Tutorial: JSONL Incremental Parser

Build a high-performance streaming JSON Lines parser using synkit’s incremental parsing infrastructure.

Source Code

📦 Complete source: examples/jsonl-parser

What You’ll Learn

1. ChunkBoundary - Define where to split token streams
2. IncrementalLexer - Buffer partial input, emit complete tokens
3. IncrementalParse - Parse from token buffers with checkpoints
4. Async streaming - tokio and futures integration
5. Stress testing - Validate memory stability under load

JSON Lines Format

JSON Lines uses newline-delimited JSON:

{"user": "alice", "action": "login"}
{"user": "bob", "action": "purchase", "amount": 42.50}
{"user": "alice", "action": "logout"}

Each line is a complete JSON value. This makes JSONL ideal for:

• Log processing
• Event streams
• Large dataset processing
• Network protocols

Why Incremental Parsing?

Traditional parsing loads entire input into memory:

let input = fs::read_to_string("10gb_logs.jsonl")?;  // ❌ OOM
let docs: Vec<Log> = parse(&input)?;

Incremental parsing processes chunks:

let mut lexer = JsonIncrementalLexer::new();
while let Some(chunk) = reader.read_chunk().await {
    for token in lexer.feed(&chunk)? {
        // Process tokens as they arrive
    }
}

Prerequisites

• Completed the TOML Parser Tutorial (or familiarity with synkit basics)
• Understanding of async Rust (for chapters 5-6)

Chapters