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Logs

FaaSr logs

Logs produced by FaaSr functions using the faasr_log() API are stored in an S3 server. This document overviews how to select an S3 server to store these logs, and the folder naming structure to help you locate a particular log

Selecting an S3 bucket for logs

  • In the typical scenario, a single S3 server/bucket can be used for both workflow files and logs, but you may also use separate buckets
  • The S3 server used for logs is configured as the Default server to store logs under Workflow settings in the FaaSr Workflow Builder Web UI

Log folder naming convention

  • Using the FaaSr Workflow Builder Web UI you must name your workflow uniquely; we'll use WorkflowName in this example
  • Using the FaaSr Workflow Builder Web UI you can also provide a name for the top-level log folder; if you do not provide one, by default the name is is set to FaaSrLog
  • Then, the path where you can find logs for a particular Action function execution is:

FaaSrLog/WorkflowName/InvocationTimestamp/InvocationID/ActionName.txt

Where: - ActionName is the name of the action (i.e. the name of a node in your DAG) - InvocationID is a specific invocation of your Action. Refer to the invocationID documentation for the different types of invocation IDs supported (UUID, user-provided, and timestamp-derived) - InvocationTimestamp is a string-formatted invocation timestamp recorded at the time your workflow's entry action starts execution. It is recorded as an ISO 8601-like timestamp with filename-safe separators

Examples

  • Suppose you run the FaaSr tutorial as an example
  • In this workflow configuration, the log folder is the default FaaSrLog and the workflow name is FaaSrTutorial
  • Suppose you also leave the InvocationID as default, which generates a unique UUID automatically at the start entry point. In this example, let's assume the UUID generated is: f81d4fae-7dec-11d0-a765-00a0c91e6bf6
  • Suppose when you invoke the workflow, the current time seen by the start action was timestamped as 2025-08-29T23-17-01

You will then be able to retrieve logs for the compute_sum action from the (unique) path:

FaaSrLog/FaaSrTutorial/2025-08-29T23-17-01/f81d4fae-7dec-11d0-a765-00a0c91e6bf6/compute_sum.txt

If you invoke the workflow again, a new timestamp and UUID will be generated

Cloud logs