Health-check fails because /consensus_params endpoint is not reliable

[andynog]

Crate

• ibc-relayer

Summary of Bug

When testing the new health-check command in Hermes, realised that the /consensus_params endpoint is not reliable when retrieving information for the latest height

Version

hermes 0.7.1+26087d57

Steps to Reproduce

Run the new hermes health-check against a Cosmos chain (tested with osmosis-1 and cosmoshub-4)

Getting error about JSON-RPC endpoint

hermes -c config.toml health-check
Sep 21 14:25:47.298  INFO [cosmoshub-4] performing health check...
Sep 21 14:25:47.552  WARN Hermes might be misconfigured for chain 'cosmoshub-4'
Sep 21 14:25:47.552  WARN     Reason: semantic config validation failed for option `max_tx_size` chain 'cosmoshub-4', reason: `max_tx_size` = 2097152 is greater than 90% of the genesis block param `max_size` = 200000
Sep 21 14:25:47.552  WARN     Some Hermes features may not work in this mode!
Sep 21 14:25:47.552 ERROR [cosmoshub-4] chain is unhealthy
Sep 21 14:25:47.555  INFO [osmosis-1] performing health check...
Sep 21 14:25:50.132  WARN Hermes might be misconfigured for chain 'osmosis-1'
Sep 21 14:25:50.132  WARN     Reason: semantic config validation: failed to reach endpoint /consensus_params on the JSON-RPC interface of chain osmosis-1:http://osmosis.decentrox.com:26657/
Sep 21 14:25:50.132  WARN     Some Hermes features may not work in this mode!
Sep 21 14:25:50.133 ERROR [osmosis-1] chain is unhealthy

Then checked the endpoint directly in the browser and get lots of erros when calling /consensus_params

{
  "jsonrpc": "2.0",
  "id": -1,
  "error": {
    "code": -32603,
    "message": "Internal error",
    "data": "could not find consensus params for height #1276406: value retrieved from db is empty"
  }
}

But if I keep trying I get eventually a valid response

{
  "jsonrpc": "2.0",
  "id": -1,
  "result": {
    "block_height": "1276410",
    "consensus_params": {
      "block": {
        "max_bytes": "10485760",
        "max_gas": "120000000",
        "time_iota_ms": "1000"
      },
      "evidence": {
        "max_age_num_blocks": "403200",
        "max_age_duration": "1209600000000000",
        "max_bytes": "1048576"
      },
      "validator": {
        "pub_key_types": [
          "ed25519"
        ]
      },
      "version": {
        "app_version": "1"
      }
    }
  }
}

Same thing with Hermes, running several times eventually don't get the RPC endpoint error

hermes -c config.toml health-check
Sep 21 14:27:53.918  INFO [cosmoshub-4] performing health check...
Sep 21 14:27:54.199  WARN Hermes might be misconfigured for chain 'cosmoshub-4'
Sep 21 14:27:54.200  WARN     Reason: semantic config validation failed for option `max_tx_size` chain 'cosmoshub-4', reason: `max_tx_size` = 2097152 is greater than 90% of the genesis block param `max_size` = 200000
Sep 21 14:27:54.200  WARN     Some Hermes features may not work in this mode!
Sep 21 14:27:54.200 ERROR [cosmoshub-4] chain is unhealthy
Sep 21 14:27:54.203  INFO [osmosis-1] performing health check...
Sep 21 14:27:56.181  INFO [osmosis-1] chain is healthy

Also, querying the /consensus_params?height=[HEIGHT] works fine

Acceptance Criteria

Since we are only calling this endpoint to get the max_bytes and the chances of this changing (only through governance) I'd suggest we change the logic instead of calling the lastest_consensus_params, we find the latest height and then query the specifying a height that is a few blocks behind the latest

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