Google Calendar Bridge

Synchronizes Google Calendars, including those belonging to different domains. Useful for synchronizing resources (like shared meeting rooms).

Use at your own risk. Seriously. See LICENSE.

Installation

Install the requirements

Download the source. Run pip install -r requirements.txt . You may need to use sudo depending on the specifics of your python installation.

Create your API key

Go to https://console.developers.google.com/

Click Create Project. Pick a name. Wait for the project to be created.

It'll redirect you to the Library tab. Click the Calendar API and click Enable.

Click Go to Credentials (or click Credentials on the left-hand tab)

Click the blue Create Credentials button. In the dropdown, select OAuth Client ID.

In the "Application type" menu, select Other. Pick a name (it doesn't matter what you use).

It will display your client ID and client secret. Close out of this. It'll show a list of your active credentials. Next to the credential you created (on the right), click the download arrow. It'll download a JSON file. Save this in your project directory or somewhere else and make a note of the file path.

Find the calendar IDs you want to sync, or create them

Calendars you want to sync must exist already (this service will not create them). You'll need the calendar ID for each. Find the calendar under My Calendars on the left side of Google Calendar's web UI, hover over it, click the dropdown arrow, and select "Calendar settings". Next to Calendar Address you'll see a line that includes (Calendar ID: foo@bar.com) or similar. Copy each calendar ID, and make a note of the domain it came from. Calendar resources (like meeting rooms) have IDs like foo.com_2213232373144913933307@resource.calendar.google.com.

Here's an example config syncing between two calendars

{
  "client_id_file": "client_id.json",
  "scopes": "https://www.googleapis.com/auth/calendar",
  "poll_time": 60,
  "max_exceptions": 5,
  "domains": {
    "bar.com": {
      "account": "user@bar.com"
    },
    "foo.com": {
      "account": "user@foo.com"
    }
  },
  "calendars": {
    "bob-office": {
      "calendars": [
        {
          "url": "foo.com_12345678900987654321@resource.calendar.google.com",
          "domain": "foo.com"
        },
        {
          "url": "bar.com_11111111111111111111@resource.calendar.google.com",
          "domain": "bar.com"
        }
      ]
    },
    "bob-conference-room": {
      "calendars": [
        {
          "url": "foo.com_22222222222222222222@resource.calendar.google.com",
          "domain": "foo.com"
        },
        {
          "url": "bar.com_33333333333333333333@resource.calendar.google.com",
          "domain": "bar.com"
        }
      ]
    }

  }
}

Parameter	Meaning
client_id_file	Path to a client ID file, as described above.
scopes	Scopes to authorize. Should stay at the default unless you know otherwise.
poll_time	Time to wait between syncs. Automatically increases if ratelimit is hit.
max_exceptions	Maximum number of times to retry when an error occurs.

Run sync.py

The first time you run sync.py, it will prompt you to authorize the app and download credentials for each domain.

$ ./sync.py
Go to this URL:
https://accounts.google.com/long/link/goes/here
authorize the app, and enter the code here:
Code:

Going to this URL will prompt you to sign in (as the user specified in the "account" parameter for each domain) and grant read/write permission on calendars. The system will save your credentials. If you want them saved in a particular location, you can specify the credfile parameter:

"domains": {
  "bar.com": {
    "account": "user@bar.com",
    "credfile": "/path/to/creds_user@bar.com.json"
  }

The system will then begin syncing your accounts.

Increase your quota

You might run into userRateLimitExceeded errors if you have a lot of events. The system is designed to use exponential backoff to avoid this problem, but this may cause your calendars to take a while to sync if you have lots of events. To get around this, go to the Google Developer Console quota page (make sure your project is selected in the top dropdown if you have more than one) and click the edit links (pencil-shaped) next to "requests per day" and "requests per 100 seconds per user" to increase your quotas.