Release 2.21.0-rc.0 (#7857)

Signed-off-by: NJulien Pivotto <roidelapluie@inuits.eu>

CHANGELOG.md

+## 2.21.0-rc.0 / 2020-08-27
+
+This release is built with Go 1.15, which deprecates [X.509
+CommonName](https://golang.org/doc/go1.15#commonname) in TLS certificates
+validation.
+
+* [CHANGE] Disable HTTP2 because of concerns with the Go HTTP/2 client. #7588 #7701
+* [CHANGE] PromQL: `query_log_file` path is now relative to the config file. #7701
+* [CHANGE] Promtool: Replace the tsdb command line tool by a promtool tsdb subcommand. #6088
+* [CHANGE] Rules: Label `rule_group_iterations` metric with group name. #7823
+* [FEATURE] Eureka SD: New service discovery. #3369
+* [FEATURE] Hetzner SD: New service discovery. #7822
+* [FEATURE] Kubernetes SD: Support Kubernetes EndpointSlices. #6838
+* [FEATURE] Scrape: Add per scrape-config targets limit. #7554
+* [ENHANCEMENT] Support composite durations in PromQL, config and UI, e.g. 1h30m. #7713 #7833
+* [ENHANCEMENT] DNS SD: Add SRV record target and port meta labels. #7678
+* [ENHANCEMENT] Docker Swarm SD: Support tasks and service without published ports. #7686
+* [ENHANCEMENT] PromQL: Reduce the amount of data queried by remote read when a subquery has an offset. #7667
+* [ENHANCEMENT] Promtool: Add `--time` option to query instant command. #7829
+* [ENHANCEMENT] UI: Move "remove graph" closer to query area. #5990
+* [BUGFIX] PromQL: Drop metric name in bool comparison between two instant vectors. #7819
+* [BUGFIX] Rules: Detect extra fields in rule files. #7767
+* [BUGFIX] Rules: Disallow overwriting the metric name in the `labels` section of recording rules. #7787
+* [BUGFIX] Rules: Keep evaluation timestamp across reloads. #7775
+* [BUGFIX] Scrape: Do not stop scrapes in progress during reload. #7752
+* [BUGFIX] TSDB: Fix `chunks.HeadReadWriter: maxt of the files are not set` error. #7856
+* [BUGFIX] TSDB: Delete blocks atomically to prevent corruption when there is a panic/crash during deletion. #7772
+* [BUGFIX] Triton SD: Fix a panic when triton_sd_config is nil. #7671
+* [BUGFIX] UI: Fix react UI bug with series going on and off. #7804
+* [BUGFIX] Web: Stop CMUX and GRPC servers even with stale connections, preventing the server to stop on SIGTERM. #7810
+
 ## 2.20.1 / 2020-08-05
 
 * [BUGFIX] SD: Reduce the Consul watch timeout to 2m and adjust the request timeout accordingly. #7724

VERSION

-2.20.1
+2.21.0-rc.0