How to access the IP of my other instance inside my app when configure for multiple instances

Question

Im going to deploy my application in BOSH and cluster it with n number of nodes. E.g., 2 So in my app, when I deploy the app in my manifest.yml I have defined below. So it starts at 10.244.15.21 and next node starts in 10.244.15.22 when give instances : 2 in my manifest.yml

static: - 10.244.15.2 - 10.244.15.20 

So in my each app I need to access each other nodes' IPs inside a XML file. How can i do this dynamically in a xml file. Please advice. Thanks

E.g.,

<parameter name="localMemberHost">127.0.0.1</parameter> 

<members> 
     <member> 
           <hostName>10.244.15.21</hostName>
           <port>4000</port> 
     </member> 
     <member> 
           <hostName>10.244.15.22</hostName> 
           <port>4000</port> 
     </member>

 </members>

Answer 1

Based on your sample you should be able to accomplish this using the combination of ERB evaluation of the job template, and a known range of IPs.

First define a specific range of IPs in your manifest matching the count for that job. You will need to increase the static reservations in the shared network definition to cover the .21 + range you need. Then the job uses an allotment of those static IPs. see https://bosh.io/docs/networks.html

jobs:
- name: clustered-job
  instances: 5
  templates:
    - name: jobname
      release: releasename
  networks:
  - name: default
    static_ips: [10.244.15.21 - 10.244.15.26] <-- you would need to make sure these are reserved in cloud config

I'm assuming the xml file in question is defined as a "template" in your job spec, this is required to enable the ERB evaluation using the properties available. https://bosh.io/docs/jobs.html#templates https://bosh.io/docs/jobs.html#properties

You'll use a loop and a few known properties to define all cluster members.

 <%= spec.networks.default.static_ips %>

To make the loop ingest whatever is specified in the manifest. You may want to add a property for the job to specify starting IP, as I forget if above gives you the IPS for the entire manifest, or just the job (I think its the latter).

<% @spec.networks.default.static_ips.each do |static_ip| %>
    <member> 
           <hostName><%= static_ip %></hostName>
           <port>4000</port> 
     </member>
<% end %>

You can also check spec.ip for the IP of current instance if you need to exclude that from the loop.