Unable to make it work for nested types in different Schema Files.

[markfarnan]

Looking for guidance on how to make rsgen-Avro and avro-rust work when there are multiple schema files, where one file relies on a type in another file.

rsgen-avro seems to create the schema's correctly.
Schema::parse_list seems to parse the schema's correct.

Writer throws validation errors. (i've also trying using more lower level primatives, such as to_avro_datum, same issue)
Line 81 in the sample code below: Err(SchemaResolutionError(Name { name: "ErrorInfo", namespace: Some("Energistics.Etp.v12.Datatypes") }))

Sample code to show the issue:
NOTES:
-- This is a subset of what I need to do. The full Schema definition I need to use is 200+ .AVSC files, with multiple nested / reused types.
-- I can't change the structure of the Schema files, as this is a Published Industry Standard in our domain for data interchange using a wire protocol. (I will actually use to_avro_datum for the final version, as we just want the raw bytes, not the headers etc).
-- I'm getting some other errors with the rsgen (serde-bytes, and unable to use derive-schemas) that might post seperatly. I can share the full set of schema's if it is usefull for debugging.

Sample code showing the problem.

// Test File
use apache_avro::{Schema, Writer};

// Structs Generated from rsgen-avro with commandline -->   rsgen-avro  "*.avsc" schema.rs
// Interestingly trying to use "--nullable" in rsgen-avro throws an error "Templating error: Failed to render 'record.tera'" might need to look at that seperatly.
//
#[derive(Debug, PartialEq, Eq, Clone, serde::Deserialize, serde::Serialize)]
pub struct ProtocolException {
   pub error: Option<ErrorInfo>,
   #[serde(default = "default_protocolexception_errors")]
   pub errors: ::std::collections::HashMap<String, ErrorInfo>,
}

#[inline(always)]
fn default_protocolexception_errors() -> ::std::collections::HashMap<String, ErrorInfo> {
   ::std::collections::HashMap::new()
}

#[derive(Debug, PartialEq, Eq, Clone, serde::Deserialize, serde::Serialize)]
pub struct ErrorInfo {
   pub message: String,
   pub code: i32,
}

// Main Test
fn main() {
   let errinfo_schema = r#"
   {
       "type": "record",
       "namespace": "Energistics.Etp.v12.Datatypes",
       "name": "ErrorInfo",
       "fields":
       [
           { "name": "message", "type": "string" },
           { "name": "code", "type": "int" }
       ]
   }
   "#;

   let protocolexception_schema = r#"
   {
       "type": "record",
       "namespace": "Energistics.Etp.v12.Protocol.Core",
       "name": "ProtocolException",
       "protocol": "0",
       "messageType": "1000",
       "senderRole": "*",
       "protocolRoles": "client, server",
       "multipartFlag": true,
       "fields":
       [
           { "name": "error", "type": ["null", "Energistics.Etp.v12.Datatypes.ErrorInfo"] },
           {
               "name": "errors",
               "type": { "type": "map", "values": "Energistics.Etp.v12.Datatypes.ErrorInfo" }, "default": {}
           }
       ]
   }
   "#;

   let schema_list: [&str; 2] = [protocolexception_schema, errinfo_schema];
   let schemas_raw = Schema::parse_list(&schema_list);

   println!("{:?}", schemas_raw);
   println!("{:?}", "--------------");

   let schemas = schemas_raw.unwrap();

   let pe = ProtocolException {
       error: Some(ErrorInfo {
           message: String::from("some Error Message"),
           code: 451,
       }),
       errors: ::std::collections::HashMap::new(),
   };

   println!("{:?}", schemas[0]); // The 'ProtocolException' Schema in the list
   println!("{:?}", "--------------");

   let mut writer = Writer::new(&schemas[0], Vec::new()); // <-- Should I be able to pass the 'list' of Schema's here somewhere, so it resolves all the sub types ?

   let result = writer.append_ser(pe); // <-- Schema Resolution Error !  Missing the ErrorInfo Subtype
   println!("{:?}", result);

   let encoded = writer.into_inner();
   println!("{:?}", encoded);

   // Equivelent READER code to go here, once WRITER works.
}

[martin-g]

@markfarnan I think the correct place to report this problem is https://issues.apache.org/jira/projects/AVRO
The best would be to create a JIRA issue and a PR with a test that fails in https://github.com/apache/avro/blob/master/lang/rust/avro/src/writer.rs
Please try to make it as minimal as possible by removing fields and attributes which are not really needed!

[markfarnan]

Thanks Martin,

So I take it this should work (in theory !) as I'm using it ?

Or put another way, that the Schema returned in the [0] element of the vector (in this case), SHOULD be a full schema ?

Didn't want to report an error if I'm just using it wrong etc.

[martin-g]

So I take it this should work (in theory !) as I'm using it ?

I am not sure what was the initial purpose of this API.
It definitely is not usable in the current version of apache_avro crate (even in master branch)!
But I think I have an idea how to implement it! I just need to find time to do it :-)

[markfarnan]

Sounds good.

Interesting, if I derive the schema's from the Objects (using --derive-schemas in rsgen-avro), the resultant schema works fine to writer!.

I've attached two files for reference in case it is usefull, the first one is the 'Failing' parsed Schema. (the result of the PrintLn) that just uses the list, the second is the 'working' schema that I obtained from. ProtocolException::get_schema()

• I couldn't find a formater for whatever this format RUST PrintLn is using for types, so I've manually 'formatted' the printed output so it's readable and comparable.

It looks like the parse_list function is just putting in references, which are unresolvable, where are the get_schema() is putting in valid Unions that embed the refered schema.

Note: I don't think I can use derive-schemas for my project, as the resultant file from rsgen-avro has dozens of errors. Some types dont' support derive.
Also I need to use. value, and to_datum as I just want bytes.

I'll try and work out how to do that test / Jira for Avro soon as I can, as using these AVRO Schemas is critical for us switching to RUST for some new work.
bad_schema.txt
good_schema.txt

[lerouxrgd]

Indeed issues related to Avro Writer/Reader should be reported to apache_avro since rsgen-avro is really just for Rust types generation. However if you have a valid Avro schema that generates invalid Rust types, then you should open an issue here.

I'm getting some other errors with the rsgen (serde-bytes, and unable to use derive-schemas)
...
I don't think I can use derive-schemas for my project, as the resultant file from rsgen-avro has dozens of errors. Some types dont' support derive.

This is strange, yes please open a separate issue for this with a basic example to reproduce the issue.

Interestingly trying to use "--nullable" in rsgen-avro throws an error "Templating error: Failed to render 'record.tera'"

This is strange too, please open a separate issue too.

Beside, if I've understood correctly the Schema you get with Schema::parse_list is different from the one in AvroSchema::get_schema ?

This is unexpected indeed, but this issue should be addressed in apache_avro instead.
@martin-g Actually Schema::parse_list originated from rsgen-avro/issues/6 which in turn created avro-rs/pull/173.

[markfarnan]

JIRA and PR Created in Apache Avro for this issue.

I'll see if I can isolate some examples for the other issues.
One shoudl be easy, as anything using serde_bytes dosn't want to compile.

The SchemaDerive one is going to be more interesting, as the schema it breaks on, has a a dozen or so dependancies.

[lerouxrgd]

One shoudl be easy, as anything using serde_bytes dosn't want to compile.

Are you including serde_bytes in your dependencies ? It is required in this case.

[markfarnan]

Yes:

[dependencies]
clap = { version = "4.0", features = ["derive"] }
serde = { version = "1.0", features = ["derive"] }
serde_bytes = "0.11.7"
apache-avro = { version = "0.15.0", features = ["derive"]}
uuid = "1.2.2"
glob = "0.3.0"

It's wierd, because several things annotated with #[serde(with = "serde_bytes")]. work fine, just a couple don't.
That said, they are complex unions, of arrays of various types. So I'm just trying to narrow it down to something reproducible.

The AvroSchema stuff breaks on some Enums. with "error: AvroSchema derive does not work for enums with non unit structs"

It dosn't like things like this it seems: (I'm too new at this to have a clue as to why)

#[derive(Debug, PartialEq, Clone, serde::Serialize, apache_avro::AvroSchema)]
pub enum UnionLongDoublePassIndexedDepth {
Long(i64),
Double(f64),
PassIndexedDepth(PassIndexedDepth),
}

[martin-g]

See apache/avro#1921

[markfarnan]

Thanks,

Unfortunatly I'm too new at Rust for that to make a lot of sense as yet !.

However, on a seperate point.
Currently using 'AvroSchema' relies on regenerating a valid schema, from the objects which rsgen-Avro has created.

rsgen already knows a fully valid, resolved schema when it creates the objects in the first place (with all the extra fields etc, like doc, and real namespaces.).
It seems counter intuitive to have to regenerate / reparse that schema to then USE those objects.

Would it be possible instead, for rsgen to store that schema with the objects themselves, so that 'getSchema' actually returns a guarenteed valid schema, by using the parsed version is used to create them in the first place?

This is the approach taken by the Avro implementation in GO. It actually takes it a step further and creates Serialize and Deserialize functions that return valid Go objects, but that dosn't seem necessary using Serde, if the schema's are correct.

[martin-g]

Would it be possible instead, for rsgen to store that schema with the objects themselves, so that 'getSchema' actually returns a guarenteed valid schema, by using the parsed version is used to create them in the first place?

This should be easy to do by providing an impl for AvroSchemaComponent

[lerouxrgd]

It's not really implementable as long as Names (which is part of the method signature) is not public.

Besides I have an implementation for this on branch impl-schema-component. It looks fine for simple cases but if the schema has dependencies etc, it might not work...

[untereiner]

The schema variable line 430 should be the expanded version of the schema to take into account of the dependencies. I was looking to add a recursive construction of the schema along the fields of the objects.

[markfarnan]

It would be ideal if it:
A: Stored the Schema used to generate a given struct, with the struct, returning it from the AvroSchem interface
B: The schema was 'complete', including all dependencies down the chain.

• This could be done by making it compelte as per the above (prob fastest), or resolving down the chain from each used struct and its schema etc. (Prob slower).