BlockScout utilizes two separate indexers in order to index the network history as well as keep up with new incoming blocks. Due to this process, a node may become overloaded and not respond to BlockScout's RPC requests within the designated timeout period.
The indexer umbrella application can be tweaked to meet your node's size and responsiveness. Outlined below are the locations and adjustments that can be made to each fetcher.
This indexer fetches the metadata for a token contract
Batch Size: 1, Concurrency: 10
Understanding Errors and Timeouts
application=indexer fetcher=coin_balance count=500 error_count=500 [error] failed to fetch: :timeout
In the error provided above, we can tell that the indexer application failed to fetch 500coin balances due to a timeout error. Usually, when an indexer starts to receive timeouts, many more timeouts from other fetchers will occur as well.
Resolving Timeout Issues
The best action to take when fetchers start to receive timeouts is to lower the batch size and concurrency of a few fetchers which will put less pressure on the node.
The two indexers that cause the most strain to the node are the block fetcher and the internal transactions fetcher. It would be advised to cut these fetchers values in half and restart the application. A restart of the node may also be required.
BlockScout comes equipped with functionality to automatically stop sending requests for n seconds if timeouts are detected. You may adjust these settings by setting a different value for wait_per_timeout.