## POST /api/v2/placement-groups/{id}/members

**Add a VPS to a placement group**

Add a VPS to Group A, B, or C inside the placement group. VPS in different groups are kept on separate hardware.

### Related Endpoints

- `DELETE /api/v2/placement-groups/{id}/members/{vpsId}`: Remove a VPS from a placement group
- `GET /api/v2/placement-groups/{id}`: Get VPS placement group detail
- `PATCH /api/v2/placement-groups/{id}`: Rename a VPS placement group

### Headers

- `Accept`: application/json
- `Authorization`: Bearer YOUR_API_KEY
- Required API scope: `write:vm`
- `Content-Type`: application/json

### Parameters

- `id` (path, string, required): Placement group public ID. Do not invent this value; use the exact ID returned by the referenced API response. Example: `pg_01hxa3b4c5d6e7f8g9h0j1k2m3`

### Request Body

- `vpsId` (string, required): VPS public ID from `GET /api/v2/placement-groups/candidates` or `GET /api/v2/vps`. Example: `vps_01hxa3b4c5d6e7f8g9h0j1k2m3`
- `placementSet` (string, optional): Customer-defined member group. VPS in different groups are kept on separate hardware. Defaults to `a`. Example: `a`
  Allowed values: a, b, c

### Request Example

```bash
curl -X POST "https://cloud.hostup.se/api/v2/placement-groups/pg_01hxa3b4c5d6e7f8g9h0j1k2m3/members" \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Accept: application/json" \
  -H "Content-Type: application/json" \
  -d '{
    "vpsId": "vps_01hxa3b4c5d6e7f8g9h0j1k2m3",
    "placementSet": "a"
  }'
```

```json
{
  "vpsId": "vps_01hxa3b4c5d6e7f8g9h0j1k2m3",
  "placementSet": "a"
}
```

### Response Schema

- `id` (string, required) Example: `pg_01hxa3b4c5d6e7f8g9h0j1k2m3`
- `name` (string, required) Example: `Production database`
- `policy` (string, required) Example: `spread`
  Allowed values: spread
- `health` (string, required) Example: `ok`
  Allowed values: ok, reconciling, violation
- `needsAttention` (boolean, required) Example: `false`
- `compatibilityKey` (string, required, nullable): Nullable (may be null when not applicable). Example: `pgcmp_9f6a3b2c1d0e8a7b`
- `members` (array<object>, required)
- `members[].vpsId` (string, required) Example: `vps_01hxa3b4c5d6e7f8g9h0j1k2m3`
- `members[].name` (string, required) Example: `db-primary`
- `members[].instanceUrl` (string, required) Example: `/instance/vps_01hxa3b4c5d6e7f8g9h0j1k2m3`
- `members[].placementSet` (string, required) Example: `a`
  Allowed values: a, b, c
- `members[].status` (string, required) Example: `placed`
  Allowed values: placed, migrating, colocated, unknown
- `members[].addedAt` (string, required) Example: `2026-06-28T10:02:00.000Z`
- `actions` (object, required)
- `actions.canRename` (object, required)
- `actions.canRename.allowed` (boolean, required) Example: `true`
- `actions.canRename.reason` (string, required, nullable): Nullable (may be null when not applicable). Example: `null`
- `actions.canDelete` (object, required)
- `actions.canDelete.allowed` (boolean, required) Example: `true`
- `actions.canDelete.reason` (string, required, nullable): Nullable (may be null when not applicable). Example: `null`
- `actions.canAddMember` (object, required)
- `actions.canAddMember.allowed` (boolean, required) Example: `true`
- `actions.canAddMember.reason` (string, required, nullable): Nullable (may be null when not applicable). Example: `null`
- `actions.canResolve` (object, required)
- `actions.canResolve.allowed` (boolean, required) Example: `false`
- `actions.canResolve.reason` (string, required, nullable): Why the resolve action is unavailable: `not_needed` when the group has no issue a restart can fix, `no_restart_target` when no suitable separate hardware is available right now. `null` when `allowed` is `true`. Example: `not_needed`
  Allowed values: not_needed, no_restart_target
- `createdAt` (string, required) Example: `2026-06-28T10:00:00.000Z`
- `updatedAt` (string, required) Example: `2026-06-28T10:05:00.000Z`

### Responses

#### 201 - Updated placement group detail.
```json
{
  "id": "pg_01hxa3b4c5d6e7f8g9h0j1k2m3",
  "name": "Production database",
  "policy": "spread",
  "health": "ok",
  "needsAttention": false,
  "compatibilityKey": "pgcmp_9f6a3b2c1d0e8a7b",
  "members": [
    {
      "vpsId": "vps_01hxa3b4c5d6e7f8g9h0j1k2m3",
      "name": "db-primary",
      "instanceUrl": "/instance/vps_01hxa3b4c5d6e7f8g9h0j1k2m3",
      "placementSet": "a",
      "status": "placed",
      "addedAt": "2026-06-28T10:02:00.000Z"
    }
  ],
  "actions": {
    "canRename": {
      "allowed": true,
      "reason": null
    },
    "canDelete": {
      "allowed": true,
      "reason": null
    },
    "canAddMember": {
      "allowed": true,
      "reason": null
    },
    "canResolve": {
      "allowed": false,
      "reason": "not_needed"
    }
  },
  "createdAt": "2026-06-28T10:00:00.000Z",
  "updatedAt": "2026-06-28T10:05:00.000Z"
}
```

#### 400 - The request body was invalid. Known `code` values are `invalid_request` (missing/invalid `vpsId`, invalid `placementSet`, or unknown fields) and `not_a_vps` (the referenced service is not a VPS).
```json
{
  "type": "https://developer.hostup.se/errors/not_a_vps",
  "title": "VPS required",
  "status": 400,
  "detail": "Only VPS services can be added to a placement group.",
  "code": "not_a_vps",
  "instance": "/api/v2/placement-groups/pg_01hxa3b4c5d6e7f8g9h0j1k2m3/members",
  "requestId": "00000000-0000-0000-0000-000000000000",
  "timestamp": "2026-06-28T10:05:00.000Z",
  "errors": [
    {
      "pointer": "/vpsId",
      "detail": "Only VPS services can be added to a placement group.",
      "code": "not_a_vps"
    }
  ]
}
```

#### 401 - Unauthorized. Authentication is required.
```json
{
  "type": "https://developer.hostup.se/errors/unauthorized",
  "title": "Unauthorized",
  "status": 401,
  "detail": "Authentication is required.",
  "code": "unauthorized",
  "instance": "/api/v2/resource",
  "requestId": "req_01hxa3b4c5d6e7f8g9h0j1k2m3",
  "timestamp": "2026-04-27T12:34:56.000Z"
}
```

#### 403 - Forbidden. The caller lacks a required scope or does not own the resource.
```json
{
  "type": "https://developer.hostup.se/errors/forbidden",
  "title": "Forbidden",
  "status": 403,
  "detail": "The caller lacks a required scope or does not own the resource.",
  "code": "forbidden",
  "instance": "/api/v2/resource",
  "requestId": "req_01hxa3b4c5d6e7f8g9h0j1k2m3",
  "timestamp": "2026-04-27T12:34:56.000Z"
}
```

#### 404 - The placement group or VPS could not be found. Known `code` values are `placement_group_not_found` and `vps_not_found`.
```json
{
  "type": "https://developer.hostup.se/errors/vps_not_found",
  "title": "VPS not found",
  "status": 404,
  "detail": "The requested VPS could not be found.",
  "code": "vps_not_found",
  "instance": "/api/v2/placement-groups/pg_01hxa3b4c5d6e7f8g9h0j1k2m3/members",
  "requestId": "00000000-0000-0000-0000-000000000000",
  "timestamp": "2026-06-28T10:05:00.000Z"
}
```

#### 409 - The VPS cannot join this placement group. Known `code` values are `already_grouped`, `different_location`, and `server_not_eligible`.
```json
{
  "type": "https://developer.hostup.se/errors/server_not_eligible",
  "title": "Server unavailable",
  "status": 409,
  "detail": "This VPS cannot be added to a placement group right now.",
  "code": "server_not_eligible",
  "instance": "/api/v2/placement-groups/pg_01hxa3b4c5d6e7f8g9h0j1k2m3/members",
  "requestId": "00000000-0000-0000-0000-000000000000",
  "timestamp": "2026-06-28T10:05:00.000Z",
  "errors": [
    {
      "pointer": "/vpsId",
      "detail": "This VPS cannot be added to a placement group right now.",
      "code": "server_not_eligible"
    }
  ]
}
```

#### 429 - Rate limited. Retry after the limit resets. 429 responses include `Retry-After` seconds plus `X-RateLimit-*` headers.
```json
{
  "type": "https://developer.hostup.se/errors/rate_limit_exceeded",
  "title": "Too many requests",
  "status": 429,
  "detail": "Too many requests. Retry after the limit resets.",
  "code": "rate_limit_exceeded",
  "instance": "/api/v2/resource",
  "requestId": "req_01hxa3b4c5d6e7f8g9h0j1k2m3",
  "timestamp": "2026-04-27T12:34:56.000Z"
}
```

#### 500 - Internal error. Retry later or contact support if the issue persists.
```json
{
  "type": "https://developer.hostup.se/errors/internal_error",
  "title": "Internal server error",
  "status": 500,
  "detail": "An unexpected error occurred. Retry later or contact support if the issue persists.",
  "code": "internal_error",
  "instance": "/api/v2/resource",
  "requestId": "req_01hxa3b4c5d6e7f8g9h0j1k2m3",
  "timestamp": "2026-04-27T12:34:56.000Z"
}
```