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X Ray Advanced

Links: 102 AWS DVA Index

Sampling

  • With sampling rules, you control the amount of data that you record
  • You can modify sampling rules without changing your code

  • By default, the X-Ray SDK records the first request each second, and five percent of any additional requests.

    • One request per second is the reservoir, which ensures that at least one trace is recorded each second as long the service is serving requests.
    • Five percent is the rate at which additional requests beyond the reservoir size are sampled.
    • For example, if you set the reservoir size to 50 and fixed rate to 10%, then if 100 requests per second match the rule, the total sampled is 55 requests per second.
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    • Rate of 1 means all requests should be sent to X-Ray. This is only good for debugging and will be very expensive in production.

  • You can create your own rules with the reservoir and rate

  • We can define many sampling rules with different priority. Lower priority takes precedence.
  • We can also specify the matching criteria which determines what requests to match.
You can very quickly change the sampling rules from the X-Ray console and there is no need of restarting the application. Daemon knows how to fetch the new sampling rules.
If you are getting a huge AWS bill for AWS X-Ray then try enabling sampling.

X-Ray APIs

X-Ray Write APIs

  • Used by the X-Ray daemon
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  • PutTraceSegments: Uploads segment documents to AWS X-Ray. Used by developer.
  • PutTelemetryRecords: Used by the AWS X-Ray daemon to upload telemetry.
    • SegmentsReceivedCount, SegmentsRejectedCounts, BackendConnectionErrors
  • GetSamplingRules: Retrieve all sampling rules (to know what/when to send)
  • GetSamplingTargets & GetSamplingStatisticSummaries: advanced
  • The X-Ray daemon needs to have an IAM policy authorising the correct API calls to function correctly

X-Ray Read APIs

  • GetServiceGraph: main graph
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  • BatchGetTraces: Retrieves a list of traces specified by ID. Each trace is a collection of segment documents that originates from a single request.
  • GetTraceSummaries: Retrieves IDs and annotations for traces available for a specified time frame using an optional filter. To get the full traces, pass the trace IDs to BatchGet Traces.
    • We filter on annotations by using this.
  • GetTraceGraph: Retrieves a service graph for one or more specific trace IDs.
A developer has instrumented an application using the X-Ray SDK to collect all data about the requests that an application serves. There is a new requirement to develop a custom debug tool which will enable them to view the full traces of their application without using the X-Ray console. What should the developer do to accomplish this task?

Use the GetTraceSummaries API to get the list of trace IDs of the application and then retrieve the list of traces using BatchGetTraces API.

X-Ray with BeanStalk

  • AWS Elastic Beanstalk platforms include the X-Ray daemon
  • You can run the daemon by setting an option in the Elastic Beanstalk console or with a configuration file (in .ebextensions/xray-daemon.config)
  • Make sure to give your instance profile the correct lAM permissions so that the X-Ray daemon can function correctly
  • Then make sure your application code is instrumented with the X-Ray SDK

X-Ray with ECS

Things to be done for using the Side Car pattern.
  • Port mapping: container port 2000 and the protocol UDP
  • Environment Variable: So that X-Ray SDK can find the X-Ray daemon.
  • Link the containers from the network standpoint.

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Because of linking the containers value of xray-daemon can be resolved.

When using X-Ray with ECS we can only deploy x-ray as a container.

Depending on the ECS type it can be either daemon or side car.

A Developer is deploying an application using Docker containers running on the Amazon Elastic Container Service (ECS). The Developer is testing application latency and wants to capture trace information between the microservices. Which solution will meet these requirements? Create a Docker image that runs the X-Ray daemon, upload it to a Docker image repository or ECR, and then deploy it to the Amazon ECS cluster.

ECS Cluster with EC2

  • X-Ray Container as a Daemon
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  • X-Ray Container as a Side Car. Also known as multi container setup.
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ECS Cluster with Fargate

  • Since we don't have control over the underlying instances we can only use the Side Car pattern.
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Last updated: 2023-02-17