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query.go
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query.go
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package clickhouse
import (
"bytes"
"context"
"errors"
"fmt"
"io"
"io/ioutil"
"net/http"
"net/url"
"regexp"
"strconv"
"strings"
"sync"
"time"
"github.com/vkcom/engine-go/srvfunc"
"github.com/zergbz1988/kittenhouse/core/destination"
)
const (
defaultTable = ""
maxResultSize = 1000000 // a little less than 1 MiB so that we can add headers and stuff to response
)
var (
// ErrMustBeSelect means that you sent something that is probably not a SELECT query.
// We do not support other queries because we do not know where to send query without a table name.
ErrMustBeSelect = errors.New("Query must be in form 'SELECT ... FROM table'")
// ErrTooBigResult means that daemon would probably exceed maximum response size if full result is sent.
ErrTooBigResult = fmt.Errorf("Result exceeds %d MiB", maxResultSize/(1<<20))
// ErrTooBigResponse means that ClickHouse server was going to send too big of a response to INSERT
ErrTooBigResponse = fmt.Errorf("Too big response from server")
// ErrTemporarilyUnavailable means that there are no servers alive that have the requested table
ErrTemporarilyUnavailable = errors.New("No servers available")
tableDstMap struct {
sync.RWMutex
m map[string]*destination.Setting
}
queryRegex = regexp.MustCompile(`(?s)(?:SELECT|select)\s.*?(?:FROM|from)\s+([a-zA-Z_][a-zA-Z0-9_.]*)`)
queryHTTPClient = &http.Client{
Transport: &http.Transport{
MaxIdleConnsPerHost: 1,
DialContext: srvfunc.CachingDialer,
},
}
)
func maybeAddTable(m map[string]*destination.Setting, table string, dst *destination.Setting) {
if _, ok := m[table]; !ok {
m[table] = dst
}
}
// Escape escapes string for MySQL. It should work for ClickHouse as well.
func Escape(txt string) string {
var (
esc string
buf bytes.Buffer
)
last := 0
for ii, bb := range txt {
switch bb {
case 0:
esc = `\0`
case '\n':
esc = `\n`
case '\r':
esc = `\r`
case '\\':
esc = `\\`
case '\'':
esc = `\'`
case '"':
esc = `\"`
case '\032':
esc = `\Z`
default:
continue
}
io.WriteString(&buf, txt[last:ii])
io.WriteString(&buf, esc)
last = ii + 1
}
io.WriteString(&buf, txt[last:])
return buf.String()
}
// UpdateDestinationsConfig is used for QueryDeadline to determine where to send query.
func UpdateDestinationsConfig(m destination.Map) {
tableDstMap.Lock()
defer tableDstMap.Unlock()
tableDstMap.m = make(map[string]*destination.Setting)
for _, settings := range m {
if settings.Default {
tableDstMap.m[defaultTable] = settings
continue
}
for _, tbl := range settings.Tables {
tableDstMap.m[tbl] = settings
maybeAddTable(tableDstMap.m, strings.TrimSuffix(tbl, "_buffer"), settings)
if !strings.Contains(tbl, ".") {
maybeAddTable(tableDstMap.m, "default."+tbl, settings)
maybeAddTable(tableDstMap.m, "default."+strings.TrimSuffix(tbl, "_buffer"), settings)
}
}
}
}
// GetDestinationSetting returns setting for specified table name
func GetDestinationSetting(tableName string) *destination.Setting {
tableDstMap.RLock()
dst, ok := tableDstMap.m[tableName]
if !ok {
dst = tableDstMap.m[defaultTable]
}
tableDstMap.RUnlock()
return dst
}
// QueryDeadline performs supplied query at appropriate server.
// There is no limit on number of concurrent queries, so use this method with care.
func QueryDeadline(deadline time.Time, query string) (httpCode int, res []byte, err error) {
if strings.HasPrefix(query, chunkQuery) {
id, err := strconv.Atoi(strings.TrimPrefix(query, chunkQuery))
if err != nil {
return 0, nil, err
}
buf, eof, err := getNextChunk(int32(id))
if err != nil {
return 0, nil, err
}
if eof {
return http.StatusNoContent, nil, nil
}
return http.StatusPartialContent, buf, err
}
matches := queryRegex.FindStringSubmatch(query)
if len(matches) == 0 {
return 0, nil, ErrMustBeSelect
}
tableName := matches[1]
dst, ok := GetDestinationSetting(tableName).ChooseNextServer()
if !ok {
return 0, nil, ErrTemporarilyUnavailable
}
return queryServer(deadline, dst, query)
}
const chunkQuery = "GET NEXT CHUNK FOR "
func queryServer(deadline time.Time, dst destination.ServerHostPort, query string) (httpCode int, res []byte, err error) {
maxExecSec := deadline.Sub(time.Now())/time.Second + 1
asyncResult := false
ctx, cancel := context.WithDeadline(context.Background(), deadline)
defer func() {
if !asyncResult {
cancel()
}
}()
req, err := http.NewRequest("GET", fmt.Sprintf("http://%s/?max_execution_time=%d&query=%s", dst, maxExecSec, url.QueryEscape(query)), nil)
if err != nil {
return 0, nil, err
}
resp, err := queryHTTPClient.Do(req.WithContext(ctx))
if err != nil {
return 0, nil, err
}
defer func() {
if !asyncResult {
resp.Body.Close()
}
}()
rd := &io.LimitedReader{
R: resp.Body,
N: maxResultSize,
}
res, err = ioutil.ReadAll(rd)
if err != nil {
return 0, nil, err
}
if rd.N > 0 {
return resp.StatusCode, res, nil
}
asyncResult = true
id := addPendingRequest(cancel, resp.Body, res)
return http.StatusTeapot, []byte(fmt.Sprintf("PENDING REQUEST ID %d", id)), nil
}