fix(pkg/stash): close etcd sessions

Athens creates a new session for each 'Stash' request and then never closes it.
The sessions (etcd leases) are consequently held forever and eventually leads
to resource exhaustion on the etcd cluster.

This has been fixed by closing the acquired session at the end of the request.

Fixes: #1886

.golangci.yml

@@ -6,6 +6,10 @@ linters-settings:
   cyclop:
     max-complexity: 12
     skip-tests: true
+  errcheck:
+    exclude-functions:
+      - (*go.etcd.io/etcd/client/v3/concurrency.Mutex).Unlock
+      - (*go.etcd.io/etcd/client/v3/concurrency.Session).Close
   gofumpt:
     extra-rules: true
 
@@ -50,15 +54,15 @@ linters:
 issues:
   exclude-use-default: false
   exclude:
-    - 'package-comments: should have a package comment'
-    - 'ST1000: at least one file in a package should have a package comment'
-    - 'G204: Subprocess launched with a potential tainted input or cmd arguments'
-    - 'G204: Subprocess launched with variable'
-    - 'G402: TLS MinVersion too low.'
-    - 'const `op` is unused'
+    - "package-comments: should have a package comment"
+    - "ST1000: at least one file in a package should have a package comment"
+    - "G204: Subprocess launched with a potential tainted input or cmd arguments"
+    - "G204: Subprocess launched with variable"
+    - "G402: TLS MinVersion too low."
+    - "const `op` is unused"
   exclude-rules:
     - path: cmd/proxy/main.go
-      text: 'G108: Profiling endpoint is automatically exposed on /debug/pprof'
+      text: "G108: Profiling endpoint is automatically exposed on /debug/pprof"
     - path: pkg/stash/stasher.go
       linters:
         - contextcheck

go.mod

@@ -26,12 +26,13 @@ require (
 	github.com/lib/pq v1.10.7
 	github.com/minio/minio-go/v6 v6.0.57
 	github.com/mitchellh/go-homedir v1.1.0
-	github.com/sirupsen/logrus v1.6.0
+	github.com/sirupsen/logrus v1.7.0
 	github.com/spf13/afero v1.8.2
-	github.com/stretchr/testify v1.7.0
+	github.com/stretchr/testify v1.8.1
 	github.com/technosophos/moniker v0.0.0-20180509230615-a5dbd03a2245
 	github.com/unrolled/secure v0.0.0-20181221173256-0d6b5bb13069
-	go.etcd.io/etcd/client/v3 v3.5.2
+	go.etcd.io/etcd/client/v3 v3.5.9
+	go.etcd.io/etcd/server/v3 v3.5.9
 	go.mongodb.org/mongo-driver v1.7.1
 	go.opencensus.io v0.23.0
 	golang.org/x/mod v0.8.0
@@ -53,28 +54,36 @@ require (
 	github.com/ajg/form v0.0.0-20160822230020-523a5da1a92f // indirect
 	github.com/apparentlymart/go-textseg v1.0.0 // indirect
 	github.com/beorn7/perks v1.0.1 // indirect
+	github.com/cenkalti/backoff/v4 v4.1.1 // indirect
 	github.com/cespare/xxhash/v2 v2.1.2 // indirect
 	github.com/codegangsta/negroni v1.0.0 // indirect
 	github.com/coreos/go-semver v0.3.0 // indirect
 	github.com/coreos/go-systemd/v22 v22.3.2 // indirect
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/dgryski/go-rendezvous v0.0.0-20200823014737-9f7001d12a5f // indirect
+	github.com/dustin/go-humanize v1.0.0 // indirect
 	github.com/go-playground/locales v0.12.1 // indirect
 	github.com/go-playground/universal-translator v0.16.0 // indirect
 	github.com/go-stack/stack v1.8.0 // indirect
 	github.com/gogo/protobuf v1.3.2 // indirect
-	github.com/golang/groupcache v0.0.0-20200121045136-8c9f03a8e57e // indirect
+	github.com/golang-jwt/jwt/v4 v4.4.2 // indirect
+	github.com/golang/groupcache v0.0.0-20210331224755-41bb18bfe9da // indirect
 	github.com/golang/protobuf v1.5.2 // indirect
 	github.com/golang/snappy v0.0.3 // indirect
+	github.com/google/btree v1.0.1 // indirect
 	github.com/googleapis/gax-go/v2 v2.1.1 // indirect
 	github.com/gorilla/context v1.1.1 // indirect
+	github.com/gorilla/websocket v1.4.2 // indirect
+	github.com/grpc-ecosystem/go-grpc-middleware v1.3.0 // indirect
+	github.com/grpc-ecosystem/go-grpc-prometheus v1.2.0 // indirect
+	github.com/grpc-ecosystem/grpc-gateway v1.16.0 // indirect
 	github.com/hashicorp/errwrap v1.0.0 // indirect
 	github.com/jmespath/go-jmespath v0.4.0 // indirect
 	github.com/joho/godotenv v1.3.0 // indirect
+	github.com/jonboulle/clockwork v0.2.2 // indirect
 	github.com/json-iterator/go v1.1.11 // indirect
 	github.com/klauspost/compress v1.9.5 // indirect
 	github.com/klauspost/cpuid v1.2.3 // indirect
-	github.com/konsorten/go-windows-terminal-sequences v1.0.3 // indirect
 	github.com/kylelemons/godebug v1.1.0 // indirect
 	github.com/markbates/hmax v1.0.0 // indirect
 	github.com/mattn/go-colorable v0.1.9 // indirect
@@ -94,22 +103,38 @@ require (
 	github.com/prometheus/common v0.26.0 // indirect
 	github.com/prometheus/procfs v0.6.0 // indirect
 	github.com/rogpeppe/go-internal v1.3.0 // indirect
+	github.com/soheilhy/cmux v0.1.5 // indirect
+	github.com/spf13/pflag v1.0.5 // indirect
 	github.com/tinylib/msgp v1.0.2 // indirect
+	github.com/tmc/grpc-websocket-proxy v0.0.0-20201229170055-e5319fda7802 // indirect
 	github.com/uber/jaeger-client-go v2.25.0+incompatible // indirect
 	github.com/xdg-go/pbkdf2 v1.0.0 // indirect
 	github.com/xdg-go/scram v1.0.2 // indirect
 	github.com/xdg-go/stringprep v1.0.2 // indirect
+	github.com/xiang90/probing v0.0.0-20190116061207-43a291ad63a2 // indirect
 	github.com/youmark/pkcs8 v0.0.0-20181117223130-1be2e3e5546d // indirect
 	github.com/zclconf/go-cty v0.0.0-20190426224007-b18a157db9e2 // indirect
-	go.etcd.io/etcd/api/v3 v3.5.2 // indirect
-	go.etcd.io/etcd/client/pkg/v3 v3.5.2 // indirect
+	go.etcd.io/bbolt v1.3.7 // indirect
+	go.etcd.io/etcd/api/v3 v3.5.9 // indirect
+	go.etcd.io/etcd/client/pkg/v3 v3.5.9 // indirect
+	go.etcd.io/etcd/client/v2 v2.305.9 // indirect
+	go.etcd.io/etcd/pkg/v3 v3.5.9 // indirect
+	go.etcd.io/etcd/raft/v3 v3.5.9 // indirect
+	go.opentelemetry.io/contrib/instrumentation/google.golang.org/grpc/otelgrpc v0.25.0 // indirect
+	go.opentelemetry.io/otel v1.0.1 // indirect
+	go.opentelemetry.io/otel/exporters/otlp/otlptrace v1.0.1 // indirect
+	go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc v1.0.1 // indirect
+	go.opentelemetry.io/otel/sdk v1.0.1 // indirect
+	go.opentelemetry.io/otel/trace v1.0.1 // indirect
+	go.opentelemetry.io/proto/otlp v0.9.0 // indirect
 	go.uber.org/atomic v1.9.0 // indirect
 	go.uber.org/multierr v1.7.0 // indirect
 	go.uber.org/zap v1.21.0 // indirect
-	golang.org/x/crypto v0.0.0-20211108221036-ceb1ce70b4fa // indirect
+	golang.org/x/crypto v0.0.0-20220411220226-7b82a4e95df4 // indirect
 	golang.org/x/net v0.8.0 // indirect
 	golang.org/x/sys v0.6.0 // indirect
 	golang.org/x/text v0.8.0 // indirect
+	golang.org/x/time v0.0.0-20210220033141-f8bda1e9f3ba // indirect
 	golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1 // indirect
 	google.golang.org/appengine v1.6.7 // indirect
 	google.golang.org/genproto v0.0.0-20220211171837-173942840c17 // indirect
@@ -118,5 +143,8 @@ require (
 	gopkg.in/DataDog/dd-trace-go.v1 v1.10.0 // indirect
 	gopkg.in/go-playground/assert.v1 v1.2.1 // indirect
 	gopkg.in/ini.v1 v1.42.0 // indirect
+	gopkg.in/natefinch/lumberjack.v2 v2.0.0 // indirect
+	gopkg.in/yaml.v2 v2.4.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
+	sigs.k8s.io/yaml v1.2.0 // indirect
 )