Category: Tech Notes

Posted on

Checklist for accessing an AWS EC2 instance with ssh

Quick checklist of items to check for enabling ssh instance into a running EC2 instance:

  • EC2 instance is started (check from AWS console)
  • From AWS console, check Security Group for the instance has an inbound rule for SSH – if only accessing remotely from your current IP, you can press ‘My IP’ to set your current public IP
  • From Network & Security, create a keypair and download the .pem file
  • Check the public DNS name for your EC2 instance from the console
  • chmod 400 your .pem file, otherwise you’ll get an error that it’s publicly readable

Connect with:

ssh -i path-to-.pem-file ec2-user@ec2-your-instance-name.compute-xyz.amazonaws.com

Posted on

Docker usage notes – continued (2)

A few rough usage notes, continuing from my first post a while back.

Delete all containers:

Run a container from an image and delete it when it exits: use –rm:

docker run -it --rm containerid

 

Pass an argument into a build:

  • use ‘ARG argname’ to declare the argument in your Dockerfile
  • pass value for argname with –build-arg argname=value

Test during build if an arg was passed:

RUN test -n "$argname"

 

Posted on

Using Netflix Eureka with Spring Cloud / Spring Boot microservices

I’ve been taking a look at this article on using Spring Cloud‘s integration/support for Netflix Eureka. I’ve started to put together a simple example using Eureka as a service registry for a couple of Spring Boot services, and what this would look like if deployed in Docker containers.

So far I’ve created the initial service that uses Spring Cloud’s @EnableEurekaServer annotation to start up the Eureka service.

Jumping ahead of the instructions, by default if you run this app it will attempt to reach out and find a local running Eureka server and register with it, but since this app is the Eureka server, you need to add config to tell the app not to do this by default. Otherwise you’ll see errors like:

com.sun.jersey.api.client.ClientHandlerException: java.net.ConnectException: Connection refused
at com.sun.jersey.client.apache4.ApacheHttpClient4Handler.handle(ApacheHttpClient4Handler.java:187) ~[jersey-apache-client4-1.19.1.jar:1.19.1]
at com.sun.jersey.api.client.filter.GZIPContentEncodingFilter.handle(GZIPContentEncodingFilter.java:123) ~[jersey-client-1.19.1.jar:1.19.1]
at com.netflix.discovery.EurekaIdentityHeaderFilter.handle(EurekaIdentityHeaderFilter.java:27) ~[eureka-client-1.6.2.jar:1.6.2]

Adding the recommended config per the article:

server:

  port: ${PORT:8761}

eureka:

  client:

    registerWithEureka: false

    fetchRegistry: false

    server: waitTimeInMsWhenSyncEmpty: 0

Now when I start up I see this:

2017-04-11 22:23:17.040  INFO 37607 - o.s.c.n.eureka.InstanceInfoFactory       : Setting initial instance status as: STARTING
2017-04-11 22:23:17.100  INFO 37607 - com.netflix.discovery.DiscoveryClient    : Initializing Eureka in region us-east-1
2017-04-11 22:23:17.101  INFO 37607 - com.netflix.discovery.DiscoveryClient    : Client configured to neither register nor query for data.
2017-04-11 22:23:17.110  INFO 37607 -com.netflix.discovery.DiscoveryClient    : Discovery Client initialized at timestamp 1491974597110 with initial instances count: 0
2017-04-11 22:23:17.192  INFO 37607 - c.n.eureka.DefaultEurekaServerContext    : Initializing ...
2017-04-11 22:23:17.195  INFO 37607 - c.n.eureka.cluster.PeerEurekaNodes       : Adding new peer nodes [http://localhost:8761/eureka/]
2017-04-11 22:23:17.359  INFO 37607 - c.n.d.provider.DiscoveryJerseyProvider   : Using JSON encoding codec LegacyJacksonJson
2017-04-11 22:23:17.359  INFO 37607 - c.n.d.provider.DiscoveryJerseyProvider   : Using JSON decoding codec LegacyJacksonJson
2017-04-11 22:23:17.359  INFO 37607 - c.n.d.provider.DiscoveryJerseyProvider   : Using XML encoding codec XStreamXml
2017-04-11 22:23:17.359  INFO 37607 - c.n.d.provider.DiscoveryJerseyProvider   : Using XML decoding codec XStreamXml
2017-04-11 22:23:22.479  INFO 37607 - c.n.eureka.cluster.PeerEurekaNodes       : Replica node URL:  http://localhost:8761/eureka/
2017-04-11 22:23:22.486  INFO 37607 - c.n.e.registry.AbstractInstanceRegistry  : Finished initializing remote region registries. All known remote regions: []
2017-04-11 22:23:22.486  INFO 37607 - c.n.eureka.DefaultEurekaServerContext    : Initialized

Hitting http://localhost:8761 I get the fancy Eureka dashboard:

Looks good so far! More to come later.

Github repo for the code so far is here.

Posted on

Deploying a git subtree to Heroku (or other PaaS)

Most of the common PaaS platforms like OpenShift and Heroku deploy code based on a source in a git repo – you push your local repo containing source to the remote repo on the platform, the build is performed remotely and then deploys the built artifacts.

What if you want to deploy an app that is prebuilt, or you have a git repo that contains various subfolders, and only part of the folder structure in the repo is what you need deployed?

I’ve been experimenting with a simple React app that also has a node.js backend. In hindsight restructuring the source tree to make the app easier to deploy may have been simpler, but it turns out you can push part of your source subtree to a remote repo, like an application deployed to Heroku, using ‘git subtree’:

git subtree push –prefix subfoldername heroku master

This is discussed in this post here.

Proudly powered by WordPress