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Kubernetes (a.k.a. k8s) London Meetup

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One of my favorite thing2do when i visit London is to participate the SkillsMatter meetups.

This time i was lucky to join to the Kubernetes meetup!

Thanks for the Google to sponsor the pizza and beers before the meetup!

There was two seperate presentations:

Martin Devlin – Consul&Vault Integration with Kubernetes

Justin Santa Barbara – Kubernetes: Prologue,Present&Predictions

The second one, which is presented by Justin Santa Barbara, was interesting, also by the help of the cool presentation skills and positive energy of Justin!

Justin is one of the top committers on k8s project. 

Although there are various topics mentinoned, now i will be focusing some of the upcoming functions of the new releases:

1. Ingress: This can be referred as ingress traffic controller, waiting for L4&L7, so seems totally no need for AWS ELB in the future? 

2. DaemonSets: We can define certain pods to run on all nodes or on some nodes. Use-case of this can be 

  • having NewRelic run on each node (Which is the case for me currently)
  • having a log collection daemon on each node like SumoLogic
  • having a storage daemon like glusterd on each node

3. PetSets: This can be referred as stateful-application support. Self-healing databases can be a use-case, still trying to digout! 

The new release 1.3 is expected to be live by the end of June, lets see:)

Here are some pictures from the meetup:

kubernetes skillsmatter kubernetes skillsmatter

Playing with AWS Autoscale Lifecycle Hooks, triggering Lambda function

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Honestly, i was not aware that terminating an instance at AWS is equal to unplugging the server cable. That’s why, i lost so much time trying to trigger a custom code before the instance shutdown using init levels. But i failed!!! Why, because when you unplug the electric cable, there is no init process!! 🙂

Later on, i found the AWS lifecycle hooks. Autoscale group triggers an SNS which them invokes a Lambda function and the basic requirement “revoking IP from Security Group” can be done. Here is the related node.js but still it is missing to parse the incoming SNS (The IP is static)

[snippet id=”26″]

Scripted monitoring on NewRelic with Javascript

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By the help of the latest requirements on customers, i am getting more familiar with node.js and getting more used to be a node.js developer:)

Here is the one of the javascript code, which parses the output of a HTML and checks if a specific result is there or no. If not, NewRelic gives alarm:


[snippet id=”25″]

MongoDB given “not master” error after creating AWS Cloudformation template

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AWS has cool documentation but sometimes not guiding you practical solutions. If you have intended you use the following mongodb Cloudformation template:

You will notice that, mongo is not operable. In order to achieve that you need to ssh and enter to mongo console by typing mongo:

When you check the repliaction set status you will see:

> rs.status ()
        "info" : "run rs.initiate(…) if not yet done for the set",
        "ok" : 0,
        "errmsg" : "no replset config has been received",
        "code" : 94

initiate the replica with:

> rs.initiate()
        "info2" : "no configuration explicitly specified — making one",
        "me" : "ip-10-0-2-241:27017",
        "ok" : 1
You can now check the status again:
s-1:PRIMARY> rs.status()
        "set" : "s-1",
        "date" : ISODate("2016-03-23T16:00:30.805Z"),
        "myState" : 1,
        "members" : [
                        "_id" : 0,
                        "name" : "ip-10-0-2-241:27017",
                        "health" : 1,
                        "state" : 1,
                        "stateStr" : "PRIMARY",
                        "uptime" : 13924,
                        "optime" : Timestamp(1458748644, 1),
                        "optimeDate" : ISODate("2016-03-23T15:57:24Z"),
                        "electionTime" : Timestamp(1458748644, 2),
                        "electionDate" : ISODate("2016-03-23T15:57:24Z"),
                        "configVersion" : 1,
                        "self" : true
        "ok" : 1

How to add a specific IP to your RDS security group on command line

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If you go towards DevOps, automated provisioning, you definetely will need to do things in automation.


Here is the command line, in case you need the new automated provisioned server to be added in your RDS security group:

aws rds rds-authorize-db-security-group-ingress –db-security-group-name mydbsecuritygroup –cidrip

How to block an IP on AWS?

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Security Groups on AWS by default blocks all, so you can just define what you allow. As a result, you cannot block an IP using Security Group, e.g. to prevent a specific IP to access to your web port

ACL is right there for that need. You need to define the IP/IPs which you want to block and remember to keep the rule 100 always in place:)


AWS Elasticbeanstalk NewRelic agent installation

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Credits for @umitunal_

    newrelic-sysmond: []
      command: nrsysmond-config –set license_key=xxxxxxxxxxxxxx
      command: echo hostname=NameOfYourServer >> /etc/newrelic/nrsysmond.cfg
      command: /etc/init.d/newrelic-sysmond start

AWS SSL Certificate cannot be added

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Although the private and public keys are valid (Already tested on another platform), AWS Web Console is giving error while i am trying to define under ELB Listeners.

In order to debug the situtation, the following command line will be helpful:

aws iam upload-server-certificate –server-certificate-name my-server-cert –certificate-body file://my-certificate.pem –private-key file://my-private-key.pem –certificate-chain file://my-certificate-chain.pem –debug

AWS instance metadata

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Just a simple best-practice for you to know in case you need to get instance related data during automation:


For example, if you want to use the hostname in your automation, just use the output:

$ curl

WordPress and CloudFront Access-Control-Allow-Origin problem a.k.a. CORS

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You may be having the following type of error after you enable CDN on your WordPress:

Font from origin '' has been blocked from loading by Cross-Origin Resource Sharing policy: No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin '' is therefore not allowed access.

That's because you do not have the "Access-Control-Allow-Origin" header set by the web-server of the origin, which is Apache or Amazon S3.

You can verify this with the following command and you will not see the header:

curl -I -s -X GET -H "Origin:"

1- With S3: In order to set that header in S3, refer to the AWS Documentation.

2- Without S3: 

2-a: CloudFront:

– Edit Behaviors

– Change "Allowed HTTP Methods" to GET, HEAD, OPTIONS, PUT, POST, PATCH, DELETE

– Change "Forward Forward" headers to "Whitelist"

– Add "origin" to Whitelist headers

2-b: Apache

You need to You just need the following to be added under the Document section in your httpd.conf:

Header set Access-Control-Allow-Origin "*"

and gracefuly restart your http server:

apachectl -k graceful

Check if the header appeared with the "curl" command previously we used.


HTTP/1.0 200 OK

Content-Type: image/png

Content-Length: 299245

Date: Wed, 16 Dec 2015 22:28:00 GMT

Server: Apache

X-Frame-Options: SAMEORIGIN

Last-Modified: Wed, 09 Dec 2015 15:07:22 GMT

ETag: "490ed-52678727d1480"

Accept-Ranges: bytes

Access-Control-Allow-Origin: *

X-Cache: Miss from cloudfront

X-Amz-Cf-Id: e14A-xV0D-ajm0S7wLe696YombjT8zKCmbr0LL8NmqlMarArJo1jnw==

X-Cache: MISS from

X-Cache-Lookup: MISS from

Via: 1.1 (CloudFront), 1.0 (squid/3.1.23)

Connection: keep-alive

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