ProxyPassReverse doesn't rewrite Location (http header) - reverse-proxy

Question

I have an apache installed in a frontend server (server1), which is as reverse proxy. I have another server (server2) with tomcat that is running a webapp.
I configured my reverse proxy (server1) like that:
ProxyPass /app1/ ajp://server2:8009/app1/
ProxyPassReverse /app1/ https://www.external_domain_name.com/
When I connect to:
https://www.external_domain_name.com/app1/
my web app is working properly. In some pages, the web app redirects me (302) to another page.
Then, I am redirected to :
https://server1_internal_ip/app1/foo_bar
When I look to the http headers, the response header contains:
Status code: 302
Location: https://server1_internal_ip/app1/foo_bar
So, my conclusion ProxyPass is working properly, but the ProxyPassReverse is not.
Can you help me please to understand what's going wrong?
Thanks

Answer 1

Actually ProxyPassReverse will replace the Location which your server returned.
Example 1 (Only URL Path)
Apache2 Setting
ProxyPass "/8080" "http://localhost:8080"
ProxyPassReverse "/8080/" "/"
Node.js Setting
const express = require("express");
const app = express()
app.get('/', (req, res) => {
res.json({a: 8080})
})
app.get("/hi", (req, res) => {
res.json({a: "8080hi"})
})
app.get("/redirect", (req, res) => {
res.redirect("/hi")
})
app.listen(8080)
Original Location is "Location: /hi".
New one is "Location: /8080/hi". (/ => /8080/)
That means Apache2 replaced the Location value with ProxyPassReverse setting.
Or you can use full FQDN to do it.
Example 2 (FQDN)
Apache2 Setting
ProxyPass "/8080" "http://localhost:8080"
ProxyPassReverse "/8080" "http://localhost:8080"
Node.js Setting
const express = require("express");
const app = express()
app.get('/', (req, res) => {
res.json({a: 8080})
})
app.get("/hi", (req, res) => {
res.json({a: "8080hi"})
})
app.get("/redirect", (req, res) => {
res.setHeader("Location", "http://localhost:8080/hi")
res.send(302)
})
app.listen(8080)
Apache2 will convert http://localhost:8080/hi to http://localhost/8080/hi.
(If my Apache2 is configured to 80 port.)

Answer 2

Set it to this instead
ProxyPassReverse /app1/ ajp://server2:8009/app1/
Seemed to work for me when I came across a similar problem.