| Safe Haskell | None |
|---|---|
| Language | GHC2021 |
LibP2P.Switch.Dial
Description
Dial logic for the Switch.
Implements connection reuse, exponential backoff, dial deduplication, and parallel staggered dialing (Happy Eyeballs, RFC 8305).
Dial flow: 1. Check connection pool for existing Open connection 2. Check per-peer backoff (reject if recently failed) 3. Deduplication: join pending dial if another thread is already dialing 4. Select transport per address, staggered parallel dial 5. Upgrade first successful raw connection 6. Add to pool / record backoff on failure
Synopsis
- dial :: Switch -> PeerId -> [Multiaddr] -> IO (Either DialError Connection)
- checkBackoff :: TVar (Map PeerId BackoffEntry) -> PeerId -> IO (Either DialError ())
- recordBackoff :: TVar (Map PeerId BackoffEntry) -> PeerId -> IO ()
- clearBackoff :: TVar (Map PeerId BackoffEntry) -> PeerId -> IO ()
- initialBackoffSeconds :: NominalDiffTime
- maxBackoffSeconds :: NominalDiffTime
- staggerDelayUs :: Int
Main entry point
dial :: Switch -> PeerId -> [Multiaddr] -> IO (Either DialError Connection) Source #
Dial a peer, reusing existing connections or establishing new ones.
Implements the full dial flow: 1. Pool reuse: return existing Open connection if available 2. Backoff check: reject if peer recently failed 3. Deduplication: coalesce concurrent dials to same peer via TMVar 4. Staggered parallel dial with 250ms delay (Happy Eyeballs) 5. First success: upgrade, add to pool, return 6. All fail: record backoff, return error
Backoff management
checkBackoff :: TVar (Map PeerId BackoffEntry) -> PeerId -> IO (Either DialError ()) Source #
Check if a peer is currently in dial backoff. Returns Right () if no backoff is active or the backoff has expired. Expired entries are cleaned up atomically.
recordBackoff :: TVar (Map PeerId BackoffEntry) -> PeerId -> IO () Source #
Record a backoff after a failed dial. First failure: 5s. Each subsequent: duration * 2, capped at 300s. Backoff formula: min(initialBackoff * 2^(attempts-1), maxBackoff)
clearBackoff :: TVar (Map PeerId BackoffEntry) -> PeerId -> IO () Source #
Clear backoff for a peer (called on successful connection).
Constants (exported for testing)
initialBackoffSeconds :: NominalDiffTime Source #
Initial backoff duration after first failure: 5 seconds.
maxBackoffSeconds :: NominalDiffTime Source #
Maximum backoff duration: 300 seconds (5 minutes).
staggerDelayUs :: Int Source #
Stagger delay between parallel dial attempts: 250ms (RFC 8305).