Kubenurse is a little service that monitors all network connections in a Kubernetes cluster. Kubenurse measures request durations, records errors and exports those metrics in Prometheus format.
Here's an overview of the checks performed by kubenurse, which are exposed as labels for the various duration/error prometheus metrics.
Once the kubenurse pods are up and running and scraped by your metrics agent, you can import the example dashboard to start scrutinizing network latencies and errors.
All performed checks expose metrics which can be used to monitor/alert:
- node-to-node network latencies and errors
- pod-to-apiserver communication
- Ingress roundtrip latencies and errors
- Service roundtrip latencies and errors (kube-proxy / your CNI)
- Major kube-apiserver issues
- kube-dns (or CoreDNS) errors
- External DNS resolution errors (ingress URL resolution)
At /metrics you will find the following metrics:
| metric name | labels | description |
|---|---|---|
kubenurse request duration |
type |
(deprecated since v1.13.0) latency histogram for request duration, replaced with the metric below. |
kubenurse httpclient request duration seconds |
type |
latency histogram for request duration, partitioned by request type |
kubenurse httpclient trace request duration seconds |
type, event |
latency histogram for httpclient trace metric instrumentation, partitioned by request type and httptrace connection events |
kubenurse httpclient requests total |
type, code, method |
counter for the total number of http requests, partitioned by HTTP code, method, and request type |
kubenurse errors total |
type, event |
error counter, partitioned by httptrace event and request type |
kubenurse neighbourhood incoming checks |
n\a | gauge which reports how many unique neighbours have queried the current pod in the last minute |
For metrics partitioned with a type label, it is possible to precisely know
which request type increased an error counter, or to compare the latencies of
multiple request types, for example compare how your service and ingress
latencies differ.
Some event labels include dns_start, got_conn, tls_handshake_done, and
more. the details can be seen in the
httptrace.go
file.
You can get the Docker image from Docker Hub. The examples directory contains manifests which can be used to deploy kubenurse to the kube-system namespace of your cluster.
You can also deploy kubenurse with Helm, the Chart can be found in repository https://postfinance.github.io/kubenurse/ or directory ./helm/kubenurse/.
The following command can be used to install kubenurse with Helm: helm upgrade [RELEASE_NAME] --install --repo https://postfinance.github.io/kubenurse/ kubenurse.
helm parameters list
| Setting | Description | Default |
|---|---|---|
| daemonset.image.repository | The repository name | postfinance/kubenurse |
| daemonset.image.tag | The tag/ version of the image | v1.4.0 |
| daemonset.podLabels | Additional labels to be added to the pods of the daemonset | [] |
| daemonset.podAnnotations | Additional annotations to be added to the pods of the daemonset | [] |
| daemonset.podSecurityContext | The security context of the daemonset | {} |
| daemonset.priorityClassName | The priority class name for the daemonset pods | "" |
| daemonset.containerSecurityContext | The security context of the containers within the pods of the daemonset | {} |
| daemonset.containerResources | The container resources of the containers within the pods of the daemonset | {} |
| daemonset.containerImagePullPolicy | The container image pull policy the pods of the daemonset | IfNotPresent |
| daemonset.tolerations | The tolerations of the daemonset | See Default tolerations below |
| daemonset.dnsConfig | Specifies the DNS parameters of the pods in the daemonset | {} |
| daemonset.volumeMounts | Additional volumeMounts to be added to the pods of the daemonset | [] |
| daemonset.volumes | Additional volumes to be added to the daemonset | [] |
| daemonset.rollingUpdate.maxUnavailable | The maximum number of DaemonSet pods that can be unavailable during the update | 34% |
| daemonset.rollingUpdate.maxSurge | The maximum number of nodes with an existing available DaemonSet pod that can have an updated pod during an update | |
| serviceMonitor.enabled | Adds a ServiceMonitor for use with Prometheus-operator | false |
| serviceMonitor.labels | Additional labels to be added to the ServiceMonitor | {} |
| serviceMonitor.relabelings | Additional relabelings to be added to the endpoint of the ServiceMonitor | [] |
| serviceAccount.name | The name of the service account which is used | Release.Name |
| service.name | The name of service which exposes the kubenurse application | 8080-8080 |
| service.port | The port number of the service | 8080 |
| service.labels | Additional labels to be added to the Service | |
| ingress.enabled | Enable/ Disable the ingress | true |
| ingress.className | The classname of the ingress controller (e.g. the nginx ingress controller) | nginx |
| ingress.url | The url of the ingress; e.g. kubenurse.westeurope.cloudapp.example.com | dummy-kubenurse.example.com |
| insecure | Set KUBENURSE_INSECURE environment variable |
true |
| allow_unschedulable | Sets KUBENURSE_ALLOW_UNSCHEDULABLE environment variable |
false |
| neighbour_filter | Sets KUBENURSE_NEIGHBOUR_FILTER environment variable |
app.kubernetes.io/name=kubenurse |
| neighbour_limit | Sets KUBENURSE_NEIGHBOUR_LIMIT environment variable |
10 |
| histogram_buckets | Sets KUBENURSE_HISTOGRAM_BUCKETS environment variable |
|
| extra_ca | Sets KUBENURSE_EXTRA_CA environment variable |
|
| extra_checks | Sets KUBENURSE_EXTRA_CHECKS environment variable |
|
| kubernetes_service_dns | Sets KUBERNETES_SERVICE_DNS environment variable |
|
| check_api_server_direct | Sets KUBENURSE_CHECK_API_SERVER_DIRECT environment variable |
true |
| check_api_server_dns | Sets KUBENURSE_CHECK_API_SERVER_DNS environment variable |
true |
| check_me_ingress | Sets KUBENURSE_CHECK_ME_INGRESS environment variable |
true |
| check_me_service | Sets KUBENURSE_CHECK_ME_SERVICE environment variable |
true |
| check_neighbourhood | Sets KUBENURSE_CHECK_NEIGHBOURHOOD environment variable |
true |
| check_interval | Sets KUBENURSE_CHECK_INTERVAL environment variable |
5s |
| reuse_connections | Sets KUBENURSE_REUSE_CONNECTIONS environment variable |
false |
| use_tls | Sets KUBENURSE_USE_TLS environment variable |
false |
| cert_file | Sets KUBENURSE_CERT_FILE environment variable |
|
| cert_key | Sets KUBENURSE_CERT_KEY environment variable |
kubenurse environment variables list
KUBENURSE_INGRESS_URL: An URL to the kubenurse in order to check the ingressKUBENURSE_SERVICE_URL: An URL to the kubenurse in order to check the Kubernetes serviceKUBENURSE_INSECURE: If "true", TLS connections will not validate the certificateKUBENURSE_EXTRA_CA: Additional CA cert path for TLS connectionsKUBENURSE_EXTRA_CHECKS: Additional checks, specified as a list (separated by a vertical bar|) where each entry of the list has the format:<metric_name>:<url_to_check>. For examplegoogle:https://www.google.ch/|cloudflare:https://www.cloudflare.com/KUBENURSE_NAMESPACE: Namespace in which to look for the neighbour kubenursesKUBENURSE_NEIGHBOUR_FILTER: A Kubernetes label selector (eg.app=kubenurse) to filter neighbour kubenursesKUBENURSE_NEIGHBOUR_LIMIT: The maximum number of neighbours each kubenurse will queryKUBENURSE_ALLOW_UNSCHEDULABLE: If this is"true", path checks to neighbouring kubenurses are made even if they are running on unschedulable nodes.KUBENURSE_CHECK_API_SERVER_DIRECT: If this is"true"kubenurse will perform the check [API Server Direct](#API Server Direct). default is "true"KUBENURSE_CHECK_API_SERVER_DNS: If this is"true", kubenurse will perform the check [API Server DNS](#API Server DNS). default is "true"KUBENURSE_CHECK_ME_INGRESS: If this is"true", kubenurse will perform the check [Me Ingress](#Me Ingress). default is "true"KUBENURSE_CHECK_ME_SERVICE: If this is"true", kubenurse will perform the check [Me Service](#Me Service). default is "true"KUBENURSE_CHECK_NEIGHBOURHOOD: If this is"true", kubenurse will perform the check Neighbourhood. default is "true"KUBENURSE_CHECK_INTERVAL: the frequency to perform kubenurse checks. the string should be formatted for time.ParseDuration. defaults to5sKUBENURSE_REUSE_CONNECTIONS: whether to reuse connections or not for all checks. default is "false"KUBENURSE_HISTOGRAM_BUCKETS: optional comma-separated list of float64, used in place of the default prometheus histogram bucketsKUBENURSE_USE_TLS: If this is"true", enable TLS endpoint on port 8443KUBENURSE_CERT_FILE: Certificate to use with TLS endpointKUBENURSE_CERT_KEY: Key to use with TLS endpoint
Following variables are injected to the Pod by Kubernetes and should not be defined manually:
KUBERNETES_SERVICE_HOST: Host to communicate to the kube-apiserverKUBERNETES_SERVICE_PORT: Port to communicate to the kube-apiserver
The DNS name of the API server can be configured with the
KUBERNETES_SERVICE_DNS environment variable, and it defaults to
kubernetes.default.svc.cluster.local.
The kubenurse service listens for http requests on port 8080 (optionally https on port 8443) and exposes endpoints:
/: Redirects to/alive/alive: Returns a pretty printed JSON with the check results, described below/alwayshappy: Returns http-200 which is used for testing itself/metrics: Exposes Prometheus metrics
The /alive endpoint returns a JSON like this with status code 200 if everything is OK else 500:
{
"api_server_direct": "ok",
"api_server_dns": "ok",
"me_ingress": "ok",
"me_service": "ok",
"hostname": "kubenurse-1234-x2bwx",
"neighbourhood_state": "ok",
"neighbourhood": [
{
"PodName": "kubenurse-1234-8fh2x",
"PodIP": "10.10.10.67",
"HostIP": "10.12.12.66",
"NodeName": "k8s-66.example.com",
"Phase": "Running"
},
{
"PodName": "kubenurse-1234-ffjbs",
"PodIP": "10.10.10.138",
"HostIP": "10.12.12.89",
"NodeName": "k8s-89.example.com",
"Phase": "Running"
}
],
"headers": {
"Accept": [
"text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8"
],
"Accept-Encoding": [
"gzip, deflate, br"
],
...
}
}Every five seconds, the checks described below are run.
Checks the /version endpoint of the Kubernetes API Server through
the direct link (KUBERNETES_SERVICE_HOST, KUBERNETES_SERVICE_PORT).
Metric type: api_server_direct
Checks the /version endpoint of the Kubernetes API Server through
the Cluster DNS URL https://kubernetes.default.svc:$KUBERNETES_SERVICE_PORT.
This also verifies a working kube-dns deployment.
Metric type: api_server_dns
Checks if the kubenurse is reachable at the /alwayshappy endpoint behind the ingress.
This address is provided by the environment variable KUBENURSE_INGRESS_URL that
could look like https://kubenurse.example.com.
This also verifies a correct upstream DNS resolution.
Metric type: me_ingress
Checks if the kubenurse is reachable at the /alwayshappy endpoint through the Kubernetes service.
The address is provided by the environment variable KUBENURSE_SERVICE_URL that
could look like http://kubenurse.mynamespace.default.svc:8080.
This also verifies a working kube-proxy setup.
Metric type: me_service
Checks if every neighbour kubenurse is reachable at the /alwayshappy endpoint.
Neighbours are discovered by querying the kube-apiserver for every Pod in the
KUBENURSE_NAMESPACE with label KUBENURSE_NEIGHBOUR_FILTER.
The request is done directly to the Pod-IP (port 8080, or 8443 if TLS is enabled) and the metric types contains the prefix
path_ and the hostname of the kubelet on which the neighbour kubenurse should run.
Only kubenurses on nodes that are schedulable are considered as neighbours,
this can be changed by setting KUBENURSE_ALLOW_UNSCHEDULABLE="true".
Metric type: path_$KUBELET_HOSTNAME
The number of checks for the neighbourhood used to grow as kubenurse impractical on large clusters, as documented in issue
#55.
To combat this, a node filtering feature was implemented, which works as follows
- kubenurse computes the
sha256checksums for all neighbours' node names - it sorts those checksums (this is actually implemented with a max-heap)
- it computes its own node name checksum, and queries the next 10 (per default) nodes in the sorted checksums list
Here's an example with 6 nodes, where each node queries the next 3 nodes:
Thanks to this, every node is making queries to the same 10 nodes, unless one of those nodes disappears, in which case kubenurse will pick the next node in the sorted checksums list. This comes with several advantages:
- because of the way we first hash the node names, the checks are randomly distributed, independant of the node names. if we only picked the 10 next nodes in a sorted list of the node names, then we might have biased the results in environments where node names are sequential
- metrics-wise, a
kubenursepod should typically only have entries for ca. 10 other neighbouring nodes worth of checks, which greatly reduces the load on your monitoring infrastructure - because we use a deterministic algorithm to choose which nodes to query, the metrics churn rate stays minimal. (that is, if we randomly picked 10 nodes for every check, then in the end there would be one prometheus bucket for every node on the cluster, which would put useless load on the monitoring infrastructure)
Per default, the neighbourhood filtering is set to 10 nodes, which means that on cluster with more than 10 nodes, each kubenurse will query exactly 10 nodes, as described above.
It is possible to check that each node receives the proper number of
neighbourhood queries with the kubenurse_neighbourhood_incoming_checks
metric. If you have the neighbourhood limit set to e.g. 10, then this
metric should be equal to 10 on all nodes, with some variations during a
rollout restart.
To bypass the node filtering feature, you simply need to set the
KUBENURSE_NEIGHBOUR_LIMIT environment variable to 0.