Configuration

This page covers Rust Fory instance configuration. Fory::builder().xlang(true).build() selects xlang mode with compatible schema evolution. Native mode is selected explicitly with .xlang(false) and also defaults to compatible schema evolution.

Wire Modes

Apache Fory™ supports two serialization modes:

Xlang Mode

Xlang mode is selected with .xlang(true) and uses the cross-language wire format. Compatible schema evolution is the xlang default and is recommended for cross-language services because schemas can diverge more easily across languages:

let fory = Fory::builder().xlang(true).build();

Use .compatible(false) for xlang payloads only when every reader and writer always uses the same schema and you want faster serialization and smaller size. Use it only after verifying that every language uses that schema, or when native types are generated from Fory schema IDL:

let fory = Fory::builder().compatible(false).build();

Native Mode

For Rust-only payloads, select native mode explicitly:

let fory = Fory::builder().xlang(false).build();

Compatible mode is enabled by default. Set .compatible(false) only when every reader and writer always uses the same Rust schema and you want faster serialization and smaller size.

Configuration

Maximum Dynamic Object Nesting Depth

Apache Fory™ provides protection against stack overflow from deeply nested dynamic objects during deserialization. By default, the maximum nesting depth is set to 5 levels for trait objects and containers.

Default configuration:

let fory = Fory::builder().build(); // max_dyn_depth = 5

Custom depth limit:

let fory = Fory::builder().max_dyn_depth(10).build(); // Allow up to 10 levels

When to adjust:

• Increase: For legitimate deeply nested data structures
• Decrease: For stricter security requirements or shallow data structures

Protected types:

• Box<dyn Any>, Rc<dyn Any>, Arc<dyn Any + Send + Sync>
• Box<dyn Trait>, Rc<dyn Trait>, Arc<dyn Trait> (trait objects)
• RcWeak<T>, ArcWeak<T>
• Collection types (Vec, HashMap, HashSet)
• Nested struct types in Compatible mode

Note: Static data types (non-dynamic types) are secure by nature and not subject to depth limits, as their structure is known at compile time.

Remote Schema Metadata Limits

Compatible mode can receive remote metadata for schema evolution. These limits bound metadata size and accepted schema versions:

let fory = Fory::builder()
    .max_type_fields(512)
    .max_type_meta_bytes(4096)
    .max_schema_versions_per_type(10)
    .max_average_schema_versions_per_type(3)
    .build();

• max_type_fields defaults to 512 and limits fields in one received struct metadata body.
• max_type_meta_bytes defaults to 4096 and limits encoded body bytes in one received TypeDef or TypeMeta body, excluding the 8-byte header and any extended-size varint.
• max_schema_versions_per_type defaults to 10 and limits accepted remote metadata versions for one logical type.
• max_average_schema_versions_per_type defaults to 3 and limits the average across accepted remote types. The effective global floor is 8192 schemas.

Explicit Xlang Examples

Set .xlang(true) explicitly for xlang serialization examples:

let fory = Fory::builder().xlang(true).build();

Builder Pattern

use fory::Fory;

// Default xlang configuration
let fory = Fory::builder().build();

// Native mode for Rust-only traffic
let fory = Fory::builder().xlang(false).build();

// Same-schema optimization for Rust-only payloads
let fory = Fory::builder().xlang(false).compatible(false).build();

// Custom depth limit
let fory = Fory::builder().max_dyn_depth(10).build();

// Combined configuration
let fory = Fory::builder()
    .xlang(false)
    .max_dyn_depth(10)
    .build();

Configuration Summary

Option	Description	Default
compatible(bool)	Enable schema evolution	true
xlang(bool)	Use xlang mode	true
max_dyn_depth(u32)	Maximum nesting depth for dynamic types	5
max_type_fields(usize)	Max fields in one received struct metadata body	512
max_type_meta_bytes(usize)	Max encoded bytes in one received metadata body	4096
max_schema_versions_per_type(usize)	Max remote metadata versions for one logical type	10
max_average_schema_versions_per_type(usize)	Average remote metadata versions across types	3

Compatible Mode

Compatible mode is enabled by default for both xlang and native mode. Keep this default when Rust structs may evolve independently, when services deploy separately, or when xlang schemas are written by hand in different languages.

Use .compatible(false) only when the schema used to deserialize every payload is always the same as the schema used to serialize it and you want faster serialization and smaller size. For xlang payloads, use .compatible(false) only after verifying that every language uses the same schema, or when native types are generated from Fory schema IDL.

Security

Security-related configuration:

• Register application structs and trait-object implementations before deserializing untrusted payloads.
• Use max_dyn_depth(...) to reject unexpectedly deep dynamic object graphs.
• Keep the remote schema metadata limits at their defaults unless the data is not malicious and a trusted peer sends larger metadata or many schema versions.
• Prefer concrete typed fields over dyn Any or broad trait-object fields for untrusted input.

Related Topics

• Basic Serialization - Using configured Fory
• Schema Evolution - Compatible mode details
• Xlang Serialization - xlang mode