Unified Logs with pulumi logs

Posted by Luke Hoban on Apr 2, 2019 2:02:16 PM
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Pulumi makes developing and deploying rich serverless and container-based applications a breeze. But how do you monitor and observe those applications while they are being developed and once they are deployed? There are many great answers: from the built-in capabilities of the underlying cloud services (Lambda, ECS, Kubernetes, and more), to great 3rd party solutions like IOpipe and Epsagon which we highlighted recently on this blog.

The Pulumi CLI provides another way to do logging, without requiring the additional setup of these existing solutions and seamlessly integrated into your Pulumi development workflow. The pulumi logs command provides a great first place to start for understanding your Pulumi application’s behaviour. Especially during development, this command provides direct insight into the behaviour of your application, bringing together logs across all of the different forms of compute you are using - from code running in serverless functions to containers to VMs.

Let’s take a quick look at pulumi logs and some of the ways it can be used as part of the inner loop of your Pulumi development.

Note: Currently pulumi logs supports only logs for applications running in AWS. In the near future it will be expanded to Kuberentes, Azure, GCP and additional cloud platforms.

Logging for Inner-Loop Development

When developing locally, it is common to use logging as an interactive part of the development process. With pulumi logs, we can bring some of these same approaches into the inner loop of the development process even for applications being actively developed/deployed in the cloud.

Let’s take a simple example:

import * as aws from '@pulumi/aws'
const bucket = new aws.s3.Bucket("mybucket");
bucket.onObjectCreated("newObject", async (ev) => {
    console.log(JSON.stringify(ev));
});
export const bucketName = bucket.id;

We can deploy this app, copy an object into the newly provisioned bucket, and then see the logs with the following:

$ pulumi up --skip-preview

$ aws s3 cp somefile.txt s3://$(pulumi stack output bucketName)

$ pulumi logs -f
Collecting logs for stack dev since 

 2019-03-28T21:10:05.667-07:00[                     newObject] {"Records":[{"eventVersion":"2.1","eventSource":"aws:s3","awsRegion":"us-west-2","eventTime":"2019-03-29T04:10:05.318Z","eventName":"ObjectCreated:Put","userIdentity":{"principalId":"AWS:AIDAIB2I7NPKMQ2QAKXZ6"},"requestParameters":{"sourceIPAddress":"24.35.94.249"},"responseElements":{"x-amz-request-id":"F2D7DF26693AEFEE","x-amz-id-2":"o2leqNNwCVXTI8jfvUGk5KE7w6CiKsJYP/Q4nT0fHqZPrqwaVlSP0lNhspv5NiLAAwutCzJwlLc="},"s3":{"s3SchemaVersion":"1.0","configurationId":"tf-s3-lambda-20190328222809603300000002","bucket":{"name":"mybucket-97f10e0","ownerIdentity":{"principalId":"A3FZDZNSWOKQHV"},"arn":"arn:aws:s3:::mybucket-97f10e0"},"object":{"key":"out.txt","size":36000,"eTag":"818ac0cf0273f7e40e673d9892405e31","sequencer":"005C9D9A9D311D5C11"}}}]}

I can use this to quickly see what kind of values I get back on an S3 Bucket Object event, using live data running in the cloud. But I can do this whole thing in just a couple of seconds - from deployment to logs. This lets me iterate on my application live in the cloud with ease.

If there are errors in my code, I find out about them immediately:

bucket.onObjectCreated("newObject", async (ev, ctx) => {
    throw new Error("oops");
});

Results in:

$ pulumi logs --since 1m
Collecting logs for stack dev since 2019-03-28T20:17:28.000-07:00.

 2019-03-28T21:17:01.269-07:00[                     newObject] {"errorMessage":"oops","errorType":"Error","stackTrace":["/var/task/__index.js:26:11","Generator.next (<anonymous>)","/var/task/__index.js:12:71","new Promise (<anonymous>)","Object.<anonymous> (/var/task/__index.js:8:12)","Object.__f1 [as __awaiter] (/var/task/__index.js:17:34)","/var/task/__index.js:24:21","__f0 (/var/task/__index.js:30:34)"]}

Aggregating Logs

As applications grow to span multiple forms of compute – such as micro services, lambdas, containers, and VMs – it becomes important to be able to correlate logs across services.

One great example of this is the video thumbnailer example which implements this simple architecture involving two buckets, a lambda event, and a long-running Fargate container task.

unnamed

The Pulumi program deploys several components, using different types of cloud resources. But using Pulumi logs we can see all logs in a single, unified view.

terminal-logs

From the image above, you can see the onNewVideo Lambda function, then triggering the ffmpegThumbTask Fargate container, and then copying a file back into S3 triggering the onNewThumbtail Lambda function. So you don’t need to jump around between different systems for viewing logs, you can get a consistent view of what’s going on in your cloud application!

Underneath the hood, these logs live in different and uncorrelated CloudWatch LogGroups, spread across an AWS account. But with pulumi logs we can get the application-centric view we need to understand the overall behaviour of our application architecture.

Controlling Log Rendering

The pulumi logs command supports a few options for controlling what gets logged.

The --since flag retrieves logs only since a given relative or absolute time. For example, pulumi logs --since 1m will get logs just since 1 minute ago - useful for limiting logs to only what’s happened very recently - especially during inner-loop development. And to get logs since a specific point in time (such as the timestamp of a known event from a previous execution of pulumi logs) you can use pulumi logs --since 2019-03-28T21:17:01.269-07:00.

A couple of the examples above used the --follow flag to follow the log output until cancelled. This is useful when waiting for log output to come in during debugging.

And for applications with many resources, it is often important to scope results down to one or more specific resources, which can be done with the --resource flag. For example, logs for just the Fargate task above could be retrieved with pulumi logs --resource ffmpegThumbTask.

Working Seamlessly with Your Cloud Provider

Like many other Pulumi features, pulumi logs works by building on top of the great building blocks provided by the underlying cloud provider services. Instead of adding new runtime logging infrastructure to your application, pulumi logs lets you easily extract out logs directly from your existing infrastructure. But because Pulumi understands the natural application scope for what resources are part of a single application, it can bring together the logs from all of those resources into one place, instead of having to think about individual resources.

Behind the scenes, pulumi logs makes the same calls to CloudWatch Logs or other backend log providers that you would make yourself via the aws CLI or AWS Console. But you don’t have to think about the physical identities of the cloud resources themselves - Pulumi takes care of finding the resources with supported logs, collecting those logs based on the requested filters, and then presenting them in unified logical view.

What’s Next?

We’ve seen Pulumi users working with Lambda, ECS and other AWS compute offerings become heavy users of pulumi logs during development. But supporting a broad set of cloud providers is key to our mission at Pulumi - so we really want to bring these benefits to all Pulumi users. We’ll be expanding pulumi logs to Kubernetes, Azure and GCP in the near future - with easy support for plugging in other cloud providers and cloud resources as sources for log data.

Even better, because Pulumi allows you to work with multiple cloud providers at once - like AWS and Kuberentes, or GCP and Azure, or even two different AWS regions - pulumi logs will be able to aggregate logs across multiple cloud providers and offer a seamless application-centric view of your logs.

Users of the Pulumi Console at https://app.pulumi.com also would love to have access to these logs at the click of a button - and this is something we’re also excited to enable in the near future.

You can take pulumi for a spin today by checking out the Getting Started guide or some of the Pulumi Examples. Then join us in the Pulumi Community Slack to chat about where you want to see us go (and where you’d like to help out!) with pulumi logs and other features of the Pulumi open source project in the coming weeks and months.

Topics: AWS, Features, Logging

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