README
¶
snowflake
snowflake is a Go package that provides
- A very simple Twitter snowflake generator.
- Methods to parse existing snowflake IDs.
- Methods to convert a snowflake ID into several other data types.
- JSON Marshal/Unmarshal functions to easily use snowflake IDs within a JSON API.
For help with this package or general Go discussion, please join the Discord Gophers chat server.
Status @ 2017-02-21
This package should be considered stable and completed. Any additions in the future will strongly avoid API changes to existing functions. Please see issues for any remaining TODO items that are planned.
ID Format
By default, the ID format follows the original Twitter snowflake format.
- The ID as a whole is a 63 bit integer stored in an int64
- 41 bits are used to store a timestamp with millisecond precision, using a custom epoch.
- 10 bits are used to store a node id - a range from 0 through 1023.
- 12 bits are used to store a sequence number - a range from 0 through 4095.
Custom Format
You can alter the number of bits used for the node id and step number (sequence) by setting the snowflake.NodeBits and snowflake.StepBits values. Remember that There is a maximum of 22 bits available that can be shared between these two values. You do not have to use all 22 bits.
Custom Epoch
By default this package uses the Twitter Epoch of 1288834974657 or Nov 04 2010 01:42:54. You can set your own epoch value by setting snowflake.Epoch to a time in milliseconds to use as the epoch.
Custom Notes
When setting custom epoch or bit values you need to set them prior to calling any functions on the snowflake package, including NewNode(). Otherwise the custom values you set will not be applied correctly.
How it Works.
Each time you generate an ID, it works, like this.
- A timestamp with millisecond precision is stored using 41 bits of the ID.
- Then the NodeID is added in subsequent bits.
- Then the Sequence Number is added, starting at 0 and incrementing for each ID generated in the same millisecond. If you generate enough IDs in the same millisecond that the sequence would roll over or overfill then the generate function will pause until the next millisecond.
The default Twitter format shown below.
+--------------------------------------------------------------------------+
| 1 Bit Unused | 41 Bit Timestamp | 10 Bit NodeID | 12 Bit Sequence ID |
+--------------------------------------------------------------------------+
Using the default settings, this allows for 4096 unique IDs to be generated every millisecond, per Node ID.
Getting Started
Installing
This assumes you already have a working Go environment, if not please see this page first.
go get github.com/bwmarrin/snowflake
Usage
Import the package into your project then construct a new snowflake Node using a unique node number. The default settings permit a node number range from 0 to 1023. If you have set a custom NodeBits value, you will need to calculate what your node number range will be. With the node object call the Generate() method to generate and return a unique snowflake ID.
Keep in mind that each node you create must have a unique node number, even across multiple servers. If you do not keep node numbers unique the generator cannot guarantee unique IDs across all nodes.
Example Program:
package main
import (
"fmt"
"github.com/bwmarrin/snowflake"
)
func main() {
// Create a new Node with a Node number of 1
node, err := snowflake.NewNode(1)
if err != nil {
fmt.Println(err)
return
}
// Generate a snowflake ID.
id := node.Generate()
// Print out the ID in a few different ways.
fmt.Printf("Int64 ID: %d\n", id)
fmt.Printf("String ID: %s\n", id)
fmt.Printf("Base2 ID: %s\n", id.Base2())
fmt.Printf("Base64 ID: %s\n", id.Base64())
// Print out the ID's timestamp
fmt.Printf("ID Time : %d\n", id.Time())
// Print out the ID's node number
fmt.Printf("ID Node : %d\n", id.Node())
// Print out the ID's sequence number
fmt.Printf("ID Step : %d\n", id.Step())
// Generate and print, all in one.
fmt.Printf("ID : %d\n", node.Generate().Int64())
}
Performance
With default settings, this snowflake generator should be sufficiently fast enough on most systems to generate 4096 unique ID's per millisecond. This is the maximum that the snowflake ID format supports. That is, around 243-244 nanoseconds per operation.
Since the snowflake generator is single threaded the primary limitation will be the maximum speed of a single processor on your system.
To benchmark the generator on your system run the following command inside the snowflake package directory.
go test -bench=.
If your curious, check out this commit that shows benchmarks that compare a few different ways of implementing a snowflake generator in Go.
Documentation
¶
Overview ¶
Package snowflake provides a very simple Twitter snowflake generator and parser.
Index ¶
- Variables
- type ID
- func (f ID) Base2() string
- func (f ID) Base32() string
- func (f ID) Base36() string
- func (f ID) Base58() string
- func (f ID) Base64() string
- func (f ID) Bytes() []byte
- func (f ID) Int64() int64
- func (f ID) IntBytes() [8]byte
- func (f ID) MarshalJSON() ([]byte, error)
- func (f ID) Node() int64
- func (f ID) Step() int64
- func (f ID) String() string
- func (f ID) Time() int64
- func (f *ID) UnmarshalJSON(b []byte) error
- type JSONSyntaxError
- type Node
Constants ¶
This section is empty.
Variables ¶
var ( // Epoch is set to the twitter snowflake epoch of Nov 04 2010 01:42:54 UTC // You may customize this to set a different epoch for your application. Epoch int64 = 1288834974657 // Number of bits to use for Node // Remember, you have a total 22 bits to share between Node/Step NodeBits uint8 = 10 // Number of bits to use for Step // Remember, you have a total 22 bits to share between Node/Step StepBits uint8 = 12 )
var ErrInvalidBase32 = errors.New("invalid base32")
ErrInvalidBase32 is returned by ParseBase32 when given an invalid []byte
var ErrInvalidBase58 = errors.New("invalid base58")
ErrInvalidBase58 is returned by ParseBase58 when given an invalid []byte
Functions ¶
This section is empty.
Types ¶
type ID ¶
type ID int64
An ID is a custom type used for a snowflake ID. This is used so we can attach methods onto the ID.
func ParseBase32 ¶
ParseBase32 parses a base32 []byte into a snowflake ID NOTE: There are many different base32 implementations so becareful when doing any interoperation interop with other packages.
func ParseBase58 ¶
ParseBase58 parses a base58 []byte into a snowflake ID
func (ID) Base32 ¶
Base32 uses the z-base-32 character set but encodes and decodes similar to base58, allowing it to create an even smaller result string. NOTE: There are many different base32 implementations so becareful when doing any interoperation interop with other packages.
func (ID) IntBytes ¶
IntBytes returns an array of bytes of the snowflake ID, encoded as a big endian integer.
func (ID) MarshalJSON ¶
MarshalJSON returns a json byte array string of the snowflake ID.
func (*ID) UnmarshalJSON ¶
UnmarshalJSON converts a json byte array of a snowflake ID into an ID type.
type JSONSyntaxError ¶
type JSONSyntaxError struct {
// contains filtered or unexported fields
}
A JSONSyntaxError is returned from UnmarshalJSON if an invalid ID is provided.
func (JSONSyntaxError) Error ¶
func (j JSONSyntaxError) Error() string
Source Files