Setup basic prom metrics endpoint

go.mod

@@ -14,13 +14,16 @@ require (
 	github.com/lib/pq v1.10.5
 	github.com/mitchellh/go-homedir v1.1.0
 	github.com/mr-tron/base58 v1.2.0
+	github.com/prometheus/client_golang v1.14.0
 	github.com/sirupsen/logrus v1.9.0
-	github.com/stretchr/testify v1.7.1
+	github.com/stretchr/testify v1.8.0
 	github.com/tuvistavie/securerandom v0.0.0-20140719024926-15512123a948
 	golang.org/x/crypto v0.0.0-20220511200225-c6db032c6c88
 )
 
 require (
+	github.com/beorn7/perks v1.0.1 // indirect
+	github.com/cespare/xxhash/v2 v2.2.0 // indirect
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/dchest/bcrypt_pbkdf v0.0.0-20150205184540-83f37f9c154a // indirect
 	github.com/gin-contrib/sse v0.1.0 // indirect
@@ -31,13 +34,17 @@ require (
 	github.com/json-iterator/go v1.1.12 // indirect
 	github.com/leodido/go-urn v1.2.1 // indirect
 	github.com/mattn/go-isatty v0.0.14 // indirect
+	github.com/matttproud/golang_protobuf_extensions v1.0.4 // indirect
 	github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd // indirect
 	github.com/modern-go/reflect2 v1.0.2 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
+	github.com/prometheus/client_model v0.3.0 // indirect
+	github.com/prometheus/common v0.39.0 // indirect
+	github.com/prometheus/procfs v0.8.0 // indirect
 	github.com/ugorji/go/codec v1.2.6 // indirect
-	golang.org/x/sys v0.2.0 // indirect
-	golang.org/x/text v0.3.7 // indirect
-	google.golang.org/protobuf v1.27.1 // indirect
+	golang.org/x/sys v0.3.0 // indirect
+	golang.org/x/text v0.5.0 // indirect
+	google.golang.org/protobuf v1.28.1 // indirect
 	gopkg.in/yaml.v2 v2.4.0 // indirect
-	gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
 )

go.sum

@@ -2,6 +2,10 @@ github.com/BurntSushi/toml v1.1.0 h1:ksErzDEI1khOiGPgpwuI7x2ebx/uXQNw7xJpn9Eq1+I
 github.com/BurntSushi/toml v1.1.0/go.mod h1:CxXYINrC8qIiEnFrOxCa7Jy5BFHlXnUU2pbicEuybxQ=
 github.com/ScaleFT/sshkeys v0.0.0-20200327173127-6142f742bca5 h1:VauE2GcJNZFun2Och6tIT2zJZK1v6jxALQDA9BIji/E=
 github.com/ScaleFT/sshkeys v0.0.0-20200327173127-6142f742bca5/go.mod h1:gxOHeajFfvGQh/fxlC8oOKBe23xnnJTif00IFFbiT+o=
+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/cespare/xxhash/v2 v2.2.0 h1:DC2CZ1Ep5Y4k3ZQ899DldepgrayRUGE6BBZ/cd9Cj44=
+github.com/cespare/xxhash/v2 v2.2.0/go.mod h1:VGX0DQ3Q6kWi7AoAeZDth3/j3BFtOZR5XLFGgcrjCOs=
 github.com/creack/pty v1.1.9/go.mod h1:oKZEueFk5CKHvIhNR5MUki03XCEU+Q6VDXinZuGJ33E=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
@@ -25,12 +29,14 @@ github.com/go-playground/validator/v10 v10.9.0 h1:NgTtmN58D0m8+UuxtYmGztBJB7VnPg
 github.com/go-playground/validator/v10 v10.9.0/go.mod h1:74x4gJWsvQexRdW8Pn3dXSGrTK4nAUsbPlLADvpJkos=
 github.com/go-sql-driver/mysql v1.6.0 h1:BCTh4TKNUYmOmMUcQ3IipzF5prigylS7XXjEkfCHuOE=
 github.com/go-sql-driver/mysql v1.6.0/go.mod h1:DCzpHaOWr8IXmIStZouvnhqoel9Qv2LBy8hT2VhHyBg=
+github.com/golang/protobuf v1.2.0/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
 github.com/golang/protobuf v1.3.3/go.mod h1:vzj43D7+SQXF/4pzW/hwtAqwc6iTitCiVSaWz5lYuqw=
+github.com/golang/protobuf v1.3.5/go.mod h1:6O5/vntMXwX2lRkT1hjjk0nAC1IDOTvTlVgjlRvqsdk=
 github.com/golang/protobuf v1.5.0/go.mod h1:FsONVRAS9T7sI+LIUmWTfcYkHO4aIWwzhcaSAoJOfIk=
 github.com/golang/protobuf v1.5.2 h1:ROPKBNFfQgOUMifHyP+KYbvpjbdoFNs+aK7DXlji0Tw=
 github.com/golang/protobuf v1.5.2/go.mod h1:XVQd3VNwM+JqD3oG2Ue2ip4fOMUkwXdXDdiuN0vRsmY=
-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 v0.5.8 h1:e6P7q2lk1O+qJJb4BtCQXlK8vWEO8V1ZeuEdJNOqZyg=
 github.com/google/gofuzz v1.0.0/go.mod h1:dBl0BpW6vV/+mYPU4Po3pmUjxk6FQPldtuIdl/M65Eg=
 github.com/jackc/pgpassfile v1.0.0 h1:/6Hmqy13Ss2zCq62VdNG8tM1wchn8zjSGOBJ6icpsIM=
 github.com/jackc/pgpassfile v1.0.0/go.mod h1:CEx0iS5ambNFdcRtxPj5JhEz+xB6uRky5eyVu/W2HEg=
@@ -60,6 +66,8 @@ github.com/mattn/go-isatty v0.0.14 h1:yVuAays6BHfxijgZPzw+3Zlu5yQgKGP2/hcQbHb7S9
 github.com/mattn/go-isatty v0.0.14/go.mod h1:7GGIvUiUoEMVVmxf/4nioHXj79iQHKdU27kJ6hsGG94=
 github.com/mattn/go-sqlite3 v1.14.6 h1:dNPt6NO46WmLVt2DLNpwczCmdV5boIZ6g/tlDrlRUbg=
 github.com/mattn/go-sqlite3 v1.14.6/go.mod h1:NyWgC/yNuGj7Q9rpYnZvas74GogHl5/Z4A/KQRfk6bU=
+github.com/matttproud/golang_protobuf_extensions v1.0.4 h1:mmDVorXM7PCGKw94cs5zkfA9PSy5pEvNWRP0ET0TIVo=
+github.com/matttproud/golang_protobuf_extensions v1.0.4/go.mod h1:BSXmuO+STAnVfrANrmjBb36TMTDstsz7MSK+HVaYKv4=
 github.com/mitchellh/go-homedir v1.1.0 h1:lukF9ziXFxDFPkA1vsr5zpc1XuPDn/wFntq5mG+4E0Y=
 github.com/mitchellh/go-homedir v1.1.0/go.mod h1:SfyaCUpYCn1Vlf4IUYiD9fPX4A5wJrkLzIz1N1q0pr0=
 github.com/modern-go/concurrent v0.0.0-20180228061459-e0a39a4cb421/go.mod h1:6dJC0mAP4ikYIbvyc7fijjWJddQyLn8Ig3JB5CqoB9Q=
@@ -73,19 +81,29 @@ github.com/mr-tron/base58 v1.2.0/go.mod h1:BinMc/sQntlIE1frQmRFPUoPA1Zkr8VRgBdjW
 github.com/pkg/diff v0.0.0-20210226163009-20ebb0f2a09e/go.mod h1:pJLUxLENpZxwdsKMEsNbx1VGcRFpLqf3715MtcvvzbA=
 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/prometheus/client_golang v1.14.0 h1:nJdhIvne2eSX/XRAFV9PcvFFRbrjbcTUj0VP62TMhnw=
+github.com/prometheus/client_golang v1.14.0/go.mod h1:8vpkKitgIVNcqrRBWh1C4TIUQgYNtG/XQE4E/Zae36Y=
+github.com/prometheus/client_model v0.3.0 h1:UBgGFHqYdG/TPFD1B1ogZywDqEkwp3fBMvqdiQ7Xew4=
+github.com/prometheus/client_model v0.3.0/go.mod h1:LDGWKZIo7rky3hgvBe+caln+Dr3dPggB5dvjtD7w9+w=
+github.com/prometheus/common v0.39.0 h1:oOyhkDq05hPZKItWVBkJ6g6AtGxi+fy7F4JvUV8uhsI=
+github.com/prometheus/common v0.39.0/go.mod h1:6XBZ7lYdLCbkAVhwRsWTZn+IN5AB9F/NXd5w0BbEX0Y=
+github.com/prometheus/procfs v0.8.0 h1:ODq8ZFEaYeCaZOJlZZdJA2AbQR98dSHSM1KW/You5mo=
+github.com/prometheus/procfs v0.8.0/go.mod h1:z7EfXMXOkbkqb9IINtpCn86r/to3BnA0uaxHdg830/4=
 github.com/rogpeppe/go-internal v1.6.1/go.mod h1:xXDCJY+GAPziupqXw64V24skbSoqbTEfhy4qGm1nDQc=
 github.com/rogpeppe/go-internal v1.8.0 h1:FCbCCtXNOY3UtUuHUYaghJg4y7Fd14rXifAYUAtL9R8=
 github.com/rogpeppe/go-internal v1.8.0/go.mod h1:WmiCO8CzOY8rg0OYDC4/i/2WRWAB6poM+XZ2dLUbcbE=
 github.com/sirupsen/logrus v1.9.0 h1:trlNQbNUG3OdDrDil03MCb1H2o9nJ1x4/5LYw7byDE0=
 github.com/sirupsen/logrus v1.9.0/go.mod h1:naHLuLoDiP4jHNo9R0sCBMtWGeIprob74mVsIT4qYEQ=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/objx v0.4.0/go.mod h1:YvHI0jy2hoMjB+UWwv71VJQ9isScKT/TqJzVSSt89Yw=
 github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
 github.com/stretchr/testify v1.4.0/go.mod h1:j7eGeouHqKxXV5pUuKE4zz7dFj8WfuZ+81PSLYec5m4=
 github.com/stretchr/testify v1.5.1/go.mod h1:5W2xD1RspED5o8YsWQXVCued0rvSQ+mT+I5cxcmMvtA=
 github.com/stretchr/testify v1.6.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
 github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
-github.com/stretchr/testify v1.7.1 h1:5TQK59W5E3v0r2duFAb7P95B6hEeOyEnHRa8MjYSMTY=
 github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+github.com/stretchr/testify v1.8.0 h1:pSgiaMZlXftHpm5L7V1+rVB+AZJydKsMxsQBIJw4PKk=
+github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
 github.com/tuvistavie/securerandom v0.0.0-20140719024926-15512123a948 h1:yL0l/u242MzDP6D0B5vGC+wxm5WRY+alQZy+dJk3bFI=
 github.com/tuvistavie/securerandom v0.0.0-20140719024926-15512123a948/go.mod h1:a06d/M1pxWi51qiSrfGMHaEydtuXT06nha8N2aNQuXk=
 github.com/ugorji/go v1.1.7/go.mod h1:kZn38zHttfInRq0xu/PH0az30d+z6vm202qpg1oXVMw=
@@ -101,6 +119,7 @@ golang.org/x/crypto v0.0.0-20220511200225-c6db032c6c88 h1:Tgea0cVUD0ivh5ADBX4Wwu
 golang.org/x/crypto v0.0.0-20220511200225-c6db032c6c88/go.mod h1:IxCIyHEi3zRg3s0A5j5BB6A9Jmi73HwBIUl50j+osU4=
 golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
 golang.org/x/net v0.0.0-20210226172049-e18ecbb05110/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
+golang.org/x/sync v0.0.0-20181221193216-37e7f081c4d4/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200116001909-b77594299b42/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
@@ -111,23 +130,22 @@ golang.org/x/sys v0.0.0-20210615035016-665e8c7367d1/go.mod h1:oPkhp1MJrh7nUepCBc
 golang.org/x/sys v0.0.0-20210630005230-0f9fa26af87c/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.0.0-20210806184541-e5e7981a1069/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.0.0-20220715151400-c0bba94af5f8/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.2.0 h1:ljd4t30dBnAvMZaQCevtY0xLLD0A+bRZXbgLMLU1F/A=
-golang.org/x/sys v0.2.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.3.0 h1:w8ZOecv6NaNa/zC8944JTU3vz4u6Lagfk4RPQxv92NQ=
+golang.org/x/sys v0.3.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1 h1:v+OssWQX+hTHEmOBgwxdZxK4zHq3yOs8F9J7mk0PY8E=
 golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.3.2/go.mod h1:bEr9sfX3Q8Zfm5fL9x+3itogRgK3+ptLWKqgva+5dAk=
 golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
 golang.org/x/text v0.3.6/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
-golang.org/x/text v0.3.7 h1:olpwvP2KacW1ZWvsR7uQhoyTYvKAupfQrRGBFM352Gk=
-golang.org/x/text v0.3.7/go.mod h1:u+2+/6zg+i71rQMx5EYifcz6MCKuco9NR6JIITiCfzQ=
+golang.org/x/text v0.5.0 h1:OLmvp0KP+FVG99Ct/qFiL/Fhk4zp4QQnZ7b2U+5piUM=
+golang.org/x/text v0.5.0/go.mod h1:mrYo+phRRbMaCq/xk9113O4dZlRixOauAjOtrjsXDZ8=
 golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
-golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543 h1:E7g+9GITq07hpfrRu66IVDexMakfv52eLZ2CXBWiKr4=
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 google.golang.org/protobuf v1.26.0-rc.1/go.mod h1:jlhhOSvTdKEhbULTjvd4ARK9grFBp09yW+WbY/TyQbw=
 google.golang.org/protobuf v1.26.0/go.mod h1:9q0QmTI4eRPtz6boOQmLYwt+qCgq0jsYwAQnmE0givc=
-google.golang.org/protobuf v1.27.1 h1:SnqbnDw1V7RiZcXPx5MEeqPv2s79L9i7BJUlG/+RurQ=
-google.golang.org/protobuf v1.27.1/go.mod h1:9q0QmTI4eRPtz6boOQmLYwt+qCgq0jsYwAQnmE0givc=
+google.golang.org/protobuf v1.28.1 h1:d0NfwRgPtno5B1Wa6L2DAG+KivqkdutMf1UhdNx175w=
+google.golang.org/protobuf v1.28.1/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 v1.0.0-20180628173108-788fd7840127/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c h1:Hei/4ADfdWqJk1ZMxUNpqntNwaWcugrBjAiHlqqRiVk=
@@ -138,5 +156,6 @@ gopkg.in/yaml.v2 v2.2.8/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v2 v2.4.0 h1:D8xgwECY7CYvx+Y2n4sBz93Jn9JRvxdiyyo8CTfuKaY=
 gopkg.in/yaml.v2 v2.4.0/go.mod h1:RDklbk79AGWmwhnvt/jBztapEOGDOx6ZbXqjP6csGnQ=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
-gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b h1:h8qDotaEPuJATrMmW04NCwg7v22aHH28wwpauUhK9Oo=
 gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b/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=

pkg/api/api.go

@@ -16,6 +16,7 @@ import (
 	"github.com/sosedoff/pgweb/pkg/client"
 	"github.com/sosedoff/pgweb/pkg/command"
 	"github.com/sosedoff/pgweb/pkg/connection"
+	"github.com/sosedoff/pgweb/pkg/metrics"
 	"github.com/sosedoff/pgweb/pkg/shared"
 	"github.com/sosedoff/pgweb/static"
 )
@@ -278,6 +279,12 @@ func Disconnect(c *gin.Context) {
 		return
 	}
 
+	if command.Opts.Sessions {
+		result := DbSessions.Remove(getSessionId(c.Request))
+		successResponse(c, gin.H{"success": result})
+		return
+	}
+
 	conn := DB(c)
 	if conn == nil {
 		badRequest(c, errNotConnected)
@@ -492,6 +499,8 @@ func GetTableConstraints(c *gin.Context) {
 
 // HandleQuery runs the database query
 func HandleQuery(query string, c *gin.Context) {
+	metrics.IncrementQueriesCount()
+
 	rawQuery, err := base64.StdEncoding.DecodeString(desanitize64(query))
 	if err == nil {
 		query = string(rawQuery)

pkg/api/routes.go

@@ -4,6 +4,7 @@ import (
 	"github.com/gin-gonic/gin"
 
 	"github.com/sosedoff/pgweb/pkg/command"
+	"github.com/sosedoff/pgweb/pkg/metrics"
 )
 
 func SetupMiddlewares(group *gin.RouterGroup) {
@@ -53,3 +54,9 @@ func SetupRoutes(router *gin.Engine) {
 	api.GET("/bookmarks", GetBookmarks)
 	api.GET("/export", DataExport)
 }
+
+func SetupMetrics(engine *gin.Engine) {
+	if command.Opts.MetricsEnabled && command.Opts.MetricsAddr == "" {
+		engine.GET("/metrics", gin.WrapH(metrics.Handler()))
+	}
+}

pkg/api/session_manager.go

@@ -7,6 +7,7 @@ import (
 	"github.com/sirupsen/logrus"
 
 	"github.com/sosedoff/pgweb/pkg/client"
+	"github.com/sosedoff/pgweb/pkg/metrics"
 )
 
 type SessionManager struct {
@@ -58,8 +59,10 @@ func (m *SessionManager) Get(id string) *client.Client {
 
 func (m *SessionManager) Add(id string, conn *client.Client) {
 	m.mu.Lock()
+	defer m.mu.Unlock()
+
 	m.sessions[id] = conn
-	m.mu.Unlock()
+	metrics.SetSessionsCount(len(m.sessions))
 }
 
 func (m *SessionManager) Remove(id string) bool {
@@ -72,6 +75,7 @@ func (m *SessionManager) Remove(id string) bool {
 		delete(m.sessions, id)
 	}
 
+	metrics.SetSessionsCount(len(m.sessions))
 	return ok
 }
 

pkg/cli/cli.go

@@ -19,6 +19,7 @@ import (
 	"github.com/sosedoff/pgweb/pkg/client"
 	"github.com/sosedoff/pgweb/pkg/command"
 	"github.com/sosedoff/pgweb/pkg/connection"
+	"github.com/sosedoff/pgweb/pkg/metrics"
 	"github.com/sosedoff/pgweb/pkg/util"
 )
 
@@ -199,9 +200,12 @@ func startServer() {
 
 	api.SetLogger(logger)
 	api.SetupRoutes(router)
+	api.SetupMetrics(router)
 
 	fmt.Println("Starting server...")
 	go func() {
+		metrics.SetHealty(true)
+
 		err := router.Run(fmt.Sprintf("%v:%v", options.HTTPHost, options.HTTPPort))
 		if err != nil {
 			fmt.Println("Cant start server:", err)
@@ -213,6 +217,18 @@ func startServer() {
 	}()
 }
 
+func startMetricsServer() {
+	serverAddr := fmt.Sprintf("%v:%v", command.Opts.HTTPHost, command.Opts.HTTPPort)
+	if options.MetricsAddr == serverAddr {
+		return
+	}
+
+	err := metrics.StartServer(logger, options.MetricsPath, options.MetricsAddr)
+	if err != nil {
+		logger.WithError(err).Fatal("unable to start prometheus metrics server")
+	}
+}
+
 func handleSignals() {
 	c := make(chan os.Signal, 1)
 	signal.Notify(c, os.Interrupt, syscall.SIGTERM)
@@ -265,6 +281,10 @@ func Run() {
 		}
 	}
 
+	if options.MetricsEnabled && options.MetricsAddr != "" {
+		go startMetricsServer()
+	}
+
 	startServer()
 	openPage()
 	handleSignals()

pkg/command/options.go

@@ -58,6 +58,9 @@ type Options struct {
 	Cors                         bool   `long:"cors" description:"Enable Cross-Origin Resource Sharing (CORS)"`
 	CorsOrigin                   string `long:"cors-origin" description:"Allowed CORS origins" default:"*"`
 	BinaryCodec                  string `long:"binary-codec" description:"Codec for binary data serialization, one of 'none', 'hex', 'base58', 'base64'" default:"none"`
+	MetricsEnabled               bool   `long:"metrics" description:"Enable Prometheus metrics endpoint"`
+	MetricsPath                  string `long:"metrics-path" description:"Path prefix for Prometheus metrics endpoint" default:"/metrics"`
+	MetricsAddr                  string `long:"metrics-addr" description:"Listen host and port for Prometheus metrics server"`
 }
 
 var Opts Options

pkg/metrics/metrics.go

@@ -0,0 +1,42 @@
+package metrics
+
+import (
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
+)
+
+var (
+	sessionsGauge = promauto.NewGauge(prometheus.GaugeOpts{
+		Namespace: "pgweb",
+		Name:      "sessions_count",
+		Help:      "Total number of database sessions",
+	})
+
+	queriesCounter = promauto.NewCounter(prometheus.CounterOpts{
+		Namespace: "pgweb",
+		Name:      "queries_count",
+		Help:      "Total number of custom queries executed",
+	})
+
+	healtyGauge = promauto.NewGauge(prometheus.GaugeOpts{
+		Name:      "healty",
+		Namespace: "pgweb",
+		Help:      "Server health status",
+	})
+)
+
+func IncrementQueriesCount() {
+	queriesCounter.Inc()
+}
+
+func SetSessionsCount(val int) {
+	sessionsGauge.Set(float64(val))
+}
+
+func SetHealty(val bool) {
+	healthy := 0.0
+	if val {
+		healthy = 1.0
+	}
+	healtyGauge.Set(float64(healthy))
+}

pkg/metrics/server.go

@@ -0,0 +1,39 @@
+package metrics
+
+import (
+	"net/http"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+	"github.com/sirupsen/logrus"
+)
+
+var (
+	registry = prometheus.NewRegistry()
+
+	handler = promhttp.HandlerFor(
+		registry,
+		promhttp.HandlerOpts{
+			EnableOpenMetrics: false,
+		},
+	)
+)
+
+func init() {
+	registry.MustRegister(
+		sessionsGauge,
+		queriesCounter,
+		healtyGauge,
+	)
+}
+
+func Handler() http.Handler {
+	return handler
+}
+
+func StartServer(logger *logrus.Logger, path string, addr string) error {
+	logger.WithField("addr", addr).WithField("path", path).Info("starting prometheus metrics server")
+
+	http.Handle(path, handler)
+	return http.ListenAndServe(addr, nil)
+}