Since version 2.0 nginx-agent began support Marathon API.

In case of using MesosDNS the project is transmitting DNS records (SRV type) to nginx configuration. It can be useful if there is some container manager system with DNS supporting for example Mesos + MesosDNS and you want use Nginx as load balancer or some gate for access to nodes.

In another hand, Marathon API can be used as a service discovery. But also this approach has some advantage we can configure NGINX directly from marathon json.

The project was inspired by https://github.com/Xorlev/gatekeeper but the one has quite wide ability since DNS was used for discovering instead of Apache Zookeeper.

• Getting started with Marathon

• git clone [email protected]:vasyaod/nginx-agent.git
• mvn install
• Create directory where Nginx Agent will put configuration file for Ngix (see property nginx-agent.config-path) Default value is /etc/nginx/services-conf and the directory can be created by mkdir /etc/nginx/services-conf
• The configuration directory should be included in a Nginx config by the directive include /etc/nginx/services-conf/*.conf
• Create some minimal config for Nginx Agent
• Run the app by java -Dconfig.file=nginx-agent.conf -cp "target/lib/*" ru.mobak.nginxagent.App where nginx-agent.conf is our configuration for Nginx Agent.

• docker build -t vasyaod/nginx-balancer .

Assume there is some service (in this example the service is called as battle-dev) with following configuration of nodes:

[nginx-agent]$ nslookup -type=SRV _battle-dev._tcp.marathon.mesos
Server:         192.168.100.1
Address:        192.168.100.1#53

_battle-dev._tcp.marathon.mesos service = 0 0 31585 battle-dev-atfbu-s8.marathon.slave.mesos.
_battle-dev._tcp.marathon.mesos service = 0 0 31934 battle-dev-cjq9x-s9.marathon.slave.mesos.
_battle-dev._tcp.marathon.mesos service = 0 0 31270 battle-dev-dy91w-s8.marathon.slave.mesos.

Nginx Agent should create following config file:

[services-conf]# cat /etc/nginx/services-conf/battle-dev.conf
upstream battle-dev {
    server 192.168.100.11:31934;
    server 192.168.100.5:31270;
    server 192.168.100.12:31585;
}

map $args $battle_dev_host {
    ~(.*)nodeId=78eeabce9bdf233fcb6e8b69bfc438a6(.*) 192.168.100.11:31934;
    ~(.*)nodeId=611958bd8b7c318ffb8aa744fca9b2df(.*) 192.168.100.5:31270;
    ~(.*)nodeId=b59102f182b8d9a90cf64d8952ce3a3a(.*) 192.168.100.12:31585;
}

That is, how you can see, two objects have been created:

• upstream battle-dev
• and map for variable $battle_dev_host

Minimal configuration for Mesos DNS is list of services which should be listened. Please notice that in case of DNS we should obligatory set up list of all services which we want to monitor.

nginx-agent {

  resolver = "dns"
  
  services = ["serice1", "service2"]
}

nginx-agent {

  resolver = "marathon"

  marathon {
    # List of marathon servers
    urls = ["127.0.0.1:8080"]
  }
  
  # In marathon case this parameter is optional since we can mark service from marathon json.
  services = ["serice1", "service2"]
}

nginx-agent {

  # Command which refreshs configuration to Nginx.
  # There are two variants:
  #  - nginx -s reload
  #  - kill -HUP {PID}
  reload-command="nginx -s reload"

  # Path to file that contains PID of Nginx. This option needs for refreshing configuration of Nginx in runtime by
  # sending signal.
  nginx-pid-file="/var/run/nginx.pid"

  # Path to where generated configs are
  config-path = "/etc/nginx/services-conf"

  # URL to a template that will be used for generation of configs in "config-path" directory.
  #
  # Examples of urls:
  #  - "file:example-template.mustache" - template in file system
  #  - "https://raw.githubusercontent.com/vasyaod/nginx-agent/master/example-template.mustache" - template in file system
  template-url = "default-template.mustache"

  # If there is no any node for a service in DNS then default server and port will be set. In one hand nginx can not work
  # with empty upstreams, in another hand it allow to us show some stub page if the service is down.
  default-server = "127.0.0.1"
  default-port = 80

  # Hash algorithm for node ID generation. Two type of hash function is supported:
  #  * "java" - standart java hash code
  #  * "md5"
  hash-type = "md5"

  # Secret key which is necessary for hash generation of nodeId.
  secret-key = ""

  # Resolve method:
  # - marathon
  # - dns
  resolver = "dns"

  dns {
    # Suffix of domain, for example, if we have record _service1._tcp.marathon.mesos that a suffix is "marathon.mesos"
    domain-suffix = "marathon.mesos"

    # Period (seconds) between requests to a DNS server.
    refresh-period = 5
  }

  # Configuration for marathon resolver
  marathon = {
    # List of marathon nodes.
    urls = "marathon.mesos:8080,127.0.0.1:8080"

    # Period (seconds) between requests to marathon API.
    refresh-period = 5
    
    # Balancer ID.
    balancer-id = "primary"    
  }

  services = [ ]
}

For balancing of load to nodes upstreams can be used which is contained within /etc/nginx/services-conf/*.conf

server {
    location / {
        proxy_pass         https://battle-dev;
    }
}

There is a approach to have access to a single node by a nodeId using special URL parameter nodeId (for example: https://battle-dev.domain.com?nodeId=b59102f182b8d9a90cf64d8952ce3a3a)

Parameter nodeId is hash function (default: md5) by string concatenation: "192.168.100.12" + "31934" + "some-secret-key". Default secret key is empty see property nginx-agent.secret-key

server {
    server_name   battle-dev.domain.com;

    location / {
        proxy_pass         https://$battle_dev_host;
    }
}

Caveat: if we going to use "access to concrete node", please, change secret-key to our value otherwise it will be possible to research our inner-network structure by busting of typical ip addresses.

Mustache template is used for creation of Nginx configuration files. Default template is contained inside of the jar, it is possible to change a path to the file by property nginx-agent.template-path but usual there is no necessary to edit this:

upstream {{SERVICE_NAME}} {
{{#NODES}}
    server {{HOST}}:{{PORT}};
{{/NODES}}
}

map $args ${{SERVICE_NAME_UNDERSCORE}}_host {
{{#NODES}}
    ~(.*)nodeId={{NODE_ID}}(.*) {{HOST}}:{{PORT}};
{{/NODES}}
}

{{#SERVER_CONFIG}}
# This part of config is relevant only for Marathon API resolver.
server {
    listen 0.0.0.0:80;
    server_name {{SERVER_NAME}};

    location / {
        proxy_pass https://{{SERVICE_NAME}};
    }
}
{{/SERVER_CONFIG}}

• Vasiliy Vazhesov ([email protected])

The MIT License

Copyright (c) 2016-present Vasiliy Vazhesov ([email protected])

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