sql: remove connExecutor.eventLog and sql.trace.session_eventlog.enabled

The `connExecutor.eventLog` was capturing session events when
`sql.trace.session_eventlog.enabled` was enabled (default false). This was
historically used by SQL engineers for debugging the pgwire connection state
machine, but is not in current use.

Epic: none

Release note (sql change): Remove sql.trace.session_eventlog.enabled and the
associated event log tracing. The information in these traces is still
available in the DEV log channel by enabling --vmodule=conn_executor=2.

pkg/settings/registry.go

@@ -236,6 +236,7 @@ var retiredSettings = map[InternalKey]struct{}{
 	"kv.rangefeed.scheduler.enabled":                       {},
 	"physical_replication.producer.mux_rangefeeds.enabled": {},
 	"kv.rangefeed.use_dedicated_connection_class.enabled":  {},
+	"sql.trace.session_eventlog.enabled":                   {},
 }
 
 // sqlDefaultSettings is the list of "grandfathered" existing sql.defaults

pkg/sql/conn_executor.go

@@ -90,7 +90,6 @@ import (
 	"github.com/cockroachdb/errors"
 	"github.com/cockroachdb/logtags"
 	"github.com/cockroachdb/redact"
-	"golang.org/x/net/trace"
 )
 
 var maxNumNonAdminConnections = settings.RegisterIntSetting(
@@ -1288,11 +1287,6 @@ func (ex *connExecutor) close(ctx context.Context, closeType closeType) {
 		}
 	}
 
-	if ex.eventLog != nil {
-		ex.eventLog.Finish()
-		ex.eventLog = nil
-	}
-
 	// Stop idle timer if the connExecutor is closed to ensure cancel session
 	// is not called.
 	ex.mu.IdleInSessionTimeout.Stop()
@@ -1371,10 +1365,6 @@ type connExecutor struct {
 	transitionCtx  transitionCtx
 	sessionTracing SessionTracing
 
-	// eventLog for SQL statements and other important session events. Will be set
-	// if traceSessionEventLogEnabled; it is used by ex.sessionEventf()
-	eventLog trace.EventLog
-
 	// extraTxnState groups fields scoped to a SQL txn that are not handled by
 	// ex.state, above. The rule of thumb is that, if the state influences state
 	// transitions, it should live in state, otherwise it can live here.
@@ -2064,16 +2054,6 @@ func (ex *connExecutor) activate(
 	ex.sessionMon.StartNoReserved(ctx, ex.mon)
 	ex.sessionPreparedMon.StartNoReserved(ctx, ex.sessionMon)
 
-	// Enable the trace if configured.
-	if traceSessionEventLogEnabled.Get(&ex.server.cfg.Settings.SV) {
-		remoteStr := "<admin>"
-		if ex.sessionData().RemoteAddr != nil {
-			remoteStr = ex.sessionData().RemoteAddr.String()
-		}
-		ex.eventLog = trace.NewEventLog(
-			fmt.Sprintf("sql session [%s]", ex.sessionData().User()), remoteStr)
-	}
-
 	ex.activated = true
 }
 
@@ -2175,7 +2155,7 @@ func (ex *connExecutor) execCmd() (retErr error) {
 		return err // err could be io.EOF
 	}
 
-	if log.ExpensiveLogEnabled(ctx, 2) || ex.eventLog != nil {
+	if log.ExpensiveLogEnabled(ctx, 2) {
 		ex.sessionEventf(ctx, "[%s pos:%d] executing %s",
 			ex.machine.CurState(), pos, cmd)
 	}
@@ -4195,9 +4175,6 @@ func (ex *connExecutor) sessionEventf(ctx context.Context, format string, args .
 	if log.ExpensiveLogEnabled(ctx, 2) {
 		log.VEventfDepth(ctx, 1 /* depth */, 2 /* level */, format, args...)
 	}
-	if ex.eventLog != nil {
-		ex.eventLog.Printf(format, args...)
-	}
 }
 
 // notifyStatsRefresherOfNewTables is called on txn commit to inform

pkg/sql/exec_util.go

@@ -272,18 +272,6 @@ var TraceStmtThreshold = settings.RegisterDurationSetting(
 	0,
 	settings.WithPublic)
 
-// traceSessionEventLogEnabled can be used to enable the event log
-// that is normally kept for every SQL connection. The event log has a
-// non-trivial performance impact and also reveals SQL statements
-// which may be a privacy concern.
-var traceSessionEventLogEnabled = settings.RegisterBoolSetting(
-	settings.ApplicationLevel,
-	"sql.trace.session_eventlog.enabled",
-	"set to true to enable session tracing; "+
-		"note that enabling this may have a negative performance impact",
-	false,
-	settings.WithPublic)
-
 // ReorderJoinsLimitClusterSettingName is the name of the cluster setting for
 // the maximum number of joins to reorder.
 const ReorderJoinsLimitClusterSettingName = "sql.defaults.reorder_joins_limit"