nginxのpassive checkの挙動確認

結論

• 特に設定しないとproxy_passで設定するupstreamのmax_failsは1
• proxy_next_upstreamに指定したstatus codeが出ると失敗扱いになってmax_failsに達すると一時的にそのupstreamは使えなくなる

検証

ポート30000, 30001で、常にHTTPステータス503を返すエンドポイントを適当にMac上で動かして

こんなnginx.confを作って

$ cat /tmp/nginx.conf
user  nginx;
worker_processes  1;

error_log  /var/log/nginx/error_log info;
pid        /var/run/nginx.pid;


events {
    worker_connections  1024;
}


http {
    include       /etc/nginx/mime.types;
    default_type  application/octet-stream;

    log_format ltsv "time:$time_local"
                "\tstatus:$status"
                "\treqtime:$request_time"
                "\tupstream:$upstream_addr"
                "\tupstream_status:$upstream_status"
                "\tvhost:$host";

    access_log  /var/log/nginx/access_log  ltsv;

    sendfile        on;
    #tcp_nopush     on;

    keepalive_timeout  65;

    #gzip  on;
    upstream myapp1 {
        server docker.for.mac.host.internal:30000;
        server docker.for.mac.host.internal:30001;
    }

    server {
        listen       80;
        server_name  localhost;
        location / {
            # ここが重要
            proxy_next_upstream error timeout http_502 http_503;
            proxy_pass   http://myapp1;
        }
    }

}

こんなコマンド打ってnginxを起動して

$ docker run --name my-custom-nginx-container -v /tmp/nginx.conf:/etc/nginx/nginx.conf:ro -p 80:80 -d nginx

$ curl localhost

こうするとこんなログが出て

2018/12/04 12:32:31 [warn] 6#6: *12 upstream server temporarily disabled while reading response header from upstream, client: 172.17.0.1, server: localhost, request: "GET / HTTP/1.1", upstream: "http://192.168.65.2:30000/", host: "localhost"

もう一度curlするとこんなログが出て502が返る

2018/12/04 12:33:03 [error] 6#6: *18 no live upstreams while connecting to upstream, client: 172.17.0.1, server: localhost, request: "GET / HTTP/1.1", upstream: "http://myapp1/", host: "localhost"

ドキュメント

Module ngx_http_upstream_module の max_fails あたり。

• By default, the number of unsuccessful attempts is set to 1.
• What is considered an unsuccessful attempt is defined by the proxy_next_upstream,

なるほどねぇ。

next step

• docker composeでやったほうが再現が楽だしブログも書きやすいしいいことづくめ。次やる時はdocker compose使う