[FLINK-24078] Remove brackets around variables

• Type: Sub-task
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Fix Version/s: 3.0.0
• Component/s: Runtime / Metrics
• Release Note: The keys in the map returned my MetricGroup#getAllVariables are no longer surrounded by brackets, e.g., <job_id> is now stored as job_id.
• Assignee: Chesnay Schepler
• Reporter: Chesnay Schepler
• Created: 31/Aug/21 10:44
• Updated: 03/Sep/24 07:05

Description

Internally, variable keys are stored with brackets, e.g., <job_id>.
In practice all reporters will filter these characters in one way or the other, and it overall is a subtle trap that we keep running into without providing any benefit.

We should get rid of them.