TTL mechanism.
+
+The TTL field in a property is used to set the time to live of the property. The property will be deleted automatically after the TTL.
+It's a string in the format of "1h", "2m", "3s", "1500ms". It defaults to 0s, which means the property never expires.
+
+For example, the following command will create a property with a TTL of 1 hour:
+
+```shell
+bydbctl property apply -f - <<EOF
+metadata:
+  container:
+    group: sw
+    name: temp_data
+  id: General-Service
+tags:
+- key: state
+  value:
+    str:
+      value: "failed"
+ttl: "1h"
+EOF
+```
+
+"General-Service" will be dropped after 1 hour. If you want to extend the TTL, you could use the "keepalive" operation. The "lease_id" is returned in the apply response. 
+You can use get operation to get the property with the lease_id as well.
+
+```shell
+bydbctl property get -g sw -n temp_data --id General-Service
+```
+
+```yaml
+...
+lease_id: 7587880824757265022
+```
+
+The lease_id is used to keep the property alive. You can use keepalive operation to keep the property alive.
+When the keepalive operation is called, the property's TTL will be reset to the original value.
+
+```shell
+bydbctl property keepalive --lease_id 7587880824757265022
+```
+
+"General-Service" lives another 1 hour.
+
+You can also manage the Property by other clients such as [Web-UI](./web-ui/property.md) or [Java-Client](java-client.md).
+
+## The API reference 
+- [Group Registration Operations](../api-reference.md#groupregistryservice)
+- [ResourceOpts Definition](../api-reference.md#resourceopts)
+- [PropertyService v1](../api-reference.md#propertyservice)

docs/menu.yml

@@ -93,8 +93,8 @@ catalog:
             path: "/interacting/web-ui/property"
       - name: "Java Client"
         path: "/interacting/java-client"
-      - name: "Deleting Data"
-        path: "/interacting/deleting-data"
+      - name: "Data Lifecycle"
+        path: "/interacting/data-lifecycle"
   - name: "Operation and Maintenance"
     catalog:
       - name: "Configure BanyanDB"