feat(ilp): QWiP durable ack

[glasstiger]

Summary

• Add opt-in STATUS_DURABLE_ACK (0x02) frame support to the QWP client. When a connection is opened with requestDurableAck(true) (builder API or request_durable_ack=on config string), the client sends an X-QWP-Request-Durable-Ack: true upgrade header. Servers with primary replication enabled then emit per-table durable-upload watermarks as WAL data reaches the object store.
• Both STATUS_OK and STATUS_DURABLE_ACK frames now carry per-table entries (tableCount + [nameLen + name + seqTxn] repeating). STATUS_OK includes a batch sequence number; STATUS_DURABLE_ACK does not (it is not tied to a specific client batch).
• Expose per-table progress on QwpWebSocketSender:
  • getHighestDurableSeqTxn(tableName) — highest seqTxn durably uploaded to object store
  • getHighestAckedSeqTxn(tableName) — highest seqTxn committed (written to WAL)
• Add ping() method that sends a WebSocket PING and drains pending frames (including durable ACKs and STATUS_OK) until the PONG arrives. The server flushes pending durable ACKs before replying, so after ping() returns the durable progress is up to date. Works in both sync and async (send-queue) modes.
• New CharSequenceLongHashMap collection for sync-mode per-table tracking.
• New WebSocketResponse.durableAck() factory and isDurableAck() / getStatus() / getTableEntryCount() / getTableName(i) / getTableSeqTxn(i) accessors on the response model.

Wire format changes

STATUS_OK (was: status + sequence; now includes table entries):

+--------+----------+------------+--------------------------------------+
| status | sequence | tableCount | table entries                         |
| 1 byte | 8 bytes  | 2 bytes    | [nameLen(2)+name(N)+seqTxn(8)] × cnt |
+--------+----------+------------+--------------------------------------+

STATUS_DURABLE_ACK (new, no batch sequence):

+--------+------------+--------------------------------------+
| status | tableCount | table entries                         |
| 1 byte | 2 bytes    | [nameLen(2)+name(N)+seqTxn(8)] × cnt |
+--------+------------+--------------------------------------+

Changed files

Area	Files
Builder / config	Sender — requestDurableAck(boolean) builder method, request_durable_ack=on|off config string parsing
WebSocket upgrade	WebSocketClient — qwpRequestDurableAck flag → X-QWP-Request-Durable-Ack: true header
Sender	QwpWebSocketSender — setRequestDurableAck, per-table getHighestDurableSeqTxn / getHighestAckedSeqTxn, ping(), sync ping loop, durable-ack + table-entry handling in waitForAck
Response model	WebSocketResponse — STATUS_DURABLE_ACK constant, per-table entry parsing/writing (readTableEntries / writeTableEntries / validateTableEntries), updated structural validation
Async I/O	WebSocketSendQueue — per-table ConcurrentHashMap<String, SeqTxn> tracking for both committed and durable seqTxns, ping() / pingAndDrain / PONG handling in I/O loop
In-flight window	InFlightWindow — getHighestAckedSequence() accessor
Collections	CharSequenceLongHashMap — new hash map for sync-mode per-table seqTxn tracking

Test plan

• WebSocketResponseTest — durable-ack factory, round-trip serialization, per-table entries on STATUS_OK and STATUS_DURABLE_ACK, structural validity, truncated entries, trailing garbage, empty table names, unknown status bytes
• QwpWebSocketSenderStateTest — default values for per-table durable/acked seqTxn, setRequestDurableAck lifecycle guards, sync ping processing (durable ACK, STATUS_OK, bare PONG), ping() after close
• QwpWebSocketAckIntegrationTest — upgrade header sent/not-sent, sync durable ACK during waitForAck, STATUS_OK with table entries updates committed seqTxns
• InFlightWindowTest — getHighestAckedSequence initial value, cumulative advancement, monotonicity
• WebSocketSendQueueTest — STATUS_OK with table entries updates committed seqTxn, durable-ack updates per-table seqTxn, monotonicity under out-of-order delivery, interleaving with STATUS_OK, ping blocks until PONG, ping with in-flight batches, ping timeout, ping transport error, initial value check
• CharSequenceLongHashMapTest — put/get, update existing key, rehash, clear, contains, custom no-entry value, valueAt with keyIndex

🤖 Generated with Claude Code

[mtopolnik]

[PR Coverage check]

😍 pass : 299 / 338 (88.46%)

file detail

	path	covered line	new line	coverage
🔵	io/questdb/client/Sender.java	2	15	13.33%
🔵	io/questdb/client/cutlass/qwp/client/WebSocketSendQueue.java	64	72	88.89%
🔵	io/questdb/client/cutlass/qwp/client/QwpWebSocketSender.java	61	69	88.41%
🔵	io/questdb/client/cutlass/qwp/client/WebSocketResponse.java	120	130	92.31%
🔵	io/questdb/client/std/CharSequenceLongHashMap.java	46	46	100.00%
🔵	io/questdb/client/cutlass/qwp/client/InFlightWindow.java	2	2	100.00%
🔵	io/questdb/client/cutlass/http/client/WebSocketClient.java	4	4	100.00%