geolocation-go

This repository contains a simple geolocation api microservice, fast, reliable, Kubernetes friendly and ready written in go as a proof of concept.

Motivations

Study the feasibility of having a geolocation REST API microservice running alongside our other microservices in Kubernetes to avoid relying on the Cloudfront-Viewer-Country http headers. The requirements are:

• Reliability
• Fast
• Concurrent

Design

geolocation-go is written in Go, a fery fast and performant garbaged collected and concurrent programming language.

It expose a simple GET /rest/v1/{ip} REST endpoint.

Parameter:

• /rest/v1/{ip} (string) - IPv4

Response:

• {"ip":"88.74.7.1","country_code":"DE","country_name":"Germany","city":"Düsseldorf","latitude":51.2217,"longitude":6.77616}

To retrieve the country code and country name of the given IP address, geolocation-go use the ip-api.com real-time Geolocation API, and then cache it in-memory and in Redis for later fast retrievals.

Flow

                                                                                          
                                                                                (2)
                                                                         +--------------> In-memory cache lookup
                                                                         |                       ^ 
                                                                         |                       *
                                              +------------------------+ |                       *
+-------------+            (1)                |                        | |                       * Update in-memory cache
|             |   GET /rest/v1/{ip}           |                        | |                       *
|             +------------------------------>|                        | |      (3)              v
|   Client    |                               |     geolocation-go     | +--------------> Redis lookup (optional)
|             |          (5)                  |                        | |                       ^ 
|             |<------------------------------+                        | |                       *
+-------------+       200 - OK                |                        | |                       * Update Redis cache
                                              +------------------------+ |                       *
                                                                         |                       *
                                                                         |      (4)              v
                                                                         +--------------> http://ip-api.com/json/{ip} lookup (optional)

1. Client make an HTTP request to /rest/v1/{ip}

2. geolocation-go will lookup for in his in-memory datastore and send the response if cache HIT. In case of cache MISS, go to step 3)

3. geolocation-go will lookup in Redis, send the response if cache HIT and add the response in his in-memory datastore asynchronously. In case of cache MISS, go to step 4)

4. geolocation-go will make an HTTP call to the ip-api.com API, send back the response to the client and add the response to Redis and the in-memory datastore asynchronously.

Configuration

geolocation-go is a 12-factor app using Viper as a configuration manager. It can read configuration from environment variables or from .env files.

Available variables

• APP_ADDR(default value: :8080). Define the TCP address for the server to listen on, in the form "host:port".

• APP_CONFIG_NAME (default value: .env). Name of the configuration file to read from.

• APP_CONFIG_PATH (default value: .). Directory containing the configuration file to read from.

• SERVER_READ_TIMEOUT (default value: 30s). Maximum duration for reading the entire request, including the body (ReadTimeout).

• SERVER_READ_HEADER_TIMEOUT (default value: 10s). Amount of time allowed to read request headers (ReadHeaderTimeout).

• SERVER_WRITE_TIMEOUT (default value: 30s). Maximum duration before timing out writes of the response (WriteTimeout).

• LOGGER_LOG_LEVEL (default value: info). Logger log level. Available values are "trace", "debug", "info", "warn", "error", "fatal", "panic" ref

• LOGGER_DURATION_FIELD_UNIT (default value: ms). Set the logger unit for time.Duration type fields. Available values are "ms", "millisecond", "s", "second".

• LOGGER_FORMAT (default value: json). Set the logger format. Available values are "json", "console".

• PROMETHEUS (default value: true). Enable publishing Prometheus metrics.

• PROMETHEUS_PATH (default value: /metrics). Metrics handler path.

• REDIS_CONNECTION_STRING (default value redis://localhost:6379). Connection string to connect to Redis. The format is the following: "redis://<user>:<pass>@<host>:<port>/<db>".

• REDIS_KEY_TTL (default 24h). TTL of a redis key: Time before the key saved in redis will expire.

• GEOLOCATION_API (default value ip-api). Define which geolocation API to use to retrieve geo IP information. Available options are:

  • ip-api
  • ipbase

• IP_API_BASE_URL (default value: http://ip-api.com/json/). Base URL for the ip-api API. Note that https is not available with the free plan.

• HTTP_CLIENT_TIMEOUT (default value: 15s). Timeout value for the http client.

• PPROF (default value: false). Enable the pprof server. When enable, pprof is available at http://127.0.0.1:6060/debug/pprof

Monitoring

geolocation-go provides Prometheus metrics and comes with a Grafana dashboard located in deploy/grafana/dashboard.json.

Installation with kube-prometheus-stack

Install kube-prometheus-stack in your Kubernetes cluster:

# Add helm repository
helm repo add prometheus-community https://prometheus-community.github.io/helm-charts
helm repo update

# Install the Prometheus operator and the kube-prometheus-stack
helm install \
       prometheus-operator \
       prometheus-community/kube-prometheus-stack \
       --create-namespace \
       --namespace monitoring

# Access the Grafana web interface through http://localhost:8080/ (default credentials: admin/prom-operator)
kubectl port-forward -n monitoring svc/prometheus-operator-grafana 8080:3000

To install the dashboard, go to "Menu" > "Create" > "Import" > "Upload json file" and upload deploy/grafana/dashboard.json.

Click to expand


TODO

• 404 and 405 custom handler

• Provide APM & tracing

• Provide a Swagger endpoint

• Support graceful shutdowns for interrupt signals (SIGTERM)