docs/vmanomaly: release 1.16.2 (#7188)

### Describe Your Changes

docs for `vmanomaly`, updated after release 1.16.2

### Checklist

The following checks are **mandatory**:

- [x] My change adheres [VictoriaMetrics contributing
guidelines](https://docs.victoriametrics.com/contributing/).

(cherry picked from commit b2e7b05918)

docs/anomaly-detection/CHANGELOG.md

@@ -11,6 +11,15 @@ aliases:
 ---
 Please find the changelog for VictoriaMetrics Anomaly Detection below.
 
+## v1.16.2
+Released: 2024-10-06
+- FEATURE: Added support for `multitenant` value in `tenant_id` arg to enable querying across multiple tenants in [VictoriaMetrics cluster](https://docs.victoriametrics.com/cluster-victoriametrics/) (option available from [v1.104.0](https://docs.victoriametrics.com/cluster-victoriametrics/#multitenancy-via-labels)):
+  - Applied when reading input data from `vmselect` via the [VmReader](https://docs.victoriametrics.com/anomaly-detection/components/reader#vm-reader).
+  - Applied when writing generated results through `vminsert` via the [VmWriter](https://docs.victoriametrics.com/anomaly-detection/components/writer#vm-writer).
+  - For more details, refer to the `tenant_id` arg description in the documentation of the mentioned components.
+
+- FIX: Resolved an issue with handling an empty `preset` value (e.g., `preset: ""`) that was preventing the [default helm chart](https://github.com/VictoriaMetrics/helm-charts/blob/7f5a2c00b14c2c088d7d8d8bcee7a440a5ff11c6/charts/victoria-metrics-anomaly/values.yaml#L139) from being deployed.
+
 ## v1.16.1
 Released: 2024-10-02
 - FIX: This patch release prevents the service from crashing by rolling back the version of a third-party dependency. Affected releases: [v1.16.0](#v1160).

docs/anomaly-detection/components/reader.md

@@ -131,10 +131,10 @@ Datasource URL address
 `tenant_id`
             </td>
             <td>
-`0:0`
+`0:0`, `multitenant`
             </td>
             <td>
-For VictoriaMetrics Cluster version only, tenants are identified by accountID or accountID:projectID. See VictoriaMetrics Cluster [multitenancy docs](https://docs.victoriametrics.com/cluster-victoriametrics/#multitenancy)
+For VictoriaMetrics Cluster version only, tenants are identified by `accountID` or `accountID:projectID`. Starting from [v1.16.2](https://docs.victoriametrics.com/anomaly-detection/changelog/#v1162), `multitenant` [endpoint](https://docs.victoriametrics.com/cluster-victoriametrics/?highlight=reads#multitenancy-via-labels) is supported, to execute queries over multiple [tenants](https://docs.victoriametrics.com/cluster-victoriametrics/#multitenancy). See VictoriaMetrics Cluster [multitenancy docs](https://docs.victoriametrics.com/cluster-victoriametrics/#multitenancy)
             </td>
         </tr>
         <tr>

docs/anomaly-detection/components/writer.md

@@ -60,11 +60,11 @@ Datasource URL address
             </td>
             <td>
 
-`0:0`
+`0:0`, `multitenant` (starting from [v1.16.2](https://docs.victoriametrics.com/anomaly-detection/changelog/#v1162))
             </td>
             <td>
 
-For VictoriaMetrics Cluster version only, tenants are identified by accountID or accountID:projectID. See VictoriaMetrics Cluster [multitenancy docs](https://docs.victoriametrics.com/cluster-victoriametrics/#multitenancy)
+For VictoriaMetrics Cluster version only, tenants are identified by `accountID` or `accountID:projectID`. Starting from [v1.16.2](https://docs.victoriametrics.com/anomaly-detection/changelog/#v1162), `multitenant` [endpoint](https://docs.victoriametrics.com/cluster-victoriametrics/?highlight=writes#multitenancy-via-labels) is supported, to write data to multiple [tenants](https://docs.victoriametrics.com/cluster-victoriametrics/#multitenancy). See VictoriaMetrics Cluster [multitenancy docs](https://docs.victoriametrics.com/cluster-victoriametrics/#multitenancy)
             </td>
         </tr>
         <!-- Additional rows for metric_format -->
@@ -240,6 +240,40 @@ writer:
   password: "bar"
 ```
 
+### Multitenancy support
+
+### Multitenancy Support
+
+> This feature applies to the VictoriaMetrics Cluster version only. Tenants are identified by either `accountID` or `accountID:projectID`. Starting with [v1.16.2](https://docs.victoriametrics.com/anomaly-detection/changelog/#v1162), the `multitenant` [endpoint](https://docs.victoriametrics.com/cluster-victoriametrics/?highlight=writes#multitenancy-via-labels) is supported for writing data across multiple [tenants](https://docs.victoriametrics.com/cluster-victoriametrics/#multitenancy). For more details, refer to the VictoriaMetrics Cluster [multitenancy documentation](https://docs.victoriametrics.com/cluster-victoriametrics/#multitenancy).
+
+Please note the different behaviors depending on the `tenant_id` value:
+
+1. **When `writer.tenant_id != 'multitenant'` (e.g., `"0:0"`) and `reader.tenant_id != 'multitenant'` (can be different but valid, like `"0:1")**:
+   - The `vm_account_id` label is **not created** in the reader, **not persisted** to the writer, and is **not expected** in the output.
+   - **Result**: Data is written successfully with no logs or errors.
+
+2. **When `writer.tenant_id = 'multitenant'` and `vm_project_id` is present in the label set**:
+   - This typically happens when `reader.tenant_id` is also set to `multitenant`, meaning the `vm_account_id` label is stored in the results returned from the queries.
+   - **Result**: Everything functions as expected. Data is written successfully with no logs or errors.
+
+3. **When `writer.tenant_id = 'multitenant'` but `vm_account_id` is missing** (e.g., due to aggregation in the reader or missing `keep_metric_names` in the query):
+   - **Result**: The data is still written to `"0:0"`, but a warning is raised:
+    ```
+    The label `vm_account_id` was not found in the label set of {query_result.key}, 
+    but tenant_id='multitenant' is set in writer. The data will be written to the default tenant 0:0. 
+    Ensure that the query retains the necessary multi-tenant labels, 
+    or adjust the aggregation settings to preserve `vm_account_id` key in the label set.
+    ```
+
+4. **When `writer.tenant_id != 'multitenant'` (e.g., `"0:0"`) and `vm_account_id` exists in the label set**:
+   - **Result**: Writing is allowed, but a warning is raised:
+    ```
+    The label set for the metric {query_result.key} contains multi-tenancy labels, 
+    but the write endpoint is configured for single-tenant mode (tenant_id != 'multitenant'). 
+    Either adjust the query in the reader to avoid multi-tenancy labels 
+    or ensure that reserved key `vm_account_id` is not explicitly set for single-tenant environments.
+    ```
+
 ### Healthcheck metrics
 
 `VmWriter` exposes [several healthchecks metrics](https://docs.victoriametrics.com/anomaly-detection/components/monitoring/#writer-behaviour-metrics).