Package dev.relism.flash.transport

Class ConnectionScratch

java.lang.Object

dev.relism.flash.transport.ConnectionScratch

public final class ConnectionScratch
extends Object

ThreadLocal on HttpServer: the decimal-formatting scratch, the streaming relay buffer, and the WebSocket-handshake MessageDigest.

Why not ThreadLocal

ThreadLocal is the right idiom for a bounded platform-thread pool, where "one per thread" means "one per core". Flash runs one virtual thread per connection (Executors.newVirtualThreadPerTaskExecutor()), so a ThreadLocal here means one per connection, not one per core — with no upper bound. At 100 000 concurrent connections, an 8 KB relay buffer alone is ~800 MB of memory that a bounded pool would instead cap. ConnectionScratch is therefore explicit and pooled (ScratchPool), not thread-local.

Lifetime and thread-safety contract

Allocated once per connection (or reused from ScratchPool), owned exclusively by the single virtual thread driving that connection for its whole lifetime, and returned to the pool when the connection closes. Never shared between two connections at once — there is no synchronization here because none is needed. class: routing has no dependency on transport today, and folding the router's the opaque-per-connection-object mechanism (AbstractRouter#newScratch) used instead. This class gains HTTP/2 write/HPACK scratch in later phases, where h2 already depends on transport and no such boundary concern applies.

Field Summary

Fields

Modifier and Type	Field	Description
static final int	RELAY_BUFFER_SIZE	Matches the relay-buffer size the ThreadLocal it replaces used.
final byte[]	relayBuffer	Scratch for relaying a streaming or chunked response body without allocating per response.
static final int	RESPONSE_HEAD_INITIAL_SIZE	Initial capacity for responseHead; grows on demand like any ByteWriter.
final ByteWriter	responseHead	(status line, Content-Type, Date, custom headers, Content-Length/ Connection, and — for small fixed bodies — the body itself) into before issuing a single bulk write(), instead of ~10 small OutputStream.write calls.
final MessageDigest	sha1	Scratch for the WebSocket handshake's Sec-WebSocket-Accept SHA-1 digest.

Method Summary

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

RELAY_BUFFER_SIZE

public static final int RELAY_BUFFER_SIZE

Matches the relay-buffer size the ThreadLocal it replaces used.

See Also:

• Constant Field Values

RESPONSE_HEAD_INITIAL_SIZE

public static final int RESPONSE_HEAD_INITIAL_SIZE

Initial capacity for responseHead; grows on demand like any ByteWriter.

See Also:

• Constant Field Values

relayBuffer

public final byte[] relayBuffer

Scratch for relaying a streaming or chunked response body without allocating per response.

responseHead

public final ByteWriter responseHead

(status line, Content-Type, Date, custom headers, Content-Length/ Connection, and — for small fixed bodies — the body itself) into before issuing a single bulk write(), instead of ~10 small OutputStream.write calls.

sha1

public final MessageDigest sha1

Scratch for the WebSocket handshake's Sec-WebSocket-Accept SHA-1 digest.