Add new analysis --count-blocks

[EncodePanda]

cabal run ouroboros-consensus-cardano:db-analyser --\
  --db db_mainnet_with_alonzo_40217333 cardano \
  --configByron dbacfg/mainnet-byron-genesis.json \
  --configShelley dbacfg/mainnet-shelley-genesis.json \
  --nonce 1a3be38bcbb7911969283716ad7aa550250226b76a61fc51cc9a9a35d9276d81 \
  --configAlonzo dbacfg/mainnet-alonzo-genesis.json \
  --only-immutable-db \
  --analyse-from 39842441 \
  --count-blocks

About to count number of blocks processed...
Counted: 16378

[nfrisby]

You don't necessarily need GetBlock here. It could be any of the following ctors, since it's unused.

https://github.com/input-output-hk/ouroboros-network/blob/c82309f403e99d916a76bb4d96d6812fb0a9db81/ouroboros-consensus/src/Ouroboros/Consensus/Storage/Common.hs#L148-L167

In particular, it could be GetPure () -- ie "get nothing". If we're wanting this command to identify eg malformed files (eg things that don't successfully deserialize), then that wouldn't work. But I don't get the sense that's what this command is for.

[EncodePanda]

I agree. Will make a change here.

[nfrisby]

I don't know the motivation for this specific command, but it doesn't seem unreasonable and the implementation here is fine. (I suggested one simplification.)

Also, right now this also counts EBBs. Is that right? Does it matter? Should we be explicit about it? If needed: there is a BlockComponent constructor that would let us simultaneously count the number of EBBs, so this command could report both counts.

So: I have clicked Approve.

If we accumulate too many of these "trivial" commands for our liking, we may wish to remember that there are lots of other ways this same query could be answered. EG reporting the first and last block no of some other "more significant" but not "too much slower" command and then printing the difference at the end.

[EncodePanda]

I don't know the motivation for this specific command, but it doesn't seem unreasonable and the implementation here is fine. (I suggested one simplification.)

There two motivations:

1. I wanted to have a clean PR showing how to add a new analysis into the tool (so I could add that to docs)
2. I actually need to learn how many blocks I see while running the tool for various snapshots, thus this command was helpful and that is why I decided to add it permanently

[EncodePanda]

changed BlockComponent to GetPure ()

[nfrisby]

Approved. Thanks!

[EncodePanda]

bors merge

[iohk-bors]

Build failed:

• buildkite/ouroboros-network

[EncodePanda]

bors merge

[iohk-bors]

Build failed:

• buildkite/ouroboros-network

[EncodePanda]

bors merge

[iohk-bors]

Build succeeded:

• buildkite/ouroboros-network
• ci/hydra:Cardano:ouroboros-network:required