New Relic provides a crazy amount of data about the running of both your servers and your applications. This includes application performance data, errors, low level metrics and even rolled up method or database query performance. $149 per host per month for our 200 hosts gives us $29,800 per month.
Librato Metrics provides a fantastic way of storing arbitrary time series data. We're already storing lots of data in New Relic but Metrics provides us with less opinionated software so we can use it for anything, for instance number of logins or searches or other business level metrics. We'll go for a plan with 200 data sources, 100 metrics each and at 10 second resolution for a cost of $3,860per month.
Pagerduty is all about the alerts side of monitoring. Most of the other SaaS tools we've chosen integrate with it so we can make sure we get actionable emails and SMS messages to the right people at the right time. Our plan costs $18 per person per month, so lets say we have 30 people at a cost of $540 per month.
Papertrail is all about logs. Simple setup your servers with syslog and Papertrail will collect, analyze and store all your log messages. You get a browser based interface, search tools and the ability to setup alerts. We like lots of logs so we'll have a plan for 2 weeks of search, 1 year archive and 100GB month of log traffic. That all costs $575 per month.
Sentry is all about exceptions. We could be simply logging these and sending them to Papertrail but Sentry provides tools for tracking and rolling up occurences. We'll go for a plan with 90 days of history and 200 events per minute at a cost of $199 a month.
Pingdom used to provide a very simple external check service, but now they have added more complex multistage checks as well as real user monitoring to the basic ping. We'll choose the plan with 250 checks, 20 Real User Monitoring sites and 500 SMS alerts for $107 a month.
In total that all comes to $35,080 (£20,922) per month, or $420,960 (£251,062) per year.
Now the first reaction of lots of people will be that's a lot of money and it is. But remember open source isn't free either. We need to pay for:
I think people with the ability to build software tend to forget they are expensive, whether as a contractor or as a full time member of staff. And people without management experience tend to forget costs like insurance, rent, management overhead, recruitment, etc.
And probably more important than these for some people we need to consider:
The time needed to put together a good monitoring stack based on for instance logstash, kibana, riemann, sensu, graphite and collectd isn't small. And don't forget the number of other moving parts like redis, rabbitmq and elasticsearch that need installing configuring and maintaining. That probably means compromising in the short term or shipping later. In a small team how core is building your monitoring stack to what you do as a business?
Source: https://spring.io/understanding/REST
An idempotent operation is an operation, action, or request that can be applied multiple times without changing the result, i.e. the state of the system, beyond the initial application.
EXAMPLES (WEB APP CONTEXT):
NULLIPOTENT: If an operation has no side effects, like purely displaying information on a web page without any change in a database (in other words you are only reading the database), we say the operation is NULLIPOTENT. All GETs should be nullipotent. Otherwise, use POST.
IDEMPOTENT: A message in an email messaging system is opened and marked as "opened" in the database. One can open the message many times but this repeated action will only ever result in that message being in the "opened" state. This is an idempotent operation.
NON-IDEMPOTENT: If an operation always causes a change in state, like POSTing the same message to a user over and over, resulting in a new message sent and stored in the database every time, we say that the operation is NON-IDEMPOTENT.
When talking about the state of the system we are obviously ignoring hopefully harmless and inevitable effects like logging and diagnostics
Source: http://stackoverflow.com/questions/1077412/what-is-an-idempotent-operation
