Which Calendar ID to use in Google Calendar API? - go

Question

I currently retrieve my organization (family) Google Calendars via the Google Calendar API, using Python.
For reference, the credentials file used in both cases is ((...) is redacted information)
{
"type": "service_account",
"project_id": "da(...)",
"private_key_id": "8(...)4",
"private_key": "-----BEGIN PRIVATE KEY-----\nMIIEvAI(...)Kag==\n-----END PRIVATE KEY-----\n",
"client_email": "da(...)#(...).iam.gserviceaccount.com",
"client_id": "1(...)9",
"auth_uri": "https://accounts.google.com/o/oauth2/auth",
"token_uri": "https://oauth2.googleapis.com/token",
"auth_provider_x509_cert_url": "https://www.googleapis.com/oauth2/v1/certs",
"client_x509_cert_url": "https://www.googleapis.com/robot/v1/metadata/x509/da(...)iam.gserviceaccount.com"
}
I would like to port this to Go. To do so, I used the following code (partly copied from the documentation)
package main
import (
"context"
"fmt"
"time"
log "github.com/sirupsen/logrus"
"google.golang.org/api/calendar/v3"
"google.golang.org/api/option"
)
func googlecalendar() (err error) {
ctx := context.Background()
calendarService, err := calendar.NewService(ctx, option.WithCredentialsFile("googlecalendar.json"))
if err != nil {
return err
}
t := time.Now().Format(time.RFC3339)
events, err := calendarService.Events.List("john#example.com").ShowDeleted(false).
SingleEvents(true).TimeMin(t).MaxResults(10).OrderBy("startTime").Do()
if err != nil {
log.Fatalf("Unable to retrieve next ten of the user's events: %v", err)
}
fmt.Println("Upcoming events:")
if len(events.Items) == 0 {
fmt.Println("No upcoming events found.")
} else {
for _, item := range events.Items {
date := item.Start.DateTime
if date == "" {
date = item.Start.Date
}
fmt.Printf("%v (%v)\n", item.Summary, date)
}
}
return nil
}
In the code above john#example.com is the "Calendar ID" provided in Google Calendar (the actual ID is used in the code of course). This outputs the error
time="2021-05-05T11:39:12+02:00" level=fatal msg="Unable to retrieve next ten of the user's events: googleapi: Error 404: Not Found, notFound"
My understanding is that this means that john#example.com was not recognized. Why?
When instead of john#example.com I use primary (as in the docs), the code runs correctly and outputs
Upcoming events:
No upcoming events found.
This means that the whole authentication part seems to work (using the same JSON credentials as in Python, retrieved from the console) - it is just that the reference to the calendar is not correct. How to fix this?
Following a request in comments, below is the general Python code (that works).
import json
import logging.config
import os
import arrow
import googleapiclient.discovery
import paho.mqtt.publish
from google.oauth2 import service_account as google_oauth2_service_account
# setup logging
logging.config.dictConfig({
'formatters': {
'standard': {
'format': "%(asctime)s [%(module)s] %(levelname)s %(message)s"
},
},
'handlers': {
'default': {
'formatter': 'standard',
'class': 'logging.StreamHandler',
},
},
'loggers': {
'': { # root logger
'handlers': ['default'],
'level': logging.ERROR,
'propagate': False
},
'googlecalendar': {
'handlers': ['default'],
'level': logging.DEBUG if os.environ.get('DEBUG', '').lower() == 'true' else logging.INFO,
'propagate': False
},
},
"disable_existing_loggers": True,
"version": 1,
})
log = logging.getLogger('googlecalendar')
def getevents(calendar=None, google_service =None):
now = arrow.now()
try:
events_result = google_service.events().list(
calendarId=calendar,
timeMin=now.shift(days=0).isoformat(),
timeMax=now.shift(days=+7).isoformat(),
singleEvents=True,
orderBy='startTime'
).execute()
except Exception as e:
log.error(f"error connecting to google for {calendar}: {e}")
return
# transform events and send out
events = []
if events_result.get('items'):
# remove multiday items (no strat or end date)
for i in events_result['items']:
# try to extract the data, some are not available so the event is not interesing (multiday, ...)
try:
events.append({
'start': arrow.get(i['start']['dateTime']).isoformat(),
'end': arrow.get(i['end']['dateTime']).isoformat(),
'timestamp': arrow.get(i['start']['dateTime']).timestamp,
'name': i['summary'],
'id': i['id'],
'important': True if i.get('colorId') else False
})
except KeyError:
pass
# send the data to MQTT
# (...)
log.debug(f"{calendar}: {events}")
google_credentials = google_oauth2_service_account.Credentials.from_service_account_info(
{
"type": "service_account",
"project_id": "da(...)",
"private_key_id": "8(...)4",
"private_key": "-----BEGIN PRIVATE KEY-----\nMIIEvAI(...)Kag==\n-----END PRIVATE KEY-----\n",
"client_email": "da(...)#(...).iam.gserviceaccount.com",
"client_id": "1(...)9",
"auth_uri": "https://accounts.google.com/o/oauth2/auth",
"token_uri": "https://oauth2.googleapis.com/token",
"auth_provider_x509_cert_url": "https://www.googleapis.com/oauth2/v1/certs",
"client_x509_cert_url": "https://www.googleapis.com/robot/v1/metadata/x509/da(...)iam.gserviceaccount.com"
},
scopes=['https://www.googleapis.com/auth/calendar'],
subject='john#example.com'
)
google_service = googleapiclient.discovery.build('calendar', 'v3', credentials=google_credentials, cache_discovery=False)
for calendar in [
"john#example.com",
"mary#example.net",
"something_idsd#group.calendar.google.com",
]:
getevents(calendar=calendar, google_service=google_service)

Answer 1

Answer
The result you are getting is normal, the problem is that you are not performing Domain-Wide Delegation correctly. I come to this conclusion because of the following scenarios:
Calendar Id: john#example.com. If the service account has not impressed the user, it is expected that the user's calendar will not be found.
Calendar Id: primary. If the primary calendar of the service account does not have any events, it is expected that the list method does not return any results.
Solution
Comparing your code with the one in the documentation, I don't see where you place config.Subject = userEmail, as #DalmTo says. Try the following code to create the calendar service:
ctx := context.Background()
jsonCredentials, err := ioutil.ReadFile("googlecalendar.json")
if err != nil {
return nil, err
}
config, err := google.JWTConfigFromJSON(jsonCredentials, "https://www.googleapis.com/auth/calendar")
if err != nil {
return nil, fmt.Errorf("JWTConfigFromJSON: %v", err)
}
config.Subject = "john#example.com"
ts := config.TokenSource(ctx)
calendarService, err := calendar.NewService(ctx, option.WithTokenSource(ts))
References:
Domain-Wide Delegation