diff --git a/server/Cargo.lock b/server/Cargo.lock
index 78e3aae..7c6678e 100644
--- a/server/Cargo.lock
+++ b/server/Cargo.lock
@@ -5,7 +5,7 @@ name = "MacTypes-sys"
 version = "2.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "libc 0.2.50 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -39,7 +39,7 @@ name = "atty"
 version = "0.2.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "libc 0.2.50 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
  "termion 1.5.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -57,7 +57,7 @@ dependencies = [
  "autocfg 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "backtrace-sys 0.1.28 (registry+https://github.com/rust-lang/crates.io-index)",
  "cfg-if 0.1.7 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.50 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc-demangle 0.1.13 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -68,7 +68,7 @@ version = "0.1.28"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "cc 1.0.35 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.50 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -179,6 +179,8 @@ dependencies = [
  "parking_lot 0.7.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "postgres 0.15.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "primitives 0.4.0 (git+https://github.com/CodeChain-io/rust-codechain-primitives.git)",
+ "r2d2 0.8.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "r2d2_postgres 0.14.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand 0.5.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "regex 1.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "sendgrid 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -237,7 +239,7 @@ version = "0.5.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "core-foundation-sys 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.50 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -245,7 +247,7 @@ name = "core-foundation-sys"
 version = "0.5.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "libc 0.2.50 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -450,7 +452,7 @@ version = "1.0.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "crc32fast 1.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.50 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
  "miniz_oxide_c_api 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -657,7 +659,7 @@ name = "iovec"
 version = "0.1.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "libc 0.2.50 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -719,7 +721,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "libc"
-version = "0.2.50"
+version = "0.2.65"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
@@ -731,6 +733,14 @@ dependencies = [
  "scopeguard 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "lock_api"
+version = "0.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "scopeguard 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "log"
 version = "0.3.9"
@@ -762,7 +772,7 @@ name = "memchr"
 version = "1.0.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "libc 0.2.50 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -828,7 +838,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "cc 1.0.35 (registry+https://github.com/rust-lang/crates.io-index)",
  "crc 1.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.50 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
  "miniz_oxide 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -842,7 +852,7 @@ dependencies = [
  "iovec 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "kernel32-sys 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "lazycell 1.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.50 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "miow 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "net2 0.2.33 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -883,7 +893,7 @@ version = "0.2.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "lazy_static 1.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.50 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "openssl 0.10.20 (registry+https://github.com/rust-lang/crates.io-index)",
  "openssl-probe 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -900,7 +910,7 @@ version = "0.2.33"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "cfg-if 0.1.7 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.50 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -927,7 +937,7 @@ name = "num_cpus"
 version = "1.10.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "libc 0.2.50 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -939,7 +949,7 @@ dependencies = [
  "cfg-if 0.1.7 (registry+https://github.com/rust-lang/crates.io-index)",
  "foreign-types 0.3.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "lazy_static 1.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.50 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
  "openssl-sys 0.9.43 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -954,7 +964,7 @@ version = "0.9.43"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "cc 1.0.35 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.50 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
  "pkg-config 0.3.14 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc_version 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "vcpkg 0.2.6 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -977,18 +987,42 @@ dependencies = [
  "parking_lot_core 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "parking_lot"
+version = "0.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "lock_api 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parking_lot_core 0.6.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rustc_version 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "parking_lot_core"
 version = "0.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "libc 0.2.50 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand 0.6.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc_version 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "smallvec 0.6.9 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "parking_lot_core"
+version = "0.6.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "cfg-if 0.1.7 (registry+https://github.com/rust-lang/crates.io-index)",
+ "cloudabi 0.0.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
+ "redox_syscall 0.1.51 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rustc_version 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "smallvec 0.6.9 (registry+https://github.com/rust-lang/crates.io-index)",
+ "winapi 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "percent-encoding"
 version = "1.0.1"
@@ -1126,12 +1160,32 @@ dependencies = [
  "proc-macro2 0.4.27 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "r2d2"
+version = "0.8.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "log 0.4.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parking_lot 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "scheduled-thread-pool 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "r2d2_postgres"
+version = "0.14.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "postgres 0.15.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "postgres-shared 0.4.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "r2d2 0.8.6 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "rand"
 version = "0.3.23"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "libc 0.2.50 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand 0.4.6 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -1141,7 +1195,7 @@ version = "0.4.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "fuchsia-cprng 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.50 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand_core 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "rdrand 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1154,7 +1208,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "cloudabi 0.0.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "fuchsia-cprng 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.50 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand_core 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -1165,7 +1219,7 @@ version = "0.6.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "autocfg 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.50 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand_chacha 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand_core 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand_hc 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1220,7 +1274,7 @@ name = "rand_jitter"
 version = "0.1.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "libc 0.2.50 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand_core 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -1232,7 +1286,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "cloudabi 0.0.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "fuchsia-cprng 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.50 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand_core 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "rdrand 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1378,11 +1432,24 @@ dependencies = [
  "winapi 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "scheduled-thread-pool"
+version = "0.2.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "parking_lot 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "scopeguard"
 version = "0.3.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "scopeguard"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
 [[package]]
 name = "security-framework"
 version = "0.2.2"
@@ -1390,7 +1457,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "core-foundation 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "core-foundation-sys 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.50 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
  "security-framework-sys 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -1401,7 +1468,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "MacTypes-sys 2.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "core-foundation-sys 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.50 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -1520,7 +1587,7 @@ version = "0.3.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "cfg-if 0.1.7 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.50 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
  "redox_syscall 0.1.51 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -1571,7 +1638,7 @@ version = "3.0.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "cfg-if 0.1.7 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.50 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand 0.6.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "redox_syscall 0.1.51 (registry+https://github.com/rust-lang/crates.io-index)",
  "remove_dir_all 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1591,7 +1658,7 @@ name = "termion"
 version = "1.5.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "libc 0.2.50 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
  "redox_syscall 0.1.51 (registry+https://github.com/rust-lang/crates.io-index)",
  "redox_termios 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -1609,7 +1676,7 @@ name = "time"
 version = "0.1.42"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "libc 0.2.50 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
  "redox_syscall 0.1.51 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -2048,8 +2115,9 @@ dependencies = [
 "checksum language-tags 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)" = "a91d884b6667cd606bb5a69aa0c99ba811a115fc68915e7056ec08a46e93199a"
 "checksum lazy_static 1.3.0 (registry+https://github.com/rust-lang/crates.io-index)" = "bc5729f27f159ddd61f4df6228e827e86643d4d3e7c32183cb30a1c08f604a14"
 "checksum lazycell 1.2.1 (registry+https://github.com/rust-lang/crates.io-index)" = "b294d6fa9ee409a054354afc4352b0b9ef7ca222c69b8812cbea9e7d2bf3783f"
-"checksum libc 0.2.50 (registry+https://github.com/rust-lang/crates.io-index)" = "aab692d7759f5cd8c859e169db98ae5b52c924add2af5fbbca11d12fefb567c1"
+"checksum libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)" = "1a31a0627fdf1f6a39ec0dd577e101440b7db22672c0901fe00a9a6fbb5c24e8"
 "checksum lock_api 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)" = "62ebf1391f6acad60e5c8b43706dde4582df75c06698ab44511d15016bc2442c"
+"checksum lock_api 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)" = "f8912e782533a93a167888781b836336a6ca5da6175c05944c86cf28c31104dc"
 "checksum log 0.3.9 (registry+https://github.com/rust-lang/crates.io-index)" = "e19e8d5c34a3e0e2223db8e060f9e8264aeeb5c5fc64a4ee9965c062211c024b"
 "checksum log 0.4.6 (registry+https://github.com/rust-lang/crates.io-index)" = "c84ec4b527950aa83a329754b01dbe3f58361d1c5efacd1f6d68c494d08a17c6"
 "checksum matches 0.1.8 (registry+https://github.com/rust-lang/crates.io-index)" = "7ffc5c5338469d4d3ea17d269fa8ea3512ad247247c30bd2df69e68309ed0a08"
@@ -2078,7 +2146,9 @@ dependencies = [
 "checksum openssl-sys 0.9.43 (registry+https://github.com/rust-lang/crates.io-index)" = "33c86834957dd5b915623e94f2f4ab2c70dd8f6b70679824155d5ae21dbd495d"
 "checksum owning_ref 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "49a4b8ea2179e6a2e27411d3bca09ca6dd630821cf6894c6c7c8467a8ee7ef13"
 "checksum parking_lot 0.7.1 (registry+https://github.com/rust-lang/crates.io-index)" = "ab41b4aed082705d1056416ae4468b6ea99d52599ecf3169b00088d43113e337"
+"checksum parking_lot 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)" = "f842b1982eb6c2fe34036a4fbfb06dd185a3f5c8edfaacdf7d1ea10b07de6252"
 "checksum parking_lot_core 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "94c8c7923936b28d546dfd14d4472eaf34c99b14e1c973a32b3e6d4eb04298c9"
+"checksum parking_lot_core 0.6.2 (registry+https://github.com/rust-lang/crates.io-index)" = "b876b1b9e7ac6e1a74a6da34d25c42e17e8862aa409cbbbdcfc8d86c6f3bc62b"
 "checksum percent-encoding 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)" = "31010dd2e1ac33d5b46a5b413495239882813e0369f8ed8a5e266f173602f831"
 "checksum phf 0.7.24 (registry+https://github.com/rust-lang/crates.io-index)" = "b3da44b85f8e8dfaec21adae67f95d93244b2ecf6ad2a692320598dcc8e6dd18"
 "checksum phf_codegen 0.7.24 (registry+https://github.com/rust-lang/crates.io-index)" = "b03e85129e324ad4166b06b2c7491ae27fe3ec353af72e72cd1654c7225d517e"
@@ -2094,6 +2164,8 @@ dependencies = [
 "checksum publicsuffix 1.5.2 (registry+https://github.com/rust-lang/crates.io-index)" = "5afecba86dcf1e4fd610246f89899d1924fe12e1e89f555eb7c7f710f3c5ad1d"
 "checksum quick-error 1.2.2 (registry+https://github.com/rust-lang/crates.io-index)" = "9274b940887ce9addde99c4eee6b5c44cc494b182b97e73dc8ffdcb3397fd3f0"
 "checksum quote 0.6.11 (registry+https://github.com/rust-lang/crates.io-index)" = "cdd8e04bd9c52e0342b406469d494fcb033be4bdbe5c606016defbb1681411e1"
+"checksum r2d2 0.8.6 (registry+https://github.com/rust-lang/crates.io-index)" = "e48fa64898ef0286b6ee4b4d8f61483f9182acf5e44e62a398b1c7f56f2f861d"
+"checksum r2d2_postgres 0.14.0 (registry+https://github.com/rust-lang/crates.io-index)" = "78c7fe9c0c3d2c298cf262bc3ce4b89cdf0eab620fd9fe759f65b34a1a00fb93"
 "checksum rand 0.3.23 (registry+https://github.com/rust-lang/crates.io-index)" = "64ac302d8f83c0c1974bf758f6b041c6c8ada916fbb44a609158ca8b064cc76c"
 "checksum rand 0.4.6 (registry+https://github.com/rust-lang/crates.io-index)" = "552840b97013b1a26992c11eac34bdd778e464601a4c2054b5f0bff7c6761293"
 "checksum rand 0.5.6 (registry+https://github.com/rust-lang/crates.io-index)" = "c618c47cd3ebd209790115ab837de41425723956ad3ce2e6a7f09890947cacb9"
@@ -2121,7 +2193,9 @@ dependencies = [
 "checksum safemem 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "e27a8b19b835f7aea908818e871f5cc3a5a186550c30773be987e155e8163d8f"
 "checksum safemem 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)" = "8dca453248a96cb0749e36ccdfe2b0b4e54a61bfef89fb97ec621eb8e0a93dd9"
 "checksum schannel 0.1.15 (registry+https://github.com/rust-lang/crates.io-index)" = "f2f6abf258d99c3c1c5c2131d99d064e94b7b3dd5f416483057f308fea253339"
+"checksum scheduled-thread-pool 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)" = "bd07742e081ff6c077f5f6b283f12f32b9e7cc765b316160d66289b74546fbb3"
 "checksum scopeguard 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)" = "94258f53601af11e6a49f722422f6e3425c52b06245a5cf9bc09908b174f5e27"
+"checksum scopeguard 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)" = "b42e15e59b18a828bbf5c58ea01debb36b9b096346de35d941dcb89009f24a0d"
 "checksum security-framework 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)" = "bfab8dda0e7a327c696d893df9ffa19cadc4bd195797997f5223cf5831beaf05"
 "checksum security-framework-sys 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)" = "3d6696852716b589dff9e886ff83778bb635150168e83afa8ac6b8a78cb82abc"
 "checksum semver 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)" = "1d7eb9ef2c18661902cc47e535f9bc51b78acd254da71d375c2f6720d9a40403"
diff --git a/server/Cargo.toml b/server/Cargo.toml
index 02ae2b6..94a5404 100644
--- a/server/Cargo.toml
+++ b/server/Cargo.toml
@@ -24,3 +24,5 @@ serde_json = "1.0"
 slack-hook = "0.8.0"
 time = "0.1"
 ws = "*"
+r2d2_postgres = "0.14.0"
+r2d2 = "0.8.6"
diff --git a/server/src/db/queries/client_extra.rs b/server/src/db/queries/client_extra.rs
index 69d7b8b..6a63783 100644
--- a/server/src/db/queries/client_extra.rs
+++ b/server/src/db/queries/client_extra.rs
@@ -1,8 +1,7 @@
-use postgres;
-
+use super::super::types::DBConnection;
 use super::super::ClientExtra;
 
-pub fn get(conn: &postgres::Connection, node_name: &str) -> postgres::Result<Option<ClientExtra>> {
+pub fn get(conn: &DBConnection, node_name: &str) -> postgres::Result<Option<ClientExtra>> {
     ctrace!("Query client extra by name {}", node_name);
 
     let rows = conn.query("SELECT * FROM client_extra WHERE name=$1;", &[&node_name])?;
@@ -16,7 +15,7 @@ pub fn get(conn: &postgres::Connection, node_name: &str) -> postgres::Result<Opt
     }))
 }
 
-pub fn upsert(conn: &postgres::Connection, node_name: &str, client_extra: &ClientExtra) -> postgres::Result<()> {
+pub fn upsert(conn: &DBConnection, node_name: &str, client_extra: &ClientExtra) -> postgres::Result<()> {
     ctrace!("Upsert client extra {:?}", client_extra);
     let result = conn.execute(
         "INSERT INTO client_extra (name, prev_env, prev_args) VALUES ($1, $2, $3) \
diff --git a/server/src/db/queries/config.rs b/server/src/db/queries/config.rs
index 4ae41be..4ae6470 100644
--- a/server/src/db/queries/config.rs
+++ b/server/src/db/queries/config.rs
@@ -1,6 +1,6 @@
-use postgres;
+use super::super::types::DBConnection;
 
-pub fn set_query_timeout(conn: &postgres::Connection) -> postgres::Result<()> {
+pub fn set_query_timeout(conn: &DBConnection) -> postgres::Result<()> {
     conn.execute("SET SESSION statement_timeout TO 2000", &[])?;
     Ok(())
 }
diff --git a/server/src/db/queries/logs.rs b/server/src/db/queries/logs.rs
index 809e5bd..d371263 100644
--- a/server/src/db/queries/logs.rs
+++ b/server/src/db/queries/logs.rs
@@ -6,10 +6,11 @@ use postgres;
 use postgres::types::ToSql;
 
 use super::super::super::common_rpc_types::StructuredLog;
+use super::super::types::DBConnection;
 use super::super::types::OrderBy;
 use super::super::types::{Log, LogQueryParams};
 
-pub fn insert(conn: &postgres::Connection, node_name: &str, logs: Vec<StructuredLog>) -> postgres::Result<()> {
+pub fn insert(conn: &DBConnection, node_name: &str, logs: Vec<StructuredLog>) -> postgres::Result<()> {
     ctrace!("Add log {} : {:?}", node_name, logs);
 
     if logs.is_empty() {
@@ -53,7 +54,7 @@ pub fn insert(conn: &postgres::Connection, node_name: &str, logs: Vec<Structured
     Ok(())
 }
 
-pub fn search(conn: &postgres::Connection, params: LogQueryParams) -> postgres::Result<Vec<Log>> {
+pub fn search(conn: &DBConnection, params: LogQueryParams) -> postgres::Result<Vec<Log>> {
     ctrace!("Search log with {:?}", params);
     let mut parameters = Parameters::default();
     let mut where_conditions = Vec::new();
@@ -145,7 +146,7 @@ impl Parameters {
     }
 }
 
-pub fn get_targets(conn: &postgres::Connection) -> postgres::Result<Vec<String>> {
+pub fn get_targets(conn: &DBConnection) -> postgres::Result<Vec<String>> {
     ctrace!("Query targets");
 
     //    let rows = conn.query("SELECT DISTINCT target FROM logs", &[])?;
diff --git a/server/src/db/queries/network_usage.rs b/server/src/db/queries/network_usage.rs
index 6ba8d4b..d4789d4 100644
--- a/server/src/db/queries/network_usage.rs
+++ b/server/src/db/queries/network_usage.rs
@@ -2,11 +2,12 @@ use chrono;
 use postgres;
 use regex::{Captures, Regex};
 
+use super::super::types::DBConnection;
 use common_rpc_types::NetworkUsage;
 use util::{floor_to_5min, start_of_day, start_of_hour};
 
 pub fn insert(
-    conn: &postgres::Connection,
+    conn: &DBConnection,
     node_name: &str,
     network_usage: NetworkUsage,
     time: chrono::DateTime<chrono::Utc>,
diff --git a/server/src/db/queries/network_usage_graph.rs b/server/src/db/queries/network_usage_graph.rs
index 28bc346..a2785a1 100644
--- a/server/src/db/queries/network_usage_graph.rs
+++ b/server/src/db/queries/network_usage_graph.rs
@@ -4,8 +4,10 @@ use common_rpc_types::{
 };
 use postgres;
 
+use super::super::types::DBConnection;
+
 pub fn query_network_out_all(
-    conn: &postgres::Connection,
+    conn: &DBConnection,
     graph_args: GraphCommonArgs,
 ) -> postgres::Result<Vec<GraphNetworkOutAllRow>> {
     let time_column_name = get_sql_column_name_by_period(graph_args.period);
@@ -38,7 +40,7 @@ fn get_sql_column_name_by_period(period: GraphPeriod) -> &'static str {
 }
 
 pub fn query_network_out_all_avg(
-    conn: &postgres::Connection,
+    conn: &DBConnection,
     graph_args: GraphCommonArgs,
 ) -> postgres::Result<Vec<GraphNetworkOutAllRow>> {
     let time_column_name = get_sql_column_name_by_period(graph_args.period);
@@ -63,7 +65,7 @@ pub fn query_network_out_all_avg(
 }
 
 pub fn query_network_out_node_extension(
-    conn: &postgres::Connection,
+    conn: &DBConnection,
     node_name: NodeName,
     graph_args: GraphCommonArgs,
 ) -> postgres::Result<Vec<GraphNetworkOutNodeExtensionRow>> {
@@ -90,7 +92,7 @@ pub fn query_network_out_node_extension(
 }
 
 pub fn query_network_out_node_peer(
-    conn: &postgres::Connection,
+    conn: &DBConnection,
     node_name: NodeName,
     graph_args: GraphCommonArgs,
 ) -> postgres::Result<Vec<GraphNetworkOutNodePeerRow>> {
diff --git a/server/src/db/queries/peer_count.rs b/server/src/db/queries/peer_count.rs
index cbf4794..ad2292e 100644
--- a/server/src/db/queries/peer_count.rs
+++ b/server/src/db/queries/peer_count.rs
@@ -1,8 +1,10 @@
 use chrono;
 use postgres;
 
+use super::super::types::DBConnection;
+
 pub fn insert(
-    conn: &postgres::Connection,
+    conn: &DBConnection,
     node_name: &str,
     peer_count: i32,
     time: chrono::DateTime<chrono::Utc>,
diff --git a/server/src/db/service.rs b/server/src/db/service.rs
index 87f6c56..321424b 100644
--- a/server/src/db/service.rs
+++ b/server/src/db/service.rs
@@ -5,8 +5,7 @@ use std::net::SocketAddr;
 use std::sync::mpsc::{channel, Sender};
 use std::thread;
 
-use postgres;
-use postgres::TlsMode;
+use r2d2_postgres::PostgresConnectionManager;
 
 use super::super::common_rpc_types as rpc_type;
 use super::super::common_rpc_types::{NodeName, NodeStatus, StructuredLog};
@@ -17,6 +16,7 @@ use common_rpc_types::{
     GraphCommonArgs, GraphNetworkOutAllAVGRow, GraphNetworkOutAllRow, GraphNetworkOutNodeExtensionRow,
     GraphNetworkOutNodePeerRow, NetworkUsage,
 };
+use db::types::DBConnection;
 use util;
 
 #[derive(Debug, Clone)]
@@ -58,7 +58,7 @@ struct State {
 pub struct Service {
     state: State,
     event_subscriber: Box<dyn EventSubscriber>,
-    db_conn: postgres::Connection,
+    pool: r2d2::Pool<PostgresConnectionManager>,
 }
 
 pub struct ServiceNewArg {
@@ -75,15 +75,20 @@ impl Service {
             db_password,
         }: ServiceNewArg,
     ) -> Self {
-        let conn_uri = format!("postgres://{}:{}@localhost", db_user, db_password);
+        let manager = PostgresConnectionManager::new(
+            format!("postgres://{}:{}@localhost", db_user, db_password),
+            r2d2_postgres::TlsMode::None,
+        )
+        .expect("Create connection manager");
+        let pool = r2d2::Pool::new(manager).expect("Create connection pool");
 
-        let conn = postgres::Connection::connect(conn_uri, TlsMode::None).unwrap();
-        queries::config::set_query_timeout(&conn).unwrap();
+        let connection = pool.get().expect("Get connection");
+        queries::config::set_query_timeout(&connection).unwrap();
 
         Self {
             state: State::default(),
             event_subscriber,
-            db_conn: conn,
+            pool,
         }
     }
 
@@ -187,8 +192,19 @@ impl Service {
         service_sender
     }
 
+    fn db_conn(&self) -> Result<DBConnection, DBError> {
+        self.pool.get().map_err(|err| DBError::Internal(err.to_string()))
+    }
+
     fn check_connection(&self, callback: Sender<Result<(), DBError>>) {
-        let result = self.db_conn.execute(&"SELECT 1", &[]).map_err(|err| DBError::Internal(err.to_string()));
+        let conn = match self.db_conn() {
+            Ok(conn) => conn,
+            Err(err) => {
+                cerror!("check_connection: {:?}", err);
+                return
+            }
+        };
+        let result = conn.execute(&"SELECT 1", &[]).map_err(|err| DBError::Internal(err.to_string()));
         if let Err(err) = callback.send(result.map(|_| ())) {
             cerror!("Cannot send callback : {}", err);
         }
@@ -299,13 +315,13 @@ impl Service {
     }
 
     fn save_start_option(&mut self, node_name: NodeName, env: &str, args: &str) -> Result<(), Box<dyn error::Error>> {
-        let before_extra = queries::client_extra::get(&self.db_conn, &node_name)?;
+        let before_extra = queries::client_extra::get(&self.db_conn()?, &node_name)?;
         let mut extra = before_extra.clone().unwrap_or_default();
 
         extra.prev_env = env.to_string();
         extra.prev_args = args.to_string();
 
-        queries::client_extra::upsert(&self.db_conn, &node_name, &extra)?;
+        queries::client_extra::upsert(&self.db_conn()?, &node_name, &extra)?;
 
         self.event_subscriber.on_event(Event::ClientExtraUpdated {
             name: node_name,
@@ -321,7 +337,7 @@ impl Service {
         node_name: &str,
         callback: Sender<Option<ClientExtra>>,
     ) -> Result<(), Box<dyn error::Error>> {
-        let extra = queries::client_extra::get(&self.db_conn, node_name)?;
+        let extra = queries::client_extra::get(&self.db_conn()?, node_name)?;
         if let Err(err) = callback.send(extra) {
             cerror!("Callback error {}", err);
         }
@@ -329,18 +345,18 @@ impl Service {
     }
 
     fn get_logs(&self, params: LogQueryParams, callback: Sender<Vec<Log>>) -> Result<(), Box<dyn error::Error>> {
-        let logs = queries::logs::search(&self.db_conn, params)?;
+        let logs = queries::logs::search(&self.db_conn()?, params)?;
         callback.send(logs)?;
         Ok(())
     }
 
     fn write_logs(&self, node_name: &str, logs: Vec<StructuredLog>) -> Result<(), Box<dyn error::Error>> {
-        queries::logs::insert(&self.db_conn, node_name, logs)?;
+        queries::logs::insert(&self.db_conn()?, node_name, logs)?;
         Ok(())
     }
 
     fn get_log_targets(&self, callback: Sender<Vec<String>>) -> Result<(), Box<dyn error::Error>> {
-        let targets = queries::logs::get_targets(&self.db_conn)?;
+        let targets = queries::logs::get_targets(&self.db_conn()?)?;
         callback.send(targets)?;
         Ok(())
     }
@@ -351,7 +367,7 @@ impl Service {
         network_usage: NetworkUsage,
         time: chrono::DateTime<chrono::Utc>,
     ) -> Result<(), Box<dyn error::Error>> {
-        queries::network_usage::insert(&self.db_conn, node_name, network_usage, time)?;
+        queries::network_usage::insert(&self.db_conn()?, node_name, network_usage, time)?;
         Ok(())
     }
 
@@ -361,7 +377,7 @@ impl Service {
         peer_count: i32,
         time: chrono::DateTime<chrono::Utc>,
     ) -> Result<(), Box<dyn error::Error>> {
-        queries::peer_count::insert(&self.db_conn, node_name, peer_count, time)?;
+        queries::peer_count::insert(&self.db_conn()?, node_name, peer_count, time)?;
         Ok(())
     }
 
@@ -369,7 +385,7 @@ impl Service {
         &self,
         args: GraphCommonArgs,
     ) -> Result<Vec<GraphNetworkOutAllRow>, Box<dyn error::Error>> {
-        let rows = queries::network_usage_graph::query_network_out_all(&self.db_conn, args)?;
+        let rows = queries::network_usage_graph::query_network_out_all(&self.db_conn()?, args)?;
         Ok(rows)
     }
 
@@ -377,7 +393,7 @@ impl Service {
         &self,
         args: GraphCommonArgs,
     ) -> Result<Vec<GraphNetworkOutAllRow>, Box<dyn error::Error>> {
-        let rows = queries::network_usage_graph::query_network_out_all_avg(&self.db_conn, args)?;
+        let rows = queries::network_usage_graph::query_network_out_all_avg(&self.db_conn()?, args)?;
         Ok(rows)
     }
 
@@ -386,7 +402,7 @@ impl Service {
         node_name: NodeName,
         args: GraphCommonArgs,
     ) -> Result<Vec<GraphNetworkOutNodeExtensionRow>, Box<dyn error::Error>> {
-        let rows = queries::network_usage_graph::query_network_out_node_extension(&self.db_conn, node_name, args)?;
+        let rows = queries::network_usage_graph::query_network_out_node_extension(&self.db_conn()?, node_name, args)?;
         Ok(rows)
     }
 
@@ -395,7 +411,7 @@ impl Service {
         node_name: NodeName,
         args: GraphCommonArgs,
     ) -> Result<Vec<GraphNetworkOutNodePeerRow>, Box<dyn error::Error>> {
-        let rows = queries::network_usage_graph::query_network_out_node_peer(&self.db_conn, node_name, args)?;
+        let rows = queries::network_usage_graph::query_network_out_node_peer(&self.db_conn()?, node_name, args)?;
         Ok(rows)
     }
 }
diff --git a/server/src/db/types.rs b/server/src/db/types.rs
index 5beecfb..c059c01 100644
--- a/server/src/db/types.rs
+++ b/server/src/db/types.rs
@@ -8,6 +8,9 @@ use std::sync::mpsc::RecvError;
 use super::super::common_rpc_types::{
     BlackList, BlockId, HardwareInfo, NodeName, NodeStatus, NodeVersion, PendingTransaction, WhiteList,
 };
+use serde::export::Formatter;
+
+pub type DBConnection = r2d2::PooledConnection<r2d2_postgres::PostgresConnectionManager>;
 
 #[derive(PartialEq, Clone, Debug, Default)]
 pub struct ClientQueryResult {
@@ -184,3 +187,13 @@ impl From<RecvError> for Error {
         Error::Internal(error.to_string())
     }
 }
+
+impl std::error::Error for Error {}
+
+impl std::fmt::Display for Error {
+    fn fmt(&self, f: &mut Formatter) -> Result<(), std::fmt::Error> {
+        match self {
+            Error::Internal(log) => write!(f, "{}", log),
+        }
+    }
+}
diff --git a/server/src/main.rs b/server/src/main.rs
index db5f392..41e3a18 100644
--- a/server/src/main.rs
+++ b/server/src/main.rs
@@ -16,6 +16,7 @@ extern crate serde;
 extern crate serde_derive;
 #[macro_use]
 extern crate serde_json;
+extern crate r2d2_postgres;
 extern crate slack_hook;
 extern crate ws;