varnish - 如何在varnishncsa中记录所选的Director>后端

Question

我有多个后端服务器，我使用导向器在它们之间“轮循”。

有没有一种方法，如果有的话，如何记录使用哪个后端(后端名称或后端主机名)？
上面提到的是将std.log("key:value")和%{VCL_Log:*key*}x与varnishncsa一起使用。

我的vcl配置:

backend aws_frontend1 {
  .host = "aws1.domain.mobi";
  .port = "80";
}
backend aws_frontend2 {
  .host = "aws2.domain.mobi";
  .port = "80";
}

director lb_aws_frontend round-robin {
  {
    .backend = aws_frontend1;
  }
  {
    .backend = aws_frontend2;
  }
}

sub vcl_recv {
  set req.backend = lb_aws_frontend;
  unset req.http.Cookie;
}
sub vcl_fetch {
  if (beresp.http.cache-control ~ "(no-cache|private)" || beresp.http.pragma ~ "no-cache") {
    set beresp.ttl = 0s;
  } else {
    set beresp.ttl = 168h;
  }
}
sub vcl_error {
  if (obj.status == 750) {
    set obj.status = 403;
    return(deliver);
  }
}

编辑:

由于NITEMAN，下面是更新的代码...
当未命中和“Varnish 缓存”命中时，此代码将打印出后端名称:

import std;

backend aws_frontend1 {
  .host = "aws1.domain.mobi";
  .port = "80";
}
backend aws_frontend2 {
  .host = "aws2.domain.mobi";
  .port = "80";
}

director lb_aws_frontend round-robin {
  {
    .backend = aws_frontend1;
  }
  {
    .backend = aws_frontend2;
  }
}

sub vcl_recv {
  set req.backend = lb_aws_frontend;
  unset req.http.Cookie;
}
sub vcl_fetch {
  if (beresp.http.cache-control ~ "(no-cache|private)" || beresp.http.pragma ~ "no-cache") {
    set beresp.ttl = 0s;
  } else {
    set beresp.ttl = 168h;
  }
  std.log("backend_used:" + beresp.backend.name);
}
sub vcl_hit {
  std.log("backend_used:varnish cache");
}
sub vcl_error {
  if (obj.status == 750) {
    set obj.status = 403;
    return(deliver);
  }
}

Answer 1

后端名称(即使使用导演)也可以在vcl_fetch上获得，出于调试目的，我通常使用:

sub vcl_fetch {
  # ...
  set beresp.http.X-Backend = beresp.backend.name;
  # ...
}