Expose client knobs through the FDBDatabaseFactory - #4488
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This allows FDB client knobs to be set via an API on the `FDBDatabaseFactory`. Knobs can be set on a running network, but we should generally encourage them to be set prior to starting the network, as some of them are not actually safe to mutate. But the FDB API is kind of unclear on which ones those are, so this does its best. There is a warning in the Javadoc discouraging souch recklnessness. The exact set of knobs that are available are pretty vast, and they also change with different FDB versions. This does add a non-exhaustive enum, `FDBClientKnob`. Every value in the enum is a known client knob, and associated with it is the type we expect it to be set to. For any knob in that list, if the user tries to set the knob, we will validate that the value is of a parseable type. There is also an escape hatch, `setKnob(String, String)`, which takes any arbitrary knob key and value. If using that secondary API, if the knob is in our known set, we validate the type. Otherwise, we let it go. As noted in the Javadoc, FDB does not throw an error if the knob fails to pass validation (or at least, it attempts not to), and just ignores the option. We call `setKnob` after calling `setTrace`, so there's a chance that we'll at least get the `TraceEvents` for it if the client is configured for it. This resolves FoundationDB#4479.
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This allows FDB client knobs to be set via an API on the
FDBDatabaseFactory. Knobs can be set on a running network, but we should generally encourage them to be set prior to starting the network, as some of them are not actually safe to mutate. But the FDB API is kind of unclear on which ones those are, so this does its best. There is a warning in the Javadoc discouraging souch recklnessness.The exact set of knobs that are available are pretty vast, and they also change with different FDB versions. This does add a non-exhaustive enum,
FDBClientKnob. Every value in the enum is a known client knob, and associated with it is the type we expect it to be set to. For any knob in that list, if the user tries to set the knob, we will validate that the value is of a parseable type. There is also an escape hatch,setKnob(String, String), which takes any arbitrary knob key and value. If using that secondary API, if the knob is in our known set, we validate the type. Otherwise, we let it go.As noted in the Javadoc, FDB does not throw an error if the knob fails to pass validation (or at least, it attempts not to), and just ignores the option. We call
setKnobafter callingsetTrace, so there's a chance that we'll at least get theTraceEventsfor it if the client is configured for it.This resolves #4479.