We don’t currently have any mechanism to configure value size or transaction size via
fdbcli. If you want to tinker with these values, I think it will be necessary for you to set the relevant knobs on every server process as well as any client process that might need to make use of the increased sizes.
Having other ways to generally configure knob values, potentially even on a live cluster, is an idea that has been considered from time to time, and I think it’s something that we’d ultimately like to have, but there is some trickiness involved that needs to be sorted out. In particular, here are some thoughts that have come up:
- Some knobs can be changed live, some can be changed on restart, and some can only be set upon database creation. Our scheme will need to take that into account.
- If we decide to allow different classes of knobs as described above, we’d need adequate testing to make sure a knob is categorized correctly and doesn’t break anything when changed.
- There are various other complexities, such as knobs that typically need to be changed in tandem or knobs where alternate values have never been tried and may not work. We can maintain the philosophy that knobs are use at your own risk, but there’s probably more likelihood for them to be misused when they are easily and prominently configurable.
If there are particular knobs that people are configuring frequently, then it may make sense to special case them and make it easier to adjust the values (we’ve done this, for example, with the size of the page cache). It’s possible these knobs fit that bill, though I don’t know how often they are being set.