以太坊geth节点同步亲测经历
看到技术讨论群中好多朋友在以太坊节点数据同步的过程中遇到很多疑问，于是亲自购买一天服务器，进行节点同步测试，本文将分享整个测试过程中遇到的问题，及解决方案。
服务器配置
服务器配置比较简单，在阿里云上购买的2核4GLinux服务器，操作系统为centos 7.4，另外挂载了一个500G的高速云盘。
如果大家条件允许，可将服务器配置进行升级，比如4核8G，8核16G等，如果配置过低会遇到后面提到的一些问题。
节点启动
安装官网提供参数正常启动节点，其中cache参数值配置为512，大家可根据自己的服务器情况适当扩大，有助于节点数据的同步。
数据同步
此步骤也是最容易出现问题的地方。针对此步骤的问题详细介绍一下。
异常一
goroutine 10855 [IO wait]:
internal/poll.runtime_pollWait(0x7f4a6599ebb0, 0x72, 0x0)
/home/travis/.gimme/versions/go1.9.2.linux.amd64/src/runtime/netpoll.go:173 +0x57
internal/poll.(*pollDesc).wait(0xc43863a198, 0x72, 0xffffffffffffff00, 0x184e740, 0x18475a0)
/home/travis/.gimme/versions/go1.9.2.linux.amd64/src/internal/poll/fd_poll_runtime.go:85 +0xae
internal/poll.(*pollDesc).waitRead(0xc43863a198, 0xc462457a00, 0x20, 0x20)
/home/travis/.gimme/versions/go1.9.2.linux.amd64/src/internal/poll/fd_poll_runtime.go:90 +0x3d
internal/poll.(*FD).Read(0xc43863a180, 0xc462457a40, 0x20, 0x20, 0x0, 0x0, 0x0)
/home/travis/.gimme/versions/go1.9.2.linux.amd64/src/internal/poll/fd_unix.go:126 +0x18a
net.(*netFD).Read(0xc43863a180, 0xc462457a40, 0x20, 0x20, 0x0, 0xc42158dcc0, 0x302b35d6a3a0)
/home/travis/.gimme/versions/go1.9.2.linux.amd64/src/net/fd_unix.go:202 +0x52
net.(*conn).Read(0xc421aac000, 0xc462457a40, 0x20, 0x20, 0x0, 0x0, 0x0)
/home/travis/.gimme/versions/go1.9.2.linux.amd64/src/net/net.go:176 +0x6d
io.ReadAtLeast(0x7f4a603b02f8, 0xc421aac000, 0xc462457a40, 0x20, 0x20, 0x20, 0xf1e900, 0x464600, 0x7f4a603b02f8)
/home/travis/.gimme/versions/go1.9.2.linux.amd64/src/io/io.go:309 +0x86
io.ReadFull(0x7f4a603b02f8, 0xc421aac000, 0xc462457a40, 0x20, 0x20, 0x20, 0x0, 0x6fc23a9b4)
/home/travis/.gimme/versions/go1.9.2.linux.amd64/src/io/io.go:327 +0x58
github.com/ethereum/go-ethereum/p2p.(*rlpxFrameRW).ReadMsg(0xc43432b650, 0xbe9568cbea77ec48, 0x5186ea4942, 0x19d4c80, 0x0, 0x0, 0x19d4c80, 0x28, 0x11, 0x0)
/home/travis/gopath/src/github.com/ethereum/go-ethereum/p2p/rlpx.go:650 +0x100
github.com/ethereum/go-ethereum/p2p.(*rlpx).ReadMsg(0xc440545da0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0)
/home/travis/gopath/src/github.com/ethereum/go-ethereum/p2p/rlpx.go:95 +0x148
github.com/ethereum/go-ethereum/p2p.(*Peer).readLoop(0xc4315cc660, 0xc4315cd0e0)
/home/travis/gopath/src/github.com/ethereum/go-ethereum/p2p/peer.go:251 +0xad
created by github.com/ethereum/go-ethereum/p2p.(*Peer).run
/home/travis/gopath/src/github.com/ethereum/go-ethereum/p2p/peer.go:189 +0xf2
goroutine 14632 [select]:
net.(*netFD).connect.func2(0x18583c0, 0xc42f87c8a0, 0xc488fcaf00, 0xc4caba3da0, 0xc4caba3d40)
/home/travis/.gimme/versions/go1.9.2.linux.amd64/src/net/fd_unix.go:129 +0xf2
created by net.(*netFD).connect
/home/travis/.gimme/versions/go1.9.2.linux.amd64/src/net/fd_unix.go:128 +0x2a3
goroutine 7089 [select]:
github.com/ethereum/go-ethereum/p2p.(*Peer).run(0xc427e1af60, 0xd80820, 0xc44e84bd80, 0x0)
/home/travis/gopath/src/github.com/ethereum/go-ethereum/p2p/peer.go:199 +0x2fe
github.com/ethereum/go-ethereum/p2p.(*Server).runPeer(0xc4201e2fc0, 0xc427e1af60)
/home/travis/gopath/src/github.com/ethereum/go-ethereum/p2p/server.go:790 +0x122
created by github.com/ethereum/go-ethereum/p2p.(*Server).run
/home/travis/gopath/src/github.com/ethereum/go-ethereum/p2p/server.go:570 +0x139c
goroutine 14620 [select]:
net.(*netFD).connect.func2(0x18583c0, 0xc47df23560, 0xc4289ccc80, 0xc4551937a0, 0xc455193740)
/home/travis/.gimme/versions/go1.9.2.linux.amd64/src/net/fd_unix.go:129 +0xf2
created by net.(*netFD).connect
/home/travis/.gimme/versions/go1.9.2.linux.amd64/src/net/fd_unix.go:128 +0x2a3程序同步抛出此异常，一般情况下为内存或IO不足导致程序挂掉。一般情况下重启程序即可。
异常二
WARN [02-03|12:54:57] Synchronisation failed, dropping peer peer=3616e2d0bcacf32f err="retrieved hash chain is invalid"
WARN [02-03|12:56:02] Ancestor below allowance peer=64e4dd3f53e5c01e number=4843643 hash=000000…000000 allowance=4843643
WARN [02-03|12:56:02] Synchronisation failed, dropping peer peer=64e4dd3f53e5c01e err="retrieved ancestor is invalid"
// 和以下异常
WARN [02-03|12:58:55] Synchronisation failed, dropping peer peer=dbf24adb86cfa3e6 err="no peers available or all tried for download"
WARN [02-03|12:59:23] Synchronisation failed, retrying err="receipt download canceled (requested)"
WARN [02-03|13:00:17] Synchronisation failed, retrying err="peer is unknown or unhealthy"
WARN [02-03|13:03:06] Synchronisation failed, retrying err="block download canceled (requested)"
WARN [02-03|13:03:07] Synchronisation failed, retrying err="peer is unknown or unhealthy"日志一致卡在此处，说明geth没有链接到其他有效的节点，通过cosole后台执行以下命令可看到链接的节点数为0：
> net.peerCount
0针对此警告等待即可，如果长时间无响应，建议重新启动节点，让节点重新寻找新的peers。同时也可以手动添加peer。星火计划提供的节点如下列表，可尝试添加：
[
"enode://6427b7e7446bb05f22fe7ce9ea175ec05858953d75a5a6e4f99a6aec0779a8bd6276f1959a42fe5948acbe14bcd0652082dc546d3b37ae8f2aea41eba4eca43b@121.201.14.181:30303",
"enode://91922b12115c067005c574844c6bbdb114eb262f90b6355cec89e13b483c3e4669c6d63ec66b6e3ca7a3a462d28edb3c659e9fa05ed4c7234524e582a8816743@120.27.164.92:13333",
"enode://3dde41a994b3b99f938f75ddf6d48318c78ddd869c70b48d00b922190bb434fc5474f6250c143723f4387273d123e02f6a38f07d0311f240d2915f6140e09850@207.226.141.212:30303",
"enode://7ab8fa90b204f2146c00939b8474549c544caa3598a0894fa639a5cdbd992cbc6135fd776f8bcf97ae95fdaa3afbfa2d107fea71549119afd7ea57356b899be5@121.201.24.236:30303",
"enode://db81152a8296089b04a21ad9bf347df3ff0450ffc8215d9f50c400ccf8d18963118010cacf03c4b71981cf9cac5394438cab3039e98db4d2aae5859ab7d1793e@139.198.1.244:30303",
"enode://68dd1360f0a4ac362b41124692e31652ffe26f6f06a284ca11f3b514b3968594ac1f4320d1aa1ca343b06327c18a2e40eded74edfb3086e1baaa27ca24226b21@113.106.85.172:30303",
"enode://58f6b6908286cefe43c166cfc4fed033c750caa1bc3f6e1e1e1507752c0b91248addb3122f8557c5f8912e702285a160ab3a10203ae1eff3807eda25d6ed6478@45.113.71.186:30303",
"enode://87190a01c02cafb97e7f49672b4c3be2937cf79c3969e0b8e7b35cac28cebfbda52a13d56fd2113c726a1dd359c9476ccf7e60651439cef56e3a71039f6a4f5e@119.29.207.90:30303",
"enode://d1fdd05a62fd9544eeb455e4f4d4bd8bb574138d82d8f909f3041d0792e3401f8695133d39ad0a3aa5d217e3c5bed0511b531505a67b03607a909ae9096720d2@120.26.129.121:30303",
"enode://a1e9cf99eca94590ae776c8dd5c6c043a8c1f0375e9e391c9fb55133385bf453ac3d3fb3ead8e63415b2ef99d54a19e2a7bc830cd1fdbbb283818e3bcb0ea31e@182.254.209.254:30303",
"enode://562796b19d43d79dfb6160abd2d7bb78a2f2efd9501a0a767c00677e0fb3a4407235f813c3003682c2a421a58709c52f595827bc15708cc5f534f55d0f8d03ad@121.40.199.54:30303",
"enode://fa2c17dcc83a6e2825668210abf7480452de4b13d8bdea8f301c3b603701918bc4dade9e68d119d7a8214e90e7ea10a2782041c98951385d97bee73358fb08f4@120.26.124.58:30303",
"enode://0b331b27e2976d797aed1d1464ac483a7f262860334cb5737a01a0188da08d79226a6973adc5f2a2c1a20192b399161eee23a0d56ecf472cbe4058d010ecc89f@47.89.49.61:30303",
"enode://0639f20fdb5af1fecd2f2bc0ddb648885483a5945686530e6b046678635d3435dd7b92fe34209f81ec6f003482aa78e407e5e6eb1b10be4773a2adbcf1fc1ba6@118.192.161.147:30303",
"enode://fd2a5d30e4f3917ee640876cc57d72a8bf5ecf049e9106c95e60cf306dd7a5dd68d1a295f3718af44a7083252686926d6e8a402f1abe6f805e10e7281967db28@121.201.29.82:30303",
"enode://0d1b9eed7afe2d5878d5d8a4c2066b600a3bcac2e5730586421af224e93a58cd03cac75bf0b2a62fd8049cd3692a085758cc1e407c8b2c94bb069814a5e8d0f0@209.9.106.245:30303",
"enode://ca087a651571d04953187753af969f7deb1582af2a06a3048b90adb3f87d4c41973aac4b5e80449efc97154dac769a5ea447b123c3aaf7a2c23825a1558804dc@182.150.37.23:30303",
"enode://9b53b9d41d964f71db60d2198cfa9013fc7808d707c5e0a32da1e22d3cacd6adbae46901df6506a752d9d4e3791df29171315fbb86f7b09331a25458158fe65b@182.150.37.24:30303"
]异常三
geth莫名其妙自动关闭，日志未呈现异常。此问题之前的文章也提到过，因为服务器内存不足触发Linux的OOM killer操作，被杀掉了。此问题除了升级内存，没有太好的办法，只能频繁的监控程序，发现问题重启即可。
其中折中的办法是设置swap，但是设置swap会大幅降低同步速度。
异常四
疯狂打印类似以下的日志：
INFO [02-03|13:07:24] Imported new state entries count=1142 elapsed=5.888ms processed=84671 pending=1907 retry=0 duplicate=0 unexpected=170长时间打印以上日志，区块同步高度未变化，在这个日志中没有其他操作日志。如果时间长达几个小时，那么趁早放弃吧，此问题是因为基础设施比如网络、硬盘等原因导致的，短则几天、长则几周，都不好说。
这种问题即使重启服务器还会重新进入这个步骤，就不浪费精力和时间了。好多朋友遇到的都是这个问题，特别是window系统下启动，有的卡到百分之九十九，一直同步不完，基本上都是在执行上面的操作。
亲身经历
昨天晚上6点部署好服务器开始节点同步，刚开始由于交易较少同步速度很快。早上起床发现凌晨2点多节点卡死，一直没同步。七点多重启重新同步，这中间经历了多次挂掉，多次程序异常，多次oom killer。
当节点数据同步到距离最新高度200块左右的时候一直加载结构体，是一个比较漫长的阶段，大家就耐心等待了，这期间最好不要重启。
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