• ETCD is a distributed, reliable key-value store that is Simple, Secure & Fast.
  • Traditionally, databases are in a tabular format - sql / relational databases.
    • These stores information in rows and colums.
    • Adding an additional colum impacts the entire table and all of the individual parts within them.
    • Every time new information is added, the entire table is affected.
    • It leads to a lot of empty cells. screenshot.png
  • A key value store stores information in documents / pages - all information about an individual is stored within the file.
  • These files can be in any format or structure and changing one file does not affect others. screenshot.png
  • To Install ETCD, we run:
    • Download Binaries
    • Extract
    • Run ETCD Service screenshot.png
  • When you run ETCD, it starts a service on port 2379 by default.
  • You can then attach any client to the ETCD service, to store and retrive information.
  • A default client that comes with etc is the etcdctl client.
    • This is a command line client for etcd.
  • Stores and retrieves key value pairs.
    • ./etcdctl set key1 value1
    • Creates an entry in the database with the information.
  • To retrieve the stored data, run the ./etcdctl get key1 command and in this example, this returns value1.
  • To view more options, run the ./etcdctl command without any arguments.
  • Important to understand etcd releases.
  • v0.1 –> August 2013
  • v0.5 –> December 2014
  • v2.0 –> February 2015
    • Raft consensus algorithm was redesigned.
    • Supported more than 10,000 writes per second.
  • v3.1 –> January 2017
    • More optimisations and improvements.
  • CNCF Incubation –> November 2018
  • Important to note the changes between v2.0 and v3.1
    • API versions changed between versions 2.0 and 3.1.
      • That means the etcdctl commands changed as well.
  • These commands are for v2.0:
    • etcdctl set key1 value1
    • etcdctl get key1
    • etcdctl
  • etcdctl is configured to work with v2.0 and v3.1 at the same time.
  • Run etcdctl --version to see what version and API version is in use.
    • etcdctl version and the API version are two different things.
  • With the release of v3.4, the default API version is set to 3.
  • To change etcdctl to work with v3.1, add the following before each command like so:
    • ETCDCTL_API=3 ./etcdctl version
    • Or you can export it as an environment variable like this:
      • export ETCDCTL_API=3
        • etcdctl version
  • With v3.1, the version command is just etcdctl version. In v2.0, this is etcdctl --version.
  • Running just etcdctl by itself also just shows the version and API as well.
  • To set a value is etcdctl put key1 value1 with the output of OK
  • To get a value, this is etcdctl get key1 and it will show 
    key1
value1

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