We are looking to horizontally scale our nginx+nchan servers so we tried to attach redis. Unfortunately, it seems that messages are either lost, or intermittently not being understood. When using in-memory there are no issues. I'm not sure if this is because of elasticache or something else. I'm hoping someone can help me understand what is configured incorrectly. so far, we have only the 1 server (since messages are lost, no point in adding a second yet)

My Config files look like this:

Server Include:

listen 80 ;
#listen [::]:80 ;
listen 443 ssl ;

ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
ssl_ciphers DEFAULT:+MEDIUM:!RC4:!3DES:!MD5!SHA1;

root /var/www/html;

autoindex off ;
index index.html index.htm ;

ssl_trusted_certificate /etc/nginx/iftapi_client_ca.crt ;
ssl_verify_client optional_no_ca ;


location ~ ^/a/([a-z]*)$ {
    fastcgi_param QUERY_STRING $query_string ;
    fastcgi_param REQUEST_METHOD $request_method ;
    fastcgi_param CGI_FUNCTION $1 ;
    fastcgi_param CGI_HTTP_AUTHORIZATION $http_authorization ;
    fastcgi_param IP_ADDR $remote_addr ;
    fastcgi_param USERAGENT $http_user_agent ;
    fastcgi_param CLIENT_CERT_VERIFY $ssl_client_verify ;
    fastcgi_param CLIENT_CERT_FINGERPRINT $ssl_client_fingerprint ;
    fastcgi_pass unix:/var/www/sockets/fcgiserv-socket;
}
location ~ ^/a/([A-Z0-9]*)/applongpoll$ {
    nchan_redis_pass primary_redis_cluster;
    nchan_subscriber;
    nchan_message_timeout 30s;
    nchan_message_buffer_length 1;
    nchan_subscriber_timeout 57;
    nchan_subscriber_compound_etag_message_id on;
    nchan_channel_id "ch_s_$1" ;
    nchan_authorize_request "/a/$1/appauth" ;
}
location ~ ^/a/([A-Za-f0-9]*)/([a-z]*)$ {
    fastcgi_param QUERY_STRING $query_string ;
    fastcgi_param REQUEST_METHOD $request_method ;
    fastcgi_param CGI_FUNCTION $2 ;
    fastcgi_param CGI_SERIAL $1 ;
    fastcgi_param CGI_AUTH none ;
    fastcgi_param CGI_HTTP_AUTHORIZATION $http_authorization ;
    fastcgi_param IP_ADDR $remote_addr ;
    fastcgi_param USERAGENT $http_user_agent ;
    fastcgi_pass unix:/var/www/sockets/fcgiserv-socket;
}
location ~ ^/a/([A-Z0-9]*)/([A-Z0-9]*)/longpoll$ {
    nchan_redis_pass primary_redis_cluster;
    nchan_subscriber;
    nchan_message_timeout 60s;
    nchan_message_buffer_length 10;
    nchan_subscriber_timeout 295;
    nchan_subscriber_compound_etag_message_id on;
    nchan_channel_id "ch_$1" ;
    nchan_authorize_request "/a/$1/$2/auth" ;
}
location ~ ^/a/([A-Z0-9]*)/([A-Z0-9]*)/longpoll2$ {
    nchan_redis_pass primary_redis_cluster;
    nchan_subscriber;
    nchan_message_timeout 60s;
    nchan_message_buffer_length 10;
    nchan_subscriber_timeout 25;
    nchan_subscriber_compound_etag_message_id on;
    nchan_channel_id "ch_$1" ;
    nchan_authorize_request "/a/$1/$2/auth" ;
}
location ~ ^/a/([A-Za-f0-9]*)/([A-Za-f0-9]*)/([a-z]*)$ {
    fastcgi_param QUERY_STRING $query_string ;
    fastcgi_param REQUEST_METHOD $request_method ;
    fastcgi_param CGI_FUNCTION $3 ;
    fastcgi_param CGI_SERIAL $1 ;
    fastcgi_param CGI_AUTH $2 ;
    fastcgi_param IP_ADDR $remote_addr ;
    fastcgi_param USERAGENT $http_user_agent ;
    fastcgi_pass unix:/var/www/sockets/fcgiserv-socket;
}
location / {
    expires epoch ;
    location /fw/ {
        autoindex on ;
    }
    charset us-ascii;
    try_files $uri $uri/ =404;
}

Publisher:

server {
    listen unix:/var/www/sockets/pubsocket ;

    root /doesnotexist;

    server_name pub.iftapi.net;

    nchan_message_timeout 10s;
    nchan_message_buffer_length 10;

    location ~ ^/a/([A-Z0-9]*)/applongpost$ {
        nchan_redis_pass primary_redis_cluster;
        nchan_publisher;
        nchan_message_timeout 30s;
        nchan_message_buffer_length 1;
        nchan_channel_id "ch_s_$1" ;
    }

    #deprecated - delete this one
    location ~ ^/a/([A-Z0-9]*)/([A-Z0-9]*)/longpost$ {
        nchan_redis_pass primary_redis_cluster;
        nchan_publisher;
        nchan_message_timeout 60s;
        nchan_message_buffer_length 10;
        nchan_channel_id "ch_$1" ;
    }

    location ~ ^/a/([A-Z0-9]*)/longpost$ {
        nchan_redis_pass primary_redis_cluster;
        nchan_publisher;
        nchan_message_timeout 60s;
        nchan_message_buffer_length 10;
        nchan_channel_id "ch_$1" ;
    }
}

nginx.conf:

user www-data;
worker_processes auto;
pid /run/nginx.pid;
include /etc/nginx/modules-enabled/*.conf;

events {
        worker_connections 768;
}

http {

        ##
        # Basic Settings
        ##

        sendfile on;
        tcp_nopush on;
        tcp_nodelay on;
        keepalive_timeout 65;
        types_hash_max_size 2048;
        include /etc/nginx/mime.types;
        default_type application/octet-stream;

        ##
        # SSL Settings
        ##

        ssl_protocols TLSv1 TLSv1.1 TLSv1.2; # Dropping SSLv3, ref: POODLE
        ssl_prefer_server_ciphers on;

        ##
        # Logging Settings
        ##

        access_log /var/log/nginx/access.log;
        error_log /var/log/nginx/error.log;

        ##
        # nchan Redis Settings
        ##
                
        upstream primary_redis_cluster {
            nchan_redis_server REDISURL;
        }  

        ##
        # Gzip Settings
        ##

        gzip on;

        ##
        # Virtual Host Configs
        ##

        include /etc/nginx/conf.d/*.conf;
        include /etc/nginx/sites-enabled/*;
}

Each website that allows sbscribers:

server {
    server_name SERVERNAME;
    include /etc/nginx/server_include.conf ;
}