Failed parsing YAML experiment: while parsing a flow sequence

[antonionovaesjr]

Failed parsing YAML experiment: while parsing a flow sequence

[cdsre]

This same question was asked in chaostoolkit-aws (issue 146). I have added a comment that explains this behaviour and what the user needs to do to remediate it but I am also posting it here for completeness

---

The issue here is with the syntax of the yaml. In most cases you can leave strings unquoted and yaml will just consider them as strings. however in some cases you need to use quotes so yaml doesn't interprete a specific char as a yaml token, which is the case here. Using your experiment2.yaml we can replicate this issue outside of chaostoolkit

import yaml

with open("experiment2.yaml") as exp:
    yaml.safe_load(exp)

OUTPUT

line 483, in parse_flow_sequence_entry
    raise ParserError("while parsing a flow sequence", self.marks[-1],
yaml.parser.ParserError: while parsing a flow sequence
  in "experiment2.yaml", line 35, column 16
expected ',' or ']', but got '{'
  in "experiment2.yaml", line 35, column 19

Also you seem to be mixing the block style and flow style with your sequences and mappings. While these yield the same result in most cases, flow style is what's causing your issue here and how it is handled by the parser.

There are two way to resolve this. Either quote your values in the flow sequence and mappings for example

method:
- type: action
  name: change-subnets-asg
  provider:
    arguments:
      subnets: [ "${subnet01}" , "${subnet02}" ]
      asg_names: ["${nodegroup_infra}","${ nodegroup_app}"]
    func: change_subnets
    module: chaosaws.asg.actions
    type: python

Or switch these to block style, this would be my prefered choice as its the more common style used and what the majority of your experiment already uses for its style

method:
- type: action
  name: change-subnets-asg
  provider:
    arguments:
      subnets:
      - ${subnet01}
      - ${subnet02}
      asg_names:
      - ${nodegroup_infra}
      - ${ nodegroup_app}
    func: change_subnets
    module: chaosaws.asg.actions
    type: python

using either method to correct the file i can successfully run

 chaos validate .\experiment2.yaml
[2024-03-02 09:14:19 INFO] Validating the experiment's syntax
[2024-03-02 09:14:19 INFO] Experiment looks valid
[2024-03-02 09:14:19 INFO] experiment syntax and semantic look valid

Where are before with your original file I got

chaos validate .\experiment2.yaml
[2024-03-02 09:16:32 ERROR] Failed parsing YAML experiment: while parsing a flow sequence
      in ".\experiment2.yaml", line 35, column 16
    expected ',' or ']', but got '{'
      in ".\experiment2.yaml", line 35, column 19