# Networking and Load Balancer Service Engines

The Service Engines screens show service engine groups by type:

* **Networking** service engines that are deployed in the region.

  The Networking category includes networking service engines such as
  **DNS** related engines and the **NAT Gateway** service.
* **Load Balancer** service engines that are deployed in the region.

Each service engine type uses the same screen layout and has the same
functional controls.

The difference is the service engine group that you select from the left
navigation.

These screens can be used to review service engine entries, check version
and status information, and manage the enabled state for each listed
engine version.

## Service Engines management

Service engines are grouped by type and opened from the group icon in
the left navigation pane.

The **Service Engines** screens show the service engines that are deployed
in the region.

This screen helps an administrator to see which service engines are
present, which version each engine uses, whether a newer version is
available, whether the engine is enabled, and the current engine
status.

The **Service Engines** screens support these lifecycle
operations when they are available for the current engine state:

* Initialization
* Reset after an initialization failure
* Enable
* Disable
* Upgrade

The screen also shows the current state of each engine entry:

* **Engine**

  The service engine name.
* **Version**

  The current engine version.
* **Upgrade Available**

  The target version that is available for upgrade.
  It indicates whether there is a newer version that can be applied.

<!-- comment - hidden for the moment.
"Pool" is actually a bug (low priority but still).
It should be a volume type in VSC systems.
Removed/hidden until it will be fixed.

*  **Pool**

   The storage pool associated with the enabled engine version indicates
   where the active engine version is placed.

   When the version is disabled, this field can be empty. -->
* **Updated At**

  The date and time when the engine version entry was last updated.
* **Enabled**

  The toggle to enable or disable the service engine version.
* **Status**

  The current engine state, such as **Active** or **Disabled**, indicates
  whether the engine version is currently in service.
* **Filter**

  The list filter box in the upper-right area of the screen. Use this
  field to narrow the list when many engine entries are shown.

### Initializing a service

When the service is not initialized, the UI shows an initialization action
instead of the normal ready-state list workflow.

To initialize a service:

1. Select **Service Engines** and then the relevant type:
   **Networking** or **Load Balancer**.
2. Locate the initialization prompt for the service.
3. Select **Initialize**.
4. Wait for the service state to change from the initialization flow
   to the normal screen state.
5. Review the screen again and confirm that engine entries are listed.

### Resetting a service after a failed initialization

When the service is in an error state, the UI shows a reset action.

To initialize a service:

1. Select **Service Engines** and then the relevant type:
   **Networking** or **Load Balancer**.
2. Locate the failed initialization prompt for the service.
3. Select **Reset**.
4. Wait for the reset and initialization flow to complete.

#.  Review the screen again and confirm that the service returns to a
usable state.

### Enabling an engine version

To place an engine version into service:

1. Select **Service Engines** and then the relevant type:
   **Networking** or **Load Balancer**.
2. Find the engine row that you want to enable.
3. In the **Enabled** column, turn on the toggle.
4. Wait for the screen to refresh.
5. Confirm that **Status** shows an active state.

### Disabling an engine version

To remove an engine version from service:

1. Select **Service Engines** and then the relevant type:
   **Networking** or **Load Balancer**.
2. Find the engine row that you want to disable.
3. In **Enabled** column, turn off the toggle.
4. Wait for the screen to refresh.
5. Confirm that **Status** shows **Disabled**.

### Upgrading an engine version

The UI provides an upgrade action only when the engine version is
marked as upgradable.

To upgrade a service engine:

1. Select **Service Engines** and then the relevant type:
   **Networking** or **Load Balancer**.
2. Select the engine row that shows a value in **Upgrade Available**.
3. From the top toolbar, select **Upgrade** for the engine version.
4. In the confirmation dialog, review the engine name and version.
5. Confirm the upgrade.
6. Wait for the upgrade operation to finish.
7. Review the **Version**, **Upgrade Available**, and **Status** columns
   to confirm the new state.

## Recommended best practices

* Review the **Status** field before making a change.
* Review **Upgrade Available** before planning maintenance.
* Use the **Enabled** toggle only for the specific engine row you
  intend to change.
* After any change, refresh your review of **Version**,
  **Updated At**, and **Status**.
* Use **Filter** to reduce the risk of changing the wrong engine
  when the list grows.
* Do not treat **Pool** as a planning field for disabled entries,
  because the screen can show that field only for enabled versions.

## Troubleshooting

### An engine shows as Disabled

A disabled engine is not currently enabled for service.

1. Check the **Enabled** toggle for the row.
2. If needed, turn on the toggle.
3. Review **Status** again after the screen refreshes.

### No engine entries are listed

The service might not be initialized yet.

1. Check whether the screen shows an initialization prompt.
2. If it does, select **Initialize**.
3. Wait for the service to finish initialization.
4. Return to the screen and review the list again.

### Initialization failed

The service can enter an error state during initialization.

1. Check whether the screen shows a reset prompt.
2. Select **Reset**.
3. Wait for the service to return to a usable state.
4. Review the screen again.

### Upgrade is not available

The engine version might not be marked as upgradable.

1. Review the **Upgrade Available** field for the row.
2. If no upgrade value is shown, no upgrade is currently available
   from this screen.
3. Continue to monitor the screen for a future upgrade entry.

### Pool is empty

This can occur when the engine version is not enabled.

1. Check the **Enabled** toggle for the row.
2. Check the **Status** field.
3. If the version is disabled, expect **Pool** to be empty on this
   screen.