feature: prometheus metrics exporterHEADmaster

6 files changed, 259 insertions, 23 deletions

diff --git a/config/config.go b/config/config.go
index 599f12c..5dfc933 100644
--- a/config/config.go
+++ b/config/config.go
@@ -14,8 +14,11 @@ type Config struct {
 		Prefix string `toml:"prefix"`
 		Proxy  string `toml:"proxy"`
 	} `toml:"servers"`
-	Debug  bool   `toml:"debug"`
-	Listen string `toml:"listen"`
+	Debug   bool   `toml:"debug"`
+	Listen  string `toml:"listen"`
+	Metrics struct {
+		Enabled bool `toml:"enabled"`
+	} `toml:"metrics"`
 }
 
 func (c Config) Validate() error {
diff --git a/go.mod b/go.mod
index f39a409..14af530 100644
--- a/go.mod
+++ b/go.mod
@@ -8,6 +8,7 @@ require (
 	github.com/avast/retry-go v3.0.0+incompatible
 	github.com/gin-gonic/gin v1.9.1
 	github.com/imroc/req v0.3.2
+	github.com/prometheus/client_golang v1.18.0
 	github.com/rs/zerolog v1.32.0
 	github.com/samber/lo v1.39.0
 	github.com/samber/mo v1.11.0
@@ -15,7 +16,9 @@ require (
 )
 
 require (
+	github.com/beorn7/perks v1.0.1 // indirect
 	github.com/bytedance/sonic v1.9.1 // indirect
+	github.com/cespare/xxhash/v2 v2.2.0 // indirect
 	github.com/chenzhuoyu/base64x v0.0.0-20221115062448-fe3a3abad311 // indirect
 	github.com/gabriel-vasile/mimetype v1.4.2 // indirect
 	github.com/gin-contrib/sse v0.1.0 // indirect
@@ -29,17 +32,21 @@ require (
 	github.com/leodido/go-urn v1.2.4 // indirect
 	github.com/mattn/go-colorable v0.1.13 // indirect
 	github.com/mattn/go-isatty v0.0.19 // indirect
+	github.com/matttproud/golang_protobuf_extensions/v2 v2.0.0 // indirect
 	github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd // indirect
 	github.com/modern-go/reflect2 v1.0.2 // indirect
 	github.com/pelletier/go-toml/v2 v2.0.8 // indirect
+	github.com/prometheus/client_model v0.5.0 // indirect
+	github.com/prometheus/common v0.45.0 // indirect
+	github.com/prometheus/procfs v0.12.0 // indirect
 	github.com/twitchyliquid64/golang-asm v0.15.1 // indirect
 	github.com/ugorji/go/codec v1.2.11 // indirect
 	golang.org/x/arch v0.3.0 // indirect
-	golang.org/x/crypto v0.9.0 // indirect
+	golang.org/x/crypto v0.14.0 // indirect
 	golang.org/x/exp v0.0.0-20220303212507-bbda1eaf7a17 // indirect
-	golang.org/x/net v0.10.0 // indirect
-	golang.org/x/sys v0.12.0 // indirect
-	golang.org/x/text v0.9.0 // indirect
-	google.golang.org/protobuf v1.30.0 // indirect
+	golang.org/x/net v0.17.0 // indirect
+	golang.org/x/sys v0.15.0 // indirect
+	golang.org/x/text v0.13.0 // indirect
+	google.golang.org/protobuf v1.31.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )
diff --git a/go.sum b/go.sum
index 3a30aca..98ef872 100644
--- a/go.sum
+++ b/go.sum
@@ -4,9 +4,13 @@ github.com/akamensky/argparse v1.4.0 h1:YGzvsTqCvbEZhL8zZu2AiA5nq805NZh75JNj4ajn
 github.com/akamensky/argparse v1.4.0/go.mod h1:S5kwC7IuDcEr5VeXtGPRVZ5o/FdhcMlQz4IZQuw64xA=
 github.com/avast/retry-go v3.0.0+incompatible h1:4SOWQ7Qs+oroOTQOYnAHqelpCO0biHSxpiH9JdtuBj0=
 github.com/avast/retry-go v3.0.0+incompatible/go.mod h1:XtSnn+n/sHqQIpZ10K1qAevBhOOCWBLXXy3hyiqqBrY=
+github.com/beorn7/perks v1.0.1 h1:VlbKKnNfV8bJzeqoa4cOKqO6bYr3WgKZxO8Z16+hsOM=
+github.com/beorn7/perks v1.0.1/go.mod h1:G2ZrVWU2WbWT9wwq4/hrbKbnv/1ERSJQ0ibhJ6rlkpw=
 github.com/bytedance/sonic v1.5.0/go.mod h1:ED5hyg4y6t3/9Ku1R6dU/4KyJ48DZ4jPhfY1O2AihPM=
 github.com/bytedance/sonic v1.9.1 h1:6iJ6NqdoxCDr6mbY8h18oSO+cShGSMRGCEo7F2h0x8s=
 github.com/bytedance/sonic v1.9.1/go.mod h1:i736AoUSYt75HyZLoJW9ERYxcy6eaN6h4BZXU064P/U=
+github.com/cespare/xxhash/v2 v2.2.0 h1:DC2CZ1Ep5Y4k3ZQ899DldepgrayRUGE6BBZ/cd9Cj44=
+github.com/cespare/xxhash/v2 v2.2.0/go.mod h1:VGX0DQ3Q6kWi7AoAeZDth3/j3BFtOZR5XLFGgcrjCOs=
 github.com/chenzhuoyu/base64x v0.0.0-20211019084208-fb5309c8db06/go.mod h1:DH46F32mSOjUmXrMHnKwZdA8wcEefY7UVqBKYGjpdQY=
 github.com/chenzhuoyu/base64x v0.0.0-20221115062448-fe3a3abad311 h1:qSGYFH7+jGhDF8vLC+iwCD4WpbV1EBDSzWkJODFLams=
 github.com/chenzhuoyu/base64x v0.0.0-20221115062448-fe3a3abad311/go.mod h1:b583jCggY9gE99b6G5LEC39OIiVsWj+R97kbl5odCEk=
@@ -32,8 +36,8 @@ github.com/goccy/go-json v0.10.2 h1:CrxCmQqYDkv1z7lO7Wbh2HN93uovUHgrECaO5ZrCXAU=
 github.com/goccy/go-json v0.10.2/go.mod h1:6MelG93GURQebXPDq3khkgXZkazVtN9CRI+MGFi0w8I=
 github.com/godbus/dbus/v5 v5.0.4/go.mod h1:xhWf0FNVPg57R7Z0UbKHbJfkEywrmjJnf7w5xrFpKfA=
 github.com/golang/protobuf v1.5.0/go.mod h1:FsONVRAS9T7sI+LIUmWTfcYkHO4aIWwzhcaSAoJOfIk=
-github.com/google/go-cmp v0.5.5 h1:Khx7svrCpmxxtHBq5j2mp/xVjsi8hQMfNLvJFAlrGgU=
 github.com/google/go-cmp v0.5.5/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
+github.com/google/go-cmp v0.5.9 h1:O2Tfq5qg4qc4AmwVlvv0oLiVAGB7enBSJ2x2DqQFi38=
 github.com/google/gofuzz v1.0.0/go.mod h1:dBl0BpW6vV/+mYPU4Po3pmUjxk6FQPldtuIdl/M65Eg=
 github.com/imroc/req v0.3.2 h1:M/JkeU6RPmX+WYvT2vaaOL0K+q8ufL5LxwvJc4xeB4o=
 github.com/imroc/req v0.3.2/go.mod h1:F+NZ+2EFSo6EFXdeIbpfE9hcC233id70kf0byW97Caw=
@@ -42,7 +46,7 @@ github.com/json-iterator/go v1.1.12/go.mod h1:e30LSqwooZae/UwlEbR2852Gd8hjQvJoHm
 github.com/klauspost/cpuid/v2 v2.0.9/go.mod h1:FInQzS24/EEf25PyTYn52gqo7WaD8xa0213Md/qVLRg=
 github.com/klauspost/cpuid/v2 v2.2.4 h1:acbojRNwl3o09bUq+yDCtZFc1aiwaAAxtcn8YkZXnvk=
 github.com/klauspost/cpuid/v2 v2.2.4/go.mod h1:RVVoqg1df56z8g3pUjL/3lE5UfnlrJX8tyFgg4nqhuY=
-github.com/kr/pretty v0.3.0 h1:WgNl7dwNpEZ6jJ9k1snq4pZsg7DOEN8hP9Xw0Tsjwk0=
+github.com/kr/pretty v0.3.1 h1:flRD4NNwYAUpkphVc1HcthR4KEIFJ65n8Mw5qdRn3LE=
 github.com/kr/text v0.2.0 h1:5Nx0Ya0ZqY2ygV366QzturHI13Jq95ApcVaJBhpS+AY=
 github.com/kr/text v0.2.0/go.mod h1:eLer722TekiGuMkidMxC/pM04lWEeraHUUmBw8l2grE=
 github.com/leodido/go-urn v1.2.4 h1:XlAE/cm/ms7TE/VMVoduSpNBoyc2dOxHs5MZSwAN63Q=
@@ -52,6 +56,8 @@ github.com/mattn/go-colorable v0.1.13/go.mod h1:7S9/ev0klgBDR4GtXTXX8a3vIGJpMovk
 github.com/mattn/go-isatty v0.0.16/go.mod h1:kYGgaQfpe5nmfYZH+SKPsOc2e4SrIfOl2e/yFXSvRLM=
 github.com/mattn/go-isatty v0.0.19 h1:JITubQf0MOLdlGRuRq+jtsDlekdYPia9ZFsB8h/APPA=
 github.com/mattn/go-isatty v0.0.19/go.mod h1:W+V8PltTTMOvKvAeJH7IuucS94S2C6jfK/D7dTCTo3Y=
+github.com/matttproud/golang_protobuf_extensions/v2 v2.0.0 h1:jWpvCLoY8Z/e3VKvlsiIGKtc+UG6U5vzxaoagmhXfyg=
+github.com/matttproud/golang_protobuf_extensions/v2 v2.0.0/go.mod h1:QUyp042oQthUoa9bqDv0ER0wrtXnBruoNd7aNjkbP+k=
 github.com/modern-go/concurrent v0.0.0-20180228061459-e0a39a4cb421/go.mod h1:6dJC0mAP4ikYIbvyc7fijjWJddQyLn8Ig3JB5CqoB9Q=
 github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd h1:TRLaZ9cD/w8PVh93nsPXa1VrQ6jlwL5oN8l14QlcNfg=
 github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd/go.mod h1:6dJC0mAP4ikYIbvyc7fijjWJddQyLn8Ig3JB5CqoB9Q=
@@ -62,7 +68,15 @@ github.com/pelletier/go-toml/v2 v2.0.8/go.mod h1:vuYfssBdrU2XDZ9bYydBu6t+6a6PYNc
 github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
-github.com/rogpeppe/go-internal v1.9.0 h1:73kH8U+JUqXU8lRuOHeVHaa/SZPifC7BkcraZVejAe8=
+github.com/prometheus/client_golang v1.18.0 h1:HzFfmkOzH5Q8L8G+kSJKUx5dtG87sewO+FoDDqP5Tbk=
+github.com/prometheus/client_golang v1.18.0/go.mod h1:T+GXkCk5wSJyOqMIzVgvvjFDlkOQntgjkJWKrN5txjA=
+github.com/prometheus/client_model v0.5.0 h1:VQw1hfvPvk3Uv6Qf29VrPF32JB6rtbgI6cYPYQjL0Qw=
+github.com/prometheus/client_model v0.5.0/go.mod h1:dTiFglRmd66nLR9Pv9f0mZi7B7fk5Pm3gvsjB5tr+kI=
+github.com/prometheus/common v0.45.0 h1:2BGz0eBc2hdMDLnO/8n0jeB3oPrt2D08CekT0lneoxM=
+github.com/prometheus/common v0.45.0/go.mod h1:YJmSTw9BoKxJplESWWxlbyttQR4uaEcGyv9MZjVOJsY=
+github.com/prometheus/procfs v0.12.0 h1:jluTpSng7V9hY0O2R9DzzJHYb2xULk9VTR1V1R/k6Bo=
+github.com/prometheus/procfs v0.12.0/go.mod h1:pcuDEFsWDnvcgNzo4EEweacyhjeA9Zk3cnaOZAZEfOo=
+github.com/rogpeppe/go-internal v1.10.0 h1:TMyTOH3F/DB16zRVcYyreMH6GnZZrwQVAoYjRBZyWFQ=
 github.com/rs/xid v1.5.0/go.mod h1:trrq9SKmegXys3aeAKXMUTdJsYXVwGY3RLcfgqegfbg=
 github.com/rs/zerolog v1.32.0 h1:keLypqrlIjaFsbmJOBdB/qvyF8KEtCWHwobLp5l/mQ0=
 github.com/rs/zerolog v1.32.0/go.mod h1:/7mN4D5sKwJLZQ2b/znpjC3/GQWY/xaDXUM0kKWRHss=
@@ -90,26 +104,26 @@ github.com/ugorji/go/codec v1.2.11/go.mod h1:UNopzCgEMSXjBc6AOMqYvWC1ktqTAfzJZUZ
 golang.org/x/arch v0.0.0-20210923205945-b76863e36670/go.mod h1:5om86z9Hs0C8fWVUuoMHwpExlXzs5Tkyp9hOrfG7pp8=
 golang.org/x/arch v0.3.0 h1:02VY4/ZcO/gBOH6PUaoiptASxtXU10jazRCP865E97k=
 golang.org/x/arch v0.3.0/go.mod h1:5om86z9Hs0C8fWVUuoMHwpExlXzs5Tkyp9hOrfG7pp8=
-golang.org/x/crypto v0.9.0 h1:LF6fAI+IutBocDJ2OT0Q1g8plpYljMZ4+lty+dsqw3g=
-golang.org/x/crypto v0.9.0/go.mod h1:yrmDGqONDYtNj3tH8X9dzUun2m2lzPa9ngI6/RUPGR0=
+golang.org/x/crypto v0.14.0 h1:wBqGXzWJW6m1XrIKlAH0Hs1JJ7+9KBwnIO8v66Q9cHc=
+golang.org/x/crypto v0.14.0/go.mod h1:MVFd36DqK4CsrnJYDkBA3VC4m2GkXAM0PvzMCn4JQf4=
 golang.org/x/exp v0.0.0-20220303212507-bbda1eaf7a17 h1:3MTrJm4PyNL9NBqvYDSj3DHl46qQakyfqfWo4jgfaEM=
 golang.org/x/exp v0.0.0-20220303212507-bbda1eaf7a17/go.mod h1:lgLbSvA5ygNOMpwM/9anMpWVlVJ7Z+cHWq/eFuinpGE=
-golang.org/x/net v0.10.0 h1:X2//UzNDwYmtCLn7To6G58Wr6f5ahEAQgKNzv9Y951M=
-golang.org/x/net v0.10.0/go.mod h1:0qNGK6F8kojg2nk9dLZ2mShWaEBan6FAoqfSigmmuDg=
+golang.org/x/net v0.17.0 h1:pVaXccu2ozPjCXewfr1S7xza/zcXTity9cCdXQYSjIM=
+golang.org/x/net v0.17.0/go.mod h1:NxSsAGuq816PNPmqtQdLE42eU2Fs7NoRIZrHJAlaCOE=
 golang.org/x/sys v0.0.0-20220704084225-05e143d24a9e/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.0.0-20220811171246-fbc7d0a398ab/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.6.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.12.0 h1:CM0HF96J0hcLAwsHPJZjfdNzs0gftsLfgKt57wWHJ0o=
 golang.org/x/sys v0.12.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/text v0.9.0 h1:2sjJmO8cDvYveuX97RDLsxlyUxLl+GHoLxBiRdHllBE=
-golang.org/x/text v0.9.0/go.mod h1:e1OnstbJyHTd6l/uOt8jFFHp6TRDWZR/bV3emEE/zU8=
+golang.org/x/sys v0.15.0 h1:h48lPFYpsTvQJZF4EKyI4aLHaev3CxivZmv7yZig9pc=
+golang.org/x/sys v0.15.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+golang.org/x/text v0.13.0 h1:ablQoSUd0tRdKxZewP80B+BaqeKJuVhuRxj/dkrun3k=
+golang.org/x/text v0.13.0/go.mod h1:TvPlkZtksWOMsz7fbANvkp4WM8x/WCo/om8BMLbz+aE=
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
-golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1 h1:go1bK/D/BFZV2I8cIQd1NKEZ+0owSTG1fDTci4IqFcE=
 google.golang.org/protobuf v1.26.0-rc.1/go.mod h1:jlhhOSvTdKEhbULTjvd4ARK9grFBp09yW+WbY/TyQbw=
-google.golang.org/protobuf v1.30.0 h1:kPPoIgf3TsEvrm0PFe15JQ+570QVxYzEvvHqChK+cng=
-google.golang.org/protobuf v1.30.0/go.mod h1:HV8QOd/L58Z+nl8r43ehVNZIU/HEI6OcFqwMG9pJV4I=
+google.golang.org/protobuf v1.31.0 h1:g0LDEJHgrBl9N9r17Ru3sqWhkIx2NB67okBHPwC7hs8=
+google.golang.org/protobuf v1.31.0/go.mod h1:HV8QOd/L58Z+nl8r43ehVNZIU/HEI6OcFqwMG9pJV4I=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
-gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15 h1:YR8cESwS4TdDjEe65xsg0ogRM/Nc3DYOhEAlW+xobZo=
+gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c h1:Hei/4ADfdWqJk1ZMxUNpqntNwaWcugrBjAiHlqqRiVk=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
 gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
diff --git a/instrument/exporter.go b/instrument/exporter.go
new file mode 100644
index 0000000..a8187be
--- /dev/null
+++ b/instrument/exporter.go
@@ -0,0 +1,149 @@
+package instrument
+
+import (
+	"github.com/gin-gonic/gin"
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
+	"time"
+)
+
+const (
+	infoKey       = "instrument"
+	labelUsername = "username"
+	labelServerID = "serverId"
+)
+
+func SetInstrument(c *gin.Context, info RequestInfo) {
+	c.Set(infoKey, info)
+}
+
+// Exporter exports the following metrics for the yggdrasil server:
+//   - request_process_time_seconds
+//   - total_request_count
+//   - success_count
+//   - fail_count
+//   - logged_in_count
+//   - not_logged_in_count
+type Exporter struct {
+	requestProcessTime prometheus.HistogramVec
+	totalRequestCount  prometheus.CounterVec
+	successCount       prometheus.CounterVec
+	failCount          prometheus.CounterVec
+	loggedInCount      prometheus.CounterVec
+	notLoggedInCount   prometheus.CounterVec
+}
+
+func (e *Exporter) initMetrics() {
+	e.requestProcessTime.WithLabelValues("", "")
+	e.totalRequestCount.WithLabelValues("", "")
+	e.successCount.WithLabelValues("", "")
+	e.failCount.WithLabelValues("", "")
+	e.loggedInCount.WithLabelValues("", "")
+	e.notLoggedInCount.WithLabelValues("", "")
+}
+
+func (e *Exporter) Describe(descs chan<- *prometheus.Desc) {
+	e.requestProcessTime.Describe(descs)
+	e.totalRequestCount.Describe(descs)
+	e.successCount.Describe(descs)
+	e.failCount.Describe(descs)
+	e.loggedInCount.Describe(descs)
+	e.notLoggedInCount.Describe(descs)
+}
+
+func (e *Exporter) Collect(metrics chan<- prometheus.Metric) {
+	e.requestProcessTime.Collect(metrics)
+	e.totalRequestCount.Collect(metrics)
+	e.successCount.Collect(metrics)
+	e.failCount.Collect(metrics)
+	e.loggedInCount.Collect(metrics)
+	e.notLoggedInCount.Collect(metrics)
+}
+
+// Instrument incoming `/hasJoined` request.
+// The handler must call SetInstrument before returning.
+func (e *Exporter) Instrument(c *gin.Context) {
+	t0 := time.Now()
+	c.Next()
+	dur := time.Since(t0)
+	ri := c.MustGet(infoKey).(RequestInfo)
+
+	labels := prometheus.Labels{
+		labelUsername: ri.Username,
+		labelServerID: ri.ServerID,
+	}
+
+	e.requestProcessTime.With(labels).Observe(dur.Seconds())
+	e.totalRequestCount.With(labels).Inc()
+	if ri.Success {
+		e.successCount.With(labels).Inc()
+		if ri.LoggedIn {
+			e.loggedInCount.With(labels).Inc()
+		} else {
+			e.notLoggedInCount.With(labels).Inc()
+		}
+	} else {
+		e.failCount.With(labels).Inc()
+	}
+}
+
+type RequestInfo struct {
+	// ProcessTime is the total time elapsed for the HTTP request
+	ProcessTime time.Duration
+	// Success is true if and only if all requests to upstreams has succeeded
+	Success bool
+	// Username is from `hasJoined` API call parameter
+	Username string
+	// ServerID is from `hasJoined` API call parameter
+	ServerID string
+	// LoggedIn is the HTTP response
+	LoggedIn bool
+}
+
+func NewExporter(r prometheus.Registerer) *Exporter {
+	const (
+		namespace = "ymux"
+		subsystem = "api"
+	)
+	labels := []string{labelUsername, labelServerID}
+	exp := &Exporter{
+		requestProcessTime: *promauto.With(r).NewHistogramVec(prometheus.HistogramOpts{
+			Namespace: namespace,
+			Subsystem: subsystem,
+			Name:      "request_process_time_seconds",
+			Help:      "time used for serving one /hasJoined request",
+		}, labels),
+		totalRequestCount: *promauto.With(r).NewCounterVec(prometheus.CounterOpts{
+			Namespace: namespace,
+			Subsystem: subsystem,
+			Name:      "total_request_count",
+			Help:      "requests processed by this process",
+		}, labels),
+		successCount: *promauto.With(r).NewCounterVec(prometheus.CounterOpts{
+			Namespace: namespace,
+			Subsystem: subsystem,
+			Name:      "success_count",
+			Help:      "successful requests",
+		}, labels),
+		failCount: *promauto.With(r).NewCounterVec(prometheus.CounterOpts{
+			Namespace: namespace,
+			Subsystem: subsystem,
+			Name:      "fail_count",
+			Help:      "errored requests",
+		}, labels),
+		loggedInCount: *promauto.With(r).NewCounterVec(prometheus.CounterOpts{
+			Namespace: namespace,
+			Subsystem: subsystem,
+			Name:      "logged_in_count",
+			Help:      "requests with 204 (not logged in) /hasJoined result",
+		}, labels),
+		notLoggedInCount: *promauto.With(r).NewCounterVec(prometheus.CounterOpts{
+			Namespace: namespace,
+			Subsystem: subsystem,
+			Name:      "not_logged_in_count",
+			Help:      "requests with 200 (logged in) /hasJoined result",
+		}, labels),
+	}
+	exp.initMetrics()
+	return exp
+}
diff --git a/ymux.go b/ymux.go
index 8b09fc8..eede160 100644
--- a/ymux.go
+++ b/ymux.go
@@ -5,13 +5,21 @@ import (
 	"github.com/akamensky/argparse"
 	"github.com/gin-gonic/gin"
 	"github.com/keuin/ymux-go/config"
+	"github.com/keuin/ymux-go/instrument"
 	"github.com/keuin/ymux-go/yggdrasil"
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/collectors"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
 	"github.com/rs/zerolog"
 	"github.com/rs/zerolog/log"
 	"os"
+	"regexp"
 	"strings"
+	"time"
 )
 
+var processStartTime = time.Now()
+
 const applicationJson = "application/json"
 
 func main() {
@@ -53,7 +61,7 @@ func main() {
 		// we need this to make them happy
 		c.Data(200, applicationJson, []byte(`{}`))
 	})
-	r.GET("/sessionserver/session/minecraft/hasJoined", func(c *gin.Context) {
+	handlers := []gin.HandlerFunc{func(c *gin.Context) {
 		var args struct {
 			Username string `form:"username"`
 			ServerID string `form:"serverId"`
@@ -61,12 +69,22 @@ func main() {
 		err := c.ShouldBindQuery(&args)
 		if err != nil {
 			_ = c.AbortWithError(400, err)
+			instrument.SetInstrument(c, instrument.RequestInfo{
+				Success:  false,
+				Username: args.Username,
+				ServerID: args.ServerID,
+			})
 			return
 		}
 		r, err := s.HasJoined(args.Username, args.ServerID)
 		if err != nil {
 			log.Error().Err(err).Msg("ymux hasJoined API failed")
 			_ = c.AbortWithError(500, err)
+			instrument.SetInstrument(c, instrument.RequestInfo{
+				Success:  false,
+				Username: args.Username,
+				ServerID: args.ServerID,
+			})
 			return
 		}
 		log.Info().
@@ -75,18 +93,60 @@ func main() {
 			Str("yggdrasilServer", r.ServerName).
 			Bool("hasJoined", r.HasJoined()).
 			Msg("ymux hasJoined API OK")
+		instrument.SetInstrument(c, instrument.RequestInfo{
+			Success:  true,
+			Username: args.Username,
+			ServerID: args.ServerID,
+			LoggedIn: r.HasJoined(),
+		})
 		if r.HasJoined() {
 			c.Data(200, applicationJson, r.RawBody)
 			return
 		}
 		c.Status(204)
-	})
+	}}
+
+	// setup prometheus metrics exporter
+	if cfg.Metrics.Enabled {
+		reg := prometheus.NewRegistry()
+		reg.MustRegister(
+			collectors.NewBuildInfoCollector(),
+			collectors.NewProcessCollector(collectors.ProcessCollectorOpts{}),
+			collectors.NewGoCollector(
+				collectors.WithGoCollectorRuntimeMetrics(
+					collectors.GoRuntimeMetricsRule{Matcher: regexp.MustCompile("/.*")},
+				),
+			),
+		)
+		r.GET("/metrics", gin.WrapH(promhttp.HandlerFor(reg, promhttp.HandlerOpts{
+			ErrorLog:            promZeroLogger{},
+			ErrorHandling:       promhttp.HTTPErrorOnError,
+			Registry:            nil,
+			DisableCompression:  true,
+			MaxRequestsInFlight: 0,
+			Timeout:             0,
+			EnableOpenMetrics:   true,
+			ProcessStartTime:    processStartTime,
+		})))
+		ex := instrument.NewExporter(reg)
+		handlers = append([]gin.HandlerFunc{ex.Instrument}, handlers...)
+		log.Info().Msg("prometheus metrics exporter enabled")
+	}
+	r.GET("/sessionserver/session/minecraft/hasJoined", handlers...)
+
 	err = r.Run(cfg.Listen)
 	if err != nil {
 		panic(fmt.Errorf("error running http server: %w", err))
 	}
 }
 
+type promZeroLogger struct {
+}
+
+func (p promZeroLogger) Println(v ...interface{}) {
+	log.Error().Str("msg", fmt.Sprintln(v...)).Msg("prometheus metrics exporter error")
+}
+
 func createServers(cfg *config.Config) ([]yggdrasil.Server, error) {
 	var servers []yggdrasil.Server
 	for _, s := range cfg.Servers {
diff --git a/ymux.toml b/ymux.toml
index d18bcfe..39ee70a 100644
--- a/ymux.toml
+++ b/ymux.toml
@@ -1,6 +1,9 @@
 debug = false
 listen = "127.0.0.1:32217"
 
+[metrics]
+enabled = true
+
 [[servers]]
 name = "official"
 prefix = "https://sessionserver.mojang.com"