How to do hash arithmetic - ruby

Question

I want to subtract the ackedOns time from the startOn time in the hash to get how many epoch seconds it took to acknowledge the alert.
Here is the code:
url = "https://xyz"
uri = URI(url)
http = Net::HTTP.new(uri.host, 443)
http.use_ssl = true
http.verify_mode = OpenSSL::SSL::VERIFY_NONE
req = Net::HTTP::Get.new(uri.request_uri)
response = http.request(req)
jsonResponse = JSON.parse(response.body)
#troubelshooting step to see how many total alerts there are
total = jsonResponse['data']['total']
pp total
# create the collected_alerts hash
collected_alerts = { 'hosts'=> [],'dataPoints' => [], 'startOns' => [], 'ackedOns' => [], 'timeToAcks' => [] }
# iterate through the json
jsonResponse['data']['alerts'].each do |alerts|
# store the interested json values into the appropriate hash
collected_alerts['hosts'] << alerts['host']
collected_alerts['dataPoints'] << alerts['dataPoint']
collected_alerts['startOns'] << alerts['startOn']
collected_alerts['ackedOns'] << alerts['ackedOn']
# Calculate mins it took to acknowledge alert and store it in timeToAcks
# Formula is Ack time - Start time which would give us seconds / 60 to give mins.
alerts['timeToAcks'] = alerts['ackedOn'].zip(alerts['startOn']).map{|a,s| a-s/60}
end
pp collected_alerts
CSV.open("data.csv", "wb") {|csv| collected_alerts.to_a.each {|elem| csv << elem} }
Here is the json response that i am trying to parse
{
"status": 200,
"data": {
"total": 3,
"alerts": [
{
"dataPoint": "average",
"ackedBy": "x",
"dataSourceInstance": "Ping50Packets",
"dataSource": "Ping50Packets",
"host": "x",
"endOn": 0,
"ackedOn": 1392218853,
"dataSourceInstanceId": 400554,
"hostId": 1829,
"type": "alert",
"dataSourceId": 560,
"ackedOnLocal": "2014-02-12 07:27:33 PST",
"id": 6862895,
"startOn": 1392197595,
"thresholds": "> 200",
"endOnLocal": "",
"level": "warn",
"ackComment": "Ack.",
"value": "206.00",
"hostDataSourceId": 137481,
"acked": true,
"hostGroups": [{
"alertEnable": true,
"createdOn": 1367604091,
"id": 106,
"parentId": 105,
"description": "",
"appliesTo": "",
"name": "x",
"fullPath": "x"
}],
"startOnLocal": "2014-02-12 01:33:15 PST"
},

Answer 1

something like;
alerts['tta'] = alerts['ackedOns'].zip(alerts['startOns']).map{|a,s| a-s/60}

Answer 2

Based on your data, you simply need to do:
collected_alerts['timeToAcks'] << (alerts['ackedOn'] - alerts['startOn'])/60
Your origin code had a spelling mistake in one of the field names.
You want to push these values into collected_alerts, not the current alert, right?
Alternatively, after your have looped through all the alerts:
ca = collected_alerts
ca['timeToAcks'] = ca['ackedOns'].zip(ca['startOns']).map{ |ack,st| (ack-st)/60 }
Further, instead of looping through the alerts one at a time and pulling out the pieces, I would do this:
alerts = jsonResponse['data']['alerts']
collected_alerts = {}
%w[host dataPoint startOn ackedOn].each do |field|
collected_alerts[field] = alerts.map{ |alert| alert[field] }
end
Or even better:
alert_fields = %w[host dataPoint startOn ackedOn]
collected_alerts = Hash[ alert_fields.map{ |f| [f,alerts.map{|a| a[f] }] } ]
Explained, roughly in execution order.
alert_fields = %w[ … ] — create a variable referencing an array of string values (space-delimited in the source code), i.e. ["ackedOn", "host", … ]
alerts.map{ |a| … } — Create a new array by taking each value in the alerts array, creating a variable named a that references that value, and use the result of the block as the value in the new array.
a[f] — for each alert in the alerts array, look up the key with the value of f. For example, when f is "ackedOn", this looks up the value of a["ackedOn"].
alert_fields.map{ |f| … } — for each element in the array create a variable named f (for 'field') and run the contents of this block. Create a new array where the contents are, for each entry, whatever the final value of the block results in.
[f, … ] — after creating an array of all the values for a particular field in all the alerts, the result of this block is a two element array that is the name of the field followed by these values. For example, [ "ackedOn", [1,3,16,4,44,7] ].
Hash[ … ] — given an array of two-valued arrays, create a hash mapping the first value in each pair to the second value, i.e. { "ackedOn" => [1,3,16,4,44,7] }
This same Hash[…] method alternatively accepts an even number of arguments, pairing each even-numbered argument with the following one.
With examples:
alert_fields = %w[ackedOn host dataPoint startOn]
#=> ["ackedOn", "host", "dataPoint", "startOn" ]
alerts.map{|a| a[f] }
#=> [5,3,4,5,1,6,8,2,…]
[f,alerts.map{|a| a[f] }]
#=> ["ackedOn",[5,3,4,5,1,6,8,2,…]]
alert_fields.map{ |f| [f,alerts.map{|a| a[f] }] }
#=> [
#=> ["host",['foo','bar',…]],
#=> …
#=> ["ackedOn",[5,3,4,5,1,6,8,2,…]]
#=> ]
Hash[ alert_fields.map{ |f| [f,alerts.map{|a| a[f] }] } ]
#=> {
#=> "host" => ['foo','bar',…],
#=> …
#=> "ackedOn" => [5,3,4,5,1,6,8,2,…]
#=> }