Tuesday, February 26, 2019

Change the Reclaim Policy of a PersistentVolume In OKE


  By default OKE(Oracle Kubernete Engine)  storageclass is oci which is OCI block volume
  If we don't specify storageclass in yaml file,  OKE would automatically create block volumes as persistent volumes and attach to pods for us which is very convenient.
 However reclaim policy of persistent volumes is "DELETE"
 It means if we delete pv and pvc OKE created, OKE would delete block volumes in OCI as well.


  To prevent potential data loss due to reclaim policy " DELETE" , we can update it to be "RETAIN"

kubectl patch pv <your-pv-name> -p '{"spec":{"persistentVolumeReclaimPolicy":"Retain"}}'

Please refer kubernete doc for more details

Monday, February 18, 2019

Docker Network Related Issue When We Build Docker Images


  When I ran "docker build -t oracle/database:19c  .  "  , it always error out on yum repo issues as below
https://yum.oracle.com/repo/OracleLinux/OL7/UEKR4/x86_64/repodata/repomd.xml: [Errno 12] Timeout on https://yum.oracle.com/repo/OracleLinux/OL7/UEKR4/x86_64/repodata/repomd.xml: (28, 'Resolving timed out after 30540 milliseconds')


I checked around proxy settings according to note. I didn't find any issues.
I added proxy settings into Dockerfile like below to inform yum to use proxy
RUN echo "proxy=http://<proxy server IP address>:80" >> /etc/yum.conf
"docker login iad.ocir.io" was working fine.
DNS entries in /etc/resolv.conf  of the container had correct settings
I  restarted docker daemon , didn't work

After checking around, I suspected it was related to docker network
We created a new bridge network in docker via "docker network create  henrynetwork"
In this way, we can force docker build to use new bridge network instead of default one
 "docker build --network=henrynetwork -t oracle/database:19c  .  "
It works.  So far I don't have any clue why default bridge network won't work.  But new bridge network will work around it. 

Tip For Size of Oracle DB Tempfiles


   You will see big difference between ls -l and du -sm  on the same Oracle DB Tempfiles
# ls -l o1_mf_temp_fpq46223_.dbf
-rw-r-----. 1 54321 54321 34358697984 Oct 14 06:21 o1_mf_temp_fpq46223_.dbf
--> 32G
# du -sm o1_mf_temp_fpq46223_.dbf
6       o1_mf_temp_fpq46223_.dbf


 ls -l  reads the attributions of files, so when the tempfile was created, it was created as 32G. So both allocated and unallocated together will be 32G.
However du is counting the actual number of allocated blocks.The unallocated blocks read as 0, take up no space on disk.
In this way, du is closer to the truth about how much space was used by DB.
ls shows us total size of allocated and unallocated blocks

Saturday, February 16, 2019

Tips of How to Understand CustomResourceDefinition in K8S

In Kubernetes world, CustomResourceDefinition (CRD) will play a big role when we extend K8S cluster.  In the future, CRD may include even core K8S components like pod, deployment, statefulset......etc.  see CNCF youtube link
The basic logic is :
Once they are defined, they will be stored in Etcd.  They are purely text file, We can define whatever we want. K8S just regard them as text config file and put them in Etcd. K8S won't check if the CRD has been implemented or not. It won't error out if CRD is not implemented.  Related kubectl commands:
lubectl get crd <name>  -o yaml    kubectl api-resources   kubectl api-versions
  • We implement the business logic via GO
This part will implement how we handle events related to the CRD we define.  K8S will send events to this part, this part will do business logic for the events. K8S cluster is events driven system. All events are put in different queues inside K8S core. 
  • We create yaml files to use the CRD we define
We create yaml to generate some events (create, update, delete....)  to K8S,  our 2nd part above will receive these events and do the business logic we implement.

Fortunately kubebuilder  does lots of scaffolding work for us. More details Refer kubebuilder book

Thursday, February 14, 2019

How To Put Binary or Text Config Files into K8s ConfigMap


  We often have all kind of config files for our Apps.  From binary wallet files to simple text config files, we need to store them somewhere where apps can access.  It is not a good idea to put these config files inside docker images or PV(persistent volume) as it would make the pod less portable and hard to scale and migrate. Fortunately from K8S v1.10 , Configmap would support both binary and text config files .  Here are some examples how we utilize configmap to achieve that. Mounted configmap are updated automatically. More details please refer kubernetes configmap doc


We plan to create 2 configmaps . One for binary files like ewallet and one for text config files  like sysctl.conf, init.ora....

  • Use kubectl create configmap walletconfigmap --from-file=ewallet1 --from-file=ewallet2
  • Use kubectl create configmap textconfigmap --from-file=sysctl.conf  --from-file=jdbc.xml  --from-file=init.ora  
  • Use kubectl get configmap walletconfigmap -o yaml . You would see ewallet would be stored as binaryData

apiVersion: v1
- apiVersion: v1
    ewallet: sdfsweffewg.....
  • Mount wallet configmap as a volume in the pod with correct config file path . ie wallet file is on /etc/oracle/tde
  • Mount text configmap as a volume in the pod with correct config file path . ie text file is on /opt/oracle/dbs
- name: wallet-volume
          name: walletconfigmap 
- name: textconfig-volume
          name: textconfigmap 

Under container section of yaml file
- name: wallet-volume
  mountPath: /etc/oracle/tde
- name: textconfig-volume
  mountPath: /opt/oracle/dbs

  • In this way, when we into the pod via kubectl exec -it  <pod name> /bin/bash , we would see ewallet1 ewallet2 in /etc/oracle/tde  and  sysctl.conf jdbc.xml and init.ora are in /opt/oracle/dbs.
  • If we do some updates on configmap , K8S will sync them periodically.

Wednesday, February 13, 2019

A Simple F5 Bigip iRule to Rewrite Urls

Rewrite example.com/test/test/mytest.html  --> example.com/test/mytest.html

    if { [string tolower [HTTP::uri]] starts_with "/test/test" } {
        set uri [string map -nocase {"/test/test" "/test"} [HTTP::uri]]
        HTTP::uri $uri

Tuesday, February 12, 2019

How to Convert Kubeconfig CA string to Readable CA Format


  In ~/.kube/config  , we have kubeconfig file which has CA string like below. We would like to convert it to a readable CA format.
$ cat config
apiVersion: v1
- cluster:
  name: kubernetes


First to use base64 decode the string to PEM
$ echo 'above string' | base64 -d  > /tmp/1.crt
Output is like:

Second to use openssl to convert it to readable format
openssl x509 -in  /tmp/1.crt  -noout -text
Output is like
        Version: 3 (0x2)
        Serial Number: 8050362270253694223 (0x6fb8a1d507adbd0f)
    Signature Algorithm: sha256WithRSAEncryption
        Issuer: CN=kubernetes
            Not Before: Oct 30 08:01:56 2018 GMT
            Not After : Oct 30 08:02:01 2019 GMT
        Subject: O=system:masters, CN=kubernetes-admin
        Subject Public Key Info:
            Public Key Algorithm: rsaEncryption
                Public-Key: (2048 bit)


Monday, February 11, 2019

How To Add OKE Worker Nodes via OCI API


  We have Kubernetes cluster running in OKE (Oracle Kubernetes Engine).  We would like to dig deeper to use OCI API to manager the node pool of our K8S cluster. ie we can add a new worker node into our new private subnet. With OCI API, we can have more flexibility to handle worker nodes in the cluster.  In this example, we plan to use curl and raw REST API calls to do that.  Later oci-cli or SDK would support such functions


  • First to install oci-curl .  It is a Bash Shell script. Please refer OCI Doc
  • Configure the oci-curl to use correct tenancyId , authUserId , keyFingerprint, privateKeyPath. More details Please refer OCI Credential Doc and  OCI API  details
  • Test oci-curl . If you can get result like below , it means it works 
# .   ./oci-curl.sh
# oci-curl containerengine.us-ashburn-1.oraclecloud.com GET "/20180222/clusterOptions/all"
  "kubernetesVersions": [
  • Prepare oke-nodepool.json The example of json file is like
  "compartmentId": "INSERT_YOUR_COMPARTMENT_ID",
  "clusterId": "INSERT_YOUR_CLUSTER_ID",
  "kubernetesVersion": "INSERT_YOUR_K8S_VERSION",
  "nodeShape": "INSERT_YOUR_SHAPE_NAME",
  "nodeMetadata": {
  "initialNodeLabels": [
      "key": "node.info/INSERT_YOUR_SAMPLE_KEY",
  "quantityPerSubnet": INSERT_YOUR_QTY_PER_SUBNET,
  "subnetIds": [
  • Create a node pool 
oci-curl containerengine.us-ashburn-1.oraclecloud.com POST ./oke-nodepool.json "/20180222/nodePools"
  • Go to the OCI ashburn console , a new nodepool would be created in OKE according to json file.

Sunday, February 10, 2019

Error: Couldn't find key username in Secret default/test-stg-secret


  We create test-stg-secret via yaml file below
apiVersion: v1
kind: Secret
type: Opaque
  config.yaml: |-
    username: test
    password:  test

 However we got "Error: Couldn't find key username in Secret default/test-stg-secret" when we create statefulset. Part of secret usages are:
            - name: TEST_USER
                     name: test-stg-secret
                     key: username
            - name: TEST_PASSWORD
                     name: test-stg-secret
                     key: password


The reason is due to when we create secret it regards the whole text as one single string as config.yaml
It does not take username or password as key
To workaround it, we need to get decoded string via base64
echo 'test' | base64  --->  dGVzdAo=
Then correct yaml file is :
apiVersion: v1kind: Secretmetadata:  name:  test-stg-secret
type: Opaque
    username: dGVzdAo=
    password:  dGVzdAo=

Wednesday, February 06, 2019

Tip of Streaming Logs to Stdout for K8S Pods


 In K8S world, we need to stream apps logs output to standard output for analysis purpose. For example, we need to gather access logs information  of our applications , so we need to redirect all access logs data to stdout of Pod.


  Find full path of the logs which we would like to stream
  ie /var/log/apache2/access_log    and /var/log/apache2/error_log

Use below ln to link to stdout
ln -sf   /proc/self/fd/1  /var/log/apache2/access_log 
ln -sf  /proc/self/fd/1   /var/log/apache2/error_log

Monday, February 04, 2019

Tip to Get K8S API Server Startup Parameters

If the API server is running in a pod, to find out details of startup parameters of K8S API
$ kubectl get po -n kube-system kube-apiserver -o yaml
- command:
    - kube-apiserver
    - --secure-port=6443
    - --requestheader-client-ca-file=/etc/kubernetes/pki/front-proxy-ca.crt
    - --proxy-client-cert-file=/etc/kubernetes/pki/front-proxy-client.crt
    - --kubelet-preferred-address-types=InternalIP,ExternalIP,Hostname
    - --tls-cert-file=/etc/kubernetes/pki/apiserver.crt
    - --kubelet-client-certificate=/etc/kubernetes/pki/apiserver-kubelet-client.crt
    - --client-ca-file=/etc/kubernetes/pki/ca.crt
    - --insecure-port=0
    - --requestheader-username-headers=X-Remote-User
    - --requestheader-allowed-names=front-proxy-client
    - --service-cluster-ip-range=
    - --proxy-client-key-file=/etc/kubernetes/pki/front-proxy-client.key
    - --enable-bootstrap-token-auth=true
    - --requestheader-extra-headers-prefix=X-Remote-Extra-
    - --advertise-address=
    - --service-account-key-file=/etc/kubernetes/pki/sa.pub
    - --tls-private-key-file=/etc/kubernetes/pki/apiserver.key
    - --kubelet-client-key=/etc/kubernetes/pki/apiserver-kubelet-client.key
    - --admission-control=NamespaceLifecycle,LimitRanger,ServiceAccount,DefaultStorageClass,DefaultTolerationSeconds,NodeRestriction,MutatingAdmissionWebhook,ValidatingAdmissionWebhook,ResourceQuota
    - --allow-privileged=true
    - --requestheader-group-headers=X-Remote-Group
    - --authorization-mode=Node,RBAC
    - --etcd-servers=
    - --etcd-cafile=/etc/kubernetes/pki/etcd/ca.crt
    - --etcd-certfile=/etc/kubernetes/pki/apiserver-etcd-client.crt
    - --etcd-keyfile=/etc/kubernetes/pki/apiserver-etcd-client.key
    image: container-registry.oracle.com/kubernetes_developer/kube-apiserver-amd64:v1.10.5

Sunday, February 03, 2019

Tip to Check K8S Core API Https Header and Contents via Kubectl

As we know, K8S core API are Https calls. We can use kubectl --v=8 to get  debug details each https call of the core API. With same way, we can other kubectl commands debug info. ie

$ kubectl --v=8 create  -f ship_v1beta1_frigate.yaml
I0203 23:37:32.108940   21540 loader.go:357] Config loaded from file /home/k8suser/.kube/config
I0203 23:37:32.111815   21540 round_trippers.go:383] GET
I0203 23:37:32.111862   21540 round_trippers.go:390] Request Headers:
I0203 23:37:32.111884   21540 round_trippers.go:393]     Accept: application/com.github.proto-openapi.spec.v2@v1.0+protobuf
I0203 23:37:32.111906   21540 round_trippers.go:393]     User-Agent: kubectl/v1.10.5+2.0.2.el7 
frigate.ship.example.com "frigate-sample-test" created

Tip of How to Verify CA chain of Kubernetes

Find root CA file of the Kubernetes cluster
Find Client certificate file
They could be in /etc/kubernetes/pki  or  /var/lib/kubelet

# openssl  verify  -CAfile ca.crt  apiserver-kubelet-client.crt
apiserver-kubelet-client.crt: OK

Saturday, February 02, 2019

Tip of How To Find When Kubernetes CA Expires

Find the locations of CA files
They could be in /etc/kubernetes/pki  or  /var/lib/kubelet
Use openssl

# openssl x509 -in  ca.crt  -noout -text
        Version: 3 (0x2)
        Serial Number: 0 (0x0)
    Signature Algorithm: sha256WithRSAEncryption
        Issuer: CN=kubernetes
            Not Before: Oct 30 08:01:56 2018 GMT
            Not After : Oct 27 08:01:56 2028 GMT
        Subject: CN=kubernetes
        Subject Public Key Info:
            Public Key Algorithm: rsaEncryption
                Public-Key: (2048 bit)