Question

Heapster作为kubernetes安装过程中默认安装的一个插件，见安装heapster插件。这对于集群监控十分有用，同时在Horizontal Pod Autoscaling中也用到了，HPA将Heapster作为Resource Metrics API，向其获取metric，做法是在kube-controller-manager 中配置--api-server指向kube-aggregator，也可以使用heapster来实现，通过在启动heapster的时候指定--api-server=true。

Heapster可以收集Node节点上的cAdvisor数据，还可以按照kubernetes的资源类型来集合资源，比如Pod、Namespace域，可以分别获取它们的CPU、内存、网络和磁盘的metric。默认的metric数据聚合时间间隔是1分钟。

架构

下面是Heapster架构图：

Heapser是用Go语言开发Kubernetes集群计算资源使用情况的数据采集工具，编译后可以直接以一个二进制文件运行，通过向heapster传递的参数来指定数据采集行为，这些数据可以选择多种sink方式，例如Graphite、influxDB、OpenTSDB、ElasticSearch、Kafka等。

使用案例

Heapster使用起来很简单，本身就是二进制文件，直接使用命令行启动，也可以放在容器里运行，在作为kubernetes插件运行时，我们是直接放在容器中的，见安装heapster插件。

运行

下面是heapster的启动参数：

Flag	Description
--allowed-users string	comma-separated list of allowed users
--alsologtostderr	log to standard error as well as files
--api-server	Enable API server for the Metrics API. If set, the Metrics API will be served on --insecure-port (internally) and --secure-port (externally).
--authentication-kubeconfig string	kubeconfig file pointing at the 'core' kubernetes server with enough rights to create tokenaccessreviews.authentication.k8s.io.
--authentication-token-webhook-cache-ttl duration	The duration to cache responses from the webhook token authenticator. (default 10s)
--authorization-kubeconfig string	kubeconfig file pointing at the ‘core' kubernetes server with enough rights to create subjectaccessreviews.authorization.k8s.io
--authorization-webhook-cache-authorized-ttl duration	The duration to cache 'authorized' responses from the webhook authorizer. (default 10s)
--authorization-webhook-cache-unauthorized-ttl duration	The duration to cache 'unauthorized' responses from the webhook authorizer. (default 10s)
--bind-address ip	The IP address on which to listen for the --secure-port port. The associated interface(s) must be reachable by the rest of the cluster, and by CLI/web clients. If blank, all interfaces will be used (0.0.0.0). (default 0.0.0.0)
--cert-dir string	The directory where the TLS certs are located (by default /var/run/kubernetes). If --tls-cert-file and --tls-private-key-file are provided, this flag will be ignored. (default "/var/run/kubernetes")
--client-ca-file string	If set, any request presenting a client certificate signed by one of the authorities in the client-ca-file is authenticated with an identity corresponding to the CommonName of the client certificate.
--contention-profiling	Enable contention profiling. Requires --profiling to be set to work.
--disable-export	Disable exporting metrics in api/v1/metric-export
--enable-swagger-ui	Enables swagger ui on the apiserver at /swagger-ui
--heapster-port int	port used by the Heapster-specific APIs (default 8082)
--historical-source string	which source type to use for the historical API (should be exactly the same as one of the sink URIs), or empty to disable the historical API
--label-seperator string	seperator used for joining labels (default ",")
--listen-ip string	IP to listen on, defaults to all IPs
--log-backtrace-at traceLocation	when logging hits line file:N, emit a stack trace (default :0)
--log-dir string	If non-empty, write log files in this directory
--log-flush-frequency duration	Maximum number of seconds between log flushes (default 5s)
--logtostderr	log to standard error instead of files (default true)
--max-procs int	max number of CPUs that can be used simultaneously. Less than 1 for default (number of cores)
--metric-resolution duration	The resolution at which heapster will retain metrics. (default 1m0s)
--profiling	Enable profiling via web interface host:port/debug/pprof/ (default true)
--requestheader-allowed-names stringSlice	List of client certificate common names to allow to provide usernames in headers specified by --requestheader-username-headers. If empty, any client certificate validated by the authorities in --requestheader-client-ca-file is allowed.
--requestheader-client-ca-file string	Root certificate bundle to use to verify client certificates on incoming requests before trusting usernames in headers specified by --requestheader-username-headers
--requestheader-extra-headers-prefix stringSlice	List of request header prefixes to inspect. X-Remote-Extra- is suggested. (default [x-remote-extra-])
--requestheader-group-headers stringSlice	List of request headers to inspect for groups. X-Remote-Group is suggested. (default [x-remote-group])
--requestheader-username-headers stringSlice	List of request headers to inspect for usernames. X-Remote-User is common. (default [x-remote-user])
--secure-port int	The port on which to serve HTTPS with authentication and authorization. If 0, don't serve HTTPS at all. (default 6443)
--sink *flags.Uris	external sink(s) that receive data (default [])
--source *flags.Uris	source(s) to watch (default [])
--stderrthreshold severity	logs at or above this threshold go to stderr (default 2)
--tls-ca-file string	If set, this certificate authority will used for secure access from Admission Controllers. This must be a valid PEM-encoded CA bundle. Altneratively, the certificate authority can be appended to the certificate provided by --tls-cert-file.
--tls-cert string	file containing TLS certificate
--tls-cert-file string	File containing the default x509 Certificate for HTTPS. (CA cert, if any, concatenated after server cert). If HTTPS serving is enabled, and --tls-cert-file and --tls-private-key-file are not provided, a self-signed certificate and key are generated for the public address and saved to /var/run/kubernetes.
--tls-client-ca string	file containing TLS client CA for client cert validation
--tls-key string	file containing TLS key
--tls-private-key-file string	File containing the default x509 private key matching --tls-cert-file.
--tls-sni-cert-key namedCertKey	A pair of x509 certificate and private key file paths, optionally suffixed with a list of domain patterns which are fully qualified domain names, possibly with prefixed wildcard segments. If no domain patterns are provided, the names of the certificate are extracted. Non-wildcard matches trump over wildcard matches, explicit domain patterns trump over extracted names. For multiple key/certificate pairs, use the --tls-sni-cert-key multiple times. Examples: "example.key,example.crt" or "*.foo.com,foo.com:foo.key,foo.crt". (default [])
--v Level	log level for V logs
--version	print version info and exit
--vmodule moduleSpec	comma-separated list of pattern=N settings for file-filtered logging

Version

version: v1.4.0 commit: 546ab66f

API使用

Heapster提供RESTful API接口，下面以获取spark-cluster namespace的memory usage为例讲解Heapster API的使用。

构造URL地址

https://172.20.0.113:6443/api/v1/proxy/namespaces/kube-system/services/heapster/api/v1/model/namespaces/spark-cluster/metrics/memory/usage?start=2017-10-16T09:14:00Z&end=2017-10-16T09:16:00Z

结果

访问该地址获取的结果是这样的：

{
  "metrics": [
   {
    "timestamp": "2017-10-16T09:14:00Z",
    "value": 322592768
   },
   {
    "timestamp": "2017-10-16T09:15:00Z",
    "value": 322592768
   },
   {
    "timestamp": "2017-10-16T09:16:00Z",
    "value": 322592768
   }
  ],
  "latestTimestamp": "2017-10-16T09:16:00Z"
 }

注意：Heapster中查询的所有值都是以最小单位为单位，比如CPU为1milicore，内存为B。

第一部分：Heapster API地址

https://172.20.0.113:6443/api/v1/proxy/namespaces/kube-system/services/heapster/

可以使用下面的命令获取:

$ kubectl cluster-info
Heapster is running at https://172.20.0.113:6443/api/v1/proxy/namespaces/kube-system/services/heapster
...

第二部分：Heapster API参数

/api/v1/model/namespaces/spark-cluster/metrics/memory/usage

表示查询的是spark-cluster namespace中的memory/usage的metrics。

第三部分：时间片

?start=2017-10-16T09:14:00Z&end=2017-10-16T09:16:00Z

查询参数为时间片：包括start和end。使用RFC-3339时间格式，在Linux系统中可以这样获取：

$ date --rfc-3339="seconds"
2017-10-16 17:23:20+08:00

该时间中的空格替换成T，最后的+08:00替换成Z代表时区。可以只指定start时间，end时间自动设置为当前时间。

参考

• kubernetes metrics
• Heapster metric model
• Heapster storage schema