Nginx中的Last＆Break机制重写

Question

Am now dealing with nginx rewrite for my project but got something out of my expectation, just share with you to see if any reasonable advice on this.

The nginx server setting list below:

location /download/ {
    rewrite ^(/download/.*)/media/(.*)\..*$ $1/mp3/$2.mp3;
    rewrite ^(/download/.*)/movie/(.*)\..*$ $1/avi/$2.mp3 break;
    rewrite ^(/download/.*)/avvvv/(.*)\..*$ $1/rmvb/$2.mp3;
}

From above section, you can see that I only add one download location with three rewrite rules.I open the debug log in nginx and start it to load this setting.

Now we enter url: localhost/download/123/movie/UBW.avi in our browser. From the log, we can see that the rules are hit, logs below:

2017/05/22 15:27:27 [notice] 1904#12520: *85 "^(/download/.*)/media/(.*)\..*$" does not match "/download/123/movie/UBW.avi", client: 127.0.0.1, server: localhost, request: "GET /download/123/movie/UBW.avi HTTP/1.1", host: "localhost"
2017/05/22 15:27:27 [notice] 1904#12520: *85 "^(/download/.*)/movie/(.*)\..*$" matches "/download/123/movie/UBW.avi", client: 127.0.0.1, server: localhost, request: "GET /download/123/movie/UBW.avi HTTP/1.1", host: "localhost"
2017/05/22 15:27:27 [notice] 1904#12520: *85 rewritten data: "/download/123/avi/UBW.mp3", args: "", client: 127.0.0.1, server: localhost, request: "GET /download/123/movie/UBW.avi HTTP/1.1", host: "localhost"
2017/05/22 15:27:27 [error] 1904#12520: *85 CreateFile() "D:\Soft\nginx-1.13.0/html/download/123/avi/UBW.mp3" failed (3: The system cannot find the path specified), client: 127.0.0.1, server: localhost, request: "GET /download/123/movie/UBW.avi HTTP/1.1", host: "localhost"

From above info, we can see that the second rule is hit and the section break due to the "break" keyword. This behavior is in our expectation.

But wen I changed the section like below and behave the same behavior as above:

location /download/ {
    rewrite ^(/download/.*)/media/(.*)\..*$ $1/mp3/$2.mp3;
    rewrite ^(/download/.*)/movie/(.*)\..*$ $1/avi/$2.mp3 last;
    rewrite ^(/download/.*)/avvvv/(.*)\..*$ $1/rmvb/$2.mp3;
}

The log below:

2017/05/22 15:33:45 [notice] 11244#11544: *92 "^(/download/.*)/media/(.*)\..*$" does not match "/download/123/movie/UBW.avi", client: 127.0.0.1, server: localhost, request: "GET /download/123/movie/UBW.avi HTTP/1.1", host: "localhost"
2017/05/22 15:33:45 [notice] 11244#11544: *92 "^(/download/.*)/movie/(.*)\..*$" matches "/download/123/movie/UBW.avi", client: 127.0.0.1, server: localhost, request: "GET /download/123/movie/UBW.avi HTTP/1.1", host: "localhost"
2017/05/22 15:33:45 [notice] 11244#11544: *92 rewritten data: "/download/123/avi/UBW.mp3", args: "", client: 127.0.0.1, server: localhost, request: "GET /download/123/movie/UBW.avi HTTP/1.1", host: "localhost"
2017/05/22 15:33:45 [notice] 11244#11544: *92 "^(/download/.*)/media/(.*)\..*$" does not match "/download/123/avi/UBW.mp3", client: 127.0.0.1, server: localhost, request: "GET /download/123/movie/UBW.avi HTTP/1.1", host: "localhost"
2017/05/22 15:33:45 [notice] 11244#11544: *92 "^(/download/.*)/movie/(.*)\..*$" does not match "/download/123/avi/UBW.mp3", client: 127.0.0.1, server: localhost, request: "GET /download/123/movie/UBW.avi HTTP/1.1", host: "localhost"
2017/05/22 15:33:45 [notice] 11244#11544: *92 "^(/download/.*)/avvvv/(.*)\..*$" does not match "/download/123/avi/UBW.mp3", client: 127.0.0.1, server: localhost, request: "GET /download/123/movie/UBW.avi HTTP/1.1", host: "localhost"
2017/05/22 15:33:45 [error] 11244#11544: *92 CreateFile() "D:\Soft\nginx-1.13.0/html/download/123/avi/UBW.mp3" failed (3: The system cannot find the path specified), client: 127.0.0.1, server: localhost, request: "GET /download/123/movie/UBW.avi HTTP/1.1", host: "localhost"

From the second row of the log, we can see that the rule is hit, but then nginx start a new loop for the download section, the strange thing is that , it didn't hit the rule, why?

Also, if we use last keyword, then how many times will the nginx try to loop the section, in default it's two, right?

Answer 1

The ngx_http_rewrite_module module is used to change request URI using PCRE regular expressions

Remember that when you rewrite the uri, the uri will change .

For last

When rewrite module meets last, it stops processing the current set and the rewritten request is passed once again to find the appropriate location (and the new set of rewriting rules).

In your configure

location /download/ {
    rewrite ^(/download/.*)/media/(.*)\..*$ $1/mp3/$2.mp3;  //a
    rewrite ^(/download/.*)/movie/(.*)\..*$ $1/avi/$2.mp3 last; //b
    rewrite ^(/download/.*)/avvvv/(.*)\..*$ $1/rmvb/$2.mp3;    //c
}

your url localhost/download/123/movie/UBW.avi

your request uri is /download/123/movie/UBW.avi

---

first pass

the /download/123/movie/UBW.avi match b ,so the uri rewrite to /download/123/avi/UBW.mp3 ,the first pass finish.

---

second pass

And then, in the second pass ,the uri is

/download/123/avi/UBW.mp3

So it do not match abc , finally , it throw error in log.