A fast Go avro codec

Overview

Install with:

go get github.com/hamba/avro/v2

Note: This project has renamed the default branch from master to main. You will need to update your local environment.

Usage

type SimpleRecord struct {
	A int64  `avro:"a"`
	B string `avro:"b"`
}

schema, err := avro.Parse(`{
    "type": "record",
    "name": "simple",
    "namespace": "org.hamba.avro",
    "fields" : [
        {"name": "a", "type": "long"},
        {"name": "b", "type": "string"}
    ]
}`)
if err != nil {
	log.Fatal(err)
}

in := SimpleRecord{A: 27, B: "foo"}

data, err := avro.Marshal(schema, in)
if err != nil {
	log.Fatal(err)
}

fmt.Println(data)
// Outputs: [54 6 102 111 111]

out := SimpleRecord{}
err = avro.Unmarshal(schema, data, &out)
if err != nil {
	log.Fatal(err)
}

fmt.Println(out)
// Outputs: {27 foo}

More examples in the godoc.

Types Conversions

Avro	Go Struct	Go Interface
null	nil	nil
boolean	bool	bool
bytes	[]byte	[]byte
float	float32	float32
double	float64	float64
long	int64, uint32*	int64, uint32
int	int, int32, int16, int8, uint8*, uint16*	int, uint8, uint16
fixed	uint64	uint64
string	string	string
array	[]T	[]any
enum	string	string
fixed	[n]byte	[n]byte
map	map[string]T{}	map[string]any
record	struct	map[string]any
union	see below	see below
int.date	time.Time	time.Time
int.time-millis	time.Duration	time.Duration
long.time-micros	time.Duration	time.Duration
long.timestamp-millis	time.Time	time.Time
long.timestamp-micros	time.Time	time.Time
long.local-timestamp-millis	time.Time	time.Time
long.local-timestamp-micros	time.Time	time.Time
bytes.decimal	*big.Rat	*big.Rat
fixed.decimal	*big.Rat	*big.Rat
string.uuid	string	string

* Please note that when the Go type is an unsigned integer care must be taken to ensure that information is not lost when converting between the Avro type and Go type. For example, storing a negative number in Avro of int = -100 would be interpreted as uint16 = 65,436 in Go. Another example would be storing numbers in Avro int = 256 that are larger than the Go type uint8 = 0.

Unions

The following union types are accepted: map[string]any, *T and any.

• map[string]any: If the union value is nil, a nil map will be en/decoded. When a non-nil union value is encountered, a single key is en/decoded. The key is the avro type name, or scheam full name in the case of a named schema (enum, fixed or record).
• *T: This is allowed in a "nullable" union. A nullable union is defined as a two schema union, with one of the types being null (ie. ["null", "string"] or ["string", "null"]), in this case a *T is allowed, with T matching the conversion table above. In the case of a slice, the slice can be used directly.
• any: An interface can be provided and the type or name resolved. Primitive types are pre-registered, but named types, maps and slices will need to be registered with the Register function. In the case of arrays and maps the enclosed schema type or name is postfix to the type with a : separator, e.g "map:string". Behavior when a type cannot be resolved will depend on your chosen configuation options:
  • !Config.UnionResolutionError && !Config.PartialUnionTypeResolution: the map type above is used
  • Config.UnionResolutionError && !Config.PartialUnionTypeResolution: an error is returned
  • !Config.UnionResolutionError && Config.PartialUnionTypeResolution: any registered type will get resolved while any unregistered type will fallback to the map type above.
  • Config.UnionResolutionError && !Config.PartialUnionTypeResolution: any registered type will get resolved while any unregistered type will return an error.

TextMarshaler and TextUnmarshaler

The interfaces TextMarshaler and TextUnmarshaler are supported for a string schema type. The object will be tested first for implementation of these interfaces, in the case of a string schema, before trying regular encoding and decoding.

Enums may also implement TextMarshaler and TextUnmarshaler, and must resolve to valid symbols in the given enum schema.

Identical Underlying Types

One type can be ConvertibleTo another type if they have identical underlying types. A non-native type is allowed be used if it can be convertible to time.Time, big.Rat or avro.LogicalDuration for the particular of LogicalTypes.

Ex.: type Timestamp time.Time

Untrusted Input With Bytes and Strings

For security reasons, the configuration Config.MaxByteSliceSize restricts the maximum size of bytes and string types created by the Reader. The default maximum size is 1MiB and is configurable. This is required to stop untrusted input from consuming all memory and crashing the application. Should this not be need, setting a negative number will disable the behaviour.

Benchmark

Benchmark source code can be found at: https://github.com/nrwiersma/avro-benchmarks

BenchmarkGoAvroDecode-8      	  788455	      1505 ns/op	     418 B/op	      27 allocs/op
BenchmarkGoAvroEncode-8      	  624343	      1908 ns/op	     806 B/op	      63 allocs/op
BenchmarkGoGenAvroDecode-8   	 1360375	       876.4 ns/op	     320 B/op	      11 allocs/op
BenchmarkGoGenAvroEncode-8   	 2801583	       425.9 ns/op	     240 B/op	       3 allocs/op
BenchmarkHambaDecode-8       	 5046832	       238.7 ns/op	      47 B/op	       0 allocs/op
BenchmarkHambaEncode-8       	 6017635	       196.2 ns/op	     112 B/op	       1 allocs/op
BenchmarkLinkedinDecode-8    	 1000000	      1003 ns/op	    1688 B/op	      35 allocs/op
BenchmarkLinkedinEncode-8    	 3170553	       381.5 ns/op	     248 B/op	       5 allocs/op

Always benchmark with your own workload. The result depends heavily on the data input.

Go structs generation

Go structs can be generated for you from the schema. The types generated follow the same logic in types conversions

Install the struct generator with:

go install github.com/hamba/avro/v2/cmd/avrogen@<version>

Example usage assuming there's a valid schema in in.avsc:

avrogen -pkg avro -o bla.go -tags json:snake,yaml:upper-camel in.avsc

Tip: Omit -o FILE to dump the generated Go structs to stdout instead of a file.

Check the options and usage with -h:

avrogen -h

Or use it as a lib in internal commands, it's the gen package

Avro schema validation

avrosv

A small Avro schema validation command-line utility is also available. This simple tool leverages the schema parsing functionality of the library, showing validation errors or optionally dumping parsed schemas to the console. It can be used in CI/CD pipelines to validate schema changes in a repository.

Install the Avro schema validator with:

go install github.com/hamba/avro/v2/cmd/avrosv@<version>

Example usage assuming there's a valid schema in in.avsc (exit status code is 0):

avrosv in.avsc

An invalid schema will result in a diagnostic output and a non-zero exit status code:

avrosv bad-default-schema.avsc; echo $?
Error: avro: invalid default for field someString. <nil> not a string
2

Schemas referencing other schemas can also be validated by providing all of them (schemas are parsed in order):

avrosv base-schema.avsc schema-withref.avsc

Check the options and usage with -h:

avrosv -h

Name Validation

Avro names are validated according to the Avro specification.

However, the official Java library does not validate said names accordingly, resulting to some files out in the wild to have invalid names. Thus, this library has a configuration option to allow for these invalid names to be parsed.

avro.SkipNameValidation = true

Note that this variable is global, so ideally you'd need to unset it after you're done with the invalid schema.

Go Version Support

This library supports the last two versions of Go. While the minimum Go version is not guarantee to increase along side Go, it may jump from time to time to support additional features. This will be not be considered a breaking change.

Who uses hamba/avro?

• confluent-kafka-go
• pulsar-client-go