$srcache_expire is always empty

Hey!

I have been trying srcache with redis for few weeks now and today I noticed that the cache keys are not expiring automatically.

I'm using this config in local docker environment:

##
# Adds internal locations for storing and getting full page cache from redis
##

srcache_default_expire 10s;
srcache_max_expire 10s;

location /redis-fetch {
    internal;

    ##
    # In order to use password authentication we use custom redis module which adds $redis_auth:
    # - https://github.com/Yongke/ngx_http_redis-0.3.7
    ##

    # Read the configuration from system envs
    set $redis_auth '';
    set $redis_db 0;

    set $redis_key $args;

    redis_pass 172.17.0.6:6379;
}

location /redis-store {
    internal;

    set_unescape_uri $exptime $arg_exptime;
    set_unescape_uri $key $arg_key;

    # redis module pipelines these 3 commands into single request
    redis2_query auth '';
    redis2_query select 0;
    redis2_query set $key $echo_request_body;
    redis2_query expire $key $srcache_expire;

    # Pass the request to redis
    redis2_pass 172.17.0.6:6379;

}

Then I open redis-cli to monitor incoming requests:

$ redis-cli
> monitor
1478704802.63890 [0 172.17.0.8:54906] "select" "0"
1478704802.638100 [0 172.17.0.8:54906] "get" "wp_:nginx:httpsGETwordpress.test/robots.txt"
1478704802.638122 [0 172.17.0.8:54900] "auth" ""
1478704802.638137 [0 172.17.0.8:54900] "select" "0"
1478704802.638148 [0 172.17.0.8:54900] "set" "wp_:nginx:httpsGETwordpress.test/robots.txt" "HTTP/1.1 200 OK\r\nContent-Type: text/plain; charset=utf-8\r\nExpires: Thu, 19 Nov 1981 08:52:00 GMT\r\nCache-Control: no-store, no-cache, must-revalidate\r\nPragma: no-cache\r\nX-Robots-Tag: noindex, follow\r\nLink: <https://wordpress.test/wp-json/>; rel=\"https://api.w.org/\"\r\nLink: <https://wordpress.test/wp-json>; rel=\"https://github.com/WP-API/WP-API\"\r\nX-Cache: MISS\r\n\r\nUser-agent: *\nDisallow: /wp-admin/\nAllow: /wp-admin/admin-ajax.php\n"
1478704802.638189 [0 172.17.0.8:54900] "expire" "wp_:nginx:httpsGETwordpress.test/robots.txt" ""

And where I should see 10s because of the srcache_max_expire directive or 0 because of the Cache-Control: no-store, no-cache, must-revalidate header instead I see "" as sent to redis.

Version:

nginx -V
nginx version: openresty/1.11.2.1
built by gcc 4.9.2 (Debian 4.9.2-10)
built with OpenSSL 1.0.2j  26 Sep 2016
TLS SNI support enabled
configure arguments: --prefix=/etc/nginx/nginx --with-cc-opt=-O2 --add-module=../ngx_devel_kit-0.3.0 --add-module=../echo-nginx-module-0.60 --add-module=../xss-nginx-module-0.05 --add-module=../ngx_coolkit-0.2rc3 --add-module=../set-misc-nginx-module-0.31 --add-module=../form-input-nginx-module-0.12 --add-module=../encrypted-session-nginx-module-0.06 --add-module=../srcache-nginx-module-0.31 --add-module=../ngx_lua-0.10.6 --add-module=../ngx_lua_upstream-0.06 --add-module=../headers-more-nginx-module-0.31 --add-module=../array-var-nginx-module-0.05 --add-module=../memc-nginx-module-0.17 --add-module=../redis2-nginx-module-0.13 --add-module=../rds-json-nginx-module-0.14 --add-module=../rds-csv-nginx-module-0.07 --with-ld-opt=-Wl,-rpath,/etc/nginx/luajit/lib --with-http_addition_module --with-http_auth_request_module --with-http_flv_module --with-http_gunzip_module --with-http_gzip_static_module --with-http_mp4_module --with-http_random_index_module --with-http_realip_module --with-http_secure_link_module --with-http_slice_module --with-http_ssl_module --with-http_stub_status_module --with-http_sub_module --with-http_v2_module --with-http_geoip_module=dynamic --with-file-aio --with-ipv6 --with-pcre-jit --with-stream --with-stream_ssl_module --with-threads --without-http_autoindex_module --without-http_browser_module --without-http_userid_module --without-mail_pop3_module --without-mail_imap_module --without-mail_smtp_module --without-http_split_clients_module --without-http_uwsgi_module --without-http_scgi_module --without-http_referer_module --user=nginx --group=nginx --sbin-path=/usr/sbin --modules-path=/usr/lib/nginx --conf-path=/etc/nginx/nginx.conf --http-log-path=/var/log/nginx/access.log --error-log-path=/var/log/nginx/error.log --pid-path=/var/run/nginx.pid --lock-path=/var/run/nginx/nginx.lock --http-fastcgi-temp-path=/tmp/nginx/fastcgi --http-proxy-temp-path=/tmp/nginx/proxy --http-client-body-temp-path=/tmp/nginx/client_body --add-module=/tmp/ngx_http_redis-0.3.7-master --add-module=/tmp/ngx_pagespeed-1.11.33.4-beta --with-openssl=/tmp/openssl-1.0.2j

Reproduce the configuration shown for the /redis-store location and inspect how the srcache_expire variable is populated before the redis2_query expire command runs. Compare the observed Redis MONITOR output with the configured expiry directives and response headers; done means the expiry value is correctly determined or the issue is documented as a configuration interaction.