berkaysynnada commented on code in PR #13424: URL: https://github.com/apache/datafusion/pull/13424#discussion_r1855421673
########## datafusion-examples/examples/thread_pools.rs: ########## @@ -0,0 +1,213 @@ +// 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. + +//! This example shows how to use a separate thread pool (tokio [`Runtime`])) to +//! run the CPU intensive parts of DataFusion plans. +//! +//! Running DataFusion plans that perform I/O, such as reading parquet files +//! directly from remote object storage (e.g. AWS S3) without care will result +//! in running CPU intensive jobs on the same thread pool, which can lead to the +//! issues described in the [Architecture section] such as throttled bandwidth +//! due to congestion control and increased latencies for processing network +//! messages. +use arrow::util::pretty::pretty_format_batches; +use datafusion::error::Result; +use datafusion::execution::SendableRecordBatchStream; +use datafusion::physical_plan::DedicatedExecutor; +use datafusion::prelude::*; +use futures::stream::StreamExt; +use object_store::http::HttpBuilder; +use object_store::ObjectStore; +use std::sync::Arc; +use url::Url; + +/// Normally, you don't need to worry about the details of the tokio runtime, +/// but for this example it is important to understand how the [`Runtime`]s work. +/// +/// There is a "current" runtime that is installed in a thread local variable +/// that is used by the `tokio::spawn` function. +/// +/// The `#[tokio::main]` macro actually creates a [`Runtime`] and installs it as +/// as the "current" runtime (on which any `async` futures, streams and tasks +/// are run). +#[tokio::main] +async fn main() -> Result<()> { + // The first two examples only do local file IO. Enable the URL table so we + // can select directly from filenames in SQL. + let ctx = SessionContext::new().enable_url_table(); + let sql = format!( + "SELECT * FROM '{}/alltypes_plain.parquet'", + datafusion::test_util::parquet_test_data() + ); + + // Run the same query on the same runtime. Note that calling `await` here + // will effectively run the future (in this case the `async` function) on + // the current runtime. + same_runtime(&ctx, &sql).await?; + + // Run the same query on a different runtime. Note that we are still calling + // `await` here, so the the `async` function still runs on the current runtime. + // We use the `DedicatedExecutor` to run the query on a different runtime. + different_runtime_basic(ctx, sql).await?; + + // Run the same query on a different runtime including remote IO + different_runtime_advanced().await?; + + Ok(()) +} + +/// Run queries directly on the current tokio `Runtime` +/// +/// This is now most examples in DataFusion are written and works well for Review Comment: ```suggestion /// This is how most examples in DataFusion are written and works well for ``` ? -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: github-unsubscr...@datafusion.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: github-unsubscr...@datafusion.apache.org For additional commands, e-mail: github-h...@datafusion.apache.org
