feat(networking): add bootstrap cache for peer discovery

Add persistent bootstrap cache to maintain a list of previously known peers,
improving network bootstrapping efficiency and reducing cold-start times.

Enhance the bootstrap cache implementation with robust corruption detection
and recovery mechanisms. This change ensures system resilience when the
cache file becomes corrupted or invalid.

Key changes:
* Add explicit cache corruption detection and error reporting
* Implement cache rebuilding from in-memory peers or endpoints
* Use atomic file operations to prevent corruption during writes
* Improve error handling with specific error variants
* Add comprehensive test suite for corruption scenarios

The system now handles corruption by:
1. Detecting invalid/corrupted JSON data during cache reads
2. Attempting recovery using in-memory peers if available
3. Falling back to endpoint discovery if needed
4. Using atomic operations for safe cache updates

Testing:
* Add tests for various corruption scenarios
* Add concurrent access tests
* Add file operation tests
* Verify endpoint fallback behavior

- Add smarter JSON format detection by checking content structure
- Improve error handling with specific InvalidResponse variant
- Reduce unnecessary warnings by only logging invalid multiaddrs
- Simplify parsing logic to handle both JSON and plain text formats
- Add better error context for failed parsing attempts

All tests passing, including JSON endpoint and plain text format tests.

feat(bootstrap_cache): implement circuit breaker with exponential backoff

- Add CircuitBreakerConfig with configurable parameters for failures and timeouts
- Implement circuit breaker states (closed, open, half-open) with state transitions
- Add exponential backoff for failed request retries
- Update InitialPeerDiscovery to support custom circuit breaker configuration
- Add comprehensive test suite with shorter timeouts for faster testing

This change improves system resilience by preventing cascading failures and
reducing load on failing endpoints through intelligent retry mechanisms.

.gitignore

@@ -36,8 +36,7 @@ sn_node_manager/.vagrant
 .venv/
 uv.lock
 *.so
-*.pyc
-
 *.pyc
 *.swp
 
+/vendor/

Cargo.toml

@@ -16,6 +16,7 @@ members = [
     "ant-token-supplies",
     "autonomi",
     "autonomi-cli",
+    "bootstrap_cache",
     "evmlib",
     "evm-testnet",
     "nat-detection",

ant-peers-acquisition/Cargo.toml

@@ -10,6 +10,7 @@ repository = "https://github.com/maidsafe/autonomi"
 version = "0.5.7"
 
 [features]
+default = ["network-contacts"]
 local = []
 network-contacts = ["ant-protocol"]
 websockets = []

bootstrap_cache/Cargo.toml

@@ -0,0 +1,25 @@
+[package]
+name = "bootstrap_cache"
+version = "0.1.0"
+edition = "2021"
+license = "GPL-3.0"
+authors = ["MaidSafe Developers <dev@maidsafe.net>"]
+description = "Bootstrap cache functionality for the Safe Network"
+
+[dependencies]
+chrono = { version = "0.4", features = ["serde"] }
+dirs = "5.0"
+fs2 = "0.4.3"
+libp2p = { version = "0.53", features = ["serde"] }
+reqwest = { version = "0.11", features = ["json"] }
+serde = { version = "1.0", features = ["derive"] }
+serde_json = "1.0"
+tempfile = "3.8.1"
+thiserror = "1.0"
+tokio = { version = "1.0", features = ["full", "sync"] }
+tracing = "0.1"
+
+[dev-dependencies]
+wiremock = "0.5"
+tokio = { version = "1.0", features = ["full", "test-util"] }
+tracing-subscriber = { version = "0.3", features = ["env-filter"] }

bootstrap_cache/README.md

@@ -0,0 +1,216 @@
+# Bootstrap Cache
+
+A decentralized peer discovery and caching system for the Safe Network.
+
+## Features
+
+- **Decentralized Design**: No dedicated bootstrap nodes required
+- **Cross-Platform Support**: Works on Linux, macOS, and Windows
+- **Shared Cache**: System-wide cache file accessible by both nodes and clients
+- **Concurrent Access**: File locking for safe multi-process access
+- **Atomic Operations**: Safe cache updates using atomic file operations
+- **Initial Peer Discovery**: Fallback web endpoints for new/stale cache scenarios
+- **Comprehensive Error Handling**: Detailed error types and logging
+- **Circuit Breaker Pattern**: Intelligent failure handling with:
+  - Configurable failure thresholds and reset timeouts
+  - Exponential backoff for failed requests
+  - Automatic state transitions (closed → open → half-open)
+  - Protection against cascading failures
+
+### Peer Management
+
+The bootstrap cache implements a robust peer management system:
+
+- **Peer Status Tracking**: Each peer's connection history is tracked, including:
+  - Success count: Number of successful connections
+  - Failure count: Number of failed connection attempts
+  - Last seen timestamp: When the peer was last successfully contacted
+
+- **Automatic Cleanup**: The system automatically removes unreliable peers:
+  - Peers that fail 3 consecutive connection attempts are marked for removal
+  - Removal only occurs if there are at least 2 working peers available
+  - This ensures network connectivity is maintained even during temporary connection issues
+
+- **Duplicate Prevention**: The cache automatically prevents duplicate peer entries:
+  - Same IP and port combinations are only stored once
+  - Different ports on the same IP are treated as separate peers
+
+## Installation
+
+Add this to your `Cargo.toml`:
+
+```toml
+[dependencies]
+bootstrap_cache = { version = "0.1.0" }
+```
+
+## Usage
+
+### Basic Example
+
+```rust
+use bootstrap_cache::{BootstrapCache, CacheManager, InitialPeerDiscovery};
+
+#[tokio::main]
+async fn main() -> Result<(), Box<dyn std::error::Error>> {
+    // Initialize the cache manager
+    let cache_manager = CacheManager::new()?;
+
+    // Try to read from the cache
+    let mut cache = match cache_manager.read_cache() {
+        Ok(cache) if !cache.is_stale() => cache,
+        _ => {
+            // Cache is stale or unavailable, fetch initial peers
+            let discovery = InitialPeerDiscovery::new();
+            let peers = discovery.fetch_peers().await?;
+            let cache = BootstrapCache {
+                last_updated: chrono::Utc::now(),
+                peers,
+            };
+            cache_manager.write_cache(&cache)?;
+            cache
+        }
+    };
+
+    println!("Found {} peers in cache", cache.peers.len());
+    Ok(())
+}
+```
+
+### Custom Endpoints
+
+```rust
+use bootstrap_cache::InitialPeerDiscovery;
+
+let discovery = InitialPeerDiscovery::with_endpoints(vec![
+    "http://custom1.example.com/peers.json".to_string(),
+    "http://custom2.example.com/peers.json".to_string(),
+]);
+```
+
+### Circuit Breaker Configuration
+
+```rust
+use bootstrap_cache::{InitialPeerDiscovery, CircuitBreakerConfig};
+use std::time::Duration;
+
+// Create a custom circuit breaker configuration
+let config = CircuitBreakerConfig {
+    max_failures: 5,                            // Open after 5 failures
+    reset_timeout: Duration::from_secs(300),    // Wait 5 minutes before recovery
+    min_backoff: Duration::from_secs(1),        // Start with 1 second backoff
+    max_backoff: Duration::from_secs(60),       // Max backoff of 60 seconds
+};
+
+// Initialize discovery with custom circuit breaker config
+let discovery = InitialPeerDiscovery::with_config(config);
+```
+
+### Peer Management Example
+
+```rust
+use bootstrap_cache::BootstrapCache;
+
+let mut cache = BootstrapCache::new();
+
+// Add a new peer
+cache.add_peer("192.168.1.1".to_string(), 8080);
+
+// Update peer status after connection attempts
+cache.update_peer_status("192.168.1.1", 8080, true);  // successful connection
+cache.update_peer_status("192.168.1.1", 8080, false); // failed connection
+
+// Clean up failed peers (only if we have at least 2 working peers)
+cache.cleanup_failed_peers();
+```
+
+## Cache File Location
+
+The cache file is stored in a system-wide location accessible to all processes:
+
+- **Linux**: `/var/safe/bootstrap_cache.json`
+- **macOS**: `/Library/Application Support/Safe/bootstrap_cache.json`
+- **Windows**: `C:\ProgramData\Safe\bootstrap_cache.json`
+
+## Cache File Format
+
+```json
+{
+    "last_updated": "2024-02-20T15:30:00Z",
+    "peers": [
+        {
+            "ip": "192.168.1.1",
+            "port": 8080,
+            "last_seen": "2024-02-20T15:30:00Z",
+            "success_count": 10,
+            "failure_count": 0
+        }
+    ]
+}
+```
+
+## Error Handling
+
+The crate provides detailed error types through the `Error` enum:
+
+```rust
+use bootstrap_cache::Error;
+
+match cache_manager.read_cache() {
+    Ok(cache) => println!("Cache loaded successfully"),
+    Err(Error::CacheStale) => println!("Cache is stale"),
+    Err(Error::CacheCorrupted) => println!("Cache file is corrupted"),
+    Err(Error::Io(e)) => println!("IO error: {}", e),
+    Err(e) => println!("Other error: {}", e),
+}
+```
+
+## Thread Safety
+
+The cache system uses file locking to ensure safe concurrent access:
+
+- Shared locks for reading
+- Exclusive locks for writing
+- Atomic file updates using temporary files
+
+## Development
+
+### Building
+
+```bash
+cargo build
+```
+
+### Running Tests
+
+```bash
+cargo test
+```
+
+### Running with Logging
+
+```rust
+use tracing_subscriber::FmtSubscriber;
+
+// Initialize logging
+let subscriber = FmtSubscriber::builder()
+    .with_max_level(tracing::Level::DEBUG)
+    .init();
+```
+
+## Contributing
+
+1. Fork the repository
+2. Create your feature branch (`git checkout -b feature/amazing-feature`)
+3. Commit your changes (`git commit -am 'Add amazing feature'`)
+4. Push to the branch (`git push origin feature/amazing-feature`)
+5. Open a Pull Request
+
+## License
+
+This project is licensed under the GPL-3.0 License - see the LICENSE file for details.
+
+## Related Documentation
+
+- [Bootstrap Cache PRD](docs/bootstrap_cache_prd.md)
+- [Implementation Guide](docs/bootstrap_cache_implementation.md)