influxdata/telegraf

persist starlark state for more starlark types

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#15,924 opened on Sep 22, 2024

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area/starlarkfeature requesthelp wantedsize/m

Description

Use Case

#15170 added the ability for the starlark processor to persist the global state to the statefile between runs. This is very nice, but it can't store lists, dicts, tuples, or metrics to the state file which severely limits its usefulness. If you try any more complex type you get an error like invalid starlark type *starlark.Metric when it tries to write the state file.

My desired use case is similar to the example for comparing a metric to the previous one. This doesn't work because it stores both a dict and a metric in the global state.

Expected behavior

Starlark standard types (lists, dicts, tuples, and maybe also metrics) can be persisted to the statefile.

Actual behavior

Error when persisting the plugin states.

Additional info

No response

Contributor guide

Tech stack
go
Domain
backend
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Go programmingStarlark knowledgeTelegraf plugin architecture
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
50
Research direction
Issue #15170 added initial persistence for some Starlark types. The current implementation in plugins/processors/starlark needs to be extended to support lists, dicts, tuples, and metrics. Review the serialization/deserialization logic in the state file handling, likely in the starlark plugin code. The goal is to make these types persistable without errors. Check the existing tests and examples, such as compare metrics.star, to ensure the new functionality works.