autophagy opened a new pull request #17821:
URL: https://github.com/apache/flink/pull/17821
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## What is the purpose of the change
This PR exchanges the self-written YAML parser for `flink-conf.yml` with
`snakeyaml`. This has several benefits. For one, it will address issues like
FLINK-15358, where the Flink configuration parser erronously considers anything
after a '#' as a comment, even when the '#' occurs within a string.
Secondly, this means that we can support nested YAML keys, such that:
```
KeyA:
KeyB:
KeyC: "Hello"
KeyD: "World"
```
and
```
KeyA.KeyB.KeyC: "Hello"
KeyA.KeyB.KeyD: "World"
```
are equivalent configurations, letting users avoid repetition in their
config files.
Thirdly, this lets the Flink config loader support any valid YAML (and
reject invalid YAML, which the parser was previously accepting).
**However, this change could result in breaking behaviour**. For one, the
old yaml parser read row-by-row and just skipped invalid yaml rows. However,
snakeyaml reads the entire document at once and rejects it if any invalid yaml
files are present, which means that configurations before this change would be
accepted, whereas now they would not.
A potential way of getting around this might be to read the configuration
file line by line as its own yaml document, discarding invalid ones, but this
would mean that we wouldnt be able to have the nested keys structure outlined
above.
## Brief change log
- *The YAML parser for the global `flink-conf.yml` file now uses `snakeyaml`*
## Verifying this change
*(Please pick either of the following options)*
This change is already covered by existing tests, such as
`GlobalConfigurationTest`.
## Does this pull request potentially affect one of the following parts:
- Dependencies (does it add or upgrade a dependency): (yes)
- The public API, i.e., is any changed class annotated with
`@Public(Evolving)`: ( no)
- The serializers: (no)
- The runtime per-record code paths (performance sensitive): (no)
- Anything that affects deployment or recovery: JobManager (and its
components), Checkpointing, Kubernetes/Yarn, ZooKeeper: (yes)
- The S3 file system connector: (no)
## Documentation
- Does this pull request introduce a new feature? (no)
- If yes, how is the feature documented? (not applicable)
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