Prometheus Parquet Common Library

Status: 🚧 Early development – expect breaking changes

A shared Go library for working with Parquet-encoded Prometheus time series data, designed for use across projects like Cortex and Thanos.

Overview

This library provides a standardized approach to storing and querying Prometheus time series data in Parquet format, enabling:

• Efficient long-term storage in object stores (S3, GCS, Azure Blob)
• Columnar compression for better storage efficiency
• Fast analytical queries on historical time series data
• Shared schema to reduce duplication across Prometheus ecosystem projects

Key Features

• TSDB Block Conversion: Convert Prometheus TSDB blocks to Parquet format
• Prometheus-Compatible Querying: Implements storage.Queryable interface
• Flexible Schema: Configurable column layout and compression options
• Performance Optimized: Built-in bloom filters, sorting, and chunking strategies
• Cloud Storage Ready: Works with any objstore.Bucket implementation

Architecture

The library is organized into several key packages:

• convert: TSDB block to Parquet conversion utilities
• schema: Parquet schema definitions and encoding/decoding logic
• queryable: Prometheus-compatible query interface implementation
• search: Query optimization and constraint handling

Quick Start

Installation

go get github.com/prometheus-community/parquet-common

Converting TSDB Blocks to Parquet

Convert Prometheus TSDB blocks to Parquet format for long-term storage:

package main

import (
    "context"
    "log/slog"
    
    "github.com/prometheus/prometheus/tsdb"
    "github.com/thanos-io/objstore/providers/filesystem"
    
    "github.com/prometheus-community/parquet-common/convert"
)

func main() {
    ctx := context.Background()
    blockDir := "/path/to/tsdb/block"
    
    // Set up storage bucket
    bkt, err := filesystem.NewBucket(blockDir)
    if err != nil {
        panic(err)
    }
    defer bkt.Close()
    
    // Open TSDB block
    tsdbBlock, err := tsdb.OpenBlock(slog.Default(), blockDir, nil, tsdb.DefaultPostingsDecoderFactory)
    if err != nil {
        panic(err)
    }
    defer tsdbBlock.Close()
    
    // Convert to Parquet
    _, err = convert.ConvertTSDBBlock(
        ctx,
        bkt,
        tsdbBlock.MinTime(),
        tsdbBlock.MaxTime(),
        []convert.Convertible{tsdbBlock},
        convert.WithSortBy("__name__"), // Sort by metric name for better compression
    )
    if err != nil {
        panic(err)
    }
}

Querying Parquet Data

Query Parquet files using the Prometheus-compatible interface:

package main

import (
	"context"
	"fmt"
	"math"

	"github.com/prometheus/prometheus/model/labels"
	"github.com/prometheus/prometheus/tsdb/chunkenc"
	"github.com/thanos-io/objstore/providers/filesystem"

	"github.com/prometheus-community/parquet-common/queryable"
	"github.com/prometheus-community/parquet-common/schema"
	"github.com/prometheus-community/parquet-common/storage"
)

func main() {
	ctx := context.Background()

	// Set up storage
	bkt, _ := filesystem.NewBucket("/path/to/parquet/data")
	bucketOpener := storage.NewParquetBucketOpener(bkt)

	// Open parquet shard
	shard, err := storage.NewParquetShardOpener(
		ctx, "shard", bucketOpener, bucketOpener, 0,
	)
	if err != nil {
		panic(err)
	}

	// Create queryable interface
	decoder := schema.NewPrometheusParquetChunksDecoder(chunkenc.NewPool())
	queryable, _ := queryable.NewParquetQueryable(decoder, func(ctx context.Context, mint, maxt int64) ([]storage.ParquetShard, error) {
		return []storage.ParquetShard{shard}, nil
	})

	// Query data
	querier, err := queryable.Querier(0, math.MaxInt64) // Query all time
	if err != nil {
		panic(err)
	}
	defer querier.Close()

	// Select series matching criteria
	matchers := []*labels.Matcher{
		labels.MustNewMatcher(labels.MatchEqual, "__name__", "cpu_usage"),
	}

	seriesSet := querier.Select(ctx, false, nil, matchers...)

	// Iterate through results
	for seriesSet.Next() {
		series := seriesSet.At()
		fmt.Printf("Series: %s\n", series.Labels().String())

		iterator := series.Iterator(nil)
		for iterator.Next() == chunkenc.ValFloat {
			ts, val := iterator.At()
			fmt.Printf("  %d: %f\n", ts, val)
		}
	}
}

Configuration Options

Conversion Options

Customize the conversion process with various options:

_, err := convert.ConvertTSDBBlock(
    ctx, bkt, minTime, maxTime, blocks,
    convert.WithName("custom-block-name"),
    convert.WithRowGroupSize(500000),                    // Rows per row group
    convert.WithColumnDuration(4*time.Hour),             // Time span per column
    convert.WithSortBy("__name__", "instance"),          // Sort order for better compression
    convert.WithBloomFilterLabels("__name__", "job"),    // Labels to create bloom filters for
    convert.WithConcurrency(8),                          // Parallel processing
    convert.WithCompression(schema.CompressionZstd),     // Compression algorithm
)

Schema Configuration

The library uses a columnar schema optimized for time series data:

• Label columns: Prefixed with l_ (e.g., l___name__, l_instance)
• Data columns: Time-partitioned chunks prefixed with s_data_
• Index column: s_col_indexes for efficient chunk lookup
• Metadata: Min/max timestamps and column duration information

Performance

The library is designed for high performance with several optimizations:

• Columnar storage with efficient compression (Zstd, Snappy)
• Bloom filters on frequently queried labels
• Time-based partitioning for faster range queries
• Parallel processing during conversion and querying

Benchmarks

Performance benchmarks are available at: https://prometheus-community.github.io/parquet-common/dev/bench/

Run benchmarks locally:

make bench-select  # Query performance benchmarks

Development

Prerequisites

• Go 1.23.4 or later
• Make

Building and Testing

# Run tests
make test-short

# Run all tests with coverage
make all-tests-with-coverage

Project Structure

├── convert/          # TSDB to Parquet conversion
├── queryable/        # Prometheus-compatible query interface
├── schema/           # Parquet schema and encoding/decoding
├── search/           # Query optimization and constraints
├── storage/          # Parquet file management
└── util/             # Common utilities

Current Status & Roadmap

Current Status: Early development with core functionality implemented

Completed:

• ✅ TSDB block to Parquet conversion
• ✅ Prometheus-compatible querying interface
• ✅ Configurable schema and compression
• ✅ Performance optimizations (bloom filters, sorting, opmistic reader)

In Progress:

• 🔄 API stabilization
• 🔄 Enhanced query performance
• 🔄 Documentation improvements

Planned:

• 📋 Streaming query capabilities

Contributing

We welcome contributions! This project is in active development, so please:

1. Check existing issues before starting work
2. Open an issue to discuss significant changes
3. Follow Go best practices and include tests
4. Update documentation for user-facing changes

Getting Help

• GitHub Issues: Bug reports and feature requests
• Slack: Join #prometheus-parquet-dev for discussions
• Documentation: Check the Go Reference

License

Licensed under the Apache License, Version 2.0. See LICENSE for details.