The `solana-watchtower` program is used to monitor the health of a cluster.  It
periodically polls the cluster over an RPC API to confirm that the transaction
count is advancing, new blockhashes are available, and no validators are
delinquent.  Results are reported as InfluxDB metrics, with an optional push
notification on sanity failure.

If you only care about the health of one specific validator, the
`--validator-identity` command-line argument can be used to restrict failure
notifications to issues only affecting that validator.

### Metrics
#### `watchtower-sanity`
On every iteration this data point will be emitted indicating the overall result
using a boolean `ok` field.

#### `watchtower-sanity-failure`
On failure this data point contains details about the specific test that failed via
the following fields:
* `test`: name of the sanity test that failed
* `err`: exact sanity failure message


### Sanity failure push notification
To receive a Slack, Discord and/or Telegram notification on sanity failure,
define environment variables before running `solana-watchtower`:
```
export SLACK_WEBHOOK=...
export DISCORD_WEBHOOK=...
```

Telegram requires the following two variables:
```
export TELEGRAM_BOT_TOKEN=...
export TELEGRAM_CHAT_ID=...
```
