Tag: cloud

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Running AWS Lambda functions on a timed schedule

AWS Lambdas can be called directly or triggered to execute based on a configured event. If you take a look at the ‘CloudWatch Events’ section, there is a configuration option for a Rule that can take a cron expression to trigger a Lambda based on a timed schedule. This could be useful for scheduling maintenance tasks or anything that needs to run on a periodic basis:

Scroll down to the ‘Configure trigger’ section and you’ll see the ‘Schedule Expression’ field where you can enter an expression like ‘rate(x minutes)’ (there’s a typo in the screenshot below it should be ‘minutes’ not ‘minute’) or define a cron style pattern:

Scroll further down and there’s an option to enable the schedule rule straight away, or disable it for testing, and you can enable it when you ready to start the schedule later:

After you’ve created the Rule, if you need to edit it you’ll find it over in the CloudWatch console page, under Events / Rules:

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Migration to new VPS running my blog in Docker containers now complete!

After many more hours than I expected or planned, I’ve migrated this site to run on a new VPS provider running in a larger KVM based VPS. The site is now running with nginx and php5-fpm in one Docker container, and MySQL in another, linked together with docker-compose.

Along the way I ran into several issues around performance and firewall configurations, which led to setting up a GitLab CI/CD pipeline (here and here) so I could more quickly iterate and deploy changes to a local test VM server on my ESXi rack server. I set up this test VM to mirror the configuration in my VPS KVM, and then used a GitLab pipeline to push the containers to my test server, and then manually push to my production VPS server when ready to deploy.

The good news is I learned plenty along the way, but also went down several rabbit holes trying to chase down performance issues that turned out to be more related to my misconfiguration of Ubuntu’s UFW and Dockers interaction with iptables that caused some weirdness.

The other good news is I have plenty of RAM and CPU to spare in this KVM based VPS where I’m running Docker, so I’ll be able to take advantage of this to deploy some other projects too (this was one of my other reasons for migrating to another server/provider). I’ll share some additional posts about some of the specifics of the GitLab CI/CD config, dockerfile and docker-compose configurations in the next few days.

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AWS Lambda cost calculator webapp

AWS Lambda usage costs are a little tricky to understand, because the usage cost is per GB seconds of usage. This is calculated from the execution time of your Lambda by the GB of memory it is configured to use. For example, a single request to a Lambda configured to use 1GB that executes for 1 sec is 1 GB-sec.

AWS offers a free tier that includes the first 400,000 GB-s for free, and the first 1,000,000 requests a month for free. Above those you’re charged $0.00001667 for each GB-s and $0.20 for every 1M additions requests. Check the details here.

I put together a simple webapp that allows you to play with the numbers and see what your costs are going to look like. You can check it out (served from AWS S3) here:

 

https://s3-us-west-1.amazonaws.com/awslambdacostcalc/index.html

If you’re interested in taking a look at the source for the React app, it’s here on Github. Create me a ticket if you find any issues.

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AWS CloudWatch default metrics for EC2 instances

AWS CloudWatch allows you to monitor events and logs from the services you are running. There are a set of default metrics provided, and you can also create you own custom metrics.

From a running EC2 instance, let’s look at the metrics displayed beneath your selected instance, on the Monitoring tab:

By default we get metrics displayed for:

  • CPU utilization
  • Disk reads/writes bytes and operations
  • Network in/out bytes and packets
  • Status checks failed

Now let’s create a new CloudWatch dashboard and add some metrics. Press ‘Create Dashboard’:

Next you can select a chart type, and then select from the available metrics. For EC2 there are 105 metrics to pick from:

Let’s see what options we have – you can enter filter values in the entry field. Let’s say I’m interested in disk reads/writes:

Notice the second column is by InstanceId, so if you have many instances (including it seems terminated instances which are showing in my list), make sure you pick the stats for the instance you want to monitor – here I’ve added a widget for Disk read/write bytes, and CPU utilization:

 

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