Use groupcache for caching postgres data (#20)

* Use groupcache for caching postgres data.

* Expose cache stats.

* Remove Println

go.mod

@@ -13,7 +13,9 @@ require (
 	github.com/ipfs/go-ipfs-exchange-interface v0.0.1
 	github.com/jmoiron/sqlx v1.2.0
 	github.com/lib/pq v1.0.0
+	github.com/mailgun/groupcache/v2 v2.2.1
 	github.com/multiformats/go-multihash v0.0.13
 	github.com/onsi/ginkgo v1.8.0
 	github.com/onsi/gomega v1.5.0
+	google.golang.org/appengine v1.6.7 // indirect
 )

go.sum

@@ -15,12 +15,14 @@ github.com/Azure/go-autorest/tracing v0.5.0/go.mod h1:r/s2XiOKccPW3HrqB+W0TQzfbt
 github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
 github.com/Kubuxu/go-os-helper v0.0.1/go.mod h1:N8B+I7vPCT80IcP58r50u4+gEEcsZETFUpAzWW2ep1Y=
 github.com/OneOfOne/xxhash v1.2.2/go.mod h1:HSdplMjZKSmBqAxg5vPj2TmRDmfkzw+cTzAElWljhcU=
+github.com/StackExchange/wmi v0.0.0-20180116203802-5d049714c4a6 h1:fLjPD/aNc3UIOA6tDi6QXUemppXK3P9BI7mr2hd6gx8=
 github.com/StackExchange/wmi v0.0.0-20180116203802-5d049714c4a6/go.mod h1:3eOhrUMpNV+6aFIbp5/iudMxNCF27Vw2OZgy4xEx0Fg=
 github.com/VictoriaMetrics/fastcache v1.5.7 h1:4y6y0G8PRzszQUYIQHHssv/jgPHAb5qQuuDNdCbyAgw=
 github.com/VictoriaMetrics/fastcache v1.5.7/go.mod h1:ptDBkNMQI4RtmVo8VS/XwRY6RoTu1dAWCbrk+6WsEM8=
 github.com/aead/siphash v1.0.1/go.mod h1:Nywa3cDsYNNK3gaciGTWPwHt0wlpNV15vwmswBAUSII=
 github.com/alecthomas/template v0.0.0-20160405071501-a0175ee3bccc/go.mod h1:LOuyumcjzFXgccqObfd/Ljyb9UuFJ6TxHnclSeseNhc=
 github.com/alecthomas/units v0.0.0-20151022065526-2efee857e7cf/go.mod h1:ybxpYRFXyAe+OPACYpWeL0wqObRcbAqCMya13uyzqw0=
+github.com/allegro/bigcache v1.2.1-0.20190218064605-e24eb225f156 h1:eMwmnE/GDgah4HI848JfFxHt+iPb26b4zyfspmqY0/8=
 github.com/allegro/bigcache v1.2.1-0.20190218064605-e24eb225f156/go.mod h1:Cb/ax3seSYIx7SuZdm2G2xzfwmv3TPSk2ucNfQESPXM=
 github.com/aristanetworks/goarista v0.0.0-20170210015632-ea17b1a17847 h1:rtI0fD4oG/8eVokGVPYJEW1F88p1ZNgXiEIs9thEE4A=
 github.com/aristanetworks/goarista v0.0.0-20170210015632-ea17b1a17847/go.mod h1:D/tb0zPVXnP7fmsLZjtdUhSsumbK/ij54UXjjVgMGxQ=
@@ -29,6 +31,7 @@ github.com/beorn7/perks v0.0.0-20180321164747-3a771d992973/go.mod h1:Dwedo/Wpr24
 github.com/btcsuite/btcd v0.0.0-20171128150713-2e60448ffcc6/go.mod h1:Dmm/EzmjnCiweXmzRIAiUWCInVmPgjkzgv5k4tVyXiQ=
 github.com/btcsuite/btcd v0.0.0-20190213025234-306aecffea32/go.mod h1:DrZx5ec/dmnfpw9KyYoQyYo7d0KEvTkk/5M/vbZjAr8=
 github.com/btcsuite/btcd v0.0.0-20190523000118-16327141da8c/go.mod h1:3J08xEfcugPacsc34/LKRU2yO7YmuT8yt28J8k2+rrI=
+github.com/btcsuite/btcd v0.0.0-20190605094302-a0d1e3e36d50 h1:4i3KsuVA0o0KoBxAC5x+MY7RbteiMK1V7gf/G08NGIQ=
 github.com/btcsuite/btcd v0.0.0-20190605094302-a0d1e3e36d50/go.mod h1:3J08xEfcugPacsc34/LKRU2yO7YmuT8yt28J8k2+rrI=
 github.com/btcsuite/btclog v0.0.0-20170628155309-84c8d2346e9f/go.mod h1:TdznJufoqS23FtqVCzL0ZqgP5MqXbb4fg/WgDys70nA=
 github.com/btcsuite/btcutil v0.0.0-20190207003914-4c204d697803/go.mod h1:+5NJ2+qvTyV9exUAL/rxXi3DcLg2Ts+ymUAY5y4NvMg=
@@ -49,6 +52,7 @@ github.com/cpuguy83/go-md2man/v2 v2.0.0-20190314233015-f79a8a8ca69d/go.mod h1:ma
 github.com/cskr/pubsub v1.0.2/go.mod h1:/8MzYXk/NJAz782G8RPkFzXTZVu63VotefPnR9TIRis=
 github.com/davecgh/go-spew v0.0.0-20171005155431-ecdeabc65495/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 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=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/deckarep/golang-set v0.0.0-20180603214616-504e848d77ea/go.mod h1:93vsz/8Wt4joVM7c2AVqh+YRMiUSc14yDtF28KmMOgQ=
 github.com/dgraph-io/badger v1.5.5-0.20190226225317-8115aed38f8f/go.mod h1:VZxzAIRPHRVNRKRo6AXrX9BJegn6il06VMTZVJYCIjQ=
@@ -64,13 +68,16 @@ github.com/ethereum/go-ethereum v1.9.15 h1:wrWl+QrtutRUJ9LZXdUqBoGoo2b1tOCYRDrAO
 github.com/ethereum/go-ethereum v1.9.15/go.mod h1:slT8bPPRhXsyNTwHQxrOnjuTZ1sDXRajW11EkJ84QJ0=
 github.com/fatih/color v1.3.0/go.mod h1:Zm6kSWBoL9eyXnKyktHP6abPY2pDugNf5KwzbycvMj4=
 github.com/fjl/memsize v0.0.0-20180418122429-ca190fb6ffbc/go.mod h1:VvhXpOYNQvB+uIk2RvXzuaQtkQJzzIx6lSBe1xv7hi0=
+github.com/fsnotify/fsnotify v1.4.7 h1:IXs+QLmnXW2CcXuY+8Mzv/fWEsPGWxqefPtCP5CnV9I=
 github.com/fsnotify/fsnotify v1.4.7/go.mod h1:jwhsz4b93w/PPRr/qN1Yymfu8t87LnFCMoQvtojpjFo=
 github.com/gballet/go-libpcsclite v0.0.0-20190607065134-2772fd86a8ff/go.mod h1:x7DCsMOv1taUwEWCzT4cmDeAkigA5/QCwUodaVOe8Ww=
 github.com/go-check/check v0.0.0-20180628173108-788fd7840127/go.mod h1:9ES+weclKsC9YodN5RgxqK/VD9HM9JsCSh7rNhMZE98=
 github.com/go-kit/kit v0.8.0/go.mod h1:xBxKIO96dXMWWy0MnWVtmwkA9/13aqxPnvrjFYMA2as=
 github.com/go-logfmt/logfmt v0.3.0/go.mod h1:Qt1PoO58o5twSAckw1HlFXLmHsOX5/0LbT9GBnD5lWE=
+github.com/go-ole/go-ole v1.2.1 h1:2lOsA72HgjxAuMlKpFiCbHTvu44PIVkZ5hqm3RSdI/E=
 github.com/go-ole/go-ole v1.2.1/go.mod h1:7FAglXiTm7HKlQRDeOQ6ZNUHidzCWXuZWq/1dTyBNF8=
 github.com/go-sourcemap/sourcemap v2.1.2+incompatible/go.mod h1:F8jJfvm2KbVjc5NqelyYJmf/v5J0dwNLS2mL4sNA1Jg=
+github.com/go-sql-driver/mysql v1.4.0 h1:7LxgVwFb2hIQtMm87NdgAVfXjnt4OePseqT1tKx+opk=
 github.com/go-sql-driver/mysql v1.4.0/go.mod h1:zAC/RDZ24gD3HViQzih4MyKcchzm+sOG5ZlKdlhCg5w=
 github.com/go-stack/stack v1.8.0 h1:5SgMzNM5HxrEjV0ww2lTmX6E2Izsfxas4+YHWRs3Lsk=
 github.com/go-stack/stack v1.8.0/go.mod h1:v0f6uXyyMGvRgIKkXu+yp6POWl0qKG85gN/melR3HDY=
@@ -80,6 +87,7 @@ github.com/gogo/protobuf v1.2.1/go.mod h1:hp+jE20tsWTFYpLwKvXlhS1hjn+gTNwPg2I6zV
 github.com/golang/protobuf v1.2.0/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
 github.com/golang/protobuf v1.3.0/go.mod h1:Qd/q+1AKNOZr9uGQzbzCmRO6sUih6GTPZv6a1/R87v0=
 github.com/golang/protobuf v1.3.1/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
+github.com/golang/protobuf v1.3.2-0.20190517061210-b285ee9cfc6c h1:zqAKixg3cTcIasAMJV+EcfVbWwLpOZ7LeoWJvcuD/5Q=
 github.com/golang/protobuf v1.3.2-0.20190517061210-b285ee9cfc6c/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
 github.com/golang/snappy v0.0.0-20180518054509-2e65f85255db/go.mod h1:/XxbfmMg8lxefKM7IXC3fBNl/7bRcc72aCRzEWrmP2Q=
 github.com/golang/snappy v0.0.1 h1:Qgr9rKW7uDUkrbSmQeiDsGa8SjGyCOGtuasMWwvp2P4=
@@ -127,6 +135,7 @@ github.com/ipfs/go-ipfs-blockstore v0.0.1/go.mod h1:d3WClOmRQKFnJ0Jz/jj/zmksX0ma
 github.com/ipfs/go-ipfs-blockstore v0.1.4/go.mod h1:Jxm3XMVjh6R17WvxFEiyKBLUGr86HgIYJW/D/MwqeYQ=
 github.com/ipfs/go-ipfs-blockstore v1.0.0 h1:pmFp5sFYsYVvMOp9X01AK3s85usVcLvkBTRsN6SnfUA=
 github.com/ipfs/go-ipfs-blockstore v1.0.0/go.mod h1:knLVdhVU9L7CC4T+T4nvGdeUIPAXlnd9zmXfp+9MIjU=
+github.com/ipfs/go-ipfs-blocksutil v0.0.1 h1:Eh/H4pc1hsvhzsQoMEP3Bke/aW5P5rVM1IWFJMcGIPQ=
 github.com/ipfs/go-ipfs-blocksutil v0.0.1/go.mod h1:Yq4M86uIOmxmGPUHv/uI7uKqZNtLb449gwKqXjIsnRk=
 github.com/ipfs/go-ipfs-delay v0.0.0-20181109222059-70721b86a9a8/go.mod h1:8SP1YXK1M1kXuc4KJZINY3TQQ03J2rwBG9QfXmbRPrw=
 github.com/ipfs/go-ipfs-delay v0.0.1/go.mod h1:8SP1YXK1M1kXuc4KJZINY3TQQ03J2rwBG9QfXmbRPrw=
@@ -136,6 +145,7 @@ github.com/ipfs/go-ipfs-ds-help v1.0.0 h1:bEQ8hMGs80h0sR8O4tfDgV6B01aaF9qeTrujrT
 github.com/ipfs/go-ipfs-ds-help v1.0.0/go.mod h1:ujAbkeIgkKAWtxxNkoZHWLCyk5JpPoKnGyCcsoF6ueE=
 github.com/ipfs/go-ipfs-exchange-interface v0.0.1 h1:LJXIo9W7CAmugqI+uofioIpRb6rY30GUu7G6LUfpMvM=
 github.com/ipfs/go-ipfs-exchange-interface v0.0.1/go.mod h1:c8MwfHjtQjPoDyiy9cFquVtVHkO9b9Ob3FG91qJnWCM=
+github.com/ipfs/go-ipfs-exchange-offline v0.0.1 h1:P56jYKZF7lDDOLx5SotVh5KFxoY6C81I1NSHW1FxGew=
 github.com/ipfs/go-ipfs-exchange-offline v0.0.1/go.mod h1:WhHSFCVYX36H/anEKQboAzpUws3x7UeEGkzQc3iNkM0=
 github.com/ipfs/go-ipfs-pq v0.0.1/go.mod h1:LWIqQpqfRG3fNc5XsnIhz/wQ2XXGyugQwls7BgUmUfY=
 github.com/ipfs/go-ipfs-routing v0.1.0/go.mod h1:hYoUkJLyAUKhF58tysKpids8RNDPO42BVMgK5dNsoqY=
@@ -167,10 +177,14 @@ github.com/karalabe/usb v0.0.0-20190919080040-51dc0efba356/go.mod h1:Od972xHfMJo
 github.com/kisielk/errcheck v1.1.0/go.mod h1:EZBBE59ingxPouuu3KfxchcWSUPOHkagtvWXihfKN4Q=
 github.com/kisielk/gotool v1.0.0/go.mod h1:XhKaO+MFFWcvkIS/tQcRk01m1F5IRFswLeQ+oQHNcck=
 github.com/kkdai/bstream v0.0.0-20161212061736-f391b8402d23/go.mod h1:J+Gs4SYgM6CZQHDETBtE9HaSEkGmuNXF86RwHhHUvq4=
+github.com/konsorten/go-windows-terminal-sequences v1.0.3 h1:CE8S1cTafDpPvMhIxNJKvHsGVBgn1xWYf1NbHQhywc8=
+github.com/konsorten/go-windows-terminal-sequences v1.0.3/go.mod h1:T0+1ngSBFLxvqU3pZ+m/2kptfBszLMUkC4ZK/EgS/cQ=
 github.com/koron/go-ssdp v0.0.0-20180514024734-4a0ed625a78b/go.mod h1:5Ky9EC2xfoUKUor0Hjgi2BJhCSXJfMOFlmyYrVKGQMk=
 github.com/kr/logfmt v0.0.0-20140226030751-b84e30acd515/go.mod h1:+0opPa2QZZtGFBFZlji/RkVcI2GknAs/DXo4wKdlNEc=
+github.com/kr/pretty v0.1.0 h1:L/CwN0zerZDmRFUapSPitk6f+Q3+0za1rQkzVuMiMFI=
 github.com/kr/pretty v0.1.0/go.mod h1:dAy3ld7l9f0ibDNOQOHHMYYIIbhfbHSm3C4ZsoJORNo=
 github.com/kr/pty v1.1.1/go.mod h1:pFQYn66WHrOpPYNljwOMqo10TkYh1fy3cYio2l3bCsQ=
+github.com/kr/text v0.1.0 h1:45sCR5RtlFHMR4UwH9sdQ5TC8v0qDQCHnXt+kaKSTVE=
 github.com/kr/text v0.1.0/go.mod h1:4Jbv+DJW3UT/LiOwJeYQe1efqtUx/iVham/4vfdArNI=
 github.com/kylelemons/godebug v1.1.0/go.mod h1:9/0rRGxNHcop5bhtWyNeEfOS8JIWk580+fNqagV/RAw=
 github.com/lib/pq v1.0.0 h1:X5PMW56eZitiTeO7tKzZxFCSpbFZJtkMMooicw2us9A=
@@ -219,6 +233,8 @@ github.com/libp2p/go-tcp-transport v0.1.0/go.mod h1:oJ8I5VXryj493DEJ7OsBieu8fcg2
 github.com/libp2p/go-ws-transport v0.1.0/go.mod h1:rjw1MG1LU9YDC6gzmwObkPd/Sqwhw7yT74kj3raBFuo=
 github.com/libp2p/go-yamux v1.2.2/go.mod h1:FGTiPvoV/3DVdgWpX+tM0OW3tsM+W5bSE3gZwqQTcow=
 github.com/libp2p/go-yamux v1.2.3/go.mod h1:FGTiPvoV/3DVdgWpX+tM0OW3tsM+W5bSE3gZwqQTcow=
+github.com/mailgun/groupcache/v2 v2.2.1 h1:OalhvLqdhiHd76CU8gn+w6UqeEa1m60ChrVwwKkmqh4=
+github.com/mailgun/groupcache/v2 v2.2.1/go.mod h1:fgFJNRQar4yVloM0SzqWhOuTF83HCO5DDXVnZQVVJ58=
 github.com/mattn/go-colorable v0.1.0/go.mod h1:9vuHe8Xs5qXnSaW/c/ABM9alt+Vo+STaOChaDxuIBZU=
 github.com/mattn/go-colorable v0.1.1/go.mod h1:FuOcm+DKB9mbwrcAfNl7/TZVBZ6rcnceauSikq3lYCQ=
 github.com/mattn/go-colorable v0.1.2 h1:/bC9yWikZXAL9uJdulbSfyVNIR3n3trXl+v8+1sx8mU=
@@ -231,6 +247,7 @@ github.com/mattn/go-isatty v0.0.8 h1:HLtExJ+uU2HOZ+wI0Tt5DtUDrx8yhUqDcp7fYERX4CE
 github.com/mattn/go-isatty v0.0.8/go.mod h1:Iq45c/XA43vh69/j3iqttzPXn0bhXyGjM0Hdxcsrc5s=
 github.com/mattn/go-runewidth v0.0.3/go.mod h1:LwmH8dsx7+W8Uxz3IHJYH5QSwggIsqBzpuz5H//U1FU=
 github.com/mattn/go-runewidth v0.0.4/go.mod h1:LwmH8dsx7+W8Uxz3IHJYH5QSwggIsqBzpuz5H//U1FU=
+github.com/mattn/go-sqlite3 v1.9.0 h1:pDRiWfl+++eC2FEFRy6jXmQlvp4Yh3z1MJKg4UeYM/4=
 github.com/mattn/go-sqlite3 v1.9.0/go.mod h1:FPy6KqzDD04eiIsT53CuJW3U88zkxoIYsOqkbpncsNc=
 github.com/matttproud/golang_protobuf_extensions v1.0.1/go.mod h1:D8He9yQNgCq6Z5Ld7szi9bcBfOoFv/3dc6xSMkL2PC0=
 github.com/miekg/dns v1.1.12/go.mod h1:W1PPwlIAgtquWBMBEV9nkV9Cazfe8ScdGz/Lj7v3Nrg=
@@ -284,6 +301,7 @@ github.com/pborman/uuid v0.0.0-20170112150404-1b00554d8222/go.mod h1:VyrYX9gd7ir
 github.com/peterh/liner v1.1.1-0.20190123174540-a2c9a5303de7/go.mod h1:CRroGNssyjTd/qIG2FyxByd2S8JEAZXBl4qUrZf8GS0=
 github.com/pkg/errors v0.8.0/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
 github.com/pkg/errors v0.8.1/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=
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@@ -294,9 +312,13 @@ github.com/rjeczalik/notify v0.9.1/go.mod h1:rKwnCoCGeuQnwBtTSPL9Dad03Vh2n40ePRr
 github.com/rs/cors v0.0.0-20160617231935-a62a804a8a00/go.mod h1:gFx+x8UowdsKA9AchylcLynDq+nNFfI8FkUZdN/jGCU=
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+github.com/segmentio/fasthash v1.0.3 h1:EI9+KE1EwvMLBWwjpRDc+fEM+prwxDYbslddQGtrmhM=
+github.com/segmentio/fasthash v1.0.3/go.mod h1:waKX8l2N8yckOgmSsXJi7x1ZfdKZ4x7KRMzBtS3oedY=
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+github.com/sirupsen/logrus v1.6.0 h1:UBcNElsrwanuuMsnGSlYmtmgbb23qDR5dG+6X6Oo89I=
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 github.com/spacemonkeygo/openssl v0.0.0-20181017203307-c2dcc5cca94a/go.mod h1:7AyxJNCJ7SBZ1MfVQCWD6Uqo2oubI2Eq2y2eqf+A5r0=
 github.com/spacemonkeygo/spacelog v0.0.0-20180420211403-2296661a0572/go.mod h1:w0SWMsp6j9O/dk4/ZpIhL+3CkG8ofA2vuv7k+ltqUMc=
 github.com/spaolacci/murmur3 v0.0.0-20180118202830-f09979ecbc72/go.mod h1:JwIasOWyU6f++ZhiEuf87xNszmSA2myDM2Kzu9HwQUA=
@@ -310,8 +332,10 @@ github.com/steakknife/hamming v0.0.0-20180906055917-c99c65617cd3/go.mod h1:hpGUW
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/testify v1.2.2/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=
 github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
+github.com/stretchr/testify v1.4.0 h1:2E4SXV/wtOkTonXsotYi4li6zVWxYlZuYNCXe9XRJyk=
 github.com/stretchr/testify v1.4.0/go.mod h1:j7eGeouHqKxXV5pUuKE4zz7dFj8WfuZ+81PSLYec5m4=
 github.com/syndtr/goleveldb v1.0.0/go.mod h1:ZVVdQEZoIme9iO1Ch2Jdy24qqXrMMOU6lpPAyBWyWuQ=
+github.com/syndtr/goleveldb v1.0.1-0.20190923125748-758128399b1d h1:gZZadD8H+fF+n9CmNhYL1Y0dJB+kLOmKd7FbPJLeGHs=
 github.com/syndtr/goleveldb v1.0.1-0.20190923125748-758128399b1d/go.mod h1:9OrXJhf154huy1nPWmuSrkgjPUtUNhA+Zmy+6AESzuA=
 github.com/tyler-smith/go-bip39 v1.0.1-0.20181017060643-dbb3b84ba2ef/go.mod h1:sJ5fKU0s6JVwZjjcUEX2zFOnvq0ASQ2K9Zr6cf67kNs=
 github.com/urfave/cli v1.22.1/go.mod h1:Gos4lmkARVdJ6EkW0WaNv/tZAAMe9V7XWyB60NtXRu0=
@@ -337,6 +361,7 @@ golang.org/x/net v0.0.0-20180906233101-161cd47e91fd/go.mod h1:mL1N/T3taQHkDXs73r
 golang.org/x/net v0.0.0-20181011144130-49bb7cea24b1/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
 golang.org/x/net v0.0.0-20190227160552-c95aed5357e7/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
 golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
+golang.org/x/net v0.0.0-20190603091049-60506f45cf65/go.mod h1:HSz+uSET+XFnRR8LxR5pz3Of3rY3CfYBVs4xY44aLks=
 golang.org/x/net v0.0.0-20190611141213-3f473d35a33a/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
 golang.org/x/net v0.0.0-20200425230154-ff2c4b7c35a0 h1:Jcxah/M+oLZ/R4/z5RzfPzGbPXnVDPkEDtf2JnuxN+U=
 golang.org/x/net v0.0.0-20200425230154-ff2c4b7c35a0/go.mod h1:qpuaurCH72eLCgpAm/N6yyVIVM9cpaDIP3A8BGJEC5A=
@@ -349,6 +374,7 @@ golang.org/x/sys v0.0.0-20190219092855-153ac476189d/go.mod h1:STP8DvDyc/dI5b8T5h
 golang.org/x/sys v0.0.0-20190222072716-a9d3bda3a223/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190228124157-a34e9553db1e/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20190422165155-953cdadca894/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20190610200419-93c9922d18ae/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200323222414-85ca7c5b95cd h1:xhmwyvizuTgC2qz7ZlMluP20uW+C3Rm0FD/WLDX8884=
 golang.org/x/sys v0.0.0-20200323222414-85ca7c5b95cd/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
@@ -359,10 +385,13 @@ golang.org/x/time v0.0.0-20190308202827-9d24e82272b4/go.mod h1:tRJNPiyCQ0inRvYxb
 golang.org/x/tools v0.0.0-20180221164845-07fd8470d635/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
 golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
 golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
+google.golang.org/appengine v1.6.7 h1:FZR1q0exgwxzPzp/aF+VccGrSfxfPpkBqjIIEq3ru6c=
+google.golang.org/appengine v1.6.7/go.mod h1:8WjMMxjGQR8xUklV/ARdw2HLXBOI7O7uCIDZVag1xfc=
 google.golang.org/genproto v0.0.0-20180831171423-11092d34479b/go.mod h1:JiN7NxoALGmiZfu7CAH4rXhgtRTLTxftemlI0sWmxmc=
 gopkg.in/alecthomas/kingpin.v2 v2.2.6/go.mod h1:FMv+mEhP44yOT+4EoQTLFTRgOQ1FBLkstjWtayDeSgw=
 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 v1.0.0-20190902080502-41f04d3bba15 h1:YR8cESwS4TdDjEe65xsg0ogRM/Nc3DYOhEAlW+xobZo=
 gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/fsnotify.v1 v1.4.7 h1:xOHLXZwVvI9hhs+cLKq5+I5onOuwQLhQwiu63xxlHs4=
 gopkg.in/fsnotify.v1 v1.4.7/go.mod h1:Tz8NjZHkW78fSQdbUxIjBTcgA1z1m8ZHf0WmKUhAMys=

postgres/batch_test.go

@@ -18,6 +18,7 @@ package pgipfsethdb_test
 
 import (
 	"math/big"
+	"time"
 
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/ethdb"
@@ -39,7 +40,14 @@ var _ = Describe("Batch", func() {
 	BeforeEach(func() {
 		db, err = pgipfsethdb.TestDB()
 		Expect(err).ToNot(HaveOccurred())
-		database = pgipfsethdb.NewDatabase(db)
+
+		cacheConfig := pgipfsethdb.CacheConfig{
+			Name:           "db",
+			Size:           3000000, // 3MB
+			ExpiryDuration: time.Hour,
+		}
+
+		database = pgipfsethdb.NewDatabase(db, cacheConfig)
 		batch = database.NewBatch()
 	})
 	AfterEach(func() {

postgres/database.go

@@ -17,12 +17,15 @@
 package pgipfsethdb
 
 import (
+	"context"
 	"errors"
 	"fmt"
 	"strings"
+	"time"
 
 	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/jmoiron/sqlx"
+	"github.com/mailgun/groupcache/v2"
 )
 
 var errNotSupported = errors.New("this operation is not supported")
@@ -38,20 +41,52 @@ var (
 // Database is the type that satisfies the ethdb.Database and ethdb.KeyValueStore interfaces for PG-IPFS Ethereum data using a direct Postgres connection
 type Database struct {
 	db    *sqlx.DB
+	cache *groupcache.Group
+}
+
+type CacheConfig struct {
+	Name           string
+	Size           int
+	ExpiryDuration time.Duration
 }
 
 // NewKeyValueStore returns a ethdb.KeyValueStore interface for PG-IPFS
-func NewKeyValueStore(db *sqlx.DB) ethdb.KeyValueStore {
+func NewKeyValueStore(db *sqlx.DB, cacheConfig CacheConfig) ethdb.KeyValueStore {
-	return &Database{
+	database := Database{db: db}
-		db: db,
+	database.InitCache(cacheConfig)
-	}
+
+	return &database
 }
 
 // NewDatabase returns a ethdb.Database interface for PG-IPFS
-func NewDatabase(db *sqlx.DB) ethdb.Database {
+func NewDatabase(db *sqlx.DB, cacheConfig CacheConfig) *Database {
-	return &Database{
+	database := Database{db: db}
-		db: db,
+	database.InitCache(cacheConfig)
+
+	return &database
+}
+
+func (d *Database) InitCache(cacheConfig CacheConfig) {
+	d.cache = groupcache.NewGroup(cacheConfig.Name, int64(cacheConfig.Size), groupcache.GetterFunc(
+		func(_ context.Context, id string, dest groupcache.Sink) error {
+			val, err := d.dbGet(id)
+
+			if err != nil {
+				return err
 			}
+
+			// Set the value in the groupcache, with expiry
+			if err := dest.SetBytes(val, time.Now().Add(cacheConfig.ExpiryDuration)); err != nil {
+				return err
+			}
+
+			return nil
+		},
+	))
+}
+
+func (d *Database) GetCacheStats() groupcache.Stats {
+	return d.cache.Stats
 }
 
 // Has satisfies the ethdb.KeyValueReader interface
@@ -65,6 +100,12 @@ func (d *Database) Has(key []byte) (bool, error) {
 	return exists, d.db.Get(&exists, hasPgStr, mhKey)
 }
 
+// Get retrieves the given key if it's present in the key-value data store
+func (d *Database) dbGet(key string) ([]byte, error) {
+	var data []byte
+	return data, d.db.Get(&data, getPgStr, key)
+}
+
 // Get satisfies the ethdb.KeyValueReader interface
 // Get retrieves the given key if it's present in the key-value data store
 func (d *Database) Get(key []byte) ([]byte, error) {
@@ -72,8 +113,12 @@ func (d *Database) Get(key []byte) ([]byte, error) {
 	if err != nil {
 		return nil, err
 	}
+
+	ctx, cancel := context.WithTimeout(context.Background(), time.Millisecond*500)
+	defer cancel()
+
 	var data []byte
-	return data, d.db.Get(&data, getPgStr, mhKey)
+	return data, d.cache.Get(ctx, mhKey, groupcache.AllocatingByteSliceSink(&data))
 }
 
 // Put satisfies the ethdb.KeyValueWriter interface
@@ -95,7 +140,17 @@ func (d *Database) Delete(key []byte) error {
 	if err != nil {
 		return err
 	}
+
 	_, err = d.db.Exec(deletePgStr, mhKey)
+	if err != nil {
+		return err
+	}
+
+	// Remove from cache.
+	ctx, cancel := context.WithTimeout(context.Background(), time.Millisecond*500)
+	defer cancel()
+	err = d.cache.Remove(ctx, mhKey)
+
 	return err
 }
 

postgres/database_test.go

@@ -18,6 +18,7 @@ package pgipfsethdb_test
 
 import (
 	"math/big"
+	"time"
 
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/ethdb"
@@ -43,7 +44,14 @@ var _ = Describe("Database", func() {
 	BeforeEach(func() {
 		db, err = pgipfsethdb.TestDB()
 		Expect(err).ToNot(HaveOccurred())
-		database = pgipfsethdb.NewDatabase(db)
+
+		cacheConfig := pgipfsethdb.CacheConfig{
+			Name:           "db",
+			Size:           3000000, // 3MB
+			ExpiryDuration: time.Hour,
+		}
+
+		database = pgipfsethdb.NewDatabase(db, cacheConfig)
 	})
 	AfterEach(func() {
 		err = pgipfsethdb.ResetTestDB(db)