vitess.io/vitess@v0.16.2/go/vt/vttablet/sysloglogger/sysloglogger.go (about)

     1  /*
     2  Copyright 2019 The Vitess Authors.
     3  
     4  Licensed under the Apache License, Version 2.0 (the "License");
     5  you may not use this file except in compliance with the License.
     6  You may obtain a copy of the License at
     7  
     8      http://www.apache.org/licenses/LICENSE-2.0
     9  
    10  Unless required by applicable law or agreed to in writing, software
    11  distributed under the License is distributed on an "AS IS" BASIS,
    12  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13  See the License for the specific language governing permissions and
    14  limitations under the License.
    15  */
    16  
    17  // Package sysloglogger implements an optional plugin that logs all queries to syslog.
    18  package sysloglogger
    19  
    20  import (
    21  	"bytes"
    22  	"log/syslog"
    23  
    24  	"github.com/spf13/pflag"
    25  
    26  	"vitess.io/vitess/go/vt/log"
    27  	"vitess.io/vitess/go/vt/servenv"
    28  	"vitess.io/vitess/go/vt/vttablet/tabletserver/tabletenv"
    29  )
    30  
    31  // syslogWriter is an interface that wraps syslog.Writer, so it can be mocked in unit tests.
    32  type syslogWriter interface {
    33  	Info(string) error
    34  	Close() error
    35  }
    36  
    37  // writer holds a persistent connection to the syslog daemon (or a mock when under test).
    38  var writer syslogWriter
    39  
    40  // ch holds the tabletserver.StatsLogger channel to which this plugin subscribes (or a mock when under test).
    41  var ch chan any
    42  
    43  var logQueries bool
    44  
    45  func registerFlags(fs *pflag.FlagSet) {
    46  	// logQueries is the vttablet startup flag that must be set for this plugin to be active.
    47  	fs.BoolVar(&logQueries, "log_queries", logQueries, "Enable query logging to syslog.")
    48  }
    49  
    50  func init() {
    51  	servenv.OnParseFor("vtcombo", registerFlags)
    52  	servenv.OnParseFor("vttablet", registerFlags)
    53  
    54  	servenv.OnRun(func() {
    55  		if logQueries {
    56  			var err error
    57  			writer, err = syslog.New(syslog.LOG_INFO, "vtquerylogger")
    58  			if err != nil {
    59  				log.Errorf("Query logger is unable to connect to syslog: %v", err)
    60  				return
    61  			}
    62  			go run()
    63  		}
    64  	})
    65  }
    66  
    67  // Run logs queries to syslog, if the "log_queries" flag is set to true when starting vttablet.
    68  func run() {
    69  	log.Info("Logging queries to syslog")
    70  	defer writer.Close()
    71  
    72  	// ch will only be non-nil in a unit test context, when a mock has been populated
    73  	if ch == nil {
    74  		ch = tabletenv.StatsLogger.Subscribe("gwslog")
    75  		defer tabletenv.StatsLogger.Unsubscribe(ch)
    76  	}
    77  
    78  	formatParams := map[string][]string{"full": {}}
    79  	for out := range ch {
    80  		stats, ok := out.(*tabletenv.LogStats)
    81  		if !ok {
    82  			log.Errorf("Unexpected value in query logs: %#v (expecting value of type %T)", out, &tabletenv.LogStats{})
    83  			continue
    84  		}
    85  		var b bytes.Buffer
    86  		if err := stats.Logf(&b, formatParams); err != nil {
    87  			log.Errorf("Error formatting logStats: %v", err)
    88  			continue
    89  		}
    90  		if err := writer.Info(b.String()); err != nil {
    91  			log.Errorf("Error writing to syslog: %v", err)
    92  			continue
    93  		}
    94  	}
    95  }