Why do we need the ```plutus-chain-index``` to run and why does it take so long to sync

Question

I'm trying to set up a PAB in order to test my contracts

Currently I have:

• fully synced a cardano-node running on testnet
• fully synced cardano-wallet tracking one wallet
• a plutus-chain-index syncing at an absurd slow rate
• a pab instance that displays

  [pab:Info:1] [2022-04-11 14:07:59.27 UTC] Restoring PAB state ...
  [pab:Info:1] [2022-04-11 14:07:59.27 UTC] No contract instance were restored in the 
  PAB state.
  [pab:Info:1] [2022-04-11 14:07:59.27 UTC] Starting PAB backend server on port 9080
  

and connecting to that instance, for example trying

http:localhost:9080/swagger/swagger-ui

does not works the first hours but it does after at least 5 hours, even if the chain-index syncing sits at 0.76% after all that time.

my questions are

1. Why do we even need a plutus-chain-index instance running if it is ok at 0.76%
2. How can I get more information on when the PAB is ready?

Answer 1

1. The chain index provides data such as datums and utxo values. Its data from the chain but organized in a way that's more convenient and faster to query than is possible with the node directly. It's intended to be a 'db-sync-lite'.

2. You can run with --verbose flag. But it will dump a lot of stuff out. You should also be able to hit localhost:9083/swagger/swagger-ui (provided you are using the default config).

They've been numerous problems with the chain index, with many being fixed recently. I recommended taking the latest version if you aren't already.