It does not require you to know the structure of the payload (eg. create structs), and allows accessing fields by providing the path to them. It is up to 10 times faster than standard encoding/json
package (depending on payload size and usage), allocates no memory. See benchmarks below.
Originally I made this for a project that relies on a lot of 3rd party APIs that can be unpredictable and complex.
I love simplicity and prefer to avoid external dependecies. encoding/json
requires you to know exactly your data structures, or if you prefer to use map[string]interface{}
instead, it will be very slow and hard to manage.
I investigated what's on the market and found that most libraries are just wrappers around encoding/json
, there is few options with own parsers (ffjson
, easyjson
), but they still requires you to create data structures.
Goal of this project is to push JSON parser to the performance limits and not sacrifice with compliance and developer user experience.
For the given JSON our goal is to extract the user's full name, number of github followers and avatar.
import "github.com/buger/jsonparser"
...
data := []byte(`{
"person": {
"name": {
"first": "Leonid",
"last": "Bugaev",
"fullName": "Leonid Bugaev"
},
"github": {
"handle": "buger",
"followers": 109
},
"avatars": [
{ "url": "https://avatars1.githubusercontent.com/u/14009?v=3&s=460", "type": "thumbnail" }
]
},
"company": {
"name": "Acme"
}
}`)
// You can specify key path by providing arguments to Get function
jsonparser.Get(data, "person", "name", "fullName")
// There is `GetInt` and `GetBoolean` helpers if you exactly know key data type
jsonparser.GetInt(data, "person", "github", "followers")
// When you try to get object, it will return you []byte slice pointer to data containing it
// In `company` it will be `{"name": "Acme"}`
jsonparser.Get(data, "company")
// If the key doesn't exist it will throw an error
var size int64
if value, err := jsonparser.GetInt(data, "company", "size"); err == nil {
size = value
}
// You can use `ArrayEach` helper to iterate items [item1, item2 .... itemN]
jsonparser.ArrayEach(data, func(value []byte, dataType jsonparser.ValueType, offset int, err error) {
fmt.Println(jsonparser.Get(value, "url"))
}, "person", "avatars")
// Or use can access fields by index!
jsonparser.GetString(data, "person", "avatars", "[0]", "url")
// You can use `ObjectEach` helper to iterate objects { "key1":object1, "key2":object2, .... "keyN":objectN }
jsonparser.ObjectEach(data, func(key []byte, value []byte, dataType jsonparser.ValueType, offset int) error {
fmt.Printf("Key: '%s'\n Value: '%s'\n Type: %s\n", string(key), string(value), dataType)
return nil
}, "person", "name")
// The most efficient way to extract multiple keys is `EachKey`
paths := [][]string{
[]string{"person", "name", "fullName"},
[]string{"person", "avatars", "[0]", "url"},
[]string{"company", "url"},
}
jsonparser.EachKey(data, func(idx int, value []byte, vt jsonparser.ValueType, err error){
switch idx {
case 0: // []string{"person", "name", "fullName"}
...
case 1: // []string{"person", "avatars", "[0]", "url"}
...
case 2: // []string{"company", "url"},
...
}
}, paths...)
// For more information see docs below
Library API is really simple. You just need the Get
method to perform any operation. The rest is just helpers around it.
You also can view API at godoc.org
Get
func Get(data []byte, keys ...string) (value []byte, dataType jsonparser.ValueType, offset int, err error)
Receives data structure, and key path to extract value from.
Returns:
value
- Pointer to original data structure containing key value, or just empty slice if nothing found or errordataType
- Can be: NotExist
, String
, Number
, Object
, Array
, Boolean
or Null
offset
- Offset from provided data structure where key value ends. Used mostly internally, for example for ArrayEach
helper.err
- If the key is not found or any other parsing issue, it should return error. If key not found it also sets dataType
to NotExist
Accepts multiple keys to specify path to JSON value (in case of quering nested structures).
If no keys are provided it will try to extract the closest JSON value (simple ones or object/array), useful for reading streams or arrays, see ArrayEach
implementation.
Note that keys can be an array indexes: jsonparser.GetInt("person", "avatars", "[0]", "url")
, pretty cool, yeah?
GetString
func GetString(data []byte, keys ...string) (val string, err error)
Returns strings properly handing escaped and unicode characters. Note that this will cause additional memory allocations.
GetUnsafeString
If you need string in your app, and ready to sacrifice with support of escaped symbols in favor of speed. It returns string mapped to existing byte slice memory, without any allocations:
s, _, := jsonparser.GetUnsafeString(data, "person", "name", "title")
switch s {
case 'CEO':
...
case 'Engineer'
...
...
}
Note that unsafe
here means that your string will exist until GC will free underlying byte slice, for most of cases it means that you can use this string only in current context, and should not pass it anywhere externally: through channels or any other way.
GetBoolean
, GetInt
and GetFloat
func GetBoolean(data []byte, keys ...string) (val bool, err error)
func GetFloat(data []byte, keys ...string) (val float64, err error)
func GetInt(data []byte, keys ...string) (val int64, err error)
If you know the key type, you can use the helpers above. If key data type do not match, it will return error.
ArrayEach
func ArrayEach(data []byte, cb func(value []byte, dataType jsonparser.ValueType, offset int, err error), keys ...string)
Needed for iterating arrays, accepts a callback function with the same return arguments as Get
.
ObjectEach
func ObjectEach(data []byte, callback func(key []byte, value []byte, dataType ValueType, offset int) error, keys ...string) (err error)
Needed for iterating object, accepts a callback function. Example:
var handler func([]byte, []byte, jsonparser.ValueType, int) error
handler = func(key []byte, value []byte, dataType jsonparser.ValueType, offset int) error {
//do stuff here
}
jsonparser.ObjectEach(myJson, handler)
EachKey
func EachKey(data []byte, cb func(idx int, value []byte, dataType jsonparser.ValueType, err error), paths ...[]string)
When you need to read multiple keys, and you do not afraid of low-level API EachKey
is your friend. It read payload only single time, and calls callback function once path is found. For example when you call multiple times Get
, it has to process payload multiple times, each time you call it. Depending on payload EachKey
can be multiple times faster than Get
. Path can use nested keys as well!
paths := [][]string{
[]string{"uuid"},
[]string{"tz"},
[]string{"ua"},
[]string{"st"},
}
var data SmallPayload
jsonparser.EachKey(smallFixture, func(idx int, value []byte, vt jsonparser.ValueType, err error){
switch idx {
case 0:
data.Uuid, _ = value
case 1:
v, _ := jsonparser.ParseInt(value)
data.Tz = int(v)
case 2:
data.Ua, _ = value
case 3:
v, _ := jsonparser.ParseInt(value)
data.St = int(v)
}
}, paths...)
Set
func Set(data []byte, setValue []byte, keys ...string) (value []byte, err error)
Receives existing data structure, key path to set, and value to set at that key. This functionality is experimental.
Returns:
value
- Pointer to original data structure with updated or added key value.err
- If any parsing issue, it should return error.Accepts multiple keys to specify path to JSON value (in case of updating or creating nested structures).
Note that keys can be an array indexes: jsonparser.Set(data, []byte("http://github.com"), "person", "avatars", "[0]", "url")
Delete
func Delete(data []byte, keys ...string) value []byte
Receives existing data structure, and key path to delete. This functionality is experimental.
Returns:
value
- Pointer to original data structure with key path deleted if it can be found. If there is no key path, then the whole data structure is deleted.Accepts multiple keys to specify path to JSON value (in case of updating or creating nested structures).
Note that keys can be an array indexes: jsonparser.Delete(data, "person", "avatars", "[0]", "url")
encoding/json
, reflection
or interface{}
, the only real package dependency is bytes
.There are 3 benchmark types, trying to simulate real-life usage for small, medium and large JSON payloads. For each metric, the lower value is better. Time/op is in nanoseconds. Values better than standard encoding/json marked as bold text. Benchmarks run on standard Linode 1024 box.
Compared libraries:
If you want to skip next sections we have 2 winner: jsonparser
and easyjson
.
jsonparser
is up to 10 times faster than standard encoding/json
package (depending on payload size and usage), and almost infinitely (literally) better in memory consumption because it operates with data on byte level, and provide direct slice pointers.
easyjson
wins in CPU in medium tests and frankly i'm impressed with this package: it is remarkable results considering that it is almost drop-in replacement for encoding/json
(require some code generation).
It's hard to fully compare jsonparser
and easyjson
(or ffson
), they a true parsers and fully process record, unlike jsonparser
which parse only keys you specified.
If you searching for replacement of encoding/json
while keeping structs, easyjson
is an amazing choice. If you want to process dynamic JSON, have memory constrains, or more control over your data you should try jsonparser
.
jsonparser
performance heavily depends on usage, and it works best when you do not need to process full record, only some keys. The more calls you need to make, the slower it will be, in contrast easyjson
(or ffjson
, encoding/json
) parser record only 1 time, and then you can make as many calls as you want.
With great power comes great responsibility! :)
Each test processes 190 bytes of http log as a JSON record. It should read multiple fields. https://github.com/buger/jsonparser/blob/master/benchmark/benchmark_small_payload_test.go
Library | time/op | bytes/op | allocs/op |
---|---|---|---|
encoding/json struct | 7879 | 880 | 18 |
encoding/json interface{} | 8946 | 1521 | 38 |
Jeffail/gabs | 10053 | 1649 | 46 |
bitly/go-simplejson | 10128 | 2241 | 36 |
antonholmquist/jason | 27152 | 7237 | 101 |
github.com/ugorji/go/codec | 8806 | 2176 | 31 |
mreiferson/go-ujson | 7008 | 1409 | 37 |
a8m/djson | 3862 | 1249 | 30 |
pquerna/ffjson | 3769 | 624 | 15 |
mailru/easyjson | 2002 | 192 | 9 |
buger/jsonparser | 1367 | 0 | 0 |
buger/jsonparser (EachKey API) | 809 | 0 | 0 |
Winners are ffjson, easyjson and jsonparser, where jsonparser is up to 9.8x faster than encoding/json and 4.6x faster than ffjson, and slightly faster than easyjson. If you look at memory allocation, jsonparser has no rivals, as it makes no data copy and operates with raw []byte structures and pointers to it.
Each test processes a 2.4kb JSON record (based on Clearbit API). It should read multiple nested fields and 1 array.
https://github.com/buger/jsonparser/blob/master/benchmark/benchmark_medium_payload_test.go
Library | time/op | bytes/op | allocs/op |
---|---|---|---|
encoding/json struct | 57749 | 1336 | 29 |
encoding/json interface{} | 79297 | 10627 | 215 |
Jeffail/gabs | 83807 | 11202 | 235 |
bitly/go-simplejson | 88187 | 17187 | 220 |
antonholmquist/jason | 94099 | 19013 | 247 |
github.com/ugorji/go/codec | 114719 | 6712 | 152 |
mreiferson/go-ujson | 56972 | 11547 | 270 |
a8m/djson | 28525 | 10196 | 198 |
pquerna/ffjson | 20298 | 856 | 20 |
mailru/easyjson | 10512 | 336 | 12 |
buger/jsonparser | 15955 | 0 | 0 |
buger/jsonparser (EachKey API) | 8916 | 0 | 0 |
The difference between ffjson and jsonparser in CPU usage is smaller, while the memory consumption difference is growing. On the other hand easyjson
shows remarkable performance for medium payload.
gabs
, go-simplejson
and jason
are based on encoding/json and map[string]interface{} and actually only helpers for unstructured JSON, their performance correlate with encoding/json interface{}
, and they will skip next round.
go-ujson
while have its own parser, shows same performance as encoding/json
, also skips next round. Same situation with ugorji/go/codec
, but it showed unexpectedly bad performance for complex payloads.
Each test processes a 24kb JSON record (based on Discourse API) It should read 2 arrays, and for each item in array get a few fields. Basically it means processing a full JSON file.
https://github.com/buger/jsonparser/blob/master/benchmark/benchmark_large_payload_test.go
Library | time/op | bytes/op | allocs/op |
---|---|---|---|
encoding/json struct | 748336 | 8272 | 307 |
encoding/json interface{} | 1224271 | 215425 | 3395 |
a8m/djson | 510082 | 213682 | 2845 |
pquerna/ffjson | 312271 | 7792 | 298 |
mailru/easyjson | 154186 | 6992 | 288 |
buger/jsonparser | 85308 | 0 | 0 |
jsonparser
now is a winner, but do not forget that it is way more lightweight parser than ffson
or easyjson
, and they have to parser all the data, while jsonparser
parse only what you need. All ffjson
, easysjon
and jsonparser
have their own parsing code, and does not depend on encoding/json
or interface{}
, thats one of the reasons why they are so fast. easyjson
also use a bit of unsafe
package to reduce memory consuption (in theory it can lead to some unexpected GC issue, but i did not tested enough)
Also last benchmark did not included EachKey
test, because in this particular case we need to read lot of Array values, and using ArrayEach
is more efficient.
All bug-reports and suggestions should go though Github Issues.
All my development happens using Docker, and repo include some Make tasks to simplify development.
make build
- builds docker image, usually can be called only oncemake test
- run testsmake fmt
- run go fmtmake bench
- run benchmarks (if you need to run only single benchmark modify BENCHMARK
variable in make file)make profile
- runs benchmark and generate 3 files- cpu.out
, mem.mprof
and benchmark.test
binary, which can be used for go tool pprof
make bash
- enter container (i use it for running go tool pprof
above)