# Upstream prematurely closed connection while reading response header from upstream

**URL:** <https://www.ruby-forum.com/t/upstream-prematurely-closed-connection-while-reading-response-header-from-upstream/241642>\
**Category:** NGINX\
**Created:** [April 21, 2015, 4:28am UTC](https://www.ruby-forum.com/t/upstream-prematurely-closed-connection-while-reading-response-header-from-upstream/241642 "2015-04-21T04:28:16Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![Detlef\_R](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/58f4c7/32.png) [@Detlef\_R](https://www.ruby-forum.com/u/Detlef_R)\
**Post date:** [April 21, 2015, 4:28am UTC](https://www.ruby-forum.com/t/upstream-prematurely-closed-connection-while-reading-response-header-from-upstream/241642/1 "2015-04-21T04:28:16Z")

</div>

Recently I tried to implemented an Nginx extension module to save the  
request body to redis list (via RPUSH command) directly .

However, I got a 502 Bad Gateway error!

The error occurs after calling ngx\_http\_redis\_create\_request, before  
ngx\_http\_redis\_process\_header() called [nginx/logs/error.log]

Anyone know what is the problem?

Here are the related log in [nginx/logs/error.log]

```
2015/04/20 13:56:54 [debug] 5759#0: *1 http process request line
2015/04/20 13:56:54 [debug] 5759#0: *1 http request line: "GET /test

```

HTTP/1.1"  
2015/04/20 13:56:54 [debug] 5759#0: \*1 http uri: “/test”  
2015/04/20 13:56:54 [debug] 5759#0: \*1 http args: “”  
2015/04/20 13:56:54 [debug] 5759#0: \*1 http exten: “”  
2015/04/20 13:56:54 [debug] 5759#0: \*1 http process request header line  
2015/04/20 13:56:54 [debug] 5759#0: \*1 http header: “User-Agent:  
Wget/1.15  
(linux-gnu)”  
2015/04/20 13:56:54 [debug] 5759#0: \*1 http header: “Accept: _/_”  
2015/04/20 13:56:54 [debug] 5759#0: \*1 http header: “Host:  
localhost:8989”  
2015/04/20 13:56:54 [debug] 5759#0: \*1 http header: “Connection:  
Keep-Alive”  
2015/04/20 13:56:54 [debug] 5759#0: \*1 http header done  
2015/04/20 13:56:54 [debug] 5759#0: \*1 event timer del: 3: 1429509474481  
2015/04/20 13:56:54 [debug] 5759#0: \*1 test location: “/”  
2015/04/20 13:56:54 [debug] 5759#0: \*1 test location: “general/test”  
2015/04/20 13:56:54 [debug] 5759#0: \*1 test location: “test”  
2015/04/20 13:56:54 [debug] 5759#0: \*1 using configuration “/test”  
2015/04/20 13:56:54 [debug] 5759#0: \*1 http cl:-1 max:1048576  
2015/04/20 13:56:54 [debug] 5759#0: \*1 generic phase: 1  
2015/04/20 13:56:54 [debug] 5759#0: \*1 generic phase: 2  
2015/04/20 13:56:54 [debug] 5759#0: \*1 access phase: 3  
2015/04/20 13:56:54 [debug] 5759#0: \*1 access phase: 4  
2015/04/20 13:56:54 [debug] 5759#0: \*1 post access phase: 5  
2015/04/20 13:56:54 [debug] 5759#0: \*1 posix\_memalign:  
00000000012627D0:4096  
@16  
2015/04/20 13:56:54 [debug] 5759#0: \*1 http init upstream, client timer:  
0  
2015/04/20 13:56:54 [debug] 5759#0: \*1 epoll add event: fd:3 op:3  
ev:80002005  
2015/04/20 13:56:54 [debug] 5759#0: \*1 http cleanup add:  
0000000001262788  
2015/04/20 13:56:54 [debug] 5759#0: \*1 get rr peer, try: 1  
2015/04/20 13:56:54 [debug] 5759#0: \*1 socket 9  
2015/04/20 13:56:54 [debug] 5759#0: \*1 epoll add connection: fd:9  
ev:80002005  
2015/04/20 13:56:54 [debug] 5759#0: \*1 connect to 127.0.0.1:6379, fd:9  
#2  
2015/04/20 13:56:54 [debug] 5759#0: \*1 http upstream connect: -2  
2015/04/20 13:56:54 [debug] 5759#0: \*1 posix\_memalign:  
000000000125B640:128  
@16  
2015/04/20 13:56:54 [debug] 5759#0: \*1 event timer add: 9:  
60000:1429509474482  
2015/04/20 13:56:54 [debug] 5759#0: \*1 http finalize request: -4,  
“/test?”  
a:1, c:2  
2015/04/20 13:56:54 [debug] 5759#0: \*1 http request count:2 blk:0  
2015/04/20 13:56:54 [debug] 5759#0: timer delta: 1  
2015/04/20 13:56:54 [debug] 5759#0: posted events 0000000000000000  
2015/04/20 13:56:54 [debug] 5759#0: worker cycle  
2015/04/20 13:56:54 [debug] 5759#0: epoll timer: 60000  
2015/04/20 13:56:54 [debug] 5759#0: epoll: fd:3 ev:0004  
d:00007F39455B51B0  
2015/04/20 13:56:54 [debug] 5759#0: \*1 http run request: “/test?”  
2015/04/20 13:56:54 [debug] 5759#0: \*1 http upstream check client, write  
event:1, “/test”  
2015/04/20 13:56:54 [debug] 5759#0: \*1 http upstream recv(): -1 (11:  
Resource temporarily unavailable)  
2015/04/20 13:56:54 [debug] 5759#0: epoll: fd:9 ev:0004  
d:00007F39455B5280  
2015/04/20 13:56:54 [debug] 5759#0: \*1 http upstream request: “/test?”  
2015/04/20 13:56:54 [debug] 5759#0: \*1 http upstream send request  
handler  
2015/04/20 13:56:54 [debug] 5759#0: \*1 http upstream send request  
2015/04/20 13:56:54 [debug] 5759#0: \*1 chain writer buf fl:0 s:30  
2015/04/20 13:56:54 [debug] 5759#0: \*1 chain writer in: 0000000001262B88  
2015/04/20 13:56:54 [debug] 5759#0: \*1 writev: 30  
2015/04/20 13:56:54 [debug] 5759#0: \*1 chain writer out:  
0000000000000000  
2015/04/20 13:56:54 [debug] 5759#0: \*1 event timer del: 9: 1429509474482  
2015/04/20 13:56:54 [debug] 5759#0: \*1 event timer add: 9:  
60000:1429509474482  
2015/04/20 13:56:54 [debug] 5759#0: timer delta: 0  
2015/04/20 13:56:54 [debug] 5759#0: posted events 0000000000000000  
2015/04/20 13:56:54 [debug] 5759#0: worker cycle  
2015/04/20 13:56:54 [debug] 5759#0: epoll timer: 60000  
2015/04/20 13:56:54 [debug] 5759#0: epoll: fd:9 ev:0005  
d:00007F39455B5280  
2015/04/20 13:56:54 [debug] 5759#0: \*1 http upstream request: “/test?”  
2015/04/20 13:56:54 [debug] 5759#0: \*1 http upstream process header  
2015/04/20 13:56:54 [debug] 5759#0: \*1 recv: fd:9 0 of 0  
2015/04/20 13:56:54 [error] 5759#0: \*1 upstream prematurely closed  
connection while reading response header from upstream, client:  
127.0.0.1,  
server: localhost,request: “GET /test HTTP/1.1”, upstream:  
“redis://127.0.0.1:6379”, host: “localhost:8989”

===============================================================================

The configuration in Nginx as following shown

redis\_pass 127.0.0.1:6379;  
redis\_db 3;  
redis\_key candice;

===============================================================================

Here are the source code of the module.

static ngx\_int\_t  
ngx\_http\_redis\_handler(ngx\_http\_request\_t \*r)  
{  
ngx\_http\_redis\_loc\_conf\_t \*rlcf;  
ngx\_http\_upstream\_t \*u;  
ngx\_int\_t rc;

```
/* set up upstream structure */
if (ngx_http_upstream_create(r) != NGX_OK)
{
    ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,

```

“ngx\_http\_upstream\_create() failed”);  
return NGX\_HTTP\_INTERNAL\_SERVER\_ERROR;  
}

```
u = r->upstream;
ngx_str_set(&u->schema, "redis://");

rlcf = ngx_http_get_module_loc_conf(r, ngx_http_redis_module);
u->conf = &rlcf->upstream;

/* attach the callback functions */
u->create_request = ngx_http_redis_create_request;
u->reinit_request = ngx_http_redis_reinit_request;
u->process_header = ngx_http_redis_process_header;
u->finalize_request = ngx_http_redis_finalize_request;

rc = ngx_http_read_client_request_body(r, ngx_http_upstream_init);
if (rc > NGX_HTTP_SPECIAL_RESPONSE)
    return rc;
return NGX_DONE;

```

}

===============================================================================

/\* callbacks - To send command “SELECT \r\nRPUSH \r\n” to redis \*/  
static ngx\_int\_t ngx\_http\_redis\_create\_request(ngx\_http\_request\_t \*r)  
{  
ngx\_http\_redis\_loc\_conf\_t \* rlcf;  
ngx\_chain\_t \*cl, \*body;  
ngx\_buf\_t \*buf, \*b;

```
/* Do not forget to change the following offset when modifying the 

```

query  
string \*/  
ngx\_str\_t query = ngx\_string("SELECT %ui\r\nRPUSH %V ");  
size\_t len = query.len - 5;

```
rlcf = ngx_http_get_module_loc_conf(r, ngx_http_redis_module);
len += (rlcf->db > 9 ? 2 : 1) + rlcf->key.len;

/* Create temporary buffer for request with size len. */
buf = ngx_create_temp_buf(r->pool, len);
if (buf == NULL) {
    return NGX_ERROR;
}
ngx_snprintf(buf->pos, len, (char*)query.data, rlcf->db, 

```

&rlcf-\>key);  
buf-\>last = buf-\>pos + len;

```
cl = ngx_alloc_chain_link(r->pool);
if (cl == NULL) {
    return NGX_ERROR;
}

cl->buf = buf;
cl->next = NULL;

body = r->upstream->request_bufs;
r->upstream->request_bufs = cl;
while (body)
{
    b = ngx_alloc_buf(r->pool);
    if (b == NULL)
        return NGX_ERROR;

    ngx_memcpy(b, body->buf, sizeof(ngx_buf_t));
    cl->next = ngx_alloc_chain_link(r->pool);
    if (cl->next == NULL)
        return NGX_ERROR;

    cl = cl->next;
    cl->buf = b;
    body = body->next;
}
*cl->buf->last++ = CR; *cl->buf->last++ = LF;
cl->next = NULL;
return NGX_OK;

```

}

Posted at Nginx Forum:

> **[upstream prematurely closed connection while reading response header from...](https://forum.nginx.org/read.php?2,258239,258239#msg-258239)**
>
> Recently I tried to implemented an Nginx extension module to save the request body to redis list (via RPUSH command) directly . However, I got a 502 Bad Gateway error! The error occurs after calling ngx\_http\_redis\_create\_request, before...