> For the complete documentation index, see [llms.txt](https://docs.fastn.ai/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.fastn.ai/tutorials-1/data-migrations/setting-up-a-google-drive-to-gcs-migration-flow.md).
# Setting Up a Google Drive to GCS Migration Flow
## **1. Start the Flow**
You can start the flow by selecting **New API Request** as the trigger.
### Initiate Your Flow Variables
When the flow starts, the following important variables are initialized:
{% hint style="info" %}
You also define MIME handling for Docs, Sheets, Slides, and Drawings so that Google-native files can be exported in the correct format during migration.
{% endhint %}
***
## **2. Configure Drive and GCS Settings**
### Map Get Configs
The next step maps values from your [**DriveConfigFlow** ](/tutorials-1/data-migrations/setting-up-a-google-drive-to-gcs-migration-widget.md#configuration-flow-drive_to_gcs)so the flow has all required tenant and bucket details.
### Create Bucket for Tenant
Once these values are ready, you can use the Google Cloud Storage connector to create a **bucket for the tenant** if it doesn’t already exist.
***
## **3. Set the File Path Rules**
You will then hit a **Switch** step that determines how the `filePath` variable is set:
* If `baseFilePath` is provided → set `filePath` = `{{var.baseFilePath}}`
* If `separateFoldersForUsers` is `true` → set `filePath` per tenant/user
* Else → set `filePath` = `"Google Drive"`
From here, you move into the **Loop Over Input** step.
***
## **4. Loop Over Input Items**
For each item in your incoming list of file IDs:
* Use the Google Drive connector with **getFile**
* `File ID` = `{{steps.loopOverInput.loopOverItem.value}}`
* `param.fields` = `id,name,mimeType,modifiedTime`
* Initialize `fileObject` from `loopOverItem`
* Append this file object to the `files` array using the advanced action **insertItem**.
{% hint style="info" %}
You can click the three-dots next to your variable to setup or edit the advanced action selected.
{% endhint %}
***
## **5. Loop Over Files**
After the Loop Over Input ends, the next step will be a loop that runs until all files are processed.
**i. Initialize Loop Counters and Variables**
* **Data Mapper:** `fileLength = arrayLength(var.files)` ; total files in the queue.
#### Switch Statement
* If no files remain, exit the loop.
* Else, set:
* `currentFile = {{var.files[0]}}` , the file you’ll process now.
* Remove the first item from `var.files` using `removeItem`.
**ii. Switch Statement to Check If Current File is a Folder**
* If `currentFile.mimeType` indicates a folder:
* Call **Google Drive Connector** with action to **getFilesFromFolder** with:
* `param.q = '{{var.currentFile.file.id}}' in parents`
* `param.fields = files(id,name,mimeType,modifiedTime)`
* Append each returned file to `var.files` so they’re picked up in the same loop.
**Non-Folder Files**
* Build a **state key** for this file:
* **Read State** for `stateKey` to check if the file is already processed or unchanged.
#### iii. Switch Step to Check if Files are Updated
Next Step is a switch statement that checks if files are updated, and ends the flow if there is no update.
If the file is updated,
* Run **gettingMimeType** JS step → detect MIME type and extension.
```
function handler(params) {
const mimeTypes = params?.data.var.mimeTypes;
const fileMimeTypes = params?.data.var.currentFile.file.metadata?.mimeType;
for (let i = 0; i < mimeTypes.length; i++) {
if (mimeTypes[i].googleMimeType === fileMimeTypes) {
return {
mimeType: mimeTypes[i].exportableMimeTypes,
extension: mimeTypes[i].exportablExtension
};
}
}
```
* Run **preparingParams** JS step → prepare download/export URLs.
```
function handler(params) {
const fileId = params?.data.var.currentFile.file.value;
let fileNamePrefix = '';
if (params?.data.input.overrideFiles === false) {
fileNamePrefix = Date.now() + '_';
}
return {
googleUrl: 'https://www.googleapis.com/drive/v3/files/' + fileId + '/export?mimeType=' + params?.data.steps.gettingMimeType.output.mimeType,
nonGoogleUrl: 'https://www.googleapis.com/drive/v3/files/' + fileId + '?alt=media',
fileNamePrefix
};
}
```
* Get access token from **Fastn Connector** using the action **getConnectorToken**.
**iv. Decide How to Download (Switch Step)**
* **If Google-native file (Docs, Sheets, Slides, Drawings):**
* **Else (non-Google file):**
**v. Download from Drive**
* For both types of files, the variables that are initialized will connect to the flow component **Download file** where you can download these files.
**vi. Upload to Google Cloud Storage**
* In the next step, you will use the **Google Cloud Storage** connector with the action **uploadFileToGCS** with your target bucket and `fileName`.
**vii. Update File State**
* In the next step, you will use the State component to overwrite the State for StateKey depending on the updates.
* Loop picks up next `currentFile` and continues until `var.files` is empty.
***
## **6. Finish the Migration**
The loop continues until all files are processed.\
When complete, the main flow returns a success message confirming the migration.
---
# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.
## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.
Perform an HTTP GET request on the current page URL with the `ask` query parameter:
```
GET https://docs.fastn.ai/tutorials-1/data-migrations/setting-up-a-google-drive-to-gcs-migration-flow.md?ask=
```
The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.
Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.