Hello,

We are using such variable for more than a year, and I suggest to add
ability to extract request_id from header. It's very usefull for systems
with frontend and backend installed on different servers.

On Tue, Apr 26, 2016 at 7:38 PM, Vladimir Homutov <vl@nginx.com> wrote:

> details: http://hg.nginx.org/nginx/rev/59f8f2dd8b31
> branches:
> changeset: 6531:59f8f2dd8b31
> user: Vladimir Homutov <vl@nginx.com>
> date: Tue Apr 26 19:31:46 2016 +0300
> description:
> Variable $request_id.
>
> The variable contains text representation based on random data, usable as
> a unique request identifier.
>
> diffstat:
>
> src/http/ngx_http_variables.c | 47
> +++++++++++++++++++++++++++++++++++++++++++
> 1 files changed, 47 insertions(+), 0 deletions(-)
>
> diffs (71 lines):
>
> diff -r 1d0e03db9f8e -r 59f8f2dd8b31 src/http/ngx_http_variables.c
> --- a/src/http/ngx_http_variables.c Fri Dec 18 19:05:27 2015 +0300
> +++ b/src/http/ngx_http_variables.c Tue Apr 26 19:31:46 2016 +0300
> @@ -98,6 +98,8 @@ static ngx_int_t ngx_http_variable_reque
> ngx_http_variable_value_t *v, uintptr_t data);
> static ngx_int_t ngx_http_variable_request_time(ngx_http_request_t *r,
> ngx_http_variable_value_t *v, uintptr_t data);
> +static ngx_int_t ngx_http_variable_request_id(ngx_http_request_t *r,
> + ngx_http_variable_value_t *v, uintptr_t data);
> static ngx_int_t ngx_http_variable_status(ngx_http_request_t *r,
> ngx_http_variable_value_t *v, uintptr_t data);
>
> @@ -274,6 +276,10 @@ static ngx_http_variable_t ngx_http_cor
> { ngx_string("request_time"), NULL, ngx_http_variable_request_time,
> 0, NGX_HTTP_VAR_NOCACHEABLE, 0 },
>
> + { ngx_string("request_id"), NULL,
> + ngx_http_variable_request_id,
> + 0, 0, 0 },
> +
> { ngx_string("status"), NULL,
> ngx_http_variable_status, 0,
> NGX_HTTP_VAR_NOCACHEABLE, 0 },
> @@ -2068,6 +2074,47 @@ ngx_http_variable_request_time(ngx_http_
>
>
> static ngx_int_t
> +ngx_http_variable_request_id(ngx_http_request_t *r,
> + ngx_http_variable_value_t *v, uintptr_t data)
> +{
> + u_char *id;
> +
> +#if (NGX_OPENSSL)
> + u_char random_bytes[16];
> +#endif
> +
> + id = ngx_pnalloc(r->pool, 32);
> + if (id == NULL) {
> + return NGX_ERROR;
> + }
> +
> + v->valid = 1;
> + v->no_cacheable = 0;
> + v->not_found = 0;
> +
> + v->len = 32;
> + v->data = id;
> +
> +#if (NGX_OPENSSL)
> +
> + if (RAND_bytes(random_bytes, 16) == 1) {
> + ngx_hex_dump(id, random_bytes, 16);
> + return NGX_OK;
> + }
> +
> + ngx_ssl_error(NGX_LOG_ERR, r->connection->log, 0, "RAND_bytes()
> failed");
> +
> +#endif
> +
> + ngx_sprintf(id, "%08xD%08xD%08xD%08xD",
> + (uint32_t) ngx_random(), (uint32_t) ngx_random(),
> + (uint32_t) ngx_random(), (uint32_t) ngx_random());
> +
> + return NGX_OK;
> +}
> +
> +
> +static ngx_int_t
> ngx_http_variable_connection(ngx_http_request_t *r,
> ngx_http_variable_value_t *v, uintptr_t data)
> {
>
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