Spring boot.jar to digital ocean droplet (Linux Ubuntu):Web 服务器启动失败。 80 端口已被使用

Question

I have an Digitalocean Droplet (virtual private server) that has Ubuntu 18.04 running on it. I installed Apache Web Server and have my website running on it. It's open to traffic on HTTP port 80. My virtual host is setup at /var/www/MyDomainNameHere/public_html/ and I do have a custom domain name pointing to the IP.

I am trying to deploy/run a executable.jar that contains a Spring boot API. It has some basic GET/POST/DELETE HTTP requests. When I run the jar by

java -jar rest-service.jar

I get this error message

***************************
APPLICATION FAILED TO START
***************************

Description:

Web server failed to start. Port 80 was already in use.

Does this mean the Apache Web Server that is open to Traffic on port 80 on this Digital ocean droplet won't let me run the API jar on the same server (The JAR loads up an Apache Tomcat embedded server, I set it to port 80 based on research)? Do I need to buy another droplet? Or can I maybe change the port number for the spring boot jar to something other than port 80? It's an API, so I need to be able to hit the end points

Answer 1

Yes, Apache Web Server using the port and you change your spring application 80 to any other port and use the reverse proxy in Apache Web server. here is the link to configure the reverse proxy

Apache as a Reverse Proxy with mod_proxy

Answer 2

So I will answer my own question. I googled and searched stackoverflow but most people were using the reverse proxy to direct traffic to their standalone embedded Tomcat server (most of time a Spring Boot app) which wasn't applicable to my situation.

However, I already had a static html website at alpizano.me hosted on Digital Ocean that I wanted to use as my Front-end, and only forward certain HTTP requests to my Spring Boot app, which was a REST API essentially.

So after installing Java and PostgreSQL on my DigitalOcean droplet, I SCP'd my JAR file (running ./mvnw clean package -Dmaven.test.skip=true to create it) to my server to a directory like, /var/myapp.

Then after researching for a few days and trying multiple things, I was able to figure out the combination that would allow me to view my website when navigating to alpizano.me , but still allow me to hit my API endpoints that were running on my server as-well, after I ran my jar via java -jar myapp.jar

So I basically had to set up my.conf file in the /etc/apache2/sites-available dir (I only used 1 virtual host for this project) as:

<VirtualHost *:80>
    ServerName yourservername.com
    DocumentRoot /var/www/yourservername.com/public_html

    ProxyPreserveHost On
    ProxyPass /api http://127.0.0.1:8080/
    ProxyPassReverse /api http://127.0.0.1:8080/
</VirtualHost>

Notice the /api route for the routing that goes to the embedded Tomcat at port 8080 (you can't use port 80 or it will conflict with Apache Server already listening on port 80), else if it's just / , then it will not allow traffic to base website anymore (alpizano.me), which isn't what I wanted.

This wouldn't be needed if you just had a standalone app that you wanted to route traffic, then you could just use / as your route obviously. I saw other posts talking about forwarding the headers but that didn't seem to make a difference for me and I believe ProxyPreserveHost On takes care of that anyway

Good luck.

References:

https://www.digitalocean.com/community/tutorials/how-to-use-apache-as-a-reverse-proxy-with-mod_proxy-on-ubuntu-16-04