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a fast DNS for Kubernetes clusters

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tiglabs/containerdns

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Introduction

ContainerDNS works as an internal DNS server for a Kubernetes cluster.

Components

  • containerdns: the main service to offer DNS query.
  • containerdns-kubeapi: monitor the changes of k8s services, and record the change in the etcd. It offered theoriginal data for containerdns, meanwhille containerdns-kubeapi offers the RESTful api for users to maintain domain records.
  • containerdns-apicmd: it is a shell cmd for user to query\update domain record, it is based on containerdns-kubeapi.
  • etcd: used to store DNS information, etcd v3 api is used.

It is based on the DNS libraryhttps://github.com/miekg/dns.

Feature:

  • fully-cached DNS records
  • backend ip automatic removed when it not avaliable
  • support multiple domain suffix
  • better performance and less jitter
  • load balancing - when a domain has multiple IPs, ContainerDNS chooses an active one randoml
  • session persistence - when a domain name is accessed multiple times from the same source, the same service IP is returned.

Design Architecture

image

Setup / Install

Then get and compile ContainerDNS:

    mkdir -p$GOPATH/src/github.com/tiglabscd$GOPATH/src/github.com/tiglabs    git clone https://github.com/tiglabs/containerdnscd$GOPATH/src/github.com/tiglabs/containerdns    make

Configuration

containerdns

  • config-file: read configs from the file, default "/etc/containerdns/containerdns.conf".

the config file like this:

    [Dns]    dns-domain = containerdns.local.    dns-addr   = 0.0.0.0:53    nameservers =""    subDomainServers =""    cacheSize   = 100000    ip-monitor-path = /containerdns/monitor/status/        [Log]    log-dir    = /export/log/containerdns    log-level  = 2    log-to-stdio =true        [Etcd]    etcd-servers = http://127.0.0.1:2379    etcd-certfile =""    etcd-keyfile =""    etcd-cafile =""        [Fun]    random-one =false    hone-one  =false        [Stats]        statsServer = 127.0.0.1:9600    statsServerAuthToken = @containerdns.com

containerdns-kubeapi

  • config-file: read configs from the file, default "/etc/containerdns/containerdns.conf".

the config file like this:

    [General]    domain=containerdns.local    host = 192.168.169.41    etcd-server = http://127.0.0.1:2379    ip-monitor-path = /containerdns/monitor/status    log-dir    = /export/log/containerdns    log-level  = 2    log-to-stdio =false        [Kube2DNS]    kube-enable = NO        [DNSApi]    api-enable = YES    api-address = 127.0.0.1:9003    containerdns-auth  = 123456789

containerdns-scanner

  • config-file: read configs from the file, default "/etc/containerdns/containerdns-scanner.conf".

the config file like this:

    [General]    core = 0    enable-check =true    hostname = hostname1    log-dir = /export/log/containerdns    log-level = 100    heartbeat-interval = 30    [Check]    check-timeout = 2    check-interval = 10    scann-ports = 22, 80, 8080    enable-icmp =true    ping-timeout = 1000    ping-count = 2    [Etcd]    etcd-machine = http://127.0.0.1:2379    tls-key =    tls-pem =    ca-cert =    status-path = /containerdns/monitor/status    report-path = /containerdns/monitor/report    heart-path = /containerdns/monitor/heart

containerdns-schedule

  • config-file: read configs from the file, default "/etc/containerdns/containerdns-schedule.conf".

the config file like this:

    [General]    schedule-interval = 60    agent-downtime = 60    log-dir = /export/log/containerdns    log-level = 100    hostname = hostname1    force-lock-time = 1800        [Etcd]    etcd-machine = http://127.0.0.1:2379    status-path = /containerdns/monitor/status    report-path = /containerdns/monitor/report    heart-path = /containerdns/monitor/heart    lock-path = /containerdns/monitor/lock

Testing

containerdns-kubeapi

    we use curl to test the user api.

typeA

    % curl -H"Content-Type:application/json;charset=UTF-8"  -X POST -d'{"type":"A","ips":["192.168.10.1","192.168.10.2","192.168.10.3"]}'  http://127.0.0.1:9001/containerdns/api/cctv2?token="123456789"          OK

typeCname

    % curl -H"Content-Type:application/json;charset=UTF-8"   -X POST -d'{"type":"cname","alias":"tv1"}' http://127.0.0.1:9001/containerdns/api/cctv2.containerdns.local?token="123456789"     OK

containerdns

typeA

    % nslookup qiyf-nginx-5.default.svc.containerdns.local 127.0.0.1    Server:         127.0.0.1    Address:        127.0.0.1#53    Name:   qiyf-nginx-5.default.svc.containerdns.local    Address: 192.168.19.113    if the domain have more than one ip, containerdns will return a radom one.    % nslookup cctv2.containerdns.local 127.0.0.1    Server:         127.0.0.1    Address:        127.0.0.1#53    Name:   cctv2.containerdns.local    Address: 192.168.10.3

typeCname

    % nslookup tv1.containerdns.local 127.0.0.1    Server:         127.0.0.1    Address:        127.0.0.1#53    tv1.containerdns.local    canonical name = cctv2.containerdns.local.    Name:   cctv2.containerdns.local    Address: 192.168.10.3

monitor

     If the domain may have multiple ips, then dns-scanner is used to monitor the ips behand the domain.      When the service is not reachable, dns-scanner will change the status of the ip. And the containerdns will monitor the ip status,      when it comes down, containerdns will choose a good one.          cctv2.containerdns.local    ips[192.168.10.1,192.168.10.2,192.168.10.3]         % nslookup cctv2.containerdns.local 127.0.0.1    Server:         127.0.0.1    Address:        127.0.0.1#53    Name:   cctv2.containerdns.local    Address: 192.168.10.3        % etcdctl get /containerdns/monitor/status/192.168.10.3    {"status":"DOWN"}    % nslookup cctv2.containerdns.local 127.0.0.1    Server:         127.0.0.1    Address:        127.0.0.1#53    Name:   cctv2.containerdns.local    Address: 192.168.10.1        we query the domain cctv2.containerdns.local form containerdns we get the ip 192.168.10.3, then we shut down the service, we query the domain again    we get the ip 192.168.10.1.

Performance Test

Testing Conditions

Physical hardware

    NIC: gigabit ethernet card    CPUs: 32    RAM: 32G    OS: CentOS-7.2

Testing Software

    queryperf

Test result

image

DPDK-based Optimization

Improve ContainerDNS throughput by leveraging the DPDK technology to reach nearly 10 million QPS,https://github.com/tiglabs/containerdns/kdns and the code is also production-ready.

Reference

Reference to cite when you use ContainerDNS in a paper or technical report: "Haifeng Liu, Shugang Chen, Yongcheng Bao, Wanli Yang, and Yuan Chen, Wei Ding, Huasong Shan. A High Performance, Scalable DNS Service for Very Large Scale Container Cloud Platforms. In 19th International Middleware Conference Industry, December 10–14, 2018, Rennes, France. "

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