QuestDB Wire Protocol (QWP)

QWP is QuestDB's columnar binary protocol for high-throughput data ingestion (/write/v4) and streaming query results (/read/v1) over WebSocket and UDP. These properties control protocol limits and the UDP receiver. WebSocket ingestion and egress share the HTTP server's network settings (port, TLS, worker threads); see HTTP server configuration for those.

Protocol limits​

qwp.max.rows.per.table​

  • Default: 1000000
  • Reloadable: no

Maximum number of rows per table block in a single QWP message. The server rejects batches that exceed this limit with a parse error.

qwp.max.tables.per.connection​

  • Default: 10000
  • Reloadable: no

Maximum number of distinct tables a single connection may write to. The server rejects messages referencing additional tables once this limit is reached.

UDP receiver​

note

The QWP UDP receiver is a fire-and-forget ingestion path for metrics workloads where occasional message loss is acceptable. It is disabled by default. For reliable ingestion, use the WebSocket transport.

qwp.udp.bind.to​

  • Default: 0.0.0.0:9007
  • Reloadable: no

IP address and port the UDP receiver binds to. The default listens on all network interfaces on port 9007.

qwp.udp.commit.interval​

  • Default: 2000 (milliseconds)
  • Reloadable: no

Time interval between commits for data received over UDP. Lower values reduce the window of uncommitted data at the cost of more frequent I/O.

qwp.udp.enabled​

  • Default: false
  • Reloadable: no

Enable or disable the QWP UDP receiver.

qwp.udp.join​

  • Default: 224.1.1.1
  • Reloadable: no

Multicast group address the UDP receiver joins. Only relevant when qwp.udp.unicast is false.

qwp.udp.max.uncommitted.datagrams​

  • Default: 1048576
  • Reloadable: no

Maximum number of uncommitted datagrams before the receiver forces a commit, regardless of the time-based commit interval.

qwp.udp.msg.buffer.size​

  • Default: 65536 (bytes)
  • Reloadable: no

Size of each message buffer allocated for the UDP receiver.

qwp.udp.msg.count​

  • Default: 10000
  • Reloadable: no

Number of message buffers to pre-allocate. Higher values absorb larger bursts at the cost of more memory.

qwp.udp.own.thread​

  • Default: true
  • Reloadable: no

When true, the UDP receiver runs in a dedicated thread with a busy-spin loop for lowest latency. When false, the receiver uses the shared worker pool.

qwp.udp.own.thread.affinity​

  • Default: -1 (no affinity)
  • Reloadable: no

CPU core affinity for the dedicated UDP receiver thread. A value of -1 lets the OS schedule the thread. Only applies when qwp.udp.own.thread is true.

qwp.udp.receive.buffer.size​

  • Default: -1 (OS default)
  • Reloadable: no

OS-level socket receive buffer size in bytes. A value of -1 uses the operating system's default. Increase this if you observe datagram drops under high throughput.

qwp.udp.unicast​

  • Default: true
  • Reloadable: no

When true, the UDP receiver operates in unicast mode. When false, it joins the multicast group specified by qwp.udp.join.