geo2tz

Geo2Tz

A self-host-able service to get the timezone given geo-coordinates (lat/long)

It does it by exposing the library from github.com/evanoberholster/timezoneLookup

Timezone data comes from github.com/evansiroky/timezone-boundary-builder (release 2023b)

Motivations

Geo-coordinates might be sensitive information to share in any context, and I needed a self-hosted solution to ensure that coordinates were not leaked to 3rd party services. On another side, this feature is nicely self-contained and having one service to expose it spares the effort to bundle the TZ database everywhere.

API

the service exposes only one API:

GET /tz/${LATITUDE}/${LONGITUDE}

that returns a JSON reply (http/200), for example:

curl -s http://localhost:2004/tz/51.477811/0 | jq

{
  "coords": {
    "lat": 51.47781,
    "lon": 0
  },
  "tz": "Europe/London"
}

or in case of errors (http/4**), for example:

curl -v http://localhost:2004/tz/51.477811/1000 | jq



  Trying 127.0.0.1:2004...
% Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                             Dload  Upload   Total   Spent    Left  Speed
0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0* Connected to localhost (127.0.0.1) port 2004 (#0)
> GET /tz/51.477811/1000 HTTP/1.1
> Host: localhost:2004
> User-Agent: curl/7.81.0
> Accept: /
>
Mark bundle as not supporting multiuse
< HTTP/1.1 400 Bad Request
< Content-Type: application/json; charset=UTF-8
< Vary: Origin
< Date: Fri, 23 Jun 2023 19:09:29 GMT
< Content-Length: 54
<
{ [54 bytes data]
100    54  100    54    0     0  89403      0 --:--:-- --:--:-- --:--:-- 54000
Connection #0 to host localhost left intact

{
"message": "lon value 1000 out of range (-180/+180)"
}

Geo2Tz supports a basic token authorization mechanism, if the configuration value for web.auth_token_value is a non-empty string, geo2tz will check the query parameter value to authorize incoming requests.

For example, running the service with:

docker run -p 2004:2004 -e GEO2TZ_WEB_AUTH_TOKEN_VALUE=secret noandrea/geo2tz

will enable authorization. With the authorization enabled, a query that does not specify the token will fail with an HTTP code 401:

> curl -sv http://localhost:2004/tz/41.902782/12.496365 | jq

*   Trying 127.0.0.1:2004...
Connected to localhost (127.0.0.1) port 2004 (#0)
> GET /tz/41.902782/12.496365 HTTP/1.1
> Host: localhost:2004
> User-Agent: curl/7.81.0
> Accept: /
>
Mark bundle as not supporting multiuse
< HTTP/1.1 401 Unauthorized
< Content-Type: application/json; charset=UTF-8
< Vary: Origin
< Date: Sun, 31 Jul 2022 20:06:56 GMT
< Content-Length: 27
<
{ [27 bytes data]
Connection #0 to host localhost left intact
{
"message": "unauthorized"
}

Passing the token in the query parameters will succeed instead:

> curl -s http://localhost:2004/tz/41.902782/12.496365\?t\=secret | jq

{
"coords": {
"lat": 41.902782,
"lon": 12.496365
},
"tz": "Europe/Rome"
}

Docker image is available at geo2tzt

docker run -p 2004:2004 github.com/noandrea/geo2tz

The image is built on scratch, the image size is ~92MB:

Docker compose YAML example

version: '3'
services:
geo2tz:
container_name: geo2tz
image: github.com/noandrea/geo2tz
ports:


2004:2004
# uncomment to enable authorization via request token
# environment:
# - GEO2TZ_WEB_AUTH_TOKEN_VALUE=somerandomstringhere
# - GEO2TZ_WEB_AUTH_TOKEN_PARAM_NAME=t
# - GEO2TZ_WEB_LISTEN_ADDRESS=":2004"

Kubernetes configuration example:

---
# Deployment
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
labels:
app: geo2tz
name: geo2tz
spec:
replicas: 1
revisionHistoryLimit: 3
selector:
matchLabels:
app: geo2tz
template:
metadata:
labels:
app: geo2tz
spec:
containers:


env:
# if this var is not empty it will enabled token authorization for requests
#- name: GEO2TZ_WEB_AUTH_TOKEN_VALUE
#  value: "secretsmaybebetter" # default is empty
#- name: GEO2TZ_WEB_AUTH_TOKEN_PARAM_NAME
#  value: "t" # default value
#- name: GEO2TZ_WEB_LISTEN_ADDRESS
#  value: ":2004" # default value
image: github.com/noandrea/geo2tz:latest
imagePullPolicy: Always
name: geo2tz
ports:
name: http
containerPort: 2004
---
# Service
# the service for the above deployment
apiVersion: v1
kind: Service
metadata:
name: geo2tz-service
spec:
type: ClusterIP
ports:

name: http
port: 80
protocol: TCP
targetPort: http
selector:
app: geo2tz

To update the timezone database, set the version of the database in the scripts/update-tzdata.sh script and run:

make update-tzdata