From 8229b4575a4c339c451ccfed17e45a9f8186b14c Mon Sep 17 00:00:00 2001
From: Aditi Ahuja <48997495+metonymic-smokey@users.noreply.github.com>
Date: Thu, 23 Sep 2021 23:30:19 +0530
Subject: [PATCH] Added experimental features flag (#4679)

* added enable features flag

Signed-off-by: metonymic-smokey <ahuja.aditi@gmail.com>

* changelog fixes

Signed-off-by: metonymic-smokey <ahuja.aditi@gmail.com>

* doc changes

Signed-off-by: metonymic-smokey <ahuja.aditi@gmail.com>

* review suggestion added

Signed-off-by: metonymic-smokey <ahuja.aditi@gmail.com>

* updated docs

Signed-off-by: metonymic-smokey <ahuja.aditi@gmail.com>
---
 CHANGELOG.md             |  1 +
 cmd/thanos/query.go      | 24 ++++++++++++++++++++++++
 docs/components/query.md |  3 +++
 3 files changed, 28 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index dde5d56aa3..3da3bf9675 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -17,6 +17,7 @@ We use *breaking :warning:* to mark changes that are not backward compatible (re
 ### Added
 
 - [#4680](https://github.com/thanos-io/thanos/pull/4680) Query: add `exemplar.partial-response` flag to control partial response.
+- [#4679](https://github.com/thanos-io/thanos/pull/4679) Added `enable-feature` flag to enable negative offsets and @ modifier, similar to Prometheus.
 - [#4696](https://github.com/thanos-io/thanos/pull/4696) Query: add cache name to tracing spans.
 
 ## v0.23.0 - In Progress
diff --git a/cmd/thanos/query.go b/cmd/thanos/query.go
index 4d893f212e..50884810e4 100644
--- a/cmd/thanos/query.go
+++ b/cmd/thanos/query.go
@@ -52,6 +52,11 @@ import (
 	"github.com/thanos-io/thanos/pkg/ui"
 )
 
+const (
+	promqlNegativeOffset = "promql-negative-offset"
+	promqlAtModifier     = "promql-at-modifier"
+)
+
 // registerQuery registers a query command.
 func registerQuery(app *extkingpin.App) {
 	comp := component.Query
@@ -146,6 +151,8 @@ func registerQuery(app *extkingpin.App) {
 	enableMetricMetadataPartialResponse := cmd.Flag("metric-metadata.partial-response", "Enable partial response for metric metadata endpoint. --no-metric-metadata.partial-response for disabling.").
 		Hidden().Default("true").Bool()
 
+	featureList := cmd.Flag("enable-feature", "Comma separated experimental feature names to enable.The current list of features is "+promqlNegativeOffset+" and "+promqlAtModifier+".").Default("").Strings()
+
 	enableExemplarPartialResponse := cmd.Flag("exemplar.partial-response", "Enable partial response for exemplar endpoint. --no-exemplar.partial-response for disabling.").
 		Hidden().Default("true").Bool()
 
@@ -163,6 +170,16 @@ func registerQuery(app *extkingpin.App) {
 			return errors.Wrap(err, "parse federation labels")
 		}
 
+		var enableNegativeOffset, enableAtModifier bool
+		for _, feature := range *featureList {
+			if feature == promqlNegativeOffset {
+				enableNegativeOffset = true
+			}
+			if feature == promqlAtModifier {
+				enableAtModifier = true
+			}
+		}
+
 		if dup := firstDuplicate(*stores); dup != "" {
 			return errors.Errorf("Address %s is duplicated for --store flag.", dup)
 		}
@@ -266,6 +283,8 @@ func registerQuery(app *extkingpin.App) {
 			*defaultMetadataTimeRange,
 			*strictStores,
 			*webDisableCORS,
+			enableAtModifier,
+			enableNegativeOffset,
 			component.Query,
 		)
 	})
@@ -329,6 +348,8 @@ func runQuery(
 	defaultMetadataTimeRange time.Duration,
 	strictStores []string,
 	disableCORS bool,
+	enableAtModifier bool,
+	enableNegativeOffset bool,
 	comp component.Component,
 ) error {
 	// TODO(bplotka in PR #513 review): Move arguments into struct.
@@ -456,6 +477,9 @@ func runQuery(
 			cancelRun()
 		})
 
+		engineOpts.EnableAtModifier = enableAtModifier
+		engineOpts.EnableNegativeOffset = enableNegativeOffset
+
 		ctxUpdate, cancelUpdate := context.WithCancel(context.Background())
 		g.Add(func() error {
 			for {
diff --git a/docs/components/query.md b/docs/components/query.md
index 63f7dd0a2c..41e2cccf89 100644
--- a/docs/components/query.md
+++ b/docs/components/query.md
@@ -252,6 +252,9 @@ Query node exposing PromQL enabled Query API with data retrieved from multiple
 store nodes.
 
 Flags:
+      --enable-feature= ...      Comma separated experimental feature names to
+                                 enable.The current list of features is
+                                 promql-negative-offset and promql-at-modifier.
       --grpc-address="0.0.0.0:10901"  
                                  Listen ip:port address for gRPC endpoints
                                  (StoreAPI). Make sure this address is routable