puppet template remove the last comma

Question

I have the following puppet example template:

{
  "servers" : [ {
    "port" : 9200,
    "host" : "localhost",

    "queries" : [
      <% @markets.each do |market| -%>
      {
      "outputWriters" : [ { "@class" : "com.googlecode.jmxtrans.model.output.StdOutWriter" } ],
      "obj" : "solr/market_<%= market %>:type=queryResultCache,id=org.apache.solr.search.LRUCache",
      "attr" : [ "hits","hitratio" ]
    },
    <% end -%>
    ],
    "numQueryThreads" : 2
  } ],
}

Applying it with market=['UK','FR','IT'], I get the following:

{
  "servers" : [ {
    "port" : 9200,
    "host" : "localhost",

    "queries" : [
            {
      "outputWriters" : [ { "@class" : "com.googlecode.jmxtrans.model.output.StdOutWriter" } ],
      "obj" : "solr/market_UK:type=queryResultCache,id=org.apache.solr.search.LRUCache",
      "attr" : [ "hits","hitratio" ]
    },
          {
      "outputWriters" : [ { "@class" : "com.googlecode.jmxtrans.model.output.StdOutWriter" } ],
      "obj" : "solr/market_FR:type=queryResultCache,id=org.apache.solr.search.LRUCache",
      "attr" : [ "hits","hitratio" ]
    },
          {
      "outputWriters" : [ { "@class" : "com.googlecode.jmxtrans.model.output.StdOutWriter" } ],
      "obj" : "solr/market_IT:type=queryResultCache,id=org.apache.solr.search.LRUCache",
      "attr" : [ "hits","hitratio" ]
    },
        ],
    "numQueryThreads" : 2
  } ],
}

The problem is the last comma, which makes it an invalid solr config.

Instead of applying markets.each do, I could use market.map and join(','). but how to use map in this case?

I can use map as follows:

<%= @markets.map{ |market| "hello_"+market }.join(',') -%>

this would print hello_UK,hello_FR,hello_IT (note that we don't have a comma after hello_IT), but I would need something like this:

{
  "servers" : [ {
    "port" : 9200,
    "host" : "localhost",

    "queries" : [
      <% @markets.map |market| -%>
      {
      "outputWriters" : [ { "@class" : "com.googlecode.jmxtrans.model.output.StdOutWriter" } ],
      "obj" : "solr/market_<%= market %>:type=queryResultCache,id=org.apache.solr.search.LRUCache",
      "attr" : [ "hits","hitratio" ]
    },
    <% }.join(',') -%>
    ],
    "numQueryThreads" : 2
  } ],
}

this does not work.

so, how to make it work? or how to modify my puppet template to remove the last comma?

Answer 1

This is actually a Ruby problem rather than a Puppet problem. Since this is an array, just change the .each to .each_with_index. Then you can wrap the final comma in a check to see whether the current index value is one less than the size of the index. For example, the following code adds a comma only if the current market is not the last one in the array:

<% @markets.each_with_index do |market, i| -%>

and then

}<%= ',' if i < (@markets.size - 1) %>

Answer 2

I saw on a puppet labs site (https://ask.puppetlabs.com/question/4195/joining-array-from-hieraconcat-other-value-in-erb/) this form of solution.

<%= quorum.map{ |srv| "#{srv}:#{portNum}" }.join(',') %>

This code lets you take an array and create a variation of each element then join them all together with the appropriate join text (not including a spurious comma at end).