"Plugins" Posts

EC2 CloudWatch graphs, trends, and alerts

By Andre Bullet_white Posted in Updates, Plugins Bullet_white Comments Comments

If you're using Amazon EC2, you may be familiar with CloudWatch, Amazon's analytic system that provides metrics on CPU usage, Network I/O, and Disk I/O of your instances. While CloudWatch collects metrics, it doesn't provide a web interface for viewing the metrics, graphs, trending, or alerting.

Enter our Scout EC2 Cloudwatch plugin. Like any other Scout plugin, you can graph the resulting metrics, set triggers, track trends, and get email alerts when the numbers go out of bounds.

What does it monitor?

The CloudWatch plugin captures the following ("measures", as EC2 calls them): NetworkIn, NetworkOut, DiskReadOps, DiskWriteOps DiskReadBytes, DiskWriteBytes, CPUUtilization.

Note, this plugin does not fetch EC2 Load Balancer Metrics, only EC2 instance metrics.

Single Instance, Autoscaling Group, etc.

The EC2 CloudWatch plugin can capture metrics from a single EC2 instance, or it can aggregate metrics across a couple of dimensions. It can aggregate metrics across a given instance type, across all instances launched from a specific image (AMI), or by a specified autoscaling group. That means you can, for example, graph the performance of your application server autoscaling group as a whole, or graph just your memcached instance.

Enabling Cloudwatch

To use this plugin, you have to enable CloudWatch for the instance(s) you want to collect metrics from. See Amazon's CloudWatch docs for details. Basically, it's just ec2-monitor-instances ##### from the command line, or passing a monitoring parameter to the ec2-run-instances. It's covered nicely in Amazon's docs.

New to Scout?

If you're learning about Scout through this plugin, sign up for a trial Scout account to give this plugin a try. You can graph all kinds of metrics and measurements from all your servers. It works with cloud instances, VPS's, and dedicated hardware.


New Plugin: iostat

By Andre Bullet_white Posted in Plugins Bullet_white Comments Comments

Thanks to Rob Lingle of Rails Machine, we have a new plugin for monitoring IO performance. See the iostat plugin here.

What is iostat and why would I use it?

iostat reports terminal and disk I/O activity. You should use it if you suspect a device is IO bound. Ilya Grigorik recently put up a good post on iostat, and the man pages are here.

What are the plugin configuration options?

There are three configuration options for the iostat plugin:

  • iostat Command -- most likely, you won't need to change this. Consult the iostat documentation for other flags and options.
  • Device -- defaults to /, or specify any defice you want to monitor.
  • Interval -- defaults to three seconds; set to a different number to have iostat report averages over that many seconds

How do I install the plugin in Scout?

Just like any other plugin, go the Scout plugin directory and select the Device Input/Output plugin.

Ensure the iostat command is installed on your server. If it's not, you probably just need to install the sysstat package. For example, on Ubuntu this is apt-get install sysstat.

Enjoy, and let us know if you have any feedback.


A tour of Scout's Ruby on Rails Monitoring Plugin

By Derek Bullet_white Posted in Plugins Bullet_white Comments Comments

Curious how data moves from your Rails app to Scout? Wondering how Scout handles high-traffic Rails apps? Where does Scout add MySQL suggestions? How are alerts generated? I’ll guide you through the process below.

Logging each web request

At a basic level, Scout’s Rails benchmarking isn’t much different than what gets written to your Rails log. Instead of writing to a log file, the Scout Rails Instrumentation plugin sends a Hash to the Scout Agent like the one below:

{:num_requests=>2, :avg_request_time=>241.0, :actions=>
:num_requests=>2, :render_runtime_avg=>8.59355926513672, :render_runtime_max=>8.73303413391113, 
:runtime_avg=>241.0, :other_runtime_avg=>77.4774407348633, 
:queries=>[[[156.152, 0]], [[153.706, 0]]], :runtime_max=>243.0, 
:other_runtime_max=>78.1149658660889, :db_runtime_avg=>154.929}}, 
:queries=>["SELECT * FROM \"users\""], 
:scout_time=>"Mon Jun 15 21:04:00 UTC 2009"}

These messages are sent to the Scout Agent every 30 seconds by the Scout#Reporter.report! method:

response = ScoutAgent::API.queue_for_mission(Scout.config[:plugin_id], report)

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Scout Checks in on Passenger

By Derek Bullet_white Posted in Updates, Plugins Bullet_white Comments Comments

The number one requested plugin for Scout has been a Phusion Passenger monitor. I’m happy to report that is now available.

Scout ~ Advance Marketing Engine

Using the new Passenger Monitor plugin, Scout can keep track of Passenger’s VM size, process count, and the amount of private memory it has squirreled away. Aside from just tracking these numbers for graphs, you can also elect to be emailed if any of these statistics crosses a line you indicate. As an added bonus, this plugin also tracks the same statistics for the Apache instance managing Passenger.

Passenger has quickly become a great new way to deploy Rails applications and we want to make sure Scout is keeping up with the curve.


Keep Process Running Plugin

By Derek Bullet_white Posted in Plugins Bullet_white Comments Comments

Sometimes, the simplest ideas make for the best plugins.

Let’s say you have some process that always needs to be running (maybe that’s a ferret server or a backgrounDRb server) or maybe it’s just Apache.

Install the Keep Process Running Plugin and Scout will help make sure that process is always running.

The plugin simply scans the active running processes, and checks to see if that process is running. If it can’t find it in the active process list, it will attempt to run the restart action. You can specify anything, so if you need to perform some special startup task (/usr/bin/apachectl start) it can do that. If you do not specify a restart action, it simply re-runs the command it is looking for. This actually works well in most cases.

If you have any feedback or suggestions on this plugin feel free to comment on the plugin itself.


Track Active Logins & more

By Derek Bullet_white Posted in Plugins Bullet_white Comments Comments

Ever wanted to track how many people are logged into your server? Mark Hasse built an Active Logins plugin that does just that, returning the total number of people logged in via console, ssh, telnet, etc.

Mark has built several other plugins as well:

It’s easy to create a Scout a plugin and we’re here to help. Some useful plugin resources:

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