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TSDB: Extract parts out of populateSeries (#6983) 

This addresses fabxc's TODO.

More importantly, it now properly defers the
querier.Close(). Previously, if a panic happened after creation of the
querier within the populateSeries function, querier.Close() was never called.

The latter was responsible for #6977.

Signed-off-by: beorn7 <beorn@grafana.com>
This commit is contained in:
Björn Rabenstein 2020-03-14 09:03:40 +01:00 committed by GitHub
parent 3128875ff4
commit a28fa010ee
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GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 22 additions and 23 deletions
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37
promql/engine.go
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@ -502,15 +502,16 @@ func durationMilliseconds(d time.Duration) int64 {
// execEvalStmt evaluates the expression of an evaluation statement for the given time range.
func (ng *Engine) execEvalStmt(ctx context.Context, query *query, s *parser.EvalStmt) (parser.Value, storage.Warnings, error) {
prepareSpanTimer, ctxPrepare := query.stats.GetSpanTimer(ctx, stats.QueryPreparationTime, ng.metrics.queryPrepareTime)
querier, warnings, err := ng.populateSeries(ctxPrepare, query.queryable, s)
mint := ng.findMinTime(s)
querier, err := query.queryable.Querier(ctxPrepare, timestamp.FromTime(mint), timestamp.FromTime(s.End))
if err != nil {
prepareSpanTimer.Finish()
// XXX(fabxc): the querier returned by populateSeries might be instantiated
// we must not return without closing irrespective of the error.
// TODO: make this semantically saner.
if querier != nil {
defer querier.Close()
return nil, nil, err
}
defer querier.Close()
warnings, err := ng.populateSeries(ctxPrepare, querier, s)
prepareSpanTimer.Finish()
if err != nil {
return nil, warnings, err
@ -616,7 +617,7 @@ func (ng *Engine) cumulativeSubqueryOffset(path []parser.Node) time.Duration {
return subqOffset
}
func (ng *Engine) populateSeries(ctx context.Context, q storage.Queryable, s *parser.EvalStmt) (storage.Querier, storage.Warnings, error) {
func (ng *Engine) findMinTime(s *parser.EvalStmt) time.Time {
var maxOffset time.Duration
parser.Inspect(s.Expr, func(node parser.Node, path []parser.Node) error {
subqOffset := ng.cumulativeSubqueryOffset(path)
@ -638,20 +639,18 @@ func (ng *Engine) populateSeries(ctx context.Context, q storage.Queryable, s *pa
}
return nil
})
mint := s.Start.Add(-maxOffset)
querier, err := q.Querier(ctx, timestamp.FromTime(mint), timestamp.FromTime(s.End))
if err != nil {
return nil, nil, err
return s.Start.Add(-maxOffset)
}
var warnings storage.Warnings
// Whenever a MatrixSelector is evaluated this variable is set to the corresponding range.
func (ng *Engine) populateSeries(ctx context.Context, querier storage.Querier, s *parser.EvalStmt) (storage.Warnings, error) {
var (
// Whenever a MatrixSelector is evaluated, evalRange is set to the corresponding range.
// The evaluation of the VectorSelector inside then evaluates the given range and unsets
// the variable.
var evalRange time.Duration
evalRange time.Duration
warnings storage.Warnings
err error
)
parser.Inspect(s.Expr, func(node parser.Node, path []parser.Node) error {
var set storage.SeriesSet
@ -703,7 +702,7 @@ func (ng *Engine) populateSeries(ctx context.Context, q storage.Queryable, s *pa
}
return nil
})
return querier, warnings, err
return warnings, err
}
// extractFuncFromPath walks up the path and searches for the first instance of