Kubernetes 排错指南工具篇

Kubernetes 排错指南工具篇

本文介绍在 Kubernetes 排错中常用的工具。

必备工具

kubectl：用于查看 Kubernetes 集群以及容器的状态，如 kubectl describe pod journalctl：用于查看 Kubernetes 组件日志，如 journalctl -u kubelet -liptables和ebtables：用于排查 Service 是否工作，如 iptables -t nat -nL 查看 kube-proxy 配置的 iptables 规则是否正常tcpdump：用于排查容器网络问题，如 tcpdump -nn host 10.240.0.8perf：Linux 内核自带的性能分析工具，常用来排查性能问题

sysdig

sysdig 是一个容器排错工具，提供了开源和商业版本。对于常规排错来说，使用开源版本即可。

除了 sysdig，还可以使用其他两个辅助工具

csysdig：与 sysdig 一起自动安装，提供了一个命令行界面sysdig-inspect：为 sysdig 保存的跟踪文件提供了一个图形界面

安装

# on Ubuntucurl -s https://s3.amazonaws.com/download.draios.com/DRAIOS-GPG-KEY.public | apt-key add -curl -s -o etc/apt/sources.list.d/draios.list http://download.draios.com/stable/deb/draios.listapt-get updateapt-get -y install linux-headers-$(uname -r)apt-get -y install sysdig# on REHLrpm --import https://s3.amazonaws.com/download.draios.com/DRAIOS-GPG-KEY.publiccurl -s -o etc/yum.repos.d/draios.repo http://download.draios.com/stable/rpm/draios.reporpm -i http://mirror.us.leaseweb.net/epel/6/i386/epel-release-6-8.noarch.rpmyum -y install kernel-devel-$(uname -r)yum -y install sysdig# on MacOSbrew install sysdig

示例

# Refer https://sysdig.org/wiki/sysdig-examples/.# View the top network connectionssudo sysdig -pc -c topconns# View the top network connections inside the wordpress1 containersudo sysdig -pc -c topconns container.name=wordpress1# Show the network data exchanged with the host 192.168.0.1sudo sysdig fd.ip=192.168.0.1sudo sysdig -s2000 -A -c echo_fds fd.cip=192.168.0.1# List all the incoming connections that are not served by apache.sudo sysdig -p"%proc.name %fd.name" "evt.type=accept and proc.name!=httpd"# View the CPU/Network/IO usage of the processes running inside the container.sudo sysdig -pc -c topprocs_cpu container.id=2e854c4525b8sudo sysdig -pc -c topprocs_net container.id=2e854c4525b8sudo sysdig -pc -c topfiles_bytes container.id=2e854c4525b8# See the files where apache spends the most time doing I/Osudo sysdig -c topfiles_time proc.name=httpd# Show all the interactive commands executed inside a given container.sudo sysdig -pc -c spy_users # Show every time a file is opened under etc.sudo sysdig evt.type=open and fd.name# View the list of processes with container contextsudo csysdig -pc

更多示例和使用方法可以参考 Sysdig User Guide。

Weave Scope

Weave Scope 是另外一款可视化容器监控和排错工具。与 sysdig 相比，它没有强大的命令行工具，但提供了一个简单易用的交互界面，自动描绘了整个集群的拓扑，并可以通过插件扩展其功能。从其官网的介绍来看，其提供的功能包括

交互式拓扑界面图形模式和表格模式过滤功能搜索功能实时度量容器排错插件扩展

Weave Scope 由 App 和 Probe 两部分组成，它们

Probe 负责收集容器和宿主的信息，并发送给 AppApp 负责处理这些信息，并生成相应的报告，并以交互界面的形式展示

安装

kubectl apply -f "https://cloud.weave.works/k8s/scope.yaml?k8s-version=$(kubectl version | base64 | tr -d '\n')&k8s-service-type=LoadBalancer"

查看界面

安装完成后，可以通过 weave-scope-app 来访问交互界面

kubectl -n weave get service weave-scope-appkubectl -n weave port-forward service/weave-scope-app :80

已知问题

在 Ubuntu 内核 4.4.0 上面开启 --probe.ebpf.connections 时（默认开启），Node 有可能会因为内核问题而不停重启：

[ 263.736006] CPU: 0 PID: 6309 Comm: scope Not tainted 4.4.0-119-generic #143-Ubuntu[ 263.736006] Hardware name: Microsoft Corporation Virtual Machine/Virtual Machine, BIOS 090007 06/02/2017[ 263.736006] task: ffff88011cef5400 ti: ffff88000a0e4000 task.ti: ffff88000a0e4000[ 263.736006] RIP: 0010:[] [] bpf_map_lookup_elem+0x6/0x20[ 263.736006] RSP: 0018:ffff88000a0e7a70 EFLAGS: 00010082[ 263.736006] RAX: ffffffff8117cd70 RBX: ffffc90000762068 RCX: 0000000000000000[ 263.736006] RDX: 0000000000000000 RSI: ffff88000a0e7cd8 RDI: 000000001cdee380[ 263.736006] RBP: ffff88000a0e7cf8 R08: 0000000005080021 R09: 0000000000000000[ 263.736006] R10: 0000000000000020 R11: ffff880159e1c700 R12: 0000000000000000[ 263.736006] R13: ffff88011cfaf400 R14: ffff88000a0e7e38 R15: ffff88000a0f8800[ 263.736006] FS: 00007f5b0cd79700(0000) GS:ffff88015b600000(0000) knlGS:0000000000000000[ 263.736006] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033[ 263.736006] CR2: 000000001cdee3a8 CR3: 000000011ce04000 CR4: 0000000000040670[ 263.736006] Stack:[ 263.736006] ffff88000a0e7cf8 ffffffff81177411 0000000000000000 00001887000018a5[ 263.736006] 000000001cdee380 ffff88000a0e7cd8 0000000000000000 0000000000000000[ 263.736006] 0000000005080021 ffff88000a0e7e38 0000000000000000 0000000000000046[ 263.736006] Call Trace:[ 263.736006] [] ? __bpf_prog_run+0x7a1/0x1360[ 263.736006] [] ? update_curr+0x79/0x170[ 263.736006] [] ? update_cfs_shares+0xbc/0x100[ 263.736006] [] ? update_curr+0x79/0x170[ 263.736006] [] ? dput+0xb8/0x230[ 263.736006] [] ? follow_managed+0x265/0x300[ 263.736006] [] ? kmem_cache_alloc_trace+0x1d4/0x1f0[ 263.736006] [] ? seq_open+0x5a/0xa0[ 263.736006] [] ? probes_open+0x33/0x100[ 263.736006] [] ? dput+0x34/0x230[ 263.736006] [] ? mntput+0x24/0x40[ 263.736006] [] trace_call_bpf+0x37/0x50[ 263.736006] [] kretprobe_perf_func+0x3d/0x250[ 263.736006] [] ? pre_handler_kretprobe+0x135/0x1b0[ 263.736006] [] kretprobe_dispatcher+0x3d/0x60[ 263.736006] [] ? do_sys_open+0x1b2/0x2a0[ 263.736006] [] ? kretprobe_trampoline_holder+0x9/0x9[ 263.736006] [] trampoline_handler+0x133/0x210[ 263.736006] [] ? do_sys_open+0x1b2/0x2a0[ 263.736006] [] kretprobe_trampoline+0x25/0x57[ 263.736006] [] ? kretprobe_trampoline_holder+0x9/0x9[ 263.736006] [] SyS_openat+0x14/0x20[ 263.736006] [] entry_SYSCALL_64_fastpath+0x1c/0xbb

解决方法有两种

禁止 eBPF 探测，如 --probe.ebpf.connections=false升级内核，如升级到 4.13.0