Crate datafusion_tracing 

DataFusion Tracing is an extension for Apache DataFusion that helps you monitor and debug queries. It uses tracing and OpenTelemetry to gather DataFusion metrics, trace execution steps, and preview partial query results.

Note: This is not an official Apache Software Foundation release.

Overview

When you run queries with DataFusion Tracing enabled, it automatically adds tracing around execution steps, records all native DataFusion metrics such as execution time and output row count, lets you preview partial results for easier debugging, and integrates with OpenTelemetry for distributed tracing. This makes it simpler to understand and improve query performance.

See it in action

Here’s what DataFusion Tracing can look like in practice:

Jaeger UI

DataDog UI

Getting Started

Installation

Include DataFusion Tracing in your project’s Cargo.toml:

[dependencies]
datafusion = "50.0.0"
datafusion-tracing = "50.0.2"

Compatibility note

The ellipsis truncation indicator in pretty_format_compact_batch is disabled in this version because it requires comfy-table >= 7.1.4, while Apache Arrow currently pins comfy-table to 7.1.2 to preserve its MSRV. Context: comfy-table 7.2.0 bumped MSRV to Rust 1.85 while Arrow remains at 1.84. See arrow-rs issue #8243 and PR #8244. Arrow used an exact pin rather than ~7.1, which would also preserve MSRV while allowing 7.1.x (including 7.1.4). We will re-enable it once Arrow relaxes the pin to allow >= 7.1.4.

Quick Start Example

use datafusion::{
    arrow::{array::RecordBatch, util::pretty::pretty_format_batches},
    error::Result,
    execution::SessionStateBuilder,
    prelude::*,
};
use datafusion_tracing::{
    instrument_with_info_spans, pretty_format_compact_batch, InstrumentationOptions,
};
use std::sync::Arc;
use tracing::field;

#[tokio::main]
async fn main() -> Result<()> {
    // Initialize tracing subscriber as usual
    // (See examples/otlp.rs for a complete example).

    // Set up tracing options (you can customize these).
    let options = InstrumentationOptions::builder()
        .record_metrics(true)
        .preview_limit(5)
        .preview_fn(Arc::new(|batch: &RecordBatch| {
            pretty_format_compact_batch(batch, 64, 3, 10).map(|fmt| fmt.to_string())
        }))
        .add_custom_field("env", "production")
        .add_custom_field("region", "us-west")
        .build();

    let instrument_rule = instrument_with_info_spans!(
        options: options,
        env = field::Empty,
        region = field::Empty,
    );

    let session_state = SessionStateBuilder::new()
        .with_default_features()
        .with_physical_optimizer_rule(instrument_rule)
        .build();

    let ctx = SessionContext::new_with_state(session_state);

    let results = ctx.sql("SELECT 1").await?.collect().await?;
    println!(
        "Query Results:\n{}",
        pretty_format_batches(results.as_slice())?
    );

    Ok(())
}

A more complete example can be found in the examples directory.

Optimizer rule ordering (put instrumentation last)

Always register the instrumentation rule last in your physical optimizer chain.

• Many optimizer rules identify nodes using as_any().downcast_ref::<ConcreteExec>(). Since instrumentation wraps each node in a private InstrumentedExec, those downcasts won’t match if instrumentation runs first, causing rules to be skipped or, in code that assumes success, to panic.
• Some rules may rewrite parts of the plan after instrumentation. While InstrumentedExec re-wraps many common mutations, placing the rule last guarantees full, consistent coverage regardless of other rules’ behaviors.

Why is InstrumentedExec private?

• To prevent downstream code from downcasting to or unwrapping the wrapper, which would be brittle and force long-term compatibility constraints on its internals. The public contract is the optimizer rule, not the concrete node.

How to ensure it is last:

• When chaining: builder.with_physical_optimizer_rule(rule_a) .with_physical_optimizer_rule(rule_b) .with_physical_optimizer_rule(instrument_rule)
• Or collect: builder.with_physical_optimizer_rules(vec![..., instrument_rule])

Macros

instrument_with_debug_spans

Constructs a new instrumentation PhysicalOptimizerRule for a DataFusion ExecutionPlan at the debug level.

instrument_with_error_spans

Constructs a new instrumentation PhysicalOptimizerRule for a DataFusion ExecutionPlan at the error level.

instrument_with_info_spans

Constructs a new instrumentation PhysicalOptimizerRule for a DataFusion ExecutionPlan at the info level.

instrument_with_spans

Constructs a new instrumentation PhysicalOptimizerRule for a DataFusion ExecutionPlan.

instrument_with_trace_spans

Constructs a new instrumentation PhysicalOptimizerRule for a DataFusion ExecutionPlan at the trace level.

instrument_with_warn_spans

Constructs a new instrumentation PhysicalOptimizerRule for a DataFusion ExecutionPlan at the warn level.

Structs

InstrumentationOptions

Configuration options for instrumented execution plans.

Functions

pretty_format_compact_batch

Formats a RecordBatch as a neatly aligned ASCII table, constraining the total width to max_width. Columns are dynamically resized or truncated, and columns that cannot fit within the given width may be dropped.