Update README.md. Add cron documentation

README.md

@@ -46,6 +46,62 @@ The `pages/api` directory is mapped to `/api/*`. Files in this directory are tre
 
 This project uses [`next/font`](https://nextjs.org/docs/basic-features/font-optimization) to automatically optimize and load Inter, a custom Google Font.
 
+## Cron Job for API Call in Docker Container
+### Overview
+
+This project contains a cron job that periodically calls an API to update validator details. The cron job is implemented in a Docker container and is scheduled to run every 5 minutes. Below is a detailed explanation of the setup.
+### Cron Job Setup
+
+The cron job is defined in the crontab file and is scheduled to run every 5 minutes:
+
+```bash
+*/5 * * * * /validator_dapp/callApi.sh 2>> /validator_dapp/logg.log
+```
+
+This command executes the callApi.sh script, which triggers a Node.js script that sends a POST request to the validator update API. Any errors encountered during execution are logged into logg.log.
+### Dockerfile Setup
+
+The cron job is copied into the Docker container using the following command in the Dockerfile.
+
+```bash
+COPY crontab /etc/crontabs/root
+```
+
+This ensures that the cron job is configured when the Docker container is built.
+### API Call Script
+
+The cron job executes a shell script (callApi.sh) which triggers the following Node.js code to make a POST request to the specified API endpoint.
+
+```javascript
+process.env.NODE_TLS_REJECT_UNAUTHORIZED = '0';
+
+const axios = require('axios');
+
+
+const callApi = async () => {
+
+    try {
+
+        const response = await axios.post('https://bloxberg-qa-traefik.mpdl.mpg.de/api/update-validators-details');
+
+        console.log('API called successfully:', response.data);
+
+    } catch (error) {
+
+        console.log('Error calling API:', error);
+
+    }
+
+};
+
+
+callApi();
+```
+
+### Note: SSL certificate verification is disabled for testing purposes by setting process.env.NODE_TLS_REJECT_UNAUTHORIZED = '0'. This should be removed in production.
+
+
+
 ## Learn More
 
 To learn more about Next.js, take a look at the following resources: