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client.go
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client.go
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package client
import (
"bytes"
"context"
"encoding/binary"
"encoding/gob"
"errors"
"net/rpc"
"time"
"github.com/gasparian/pure-kv/internal/server"
)
var (
errCantGetSize = errors.New("unable to get number of stored elements")
errCantDeleteKey = errors.New("unable to delete key")
errCantDeleteAll = errors.New("unable to clean the store")
errCantSetKeyValuePair = errors.New("unable to set the key-value pair")
)
// Client holds client connection
type Client struct {
timeout time.Duration
client *rpc.Client
address string
}
// Serialize dumps object to byte array via gob encoder
func Serialize(obj interface{}) ([]byte, error) {
buf := &bytes.Buffer{}
enc := gob.NewEncoder(buf)
err := enc.Encode(obj)
if err != nil {
return nil, err
}
return buf.Bytes(), nil
}
// Deserialize decodes recieved gob encoded data and writes to input object by reference
func Deserialize(inp []byte, obj interface{}) error {
buf := &bytes.Buffer{}
buf.Write(inp)
dec := gob.NewDecoder(buf)
err := dec.Decode(obj)
if err != nil {
return err
}
return nil
}
// New instantiates rpc client
func New(address string, timeout int) *Client {
return &Client{
address: address,
timeout: time.Duration(timeout) * time.Millisecond,
}
}
// Open creates connection to the rpc server
func (c *Client) Open() error {
client, err := rpc.Dial("tcp", c.address)
if err != nil {
return err
}
c.client = client
return nil
}
// Close terminates the underlying client
func (c *Client) Close() error {
if c.client != nil {
err := c.client.Close()
return err
}
return nil
}
// execute runs rpc any given function by it's name
func (c *Client) execute(methodName string, req *server.PayLoad) chan *server.PayLoad {
respChan := make(chan *server.PayLoad)
go func() {
response := new(server.PayLoad)
err := c.client.Call(methodName, req, response)
if err != nil {
response.Ok = false
}
respChan <- response
}()
return respChan
}
// executeWrapper wraps execute function into context
func (c *Client) executeWrapper(methodName string, req *server.PayLoad) *server.PayLoad {
ctx, cancel := context.WithTimeout(context.Background(), c.timeout)
defer cancel()
respChan := c.execute(methodName, req)
select {
case <-ctx.Done():
return &server.PayLoad{}
case response := <-respChan:
return response
}
}
// Size requests number of elements in the storage
func (c *Client) Size() (uint64, error) {
request := &server.PayLoad{}
resp := c.executeWrapper(server.Size, request)
if !resp.Ok {
return 0, errCantGetSize
}
var size uint64
buf := bytes.NewReader(resp.Value)
err := binary.Read(buf, binary.LittleEndian, &size)
if err != nil {
return 0, err
}
return size, nil
}
// Del makes RPC for deleting any record from the bucket by a given key
func (c *Client) Del(key string) error {
request := &server.PayLoad{
Key: key,
}
resp := c.executeWrapper(server.Del, request)
if !resp.Ok {
return errCantDeleteKey
}
return nil
}
// DestroyAll makes RPC for deleting entire db
func (c *Client) DelAll() error {
resp := c.executeWrapper(server.DelAll, &server.PayLoad{})
if !resp.Ok {
return errCantDeleteAll
}
return nil
}
// Set makes RPC for creating the new key value pair in specified bucket
func (c *Client) Set(key string, val []byte, ttl int) error {
request := &server.PayLoad{
Key: key,
Value: val,
TTL: ttl,
}
resp := c.executeWrapper(server.Set, request)
if !resp.Ok {
return errCantSetKeyValuePair
}
return nil
}
// Get makes RPC that returns value by key from one of the buckets
func (c *Client) Has(key string) bool {
request := &server.PayLoad{
Key: key,
}
resp := c.executeWrapper(server.Has, request)
return resp.Ok
}
// Get makes RPC that returns value by key from one of the buckets
func (c *Client) Get(key string) ([]byte, bool) {
request := &server.PayLoad{
Key: key,
}
resp := c.executeWrapper(server.Get, request)
if !resp.Ok {
return nil, false
}
return resp.Value, true
}