Introduction
------------
- proxy server
servers content in behalf of another server
- proxy servers are
used to hide the identity of other servers
- a proxied request
means that the client request was redirected to a backend
server
- when nginx proxies
a request, it sends it to the proxied server, fetches the
response, and sends the response back to the
client
- examples of proxied
servers are:
a. another Nginx server
b. any kind of HTTP server
c. a non-HTTP server w/c can run
applications built on python, php, etc..
- nginx proxies
request using any specified protocol like:
a. FastCGI
b. uwsgi
c. SCGI
d. memcached
- a proxied server is
also known as backend/upstream server
- common use of
reverse proxy is to provide load balancing
- a proxied request
has a "Via" header field
Ways of proxying requests
-------------------------
|
Simple way of
passing a request
to an HTTP proxied
server
|
server {
listen 80;
server_name proxy.example.com;
location /backend/ {
proxy_pass http://backend.example.com/;
# this will proxy the request by
re-writing the url
# from:
# to:
...
}
location /proxy2 {
proxy_pass http://proxy2.example.com/;
# this version is valid
}
location ~ /proxy3/? {
proxy_pass http://proxy3.example.com/;
# this version is also valid
}
location /proxy4 {
proxy_pass http://proxy4.example.com;
# this doesn't work correctly
# in my testing (nginx/1.10.2)
}
}
|
|
If using a regex to
specify
location, appending
`/` or
`/any/path` at the
end of the
proxied host is not
allowed
related error:
"proxy_pass"
cannot have URI part
in location given
by regular
expression
|
location ~ /notes/?
{
proxy_pass http://www.example.com;
}
|
|
A proxied server
can also be set
as an IP:PORT
combination
|
location ~ \.php {
proxy_pass http://127.0.0.1:8000;
# I'm encoutering "failed (13:
Permission denied)
# while connecting to upstream" on
this (nginx/1.10.2)
}
location /notes/ {
proxy_pass http://192.168.1.11:8000/pages/notes/;
# I'm encoutering "failed (13:
Permission denied)
# while connecting to upstream" on
this (nginx/1.10.2)
}
|
Protocols for proxying a request
--------------------------------
fastcgi_pass -- passes a request to a FastCGI server
uwsgi_pass -- passes a request to a uwsgi server
scgi_pass -- passes a request to an SCGI server
memcached_pass --
passes a request to a memcached server
Passing request Headers
-----------------------
- by default, nginx
redefines 2 headers: "Host" and "Connection"
- nginx eliminate
empty header fields
- "Host" is
set to $proxy_host
-
"Connection" is set to "close"
Example of HTTP
headers:
|
To redefine value
for a header
|
location
/some/path/ {
proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_pass http://localhost:8000;
}
|
|
To prevent a header
from being
passed to the
proxied server,
set it to empty
string
|
location
/some/path/ {
proxy_set_header Accept-Encoding
"";
proxy_pass http://localhost:8000;
}
|
Buffering
---------
- by default, a
response from proxied servers is put into internal buffers and
is not sent to client until the whole
response is received
- this allows the
proxied server to process response quickly
- `proxy_buffering`
is set to on by default
- `proxy_buffers`
sets the size and number of buffers allocated per request
- `proxy_buffer_size`
controls the size of the 1st part of the response from
the proxied server which usually contains
smaller response header compared
to the rest of the response
- if buffering is
disabled, the response from the proxied server is sent
synchronously to client while being received
by the proxy server (this
behaviour is desirable for clients who needs
to get response as soon as
possible)
|
Size of the buffer
for the first
part is set smaller
(2k) compared
to the size of
buffers for the
rest of the
response (4k)
|
location
/some/path/ {
proxy_buffers 16 4k;
proxy_buffer_size 2k;
proxy_pass http://localhost:8000;
}
|
|
Disables buffering
on a specific
location
|
location
/some/path/ {
proxy_buffering off;
proxy_pass http://localhost:8000;
}
|
Choosing an outgoing address
----------------------------
- if a proxy server
has multiple IPs, you can choose an IP for connecting to the
proxied server by using `proxy_bind`
directive
- useful if the
proxied server can only accept connections from an IP range
|
Sets different IPs
in connecting
to proxied server
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location /app1/ {
proxy_bind 127.0.0.1;
proxy_pass http://example.com/app1/;
}
location /app2/ {
proxy_bind 127.0.0.2;
proxy_pass http://example.com/app2/;
}
|
|
IP address can also
be a variable
|
location /app3/ {
proxy_bind $server_addr;
proxy_pass http://example.com/app3/;
}
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