https://github.com/gambol99/etcd-discovery

Discovery service for etcd to permit AWS Auto-scaling group
https://github.com/gambol99/etcd-discovery

Last synced: 11 days ago
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Discovery service for etcd to permit AWS Auto-scaling group

• Host: GitHub
• URL: https://github.com/gambol99/etcd-discovery
• Owner: gambol99
• License: apache-2.0
• Created: 2016-01-26T11:18:15.000Z (almost 9 years ago)
• Default Branch: master
• Last Pushed: 2016-04-23T11:07:48.000Z (over 8 years ago)
• Last Synced: 2024-06-20T13:37:31.045Z (7 months ago)
• Language: Go
• Homepage:
• Size: 19.5 KB
• Stars: 4
• Watchers: 3
• Forks: 1
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE
  • Authors: AUTHORS

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README

        
### **Etcd Discovery**

----

The Etcd Discovery service is small utility for running a [Etcd](https://github.com/coreos/etcd) cluster within a AWS auto-scaling group. The service provides the means to add, remove and discovery instances in the auto-scaling group and to reconcile the cluster when things change. 

##### **Building**

A [Makefile](https://github.com/gambol99/etcd-discovery/blob/master/Makefile) exists in the source root, so assuming you've Go and make; running *make* should suffice. Alternatively you can build the project inside a golang container by typing **make docker-build**

#### **Configuration**

----

```shell

[jest@starfury etcd-discovery]$ bin/etcd-discovery -h

Usage of bin/etcd-discovery:

  -alsologtostderr

    	log to standard error as well as files

  -environment-file string

    	the file to write the etcd environment variables

  -etcd-client-port int

    	is the port the etcd client should be listening on (default 2379)

  -etcd-client-schema string

    	is the protocol schema we should use for client connections (default "https")

  -etcd-peer-port int

    	is the port the etcd peer should be listening on (default 2380)

  -etcd-peer-scheme string

    	is the protocol schema we should use for etcd peer connections (default "https")

  -log_backtrace_at value

    	when logging hits line file:N, emit a stack trace (default :0)

  -log_dir string

    	If non-empty, write log files in this directory

  -logtostderr

    	log to standard error instead of files

  -private-addresses

    	add the etcd peers using their ip addresses rather than domain names

  -private-hostnames

    	add the etcd peers using the dns names rather than up addresses (default true)

  -proxy-mode

    	whether or not we are operating in etcd proxy mode

  -scaling-group-name string

    	is the name of the aws auto-scaling group which has the etcd masters

  -stderrthreshold value

    	logs at or above this threshold go to stderr

  -v value

    	log level for V logs

  -vmodule value

    	comma-separated list of pattern=N settings for file-filtered logging

```

#### **Example Usage**

Lets assume you have two auto-scaling groups, the etcd cluster and another cluster whom are proxy-mode only node i.e. consumers. Taken from the cloudinit userdata (CoreOS), systemd unit could like like

```YAML

# Download the etcd-discovery binary

- name: install-etcd-discovery.service

  command: start

  content: |

    [Unit]

    Description=Etcd Discovery Service

    Before=etcd2.service

    [Service]

    RemainAfterExit=yes

    Restart=always

    RestartSec=10

    Environment="URL=${etcd_discovery_url}"

    Environment="FILENAME=/opt/bin/etcd-discovery"

    Environment="FILENAME_GZ=/opt/bin/etcd-discovery.gz"

    Environment="MD5=${etcd_discovery_md5}"

    ExecStartPre=/usr/bin/mkdir -p /opt/bin /etc/sysconfig

    ExecStartPre=-/usr/bin/rm -f /opt/bin/etcd-discovery

    ExecStart=/usr/bin/bash -c 'until [[ -x $${FILENAME} ]] && [[ $(md5sum $${FILENAME} | cut -f1 -d" ") == $${MD5} ]]; \

      do wget -q -O $${FILENAME_GZ} $${URL} && gunzip $${FILENAME_GZ} && chmod +x $${FILENAME}; done'

# Start the etcd-discovery (running in master mode), find the nodes in the cluster and template

# out peer configuration to /etc/sysconfig/etcd-discovery file

- name: etcd-discovery.service

  command: start

  content: |

    [Unit]

    Description=Etcd Discovery Service

    Requires=install-etcd-discovery.service

    After=install-etcd-discovery.service

    Before=etcd2.service

    [Service]

    RemainAfterExit=yes

    Restart=always

    RestartSec=10

    ExecStart=/opt/bin/etcd-discovery -environment-file=/etc/sysconfig/etcd-discovery -logtostderr -v=10

- name: etcd2.service

  command: start

  enable: true

  drop-ins:

  # read in the peer configuration generated by etcd-discovery service    

  - name: 30-etcd_peers.conf

    content: |

      [Service]

      EnvironmentFile=/etc/sysconfig/etcd-discovery

  - name: 12-advertized.conf

    content: |

      [Service]

      Environment="ETCD_ADVERTISE_CLIENT_URLS=https://%H:2379"

      Environment="ETCD_INITIAL_ADVERTISE_PEER_URLS=https://%H:2380"

```

The logic for this is fairly simple

  - Get the auto-scaling group my instance is in

  - Get all the instances from the auto-scaling group

  - Check to see if the cluster has formed yet

    - Check for any terminated instances in the cluster, check if theses instances are referenced in the etcd cluster and remove them

    - Check with etcd that my instances is a cluster member and if not, add myself as a member

  - Template out the peer configuration to the file

For the consumer nodes we can use something similar to the below.

```YAML

- name: install-etcd-discovery.service

  command: start

  content: |

    [Unit]

    Description=Etcd Discovery Service

    Before=etcd2.service

    [Service]

    RemainAfterExit=yes

    Restart=always

    RestartSec=10

    Environment="URL=${etcd_discovery_url}"

    Environment="FILENAME=/opt/bin/etcd-discovery"

    Environment="FILENAME_GZ=/opt/bin/etcd-discovery.gz"

    Environment="MD5=${etcd_discovery_md5}"

    ExecStartPre=/usr/bin/mkdir -p /opt/bin /etc/sysconfig

    ExecStartPre=-/usr/bin/rm -f /opt/bin/etcd-discovery

    ExecStart=/usr/bin/bash -c 'until [[ -x $${FILENAME} ]] && [[ $(md5sum $${FILENAME} | cut -f1 -d" ") == $${MD5} ]]; \

      do wget -q -O $${FILENAME_GZ} $${URL} && gunzip $${FILENAME_GZ} && chmod +x $${FILENAME}; done'

- name: etcd-discovery.service

  command: start

  content: |

    [Unit]

    Description=Etcd Discovery Service

    Requires=install-etcd-discovery.service

    After=install-etcd-discovery.service

    Before=etcd2.service

    [Service]

    RemainAfterExit=yes

    Restart=always

    RestartSec=10

    ExecStart=/opt/bin/etcd-discovery \

      -scaling-group-name=THE_NAME_OF_ETCD_SCALING_GROUP \

      -proxy-mode=true \

      -environment-file=/etc/sysconfig/etcd-discovery \

      -logtostderr \

      -v=10

- name: etcd2.service

  command: start

  enable: true

  drop-ins:

  - name: 30-etcd_peers.conf

    content: |

      [Service]

      EnvironmentFile=/etc/sysconfig/etcd-discovery

```