vouch/docs/graffiti.md

Graffiti providers

Static

The static graffiti provider uses the same single value for all proposed blocks. The graffiti is supplied in the "graffiti.static.value" configuration parameter. For example, to specify the graffiti "my graffiti" in a YAML configuration file the configuration would be:

graffiti:
  static:
    value: my graffiti

Note that Ethereum 2 block graffiti is a maximum of 32 bytes in length.

Dynamic

The dynamic graffiti provider uses a majordomo URL to obtain one or more values for proposed blocks. The graffiti is supplied in the "graffiti.dynamic.location" configuration parameter. For example, to fetch graffiti from the file "/home/me/graffiti.txt" in a YAML configuration file the configuration would be:

graffiti:
  dyanmic:
    location: file:///home/me/graffiti.txt

The location is a majordomo URL. It re-evalulated each time a block is proposed, so if in the above example the contents of the file change the graffiti in the next proposed block will alter likewise.

The dynamic graffiti provider has a number of additional features. Firstly, the majordomo URL undergoes variable replacement. The variables that are available for replacement are:

• {{SLOT}} the slot of the block being proposed
• {{VALIDATORINDEX}} the index of the validator proposing the block

For example, if the majordomo URL was file:///home/me/graffiti-{{VALIDATORINDEX}}.txt then a block being propopsed by validator 15 would result in the majordomo URL file:///home/me/graffiti-15.txt being used to fetch the graffiti.

Once the majordomo URL has been resolved the resultant data is separated in to multiple lines (blank lines are removed). If there is more than one line in the data then one of the lines is picked at random (note that vouch retains no memory of which lines have or have not been selected, so it is possible for the same line to be picked multiple times before another line is picked once).

The graffiti line also undergoes variable replacement, as per above. At this point the final result is used as the graffiti for the proposed block.

Note that Ethereum 2 block graffiti is a maximum of 32 bytes in length.