Kubernetes 集群文件描述符测漏了...
问题现象
某个客户的 Kubernetes 环境由于 too many open files（文件描述符泄漏）导致集群不正常。
已查明由该客户 Kubernetes 环境外置存储 NFS 服务器宕机导致。以下分析基于通过手动关闭 NFS 服务复现的测试环境。
初步分析
我们首先确定 Kubernetes 节点上的 Linux 系统最大可打开文件数量：
$ cat /proc/sys/fs/file-max
100000
再看到当前已打开的文件数量：
$ cat /proc/sys/fs/file-nr
83552 0 100000
$ cat /proc/sys/fs/file-nr
84640 0 100000
不断上涨中，已逼近系统的最大可打开文件数量极限。
在客户的环境上排查时我们片面地只分析了 socket 统计信息，错误地认为由某个进程疯狂打开 /var/run/docker.sock 导致，并未查出真正的罪魁祸首：
$ ss -a | grep "docker.sock" | wc -l
1176
$ ss -a | grep "docker.sock" | wc -l
1220
这里说一下 Docker 默认使用 unix domain socket (IPC socket) 进行本地通讯，而 kubelet 通过 dockershim 将 CRI 请求转换成相应的 Docker API 请求发给 dockerd (Docker Daemon) 进程，所以 /var/run/docker.sock 是由 kubelet 使用。
要查看某个进程到底打开了多少文件，正常情况下 lsof 当然可以做到，但是在极端情况下，lsof 都是无法正常使用的，我们这时就要通过 /proc 虚拟文件系统来查看进程的数据，/proc/${pid}/fd 这个路径下的文件与进程所打开的文件是一对一的关系，所以我们统计 /proc/${pid}/fd 路径下文件的数量就能够得到进程打开文件的数量：
$ ps -ef | grep kubelet
root 28051 1 7 15:37 ? 00:29:57 /usr/bin/kubelet --bootstrap-kubeconfig=/etc/kubernetes/bootstrap-kubelet.conf --kubeconfig=/etc/kubernetes/kubelet.conf --config=/var/lib/kubelet/config.yaml --cgroup-driver=systemd --network-plugin=cni --pod-infra-container-image=10.10.10.254:5000/pause:3.2
$ ls /proc/28051/fd | wc -l
1253
$ ls /proc/28051/fd | wc -l
1256
我使用脚本持续打印出 kubelet 与全局已打开文件数量，发现 kubelet 打开文件数的增量比 file-nr 要小很多：
$ cat << EOF > kubelet.sh
while true
do
sock=$(ss -a | grep "docker.sock" | wc -l)
fd=$(ls /proc/28051/fd | wc -l)
file_nr=$(cat /proc/sys/fs/file-nr)
echo "docker.sock: $sock; file opened: $fd; file-nr: $file_nr"
sleep 10
done
EOF
$ sh kubelet.sh
docker.sock: 1280; file opened: 1316; file-nr: 92224 0 100000
docker.sock: 1280; file opened: 1315; file-nr: 92192 0 100000
docker.sock: 1280; file opened: 1315; file-nr: 92224 0 100000
docker.sock: 1281; file opened: 1316; file-nr: 92256 0 100000
docker.sock: 1283; file opened: 1318; file-nr: 92416 0 100000
docker.sock: 1283; file opened: 1318; file-nr: 92448 0 100000
docker.sock: 1284; file opened: 1319; file-nr: 92480 0 100000
docker.sock: 1285; file opened: 1321; file-nr: 92544 0 100000
docker.sock: 1286; file opened: 1321; file-nr: 92640 0 100000
docker.sock: 1286; file opened: 1321; file-nr: 92640 0 100000
docker.sock: 1286; file opened: 1321; file-nr: 92608 0 100000
docker.sock: 1286; file opened: 1321; file-nr: 92608 0 100000
docker.sock: 1286; file opened: 1321; file-nr: 92608 0 100000
docker.sock: 1286; file opened: 1321; file-nr: 92640 0 100000
docker.sock: 1286; file opened: 1321; file-nr: 92576 0 100000
docker.sock: 1287; file opened: 1322; file-nr: 92672 0 100000
docker.sock: 1289; file opened: 1324; file-nr: 92768 0 100000
这就说明还有其他进程在持续打开文件。
深入分析
所以我们要使用脚本来观察所有进程使用文件的增量情况：
$ cat << EOF > all.sh
while true
do
for proc in $(find /proc/ -maxdepth 1 -type d -name "[0-9]*")
do
fd=$(ls $proc/fd | wc -l)
if [[ $fd -gt 1000 ]]; then
pid=$(echo $proc | awk -F/ '{print $3}')
echo "process $pid opened $fd files\n"
fi
done
echo ==========================
sleep 10
done
EOF
$ sh all.sh
process 21932 opened 4441 files
ls: cannot access /proc/25665/fd: No such file or directory
process 26140 opened 7035 files
process 26659 opened 4441 files
process 27160 opened 4441 files
process 28051 opened 1366 files
==========================
ls: cannot access /proc/21786/fd: No such file or directory
process 21932 opened 4441 files
process 26140 opened 7040 files
process 26659 opened 4441 files
process 27160 opened 4451 files
process 28051 opened 1368 files
==========================
ls: cannot access /proc/3912/fd: No such file or directory
ls: cannot access /proc/3917/fd: No such file or directory
ls: cannot access /proc/3935/fd: No such file or directory
ls: cannot access /proc/3938/fd: No such file or directory
process 21932 opened 4451 files
process 26140 opened 7060 files
process 26659 opened 4461 files
process 27160 opened 4461 files
process 28051 opened 1371 files
ls: cannot access /proc/21122/fd: No such file or directory
process 21932 opened 4481 files
process 26140 opened 7095 files
process 26659 opened 4481 files
process 27160 opened 4481 files
process 28051 opened 1379 files
直接根据 PID 来看一下进程树：
$ pstree 21932 -s
systemd───containerd───containerd-shim─┬─patroni─┬─patroni───463*[{patroni}]
│ ├─postgres───14*[postgres]
│ └─sshd
├─221*[pgha-liveness.s───curl]
├─237*[pgha-readiness.───pgha-readiness.───curl]
└─10*[{containerd-shim}]
$ pstree 26659 -s
systemd───containerd───containerd-shim─┬─patroni─┬─patroni───463*[{patroni}]
│ ├─postgres───7*[postgres]
│ └─sshd
├─221*[pgha-liveness.s───curl]
├─237*[pgha-readiness.───pgha-readiness.───curl]
└─10*[{containerd-shim}]
$ pstree 27160 -s
systemd───containerd───containerd-shim─┬─patroni─┬─patroni───464*[{patroni}]
│ ├─postgres───7*[postgres]
│ └─sshd
├─221*[pgha-liveness.s───curl]
├─238*[pgha-readiness.───pgha-readiness.───curl]
└─10*[{containerd-shim}]
$ pstree 26140 -s
systemd───dockerd───40*[{dockerd}]
$ pstree 28051 -s
systemd───kubelet───31*[{kubelet}]
到处都是 patroni 和 curl 进程，不出问题才有鬼呢。
lsof 已经废了，我们手动去看看 21932 号进程打开了哪些文件：
$ ll -tr /proc/21932/fd | tail -n 50
lr-x------ 1 root root 64 Feb 26 23:56 4563 -> pipe:[4883358]
lr-x------ 1 root root 64 Feb 26 23:56 4561 -> pipe:[4883357]
lr-x------ 1 root root 64 Feb 26 23:56 4560 -> /run/docker/containerd/46f400679dc5867a1bd4de1cc97deadeb049bec0ad4e3c74b3cc2cd77aa9afc8/2b6b459b99e213722d3b36b4ac447fb63d1e77908e8583a443443350eb8b6dbe-stderr
l-wx------ 1 root root 64 Feb 26 23:56 4558 -> /run/docker/containerd/46f400679dc5867a1bd4de1cc97deadeb049bec0ad4e3c74b3cc2cd77aa9afc8/2b6b459b99e213722d3b36b4ac447fb63d1e77908e8583a443443350eb8b6dbe-stderr
lr-x------ 1 root root 64 Feb 26 23:56 4556 -> /run/docker/containerd/46f400679dc5867a1bd4de1cc97deadeb049bec0ad4e3c74b3cc2cd77aa9afc8/2b6b459b99e213722d3b36b4ac447fb63d1e77908e8583a443443350eb8b6dbe-stdout
l-wx------ 1 root root 64 Feb 26 23:56 4554 -> /run/docker/containerd/46f400679dc5867a1bd4de1cc97deadeb049bec0ad4e3c74b3cc2cd77aa9afc8/2b6b459b99e213722d3b36b4ac447fb63d1e77908e8583a443443350eb8b6dbe-stdout
lr-x------ 1 root root 64 Feb 26 23:56 4553 -> pipe:[4874646]
lr-x------ 1 root root 64 Feb 26 23:56 4551 -> pipe:[4874645]
lr-x------ 1 root root 64 Feb 26 23:56 4550 -> /run/docker/containerd/46f400679dc5867a1bd4de1cc97deadeb049bec0ad4e3c74b3cc2cd77aa9afc8/7ae25e44f7286fe796a51546f0311bbedad89ff3c12cde6089665b814cc7abb8-stderr
l-wx------ 1 root root 64 Feb 26 23:56 4548 -> /run/docker/containerd/46f400679dc5867a1bd4de1cc97deadeb049bec0ad4e3c74b3cc2cd77aa9afc8/7ae25e44f7286fe796a51546f0311bbedad89ff3c12cde6089665b814cc7abb8-stderr
lr-x------ 1 root root 64 Feb 26 23:56 4546 -> /run/docker/containerd/46f400679dc5867a1bd4de1cc97deadeb049bec0ad4e3c74b3cc2cd77aa9afc8/7ae25e44f7286fe796a51546f0311bbedad89ff3c12cde6089665b814cc7abb8-stdout
l-wx------ 1 root root 64 Feb 26 23:56 4544 -> /run/docker/containerd/46f400679dc5867a1bd4de1cc97deadeb049bec0ad4e3c74b3cc2cd77aa9afc8/7ae25e44f7286fe796a51546f0311bbedad89ff3c12cde6089665b814cc7abb8-stdout
lr-x------ 1 root root 64 Feb 26 23:56 4543 -> pipe:[4869051]
lr-x------ 1 root root 64 Feb 26 23:56 4541 -> pipe:[4869050]
lr-x------ 1 root root 64 Feb 26 23:56 4540 -> /run/docker/containerd/46f400679dc5867a1bd4de1cc97deadeb049bec0ad4e3c74b3cc2cd77aa9afc8/a491b0b22bdaa8950fa83d44a350683fa2b2fe8b45b46281ff09025cb1640285-stderr
l-wx------ 1 root root 64 Feb 26 23:56 4538 -> /run/docker/containerd/46f400679dc5867a1bd4de1cc97deadeb049bec0ad4e3c74b3cc2cd77aa9afc8/a491b0b22bdaa8950fa83d44a350683fa2b2fe8b45b46281ff09025cb1640285-stderr
lr-x------ 1 root root 64 Feb 26 23:56 4536 -> /run/docker/containerd/46f400679dc5867a1bd4de1cc97deadeb049bec0ad4e3c74b3cc2cd77aa9afc8/a491b0b22bdaa8950fa83d44a350683fa2b2fe8b45b46281ff09025cb1640285-stdout
l-wx------ 1 root root 64 Feb 26 23:56 4534 -> /run/docker/containerd/46f400679dc5867a1bd4de1cc97deadeb049bec0ad4e3c74b3cc2cd77aa9afc8/a491b0b22bdaa8950fa83d44a350683fa2b2fe8b45b46281ff09025cb1640285-stdout
lr-x------ 1 root root 64 Feb 26 23:56 4533 -> pipe:[4859412]
lr-x------ 1 root root 64 Feb 26 23:56 4531 -> pipe:[4859411]
lr-x------ 1 root root 64 Feb 26 23:56 4530 -> /run/docker/containerd/46f400679dc5867a1bd4de1cc97deadeb049bec0ad4e3c74b3cc2cd77aa9afc8/4b19d3a6fc67b5a8aeccfff3edb671315743ebb3fef07f55d76bac37a36e62c3-stderr
l-wx------ 1 root root 64 Feb 26 23:56 4528 -> /run/docker/containerd/46f400679dc5867a1bd4de1cc97deadeb049bec0ad4e3c74b3cc2cd77aa9afc8/4b19d3a6fc67b5a8aeccfff3edb671315743ebb3fef07f55d76bac37a36e62c3-stderr
lr-x------ 1 root root 64 Feb 26 23:56 4526 -> /run/docker/containerd/46f400679dc5867a1bd4de1cc97deadeb049bec0ad4e3c74b3cc2cd77aa9afc8/4b19d3a6fc67b5a8aeccfff3edb671315743ebb3fef07f55d76bac37a36e62c3-stdout
l-wx------ 1 root root 64 Feb 26 23:56 4524 -> /run/docker/containerd/46f400679dc5867a1bd4de1cc97deadeb049bec0ad4e3c74b3cc2cd77aa9afc8/4b19d3a6fc67b5a8aeccfff3edb671315743ebb3fef07f55d76bac37a36e62c3-stdout
lr-x------ 1 root root 64 Feb 26 23:56 4523 -> pipe:[4857797]
lr-x------ 1 root root 64 Feb 26 23:56 4521 -> pipe:[4857796]
lr-x------ 1 root root 64 Feb 26 23:56 4520 -> /run/docker/containerd/46f400679dc5867a1bd4de1cc97deadeb049bec0ad4e3c74b3cc2cd77aa9afc8/e9315eacd861101be78d7b1b7eabf139f8bd27e902908e915798830341db8ab4-stderr
l-wx------ 1 root root 64 Feb 26 23:56 4518 -> /run/docker/containerd/46f400679dc5867a1bd4de1cc97deadeb049bec0ad4e3c74b3cc2cd77aa9afc8/e9315eacd861101be78d7b1b7eabf139f8bd27e902908e915798830341db8ab4-stderr
lr-x------ 1 root root 64 Feb 26 23:56 4516 -> /run/docker/containerd/46f400679dc5867a1bd4de1cc97deadeb049bec0ad4e3c74b3cc2cd77aa9afc8/e9315eacd861101be78d7b1b7eabf139f8bd27e902908e915798830341db8ab4-stdout
l-wx------ 1 root root 64 Feb 26 23:56 4514 -> /run/docker/containerd/46f400679dc5867a1bd4de1cc97deadeb049bec0ad4e3c74b3cc2cd77aa9afc8/e9315eacd861101be78d7b1b7eabf139f8bd27e902908e915798830341db8ab4-stdout
lr-x------ 1 root root 64 Feb 26 23:56 4513 -> pipe:[4847408]
lr-x------ 1 root root 64 Feb 26 23:56 4511 -> pipe:[4847407]
lr-x------ 1 root root 64 Feb 26 23:56 4510 -> /run/docker/containerd/46f400679dc5867a1bd4de1cc97deadeb049bec0ad4e3c74b3cc2cd77aa9afc8/a8ed17bac296cb67aa9e09b26b6556d98ca35f89a8d4872aedf93165ce6e771c-stderr
l-wx------ 1 root root 64 Feb 26 23:56 4508 -> /run/docker/containerd/46f400679dc5867a1bd4de1cc97deadeb049bec0ad4e3c74b3cc2cd77aa9afc8/a8ed17bac296cb67aa9e09b26b6556d98ca35f89a8d4872aedf93165ce6e771c-stderr
lr-x------ 1 root root 64 Feb 26 23:56 4506 -> /run/docker/containerd/46f400679dc5867a1bd4de1cc97deadeb049bec0ad4e3c74b3cc2cd77aa9afc8/a8ed17bac296cb67aa9e09b26b6556d98ca35f89a8d4872aedf93165ce6e771c-stdout
l-wx------ 1 root root 64 Feb 26 23:56 4504 -> /run/docker/containerd/46f400679dc5867a1bd4de1cc97deadeb049bec0ad4e3c74b3cc2cd77aa9afc8/a8ed17bac296cb67aa9e09b26b6556d98ca35f89a8d4872aedf93165ce6e771c-stdout
lr-x------ 1 root root 64 Feb 26 23:56 4503 -> pipe:[4842434]
lr-x------ 1 root root 64 Feb 26 23:56 4501 -> pipe:[4842433]
lr-x------ 1 root root 64 Feb 26 23:56 4500 -> /run/docker/containerd/46f400679dc5867a1bd4de1cc97deadeb049bec0ad4e3c74b3cc2cd77aa9afc8/59e1ada1cda0fed1656465b371b410973db83c420a285a3b270e148896218117-stderr
l-wx------ 1 root root 64 Feb 26 23:56 4498 -> /run/docker/containerd/46f400679dc5867a1bd4de1cc97deadeb049bec0ad4e3c74b3cc2cd77aa9afc8/59e1ada1cda0fed1656465b371b410973db83c420a285a3b270e148896218117-stderr
lr-x------ 1 root root 64 Feb 26 23:56 4496 -> /run/docker/containerd/46f400679dc5867a1bd4de1cc97deadeb049bec0ad4e3c74b3cc2cd77aa9afc8/59e1ada1cda0fed1656465b371b410973db83c420a285a3b270e148896218117-stdout
l-wx------ 1 root root 64 Feb 26 23:56 4494 -> /run/docker/containerd/46f400679dc5867a1bd4de1cc97deadeb049bec0ad4e3c74b3cc2cd77aa9afc8/59e1ada1cda0fed1656465b371b410973db83c420a285a3b270e148896218117-stdout
lr-x------ 1 root root 64 Feb 26 23:56 4493 -> pipe:[4800931]
lr-x------ 1 root root 64 Feb 26 23:56 4491 -> pipe:[4800930]
lr-x------ 1 root root 64 Feb 26 23:56 4490 -> /run/docker/containerd/46f400679dc5867a1bd4de1cc97deadeb049bec0ad4e3c74b3cc2cd77aa9afc8/6dc135d11312e1033360fb714bc3f2aac04dad9fb494cb70c924c54091c54e68-stderr
l-wx------ 1 root root 64 Feb 26 23:56 4488 -> /run/docker/containerd/46f400679dc5867a1bd4de1cc97deadeb049bec0ad4e3c74b3cc2cd77aa9afc8/6dc135d11312e1033360fb714bc3f2aac04dad9fb494cb70c924c54091c54e68-stderr
lr-x------ 1 root root 64 Feb 26 23:56 4486 -> /run/docker/containerd/46f400679dc5867a1bd4de1cc97deadeb049bec0ad4e3c74b3cc2cd77aa9afc8/6dc135d11312e1033360fb714bc3f2aac04dad9fb494cb70c924c54091c54e68-stdout
l-wx------ 1 root root 64 Feb 26 23:56 4484 -> /run/docker/containerd/46f400679dc5867a1bd4de1cc97deadeb049bec0ad4e3c74b3cc2cd77aa9afc8/6dc135d11312e1033360fb714bc3f2aac04dad9fb494cb70c924c54091c54e68-stdout
lr-x------ 1 root root 64 Feb 26 23:56 4483 -> pipe:[4800791]
lr-x------ 1 root root 64 Feb 26 23:56 4481 -> pipe:[4800790]
$ ll /run/docker/containerd/46f400679dc5867a1bd4de1cc97deadeb049bec0ad4e3c74b3cc2cd77aa9afc8/6dc135d11312e1033360fb714bc3f2aac04dad9fb494cb70c924c54091c54e68-stderr
prwx------ 1 root root 0 Feb 26 23:31 /run/docker/containerd/46f400679dc5867a1bd4de1cc97deadeb049bec0ad4e3c74b3cc2cd77aa9afc8/6dc135d11312e1033360fb714bc3f2aac04dad9fb494cb70c924c54091c54e68-stderr
这些都是命名管道文件，而我们常用的 | 竖线符号是匿名管道，管道经常被用于父子进程间通讯。
这些管道文件的命名都是以 /run/docker/containerd/46f400679dc5 为前缀，盲猜一把 46f400679dc5 是某个容器的 ID：
$ docker ps | grep 46f400679dc5
46f400679dc5 10.10.10.254:5000/caas4/crunchy-postgres-ha "/opt/cpm/bin/bootst…" 9 hours ago Up 9 hours k8s_database_host-7f49c5c448-5vkdh_pgo-namespace_ac0a3524-3b65-4876-ab87-9610a70afda2_0
正是 21932 号 containerd-shim 进程创建的容器。
$ pstree 21932 -s
systemd───containerd───containerd-shim─┬─patroni─┬─patroni───475*[{patroni}]
│ ├─postgres───14*[postgres]
│ └─sshd
├─226*[pgha-liveness.s───curl]
├─244*[pgha-readiness.───pgha-readiness.───curl]
├─runc───5*[{runc}]
└─10*[{containerd-shim}]
上面就是 ID 为 46f400679dc5 容器的进程树。
/proc/21932/fd 路径下的那些软链接都指向了 /run/docker/containerd/46f400679dc5 路径：
$ ll -t /run/docker/containerd/46f400679dc5867a1bd4de1cc97deadeb049bec0ad4e3c74b3cc2cd77aa9afc8/ | head -20
total 0
prwx------ 1 root root 0 Feb 27 01:17 init-stderr
prwx------ 1 root root 0 Feb 27 00:09 fdbf8eb06956db4b897ed0fd7bf9ef51b74bab74499d609e14c42f99991b4c56-stderr
prwx------ 1 root root 0 Feb 27 00:09 fdbf8eb06956db4b897ed0fd7bf9ef51b74bab74499d609e14c42f99991b4c56-stdout
prwx------ 1 root root 0 Feb 27 00:07 763baa451bc729810eeb9ba0bbb9bf52161a9e2e352c09c5fe2c60ef697444f2-stderr
prwx------ 1 root root 0 Feb 27 00:07 763baa451bc729810eeb9ba0bbb9bf52161a9e2e352c09c5fe2c60ef697444f2-stdout
prwx------ 1 root root 0 Feb 27 00:07 9429e6fdb63269d484c26f6391177d269400e2e4fec8f8a594f50fbd0905f8a9-stderr
prwx------ 1 root root 0 Feb 27 00:07 9429e6fdb63269d484c26f6391177d269400e2e4fec8f8a594f50fbd0905f8a9-stdout
prwx------ 1 root root 0 Feb 27 00:06 8b4a7652cddebb52294a7a66fd620f6ac4258077cfde21531cce6ee86ac1ccda-stderr
prwx------ 1 root root 0 Feb 27 00:06 8b4a7652cddebb52294a7a66fd620f6ac4258077cfde21531cce6ee86ac1ccda-stdout
prwx------ 1 root root 0 Feb 26 23:51 25cb04f4897dc47670ef5fe5dcdb7725cba9dca76bf0991c199acfd77b87faaa-stderr
prwx------ 1 root root 0 Feb 26 23:51 25cb04f4897dc47670ef5fe5dcdb7725cba9dca76bf0991c199acfd77b87faaa-stdout
prwx------ 1 root root 0 Feb 26 23:50 fd13511325a0bd065bd0ab99c83dca555580dba0f8d51c95fb8d388bee659eaf-stderr
prwx------ 1 root root 0 Feb 26 23:50 fd13511325a0bd065bd0ab99c83dca555580dba0f8d51c95fb8d388bee659eaf-stdout
prwx------ 1 root root 0 Feb 26 23:49 c8dce3743c86adebee9043a2adf80eab08b4c565b90d62d85f1e542a4c84b19a-stderr
prwx------ 1 root root 0 Feb 26 23:49 c8dce3743c86adebee9043a2adf80eab08b4c565b90d62d85f1e542a4c84b19a-stdout
prwx------ 1 root root 0 Feb 26 23:48 fc4a2b410671cbe1e3a3706e3e281bde89be0de537af60aa676365aeba911386-stderr
prwx------ 1 root root 0 Feb 26 23:48 fc4a2b410671cbe1e3a3706e3e281bde89be0de537af60aa676365aeba911386-stdout
prwx------ 1 root root 0 Feb 26 23:47 c5a0233a9651a3bf629004cfd94b79f2f96688fce59764d1adda5bc4d8f7622c-stderr
prwx------ 1 root root 0 Feb 26 23:47 c5a0233a9651a3bf629004cfd94b79f2f96688fce59764d1adda5bc4d8f7622c-stdout
$ ls /run/docker/containerd/46f400679dc5867a1bd4de1cc97deadeb049bec0ad4e3c74b3cc2cd77aa9afc8 | wc -l
944
这些文件都是用来做啥的？
先看看 Docker 源码 https://github.com/moby/moby，创建命名管道也就是 Linux FIFO 的源码在 https://github.com/moby/moby/blob/v19.03.12/libcontainerd/remote/client_linux.go#L97-L122：
func newFIFOSet(bundleDir, processID string, withStdin, withTerminal bool) *cio.FIFOSet {
config := cio.Config{
Terminal: withTerminal,
Stdout: filepath.Join(bundleDir, processID+"-stdout"),
}
paths := []string{config.Stdout}
if withStdin {
config.Stdin = filepath.Join(bundleDir, processID+"-stdin")
paths = append(paths, config.Stdin)
}
if !withTerminal {
config.Stderr = filepath.Join(bundleDir, processID+"-stderr")
paths = append(paths, config.Stderr)
}
closer := func() error {
for _, path := range paths {
if err := os.RemoveAll(path); err != nil {
logrus.Warnf("libcontainerd: failed to remove fifo %v: %v", path, err)
}
}
return nil
}
return cio.NewFIFOSet(config, closer)
}
再找到 newFIFOSet 调用处 https://github.com/moby/moby/blob/v19.03.12/libcontainerd/remote/client.go#L194
// Exec creates exec process.
//
// The containerd client calls Exec to register the exec config in the shim side.
// When the client calls Start, the shim will create stdin fifo if needs. But
// for the container main process, the stdin fifo will be created in Create not
// the Start call. stdinCloseSync channel should be closed after Start exec
// process.
func (c *client) Exec(ctx context.Context, containerID, processID string, spec *specs.Process, withStdin bool, attachStdio libcontainerdtypes.StdioCallback) (int, error) {
// a lot of code here
fifos := newFIFOSet(labels[DockerContainerBundlePath], processID, withStdin, spec.Terminal)
p, err = t.Exec(ctx, processID, spec, func(id string) (cio.IO, error) {
rio, err = c.createIO(fifos, containerID, processID, stdinCloseSync, attachStdio)
return rio, err
})
// a lot of code here
}
看上去每当 exec 新进程，都会创建 Linux FIFO 也就是命名管道。我们找个 Kubernetes 环境来验证一下：
$ docker ps | grep grafana-646d9cfddf-w8xt4
10669996b0c8 10.10.10.158:5000/caas4/grafana "/run.sh" 16 hours ago Up 16 hours k8s_grafana_grafana-646d9cfddf-w8xt4_gap_f385ebe8-58e8-45bc-919a-4353db754b79_0
$ docker inspect -f {{.State.Pid}} 10669996b0c8
7612
$ pstree 7612 -p -s
systemd(1)───containerd(22719)───containerd-shim(7585)───grafana-server(7612)─┬─{grafana-server}(7666)
├─{grafana-server}(7667)
├─{grafana-server}(7668)
├─{grafana-server}(7669)
├─{grafana-server}(7670)
├─{grafana-server}(7672)
├─{grafana-server}(7673)
├─{grafana-server}(7703)
├─{grafana-server}(8197)
├─{grafana-server}(8198)
├─{grafana-server}(8199)
├─{grafana-server}(8200)
├─{grafana-server}(12076)
├─{grafana-server}(17397)
└─{grafana-server}(29134)
我们找到负责操作 grafana 容器的 containerd-shim 进程打开的文件：
$ ll /proc/7585/fd
total 0
lr-x------ 1 root root 64 Feb 27 23:15 0 -> /dev/null
l-wx------ 1 root root 64 Feb 27 23:15 1 -> /dev/null
lrwx------ 1 root root 64 Feb 27 23:15 10 -> socket:[230322]
lr-x------ 1 root root 64 Feb 27 23:15 11 -> pipe:[230333]
l--------- 1 root root 64 Feb 27 23:15 12 -> /run/docker/containerd/10669996b0c8ef8a6e84c33bd54fb78c1776ef3a93abccca96f92337aaf8cfcc/init-stdout
lr-x------ 1 root root 64 Feb 27 23:15 13 -> pipe:[230334]
l-wx------ 1 root root 64 Feb 27 23:15 14 -> /run/docker/containerd/10669996b0c8ef8a6e84c33bd54fb78c1776ef3a93abccca96f92337aaf8cfcc/init-stdout
l--------- 1 root root 64 Feb 27 23:15 15 -> /run/docker/containerd/10669996b0c8ef8a6e84c33bd54fb78c1776ef3a93abccca96f92337aaf8cfcc/init-stdout
lr-x------ 1 root root 64 Feb 27 23:15 16 -> /run/docker/containerd/10669996b0c8ef8a6e84c33bd54fb78c1776ef3a93abccca96f92337aaf8cfcc/init-stdout
l--------- 1 root root 64 Feb 27 23:15 17 -> /run/docker/containerd/10669996b0c8ef8a6e84c33bd54fb78c1776ef3a93abccca96f92337aaf8cfcc/init-stderr
l-wx------ 1 root root 64 Feb 27 23:15 18 -> /run/docker/containerd/10669996b0c8ef8a6e84c33bd54fb78c1776ef3a93abccca96f92337aaf8cfcc/init-stderr
l--------- 1 root root 64 Feb 27 23:15 19 -> /run/docker/containerd/10669996b0c8ef8a6e84c33bd54fb78c1776ef3a93abccca96f92337aaf8cfcc/init-stderr
l-wx------ 1 root root 64 Feb 27 23:15 2 -> /dev/null
lr-x------ 1 root root 64 Feb 27 23:15 20 -> /run/docker/containerd/10669996b0c8ef8a6e84c33bd54fb78c1776ef3a93abccca96f92337aaf8cfcc/init-stderr
lrwx------ 1 root root 64 Feb 27 23:15 3 -> socket:[230331]
l--------- 1 root root 64 Feb 27 23:15 4 -> /var/lib/containerd/io.containerd.runtime.v1.linux/moby/10669996b0c8ef8a6e84c33bd54fb78c1776ef3a93abccca96f92337aaf8cfcc/shim.stdout.log
lrwx------ 1 root root 64 Feb 27 23:15 5 -> anon_inode:[eventpoll]
lrwx------ 1 root root 64 Feb 27 23:15 6 -> /var/lib/containerd/io.containerd.runtime.v1.linux/moby/10669996b0c8ef8a6e84c33bd54fb78c1776ef3a93abccca96f92337aaf8cfcc/shim.stdout.log
l--------- 1 root root 64 Feb 27 23:15 7 -> /var/lib/containerd/io.containerd.runtime.v1.linux/moby/10669996b0c8ef8a6e84c33bd54fb78c1776ef3a93abccca96f92337aaf8cfcc/shim.stderr.log
lrwx------ 1 root root 64 Feb 27 23:15 8 -> /var/lib/containerd/io.containerd.runtime.v1.linux/moby/10669996b0c8ef8a6e84c33bd54fb78c1776ef3a93abccca96f92337aaf8cfcc/shim.stderr.log
lrwx------ 1 root root 64 Feb 27 23:15 9 -> anon_inode:[eventpoll]
$ ls /proc/7585/fd | wc -l
21
接着手动进入 grafana 容器运行 bash 进程：
$ kubectl exec -it grafana-646d9cfddf-w8xt4 -n gap bash
在主机上查看 containerd-shim 进程打开的文件：
$ ll /proc/7585/fd
total 0
lr-x------ 1 root root 64 Feb 27 23:15 0 -> /dev/null
l-wx------ 1 root root 64 Feb 27 23:15 1 -> /dev/null
lrwx------ 1 root root 64 Feb 27 23:15 10 -> socket:[230322]
lr-x------ 1 root root 64 Feb 27 23:15 11 -> pipe:[230333]
l--------- 1 root root 64 Feb 27 23:15 12 -> /run/docker/containerd/10669996b0c8ef8a6e84c33bd54fb78c1776ef3a93abccca96f92337aaf8cfcc/init-stdout
lr-x------ 1 root root 64 Feb 27 23:15 13 -> pipe:[230334]
l-wx------ 1 root root 64 Feb 27 23:15 14 -> /run/docker/containerd/10669996b0c8ef8a6e84c33bd54fb78c1776ef3a93abccca96f92337aaf8cfcc/init-stdout
l--------- 1 root root 64 Feb 27 23:15 15 -> /run/docker/containerd/10669996b0c8ef8a6e84c33bd54fb78c1776ef3a93abccca96f92337aaf8cfcc/init-stdout
lr-x------ 1 root root 64 Feb 27 23:15 16 -> /run/docker/containerd/10669996b0c8ef8a6e84c33bd54fb78c1776ef3a93abccca96f92337aaf8cfcc/init-stdout
l--------- 1 root root 64 Feb 27 23:15 17 -> /run/docker/containerd/10669996b0c8ef8a6e84c33bd54fb78c1776ef3a93abccca96f92337aaf8cfcc/init-stderr
l-wx------ 1 root root 64 Feb 27 23:15 18 -> /run/docker/containerd/10669996b0c8ef8a6e84c33bd54fb78c1776ef3a93abccca96f92337aaf8cfcc/init-stderr
l--------- 1 root root 64 Feb 27 23:15 19 -> /run/docker/containerd/10669996b0c8ef8a6e84c33bd54fb78c1776ef3a93abccca96f92337aaf8cfcc/init-stderr
l-wx------ 1 root root 64 Feb 27 23:15 2 -> /dev/null
lr-x------ 1 root root 64 Feb 27 23:15 20 -> /run/docker/containerd/10669996b0c8ef8a6e84c33bd54fb78c1776ef3a93abccca96f92337aaf8cfcc/init-stderr
l--------- 1 root root 64 Feb 27 23:18 22 -> /run/docker/containerd/10669996b0c8ef8a6e84c33bd54fb78c1776ef3a93abccca96f92337aaf8cfcc/9cf438e02f7ff6e96466a2a9e5316ff4fea819a69f6f197534409be6be561464-stdin
l--------- 1 root root 64 Feb 27 23:18 23 -> /run/docker/containerd/10669996b0c8ef8a6e84c33bd54fb78c1776ef3a93abccca96f92337aaf8cfcc/9cf438e02f7ff6e96466a2a9e5316ff4fea819a69f6f197534409be6be561464-stdin
lrwx------ 1 root root 64 Feb 27 23:18 24 -> /dev/pts/ptmx
l-wx------ 1 root root 64 Feb 27 23:18 25 -> /run/docker/containerd/10669996b0c8ef8a6e84c33bd54fb78c1776ef3a93abccca96f92337aaf8cfcc/9cf438e02f7ff6e96466a2a9e5316ff4fea819a69f6f197534409be6be561464-stdin
lr-x------ 1 root root 64 Feb 27 23:18 26 -> /run/docker/containerd/10669996b0c8ef8a6e84c33bd54fb78c1776ef3a93abccca96f92337aaf8cfcc/9cf438e02f7ff6e96466a2a9e5316ff4fea819a69f6f197534409be6be561464-stdin
l--------- 1 root root 64 Feb 27 23:18 27 -> /run/docker/containerd/10669996b0c8ef8a6e84c33bd54fb78c1776ef3a93abccca96f92337aaf8cfcc/9cf438e02f7ff6e96466a2a9e5316ff4fea819a69f6f197534409be6be561464-stdout
l-wx------ 1 root root 64 Feb 27 23:18 28 -> /run/docker/containerd/10669996b0c8ef8a6e84c33bd54fb78c1776ef3a93abccca96f92337aaf8cfcc/9cf438e02f7ff6e96466a2a9e5316ff4fea819a69f6f197534409be6be561464-stdout
l--------- 1 root root 64 Feb 27 23:18 29 -> /run/docker/containerd/10669996b0c8ef8a6e84c33bd54fb78c1776ef3a93abccca96f92337aaf8cfcc/9cf438e02f7ff6e96466a2a9e5316ff4fea819a69f6f197534409be6be561464-stdout
lrwx------ 1 root root 64 Feb 27 23:15 3 -> socket:[230331]
lr-x------ 1 root root 64 Feb 27 23:18 30 -> /run/docker/containerd/10669996b0c8ef8a6e84c33bd54fb78c1776ef3a93abccca96f92337aaf8cfcc/9cf438e02f7ff6e96466a2a9e5316ff4fea819a69f6f197534409be6be561464-stdout
l--------- 1 root root 64 Feb 27 23:15 4 -> /var/lib/containerd/io.containerd.runtime.v1.linux/moby/10669996b0c8ef8a6e84c33bd54fb78c1776ef3a93abccca96f92337aaf8cfcc/shim.stdout.log
lrwx------ 1 root root 64 Feb 27 23:15 5 -> anon_inode:[eventpoll]
lrwx------ 1 root root 64 Feb 27 23:15 6 -> /var/lib/containerd/io.containerd.runtime.v1.linux/moby/10669996b0c8ef8a6e84c33bd54fb78c1776ef3a93abccca96f92337aaf8cfcc/shim.stdout.log
l--------- 1 root root 64 Feb 27 23:15 7 -> /var/lib/containerd/io.containerd.runtime.v1.linux/moby/10669996b0c8ef8a6e84c33bd54fb78c1776ef3a93abccca96f92337aaf8cfcc/shim.stderr.log
lrwx------ 1 root root 64 Feb 27 23:15 8 -> /var/lib/containerd/io.containerd.runtime.v1.linux/moby/10669996b0c8ef8a6e84c33bd54fb78c1776ef3a93abccca96f92337aaf8cfcc/shim.stderr.log
lrwx------ 1 root root 64 Feb 27 23:15 9 -> anon_inode:[eventpoll]
$ ls /proc/7585/fd | wc -l
30
果然增加了，当 ctrl + C 终止 bash 进程后，containerd-shim 进程打开的文件数量又恢复至 21：
$ ls /proc/7585/fd | wc -l
21
问题总结
至此一切都能串起来了，NFS 服务器宕机后，我们的 Kubernetes 环境中 Postgres 集群的某些组件（说的就是你 patroni 同学）疯狂创建子进程导致操作容器的 containerd-shim 进程打开的命名管道数量急剧上升，最终超过了 Linux 系统的限制，也就是 too many open files。
原文链接：https://blog.crazytaxii.com/posts/k8s_file_descriptor_leaks/
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