nginx rewrite POST request - post

Question

I need send POST request to my nginx frontend server which should redirect it to upstream servers.
In details:
send request to http://192.168.0.10/foo/bar/blah and URL in this request should be changed to http://192.168.0.21[22,23]:8080/foo/blah
upstream myapp {
server 192.168.0.21:8080;
server 192.168.0.22:8080;
server 192.168.0.23:8080;
}
server {
listen 80;
server_name localhost;
location /foo/bar/blah/ {
rewrite ^/foo/blah^/ /$1 break;
proxy_pass http://myapp;
}
but in nginx error log I see that my request changed from POST to GET and also seems didn't change URL:
"POST /foo/bar/blah HTTP/1.1" 301 185 "-" "Mozilla/5.0 (Windows NT 6.1; WOW64)
"GET /foo/bar/blah/ HTTP/1.1" 404 117 "-" "Mozilla/5.0 (Windows NT 6.1; WOW64)
How can I keep my POST request and change the URL?
Also about my rewrite rule
rewrite ^/foo/blah^/ /$1 break;
I found a lot of examples for changing URL and all of them looks the same.
And it is really strange for me, how this rewrite rule can change URL from /foo/bar/blah/ to /foo/blah/:
in documentaion says:
http://nginx.org/en/docs/http/ngx_http_rewrite_module.html#rewrite
If the specified regular expression matches a request URI, URI is
changed as specified in the replacement string.
but in my case request URI is /foo/bar/blah/ so regular expression /foo/blah^/ doesn't matches URI, so this rule shouldn't work.
Am I right?
Would be helpful any advises.
UPD:
fixed:
location = /foo/bar/blah {
proxy_pass http://myapp/foo/blah;
}

Answer 1

My guess, you don't need rewrite.
location /foo/bar/ {
proxy_pass http://myapp/;
}
This should remove /foo/bar part from proxied URL.