Parse flag defaults from a file in assemble_cvd. #1766
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jemoreira
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jemoreira
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New features and the code paths enabling them are often gated behind flags; initially, the defaults have these code paths disabled, i.e., the flags are off by default. That default value is statically defined in the flag's definition, and in order to change them to ramp up exposure to the new feature, we need to modify the flags before they are parsed. Here, we do this as follows. We introduce a key-equals-value file, where the keys are the flag names and the values are the new default value for the flag. If the file exists, then it is read and the defaults changed according to the key-value pairs in the file; otherwise, the statically defined defaults are used. This enables deployment of new features by deploying a new defaults file rather than by deploying the entire package, and lets new functionality be disabled by modifying or removing the defaults file, rather than rolling back the entire software package.
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New features and the code paths enabling them are often gated behind flags; initially, the defaults have these code paths disabled, i.e., the flags are off by default. That default value is statically defined in the flag's definition, and in order to change them to ramp up exposure to the new feature, we need to modify the flags before they are parsed.
Here, we do this as follows. We introduce a key-equals-value file, where the keys are the flag names and the values are the new default value for the flag. If the file exists, then it is read and the defaults changed according to the key-value pairs in the file; otherwise, the statically defined defaults are used.
This enables deployment of new features by deploying a new defaults file rather than by deploying the entire package, and lets new functionality be disabled by modifying or removing the defaults file, rather than rolling back the entire software package.