explorer: introducing metrics store

This commit introduces a metrics store that serves as entry point for managing metrics, providing an API for fetching, inserting, and resetting metric data backed by a Sled database. The store organizes data into separate trees, including main storage for gas metrics by a defined time interval, a tree containing metrics by height for handling reorgs, and a transaction-specific gas data tree. It uses an overlay pattern for write operations, enabling unified management of metrics by delegating tasks such as adding metrics and handling reorgs to the MetricsStoreOverlay.

Additionally, the commit introduces the GasMetrics struct, which is used for managing gas metrics across all transactions in the metrics store. This struct maintains running totals, min/max extrema, and transaction counts, allowing efficient calculations of total gas, WASM gas, ZK circuit gas, and signature gas without needing to iterate through previous transactions. With O(1) performance for calculating averages and updating min/max values, GasMetrics builds a comprehensive view of gas metrics throughout the blockchain's history. It includes methods for creating new instances, calculating average gas usage, and adding new gas data in real-time.

Furthermore, the GasMetricsKey struct is introduced to facilitate storing and retrieving metrics by time interval. The initial implementation stores metrics on an hourly basis, with flexibility for future adjustments to different intervals with minimal code changes. This struct provides methods for creating, serializing, and deserializing keys from various time representations, including [Timestamp], u64 timestamps, and &str timestamps. It also features conversion methods to ensure compatibility with the Sled database.

Test coverage has been added to validate functionality across various scenarios. Tests include inserting gas metrics, searching metrics by hour, fetching metrics by timestamp string, transaction gas usage, and resetting metrics under different conditions. Additionally, functions were added to load test data, simulating random, fixed, and reset scenarios while generating varied gas data.

Core Updates Summary:

- Created the `MetricsStore` struct to manage metric storage, providing an API for fetching, inserting, and resetting metrics backed by a Sled database.
- Developed `MetricsStoreOverlay` to facilitate write operations, including adding and reverting metrics for handling reorgs.
- Introduced the `GasMetrics` struct to encapsulate gas metrics across transactions, with methods to efficiently add data and compute extrema and averages.
- Implemented `GasMetricsKey` for storing and retrieving fee metrics based on hourly intervals.
- Introduced the `GasMetricsKeySource` trait for unified key creation using various time representations: `[Timestamp]`, `u64` timestamps, or `&str` timestamps.

Test Functions:
- `test_insert_gas_metrics`: Verifies correctness of inserted gas metrics into the main tree.
- `test_insert_by_height_gas_metrics`: Tests gas metrics insertion into the metrics by height tree.
- `test_search_metrics_by_hour`: Validates searching gas metrics by hour.
- `test_get_metrics_by_timestamp_str`: Ensures correct retrieval of metrics by timestamp string.
- `test_tx_gas_data`: Verifies transaction gas data insertion and retrieval, including handling of non-existent transactions.
- `test_reset_metrics_within_height_range`: Tests resetting metrics within a specified height range.
- `test_reset_metrics_height_to_0`: Ensures graceful handling of resetting the metrics store to height 0.
- `test_reset_metrics_beyond_height`: Validates behavior when resetting beyond available metrics.
- `test_reset_metrics_at_height`: Tests resetting metrics at the last available height.
- `test_reset_empty_store`: Confirms that resetting an empty store is handled without errors.

Test Data Load Functions:
- `load_random_metrics`: Simulates loading random gas metrics data at hourly intervals from height 0 as the genesis block.
- `load_fixed_metrics`: Loads fixed test data with timestamps.
- `load_reset_metrics`: Returns accumulated gas metrics at a specified reset height.
- `load_tx_gas_data`: Loads test transaction gas data, returning pairs of transaction hashes and gas data.
- `random_gas_data`: Generates varied gas data based on a provided seed value.

script/research/blockchain-explorer/src/main.rs

@@ -59,6 +59,9 @@ mod statistics;
 /// Test utilities used for unit and integration testing
 mod test_utils;
 
+/// Database store functionality related to metrics
+mod metrics_store;
+
 const CONFIG_FILE: &str = "blockchain_explorer_config.toml";
 const CONFIG_FILE_CONTENTS: &str = include_str!("../blockchain_explorer_config.toml");