如何创建下限为负无穷（-∞）的伸缩步骤？规则与实操疑问

Let's tackle your two questions based on the step adjustment rules you outlined for scaling policies:

1. Why is a "negative infinity" lower limit required? #

The requirement for a negative infinity lower limit ties directly to rules 1 and 3 from your document:

• Rule 1 mandates that step ranges can't have overlaps or gaps. If any step has a negative lower limit (e.g., a step that applies when the metric is between -50 and 0), we need a way to cover all metric values below that negative lower limit. Without a negative infinity step, there would be a gap in the policy's coverage—values less than -50 wouldn't trigger any adjustment, which breaks the "no gaps" rule.
• Rule 3 enforces this: if you have a step with a negative lower bound, you must include a negative infinity step to cover the entire negative range below it. This ensures your scaling policy handles all possible metric values, even edge cases where metrics dip into negative territory (like custom metrics tracking resource usage deficits or error rate offsets).

2. How to create a step adjustment with a negative infinity lower limit (when you don't see the "-∞" option)? #

It's common for UI interfaces to label or handle negative infinity differently than the "+∞" option you're used to. Here are a few things to try:

• Check for a dropdown or "no lower limit" option: Look next to the lower limit input field—some platforms use a dropdown with options like "None", "Negative Infinity", or "No Minimum" instead of showing "-∞" directly. Selecting this will set the lower bound to negative infinity.
• Leave the lower limit field empty: If there's no dropdown, try not entering any value in the lower limit box, while setting a valid upper limit (remember rule 6: you can't leave both upper and lower limits empty). Many systems interpret an empty lower limit as negative infinity by default.
• Verify compliance with other rules: Make sure you only create one such step (rule 2), and if you have steps with negative lower bounds, this negative infinity step must exist in your policy (rule 3).
• Check platform-specific UI cues: Sometimes the label might be subtle—like "Start from lowest value" or "Minimum possible" instead of explicit "-∞". If you're still stuck, look for inline help text in the policy editor (small question marks or tooltips) that explains how to set unbounded lower limits.

Quick recap of the key rules you shared for context:

1. Step adjustment ranges cannot overlap or have gaps
2. Only one step can have an empty lower limit (negative infinity)
3. If a step has a negative lower limit, a negative infinity step must exist
4. Only one step can have an empty upper limit (positive infinity)
5. If a step has a positive upper limit, a positive infinity step must exist
6. A single step cannot have both empty upper and lower limits
7. When the metric value is above the threshold: lower limit is inclusive, upper limit is exclusive; when below: lower limit is exclusive, upper limit is inclusive

内容的提问来源于stack exchange，提问作者red888