alamb commented on code in PR #10600:
URL: https://github.com/apache/datafusion/pull/10600#discussion_r1618678318
##########
datafusion/core/src/datasource/stream.rs:
##########
@@ -103,19 +105,46 @@ impl FromStr for StreamEncoding {
}
}
-/// The configuration for a [`StreamTable`]
+/// The StreamProvider trait is used as a generic interface for reading and
writing from streaming
+/// data sources (such as FIFO, Websocket, Kafka, etc.). Implementations of
the provider are
+/// responsible for providing a `RecordBatchReader` and optionally a
`RecordBatchWriter`.
+pub trait StreamProvider: std::fmt::Debug + Send + Sync {
+ /// Get a reference to the schema for this stream
+ fn schema(&self) -> SchemaRef;
+ /// Needed for `PartitionStream` - maybe there is a better way to do this.
Review Comment:
I think changing `schema` to return `&SchemaRef` would be enough -- then
anyone who needed an owned `SchemaRef` could clone the result. I don't think we
need separate methods
##########
datafusion-examples/examples/file_stream_provider.rs:
##########
@@ -0,0 +1,185 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements. See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership. The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License. You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied. See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+use datafusion::assert_batches_eq;
+use datafusion_common::instant::Instant;
+use std::fs::{File, OpenOptions};
+use std::io::Write;
+use std::path::PathBuf;
+use std::sync::atomic::{AtomicBool, Ordering};
+use std::sync::Arc;
+use std::thread;
+use std::time::Duration;
+
+use arrow::datatypes::{DataType, Field, Schema};
+use arrow_schema::SchemaRef;
+use futures::StreamExt;
+use nix::sys::stat;
+use nix::unistd;
+use tempfile::TempDir;
+use tokio::task::{spawn_blocking, JoinHandle};
+
+use datafusion::datasource::stream::{FileStreamProvider, StreamConfig,
StreamTable};
+use datafusion::datasource::TableProvider;
+use datafusion::prelude::{SessionConfig, SessionContext};
+use datafusion_common::{exec_err, Result};
+use datafusion_expr::Expr;
+
+// Number of lines written to FIFO
+const TEST_BATCH_SIZE: usize = 5;
+const TEST_DATA_SIZE: usize = 5;
+
+/// Makes a TableProvider for a fifo file using `StreamTable` with the
`StreamProvider` trait
+fn fifo_table(
+ schema: SchemaRef,
+ path: impl Into<PathBuf>,
+ sort: Vec<Vec<Expr>>,
+) -> Arc<dyn TableProvider> {
+ let source = FileStreamProvider::new_file(schema, path.into())
+ .with_batch_size(TEST_BATCH_SIZE)
+ .with_header(true);
+ let config = StreamConfig::new(Arc::new(source)).with_order(sort);
+ Arc::new(StreamTable::new(Arc::new(config)))
+}
+
+fn create_fifo_file(tmp_dir: &TempDir, file_name: &str) -> Result<PathBuf> {
+ let file_path = tmp_dir.path().join(file_name);
+ // Simulate an infinite environment via a FIFO file
+ if let Err(e) = unistd::mkfifo(&file_path, stat::Mode::S_IRWXU) {
+ exec_err!("{}", e)
+ } else {
+ Ok(file_path)
+ }
+}
+
+fn write_to_fifo(
+ mut file: &File,
+ line: &str,
+ ref_time: Instant,
+ broken_pipe_timeout: Duration,
+) -> Result<()> {
+ // We need to handle broken pipe error until the reader is ready. This
+ // is why we use a timeout to limit the wait duration for the reader.
+ // If the error is different than broken pipe, we fail immediately.
+ while let Err(e) = file.write_all(line.as_bytes()) {
+ if e.raw_os_error().unwrap() == 32 {
+ let interval = Instant::now().duration_since(ref_time);
+ if interval < broken_pipe_timeout {
+ thread::sleep(Duration::from_millis(100));
+ continue;
+ }
+ }
+ return exec_err!("{}", e);
+ }
+ Ok(())
+}
+
+fn create_writing_thread(
+ file_path: PathBuf,
+ maybe_header: Option<String>,
+ lines: Vec<String>,
+ waiting_lock: Arc<AtomicBool>,
+ wait_until: usize,
+) -> JoinHandle<()> {
+ // Timeout for a long period of BrokenPipe error
+ let broken_pipe_timeout = Duration::from_secs(10);
+ let sa = file_path.clone();
+ // Spawn a new thread to write to the FIFO file
+ #[allow(clippy::disallowed_methods)] // spawn allowed only in tests
+ spawn_blocking(move || {
+ let file = OpenOptions::new().write(true).open(sa).unwrap();
+ // Reference time to use when deciding to fail the test
+ let execution_start = Instant::now();
+ if let Some(header) = maybe_header {
+ write_to_fifo(&file, &header, execution_start,
broken_pipe_timeout).unwrap();
+ }
+ for (cnt, line) in lines.iter().enumerate() {
+ while waiting_lock.load(Ordering::SeqCst) && cnt > wait_until {
+ thread::sleep(Duration::from_millis(50));
+ }
+ write_to_fifo(&file, line, execution_start,
broken_pipe_timeout).unwrap();
+ }
+ drop(file);
+ })
+}
+
+/// This example demonstrates a scanning against an Arrow data source (JSON)
and
+/// fetching results
+#[tokio::main]
+async fn main() -> Result<()> {
+ // Create session context
+ let config = SessionConfig::new()
+ .with_batch_size(TEST_BATCH_SIZE)
+ .with_collect_statistics(false)
+ .with_target_partitions(1);
+ let ctx = SessionContext::new_with_config(config);
+ let tmp_dir = TempDir::new()?;
+ let fifo_path = create_fifo_file(&tmp_dir, "fifo_unbounded.csv")?;
+
+ let mut tasks: Vec<JoinHandle<()>> = vec![];
Review Comment:
BTW using a `JoinSet`
https://docs.rs/tokio/latest/tokio/task/struct.JoinSet.html might be easier
here (it encapsulates managing tasks like this)
##########
datafusion-examples/examples/file_stream_provider.rs:
##########
@@ -0,0 +1,185 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements. See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership. The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License. You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied. See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+use datafusion::assert_batches_eq;
+use datafusion_common::instant::Instant;
+use std::fs::{File, OpenOptions};
+use std::io::Write;
+use std::path::PathBuf;
+use std::sync::atomic::{AtomicBool, Ordering};
+use std::sync::Arc;
+use std::thread;
+use std::time::Duration;
+
+use arrow::datatypes::{DataType, Field, Schema};
+use arrow_schema::SchemaRef;
+use futures::StreamExt;
+use nix::sys::stat;
+use nix::unistd;
+use tempfile::TempDir;
+use tokio::task::{spawn_blocking, JoinHandle};
+
+use datafusion::datasource::stream::{FileStreamProvider, StreamConfig,
StreamTable};
+use datafusion::datasource::TableProvider;
+use datafusion::prelude::{SessionConfig, SessionContext};
+use datafusion_common::{exec_err, Result};
+use datafusion_expr::Expr;
+
+// Number of lines written to FIFO
+const TEST_BATCH_SIZE: usize = 5;
+const TEST_DATA_SIZE: usize = 5;
+
+/// Makes a TableProvider for a fifo file using `StreamTable` with the
`StreamProvider` trait
+fn fifo_table(
+ schema: SchemaRef,
+ path: impl Into<PathBuf>,
+ sort: Vec<Vec<Expr>>,
+) -> Arc<dyn TableProvider> {
+ let source = FileStreamProvider::new_file(schema, path.into())
+ .with_batch_size(TEST_BATCH_SIZE)
+ .with_header(true);
+ let config = StreamConfig::new(Arc::new(source)).with_order(sort);
+ Arc::new(StreamTable::new(Arc::new(config)))
+}
+
+fn create_fifo_file(tmp_dir: &TempDir, file_name: &str) -> Result<PathBuf> {
+ let file_path = tmp_dir.path().join(file_name);
+ // Simulate an infinite environment via a FIFO file
+ if let Err(e) = unistd::mkfifo(&file_path, stat::Mode::S_IRWXU) {
+ exec_err!("{}", e)
+ } else {
+ Ok(file_path)
+ }
+}
+
+fn write_to_fifo(
+ mut file: &File,
+ line: &str,
+ ref_time: Instant,
+ broken_pipe_timeout: Duration,
+) -> Result<()> {
+ // We need to handle broken pipe error until the reader is ready. This
+ // is why we use a timeout to limit the wait duration for the reader.
+ // If the error is different than broken pipe, we fail immediately.
+ while let Err(e) = file.write_all(line.as_bytes()) {
+ if e.raw_os_error().unwrap() == 32 {
+ let interval = Instant::now().duration_since(ref_time);
+ if interval < broken_pipe_timeout {
+ thread::sleep(Duration::from_millis(100));
+ continue;
+ }
+ }
+ return exec_err!("{}", e);
+ }
+ Ok(())
+}
+
+fn create_writing_thread(
+ file_path: PathBuf,
+ maybe_header: Option<String>,
+ lines: Vec<String>,
+ waiting_lock: Arc<AtomicBool>,
+ wait_until: usize,
+) -> JoinHandle<()> {
+ // Timeout for a long period of BrokenPipe error
+ let broken_pipe_timeout = Duration::from_secs(10);
+ let sa = file_path.clone();
+ // Spawn a new thread to write to the FIFO file
+ #[allow(clippy::disallowed_methods)] // spawn allowed only in tests
+ spawn_blocking(move || {
+ let file = OpenOptions::new().write(true).open(sa).unwrap();
+ // Reference time to use when deciding to fail the test
+ let execution_start = Instant::now();
+ if let Some(header) = maybe_header {
+ write_to_fifo(&file, &header, execution_start,
broken_pipe_timeout).unwrap();
+ }
+ for (cnt, line) in lines.iter().enumerate() {
+ while waiting_lock.load(Ordering::SeqCst) && cnt > wait_until {
+ thread::sleep(Duration::from_millis(50));
+ }
+ write_to_fifo(&file, line, execution_start,
broken_pipe_timeout).unwrap();
+ }
+ drop(file);
+ })
+}
+
+/// This example demonstrates a scanning against an Arrow data source (JSON)
and
+/// fetching results
+#[tokio::main]
+async fn main() -> Result<()> {
+ // Create session context
+ let config = SessionConfig::new()
+ .with_batch_size(TEST_BATCH_SIZE)
+ .with_collect_statistics(false)
+ .with_target_partitions(1);
+ let ctx = SessionContext::new_with_config(config);
+ let tmp_dir = TempDir::new()?;
+ let fifo_path = create_fifo_file(&tmp_dir, "fifo_unbounded.csv")?;
+
+ let mut tasks: Vec<JoinHandle<()>> = vec![];
+ let waiting = Arc::new(AtomicBool::new(true));
+
+ let data_iter = 0..TEST_DATA_SIZE;
+ let lines = data_iter
+ .map(|i| format!("{},{}\n", i, i + 1))
+ .collect::<Vec<_>>();
+ // Create writing threads for the left and right FIFO files
+ tasks.push(create_writing_thread(
+ fifo_path.clone(),
+ Some("a1,a2\n".to_owned()),
+ lines.clone(),
+ waiting.clone(),
+ TEST_DATA_SIZE,
+ ));
+
+ // Create schema
+ let schema = Arc::new(Schema::new(vec![
+ Field::new("a1", DataType::UInt32, false),
+ Field::new("a2", DataType::UInt32, false),
+ ]));
+
+ // Specify the ordering:
+ let order = vec![vec![datafusion_expr::col("a1").sort(true, false)]];
+
+ let provider = fifo_table(schema.clone(), fifo_path, order.clone());
+ ctx.register_table("fifo", provider)?;
+
+ let df = ctx.sql("SELECT * FROM fifo").await.unwrap();
+ let mut stream = df.execute_stream().await.unwrap();
+
+ futures::future::join_all(tasks).await;
Review Comment:
I wonder if you need to join all here (it kind of makes the streaming nature
of this example less clear) -- could you potentially do after you read the
batches?
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