forked from grafana/loki
/
downstreamer.go
244 lines (214 loc) · 6.56 KB
/
downstreamer.go
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package queryrange
import (
"context"
"fmt"
"github.com/go-kit/log/level"
"github.com/grafana/dskit/tenant"
"github.com/prometheus/prometheus/model/labels"
"github.com/prometheus/prometheus/promql"
"github.com/prometheus/prometheus/promql/parser"
"github.com/grafana/loki/pkg/loghttp"
"github.com/grafana/loki/pkg/logql"
"github.com/grafana/loki/pkg/logqlmodel"
"github.com/grafana/loki/pkg/querier/queryrange/queryrangebase"
"github.com/grafana/loki/pkg/util/spanlogger"
)
const (
DefaultDownstreamConcurrency = 128
)
type DownstreamHandler struct {
limits Limits
next queryrangebase.Handler
}
func ParamsToLokiRequest(params logql.Params, shards logql.Shards) queryrangebase.Request {
if params.Start().Equal(params.End()) {
return &LokiInstantRequest{
Query: params.Query(),
Limit: params.Limit(),
TimeTs: params.Start(),
Direction: params.Direction(),
Path: "/loki/api/v1/query", // TODO(owen-d): make this derivable
Shards: shards.Encode(),
}
}
return &LokiRequest{
Query: params.Query(),
Limit: params.Limit(),
Step: params.Step().Milliseconds(),
Interval: params.Interval().Milliseconds(),
StartTs: params.Start(),
EndTs: params.End(),
Direction: params.Direction(),
Path: "/loki/api/v1/query_range", // TODO(owen-d): make this derivable
Shards: shards.Encode(),
}
}
// Note: After the introduction of the LimitedRoundTripper,
// bounding concurrency in the downstreamer is mostly redundant
// The reason we don't remove it is to prevent malicious queries
// from creating an unreasonably large number of goroutines, such as
// the case of a query like `a / a / a / a / a ..etc`, which could try
// to shard each leg, quickly dispatching an unreasonable number of goroutines.
// In the future, it's probably better to replace this with a channel based API
// so we don't have to do all this ugly edge case handling/accounting
func (h DownstreamHandler) Downstreamer(ctx context.Context) logql.Downstreamer {
p := DefaultDownstreamConcurrency
// We may increase parallelism above the default,
// ensure we don't end up bottlenecking here.
if user, err := tenant.TenantID(ctx); err == nil {
if x := h.limits.MaxQueryParallelism(user); x > 0 {
p = x
}
}
locks := make(chan struct{}, p)
for i := 0; i < p; i++ {
locks <- struct{}{}
}
return &instance{
parallelism: p,
locks: locks,
handler: h.next,
}
}
// instance is an intermediate struct for controlling concurrency across a single query
type instance struct {
parallelism int
locks chan struct{}
handler queryrangebase.Handler
}
func (in instance) Downstream(ctx context.Context, queries []logql.DownstreamQuery) ([]logqlmodel.Result, error) {
return in.For(ctx, queries, func(qry logql.DownstreamQuery) (logqlmodel.Result, error) {
req := ParamsToLokiRequest(qry.Params, qry.Shards).WithQuery(qry.Expr.String())
logger, ctx := spanlogger.New(ctx, "DownstreamHandler.instance")
defer logger.Finish()
level.Debug(logger).Log("shards", fmt.Sprintf("%+v", qry.Shards), "query", req.GetQuery(), "step", req.GetStep())
res, err := in.handler.Do(ctx, req)
if err != nil {
return logqlmodel.Result{}, err
}
return ResponseToResult(res)
})
}
// For runs a function against a list of queries, collecting the results or returning an error. The indices are preserved such that input[i] maps to output[i].
func (in instance) For(
ctx context.Context,
queries []logql.DownstreamQuery,
fn func(logql.DownstreamQuery) (logqlmodel.Result, error),
) ([]logqlmodel.Result, error) {
type resp struct {
i int
res logqlmodel.Result
err error
}
ctx, cancel := context.WithCancel(ctx)
defer cancel()
ch := make(chan resp)
// Make one goroutine to dispatch the other goroutines, bounded by instance parallelism
go func() {
for i := 0; i < len(queries); i++ {
select {
case <-ctx.Done():
break
case <-in.locks:
go func(i int) {
// release lock back into pool
defer func() {
in.locks <- struct{}{}
}()
res, err := fn(queries[i])
response := resp{
i: i,
res: res,
err: err,
}
// Feed the result into the channel unless the work has completed.
select {
case <-ctx.Done():
case ch <- response:
}
}(i)
}
}
}()
results := make([]logqlmodel.Result, len(queries))
for i := 0; i < len(queries); i++ {
select {
case <-ctx.Done():
return nil, ctx.Err()
case resp := <-ch:
if resp.err != nil {
return nil, resp.err
}
results[resp.i] = resp.res
}
}
return results, nil
}
// convert to matrix
func sampleStreamToMatrix(streams []queryrangebase.SampleStream) parser.Value {
xs := make(promql.Matrix, 0, len(streams))
for _, stream := range streams {
x := promql.Series{}
x.Metric = make(labels.Labels, 0, len(stream.Labels))
for _, l := range stream.Labels {
x.Metric = append(x.Metric, labels.Label(l))
}
x.Points = make([]promql.Point, 0, len(stream.Samples))
for _, sample := range stream.Samples {
x.Points = append(x.Points, promql.Point{
T: sample.TimestampMs,
V: sample.Value,
})
}
xs = append(xs, x)
}
return xs
}
func sampleStreamToVector(streams []queryrangebase.SampleStream) parser.Value {
xs := make(promql.Vector, 0, len(streams))
for _, stream := range streams {
x := promql.Sample{}
x.Metric = make(labels.Labels, 0, len(stream.Labels))
for _, l := range stream.Labels {
x.Metric = append(x.Metric, labels.Label(l))
}
x.Point = promql.Point{
T: stream.Samples[0].TimestampMs,
V: stream.Samples[0].Value,
}
xs = append(xs, x)
}
return xs
}
func ResponseToResult(resp queryrangebase.Response) (logqlmodel.Result, error) {
switch r := resp.(type) {
case *LokiResponse:
if r.Error != "" {
return logqlmodel.Result{}, fmt.Errorf("%s: %s", r.ErrorType, r.Error)
}
streams := make(logqlmodel.Streams, 0, len(r.Data.Result))
for _, stream := range r.Data.Result {
streams = append(streams, stream)
}
return logqlmodel.Result{
Statistics: r.Statistics,
Data: streams,
}, nil
case *LokiPromResponse:
if r.Response.Error != "" {
return logqlmodel.Result{}, fmt.Errorf("%s: %s", r.Response.ErrorType, r.Response.Error)
}
if r.Response.Data.ResultType == loghttp.ResultTypeVector {
return logqlmodel.Result{
Statistics: r.Statistics,
Data: sampleStreamToVector(r.Response.Data.Result),
}, nil
}
return logqlmodel.Result{
Statistics: r.Statistics,
Data: sampleStreamToMatrix(r.Response.Data.Result),
}, nil
default:
return logqlmodel.Result{}, fmt.Errorf("cannot decode (%T)", resp)
}
}