io.mode (default: NIO) — the IO mode: nio or epoll.

io.preferDirectBufs (default: true) — a flag to control whether Spark prefers allocating off-heap byte buffers within Netty (true) or not (false).

io.connectionTimeout (default: spark.network.timeout or 120s) — the connection timeout in milliseconds.

io.backLog (default: -1 for no backlog) — the requested maximum length of the queue of incoming connections.

io.numConnectionsPerPeer (default: 1) — the number of concurrent connections between two nodes for fetching data.

io.serverThreads (default: 0 i.e. 2x#cores) — the number of threads used in the server thread pool.

io.clientThreads (default: 0 i.e. 2x#cores) — the number of threads used in the client thread pool.

io.receiveBuffer (default: -1) — the receive buffer size (SO_RCVBUF).

io.sendBuffer (default: -1) — the send buffer size (SO_SNDBUF).

sasl.timeout (default: 30s) — the timeout (in milliseconds) for a single round trip of SASL token exchange.

io.maxRetries (default: 3) — the maximum number of times Spark will try IO exceptions (such as connection timeouts) per request. If set to 0, Spark will not do any retries.

io.retryWait (default: 5s) — the time (in milliseconds) that Spark will wait in order to perform a retry after an IOException. Only relevant if io.maxRetries > 0.

io.lazyFD (default: true) — controls whether to initialize FileDescriptor lazily (true) or not (false). If true, file descriptors are created only when data is going to be transferred. This can reduce the number of open files.