etcd is a key-value DB written in Go. It has an HTTP API, which this R package wraps.

etcd API docs

Installing etcd

See the etcd Github repo for help on installing etcd.

There are various ways to install it, and they depend on your operating sytsem.

You can install via homebrew, install from source, and via Docker.

Start etcd

at the command line

etcd

how to start etcd may differ depending on your setup

Installing etseed

Install etseed

install.packages("etseed")

Development version

install.packages("devtools")
devtools::install_github("ropensci/etseed")

library("etseed")

Make a client

First task when using this package is to initialize a client with the etcd() function. it's a wrapper around an R6 class.

(client <- etcd())
#> <etcd client>
#>   host: 127.0.0.1
#>   port: 2379
#>   api_version: v2
#>   scheme: http
#>   allow redirect: TRUE

Default settings in etcd() connect you to localhost, and port 2379, using etcd API version 2, with an http scheme.

Get version

client$version()
#> $etcdserver
#> [1] "3.0.7"
#> 
#> $etcdcluster
#> [1] "3.0.0"

Create a directory

client$create("/neighbor", dir = TRUE)
#> $action
#> [1] "set"
#> 
#> $node
#> $node$key
#> [1] "/neighbor"
#> 
#> $node$dir
#> [1] TRUE
#> 
#> $node$modifiedIndex
#> [1] 14
#> 
#> $node$createdIndex
#> [1] 14

Create a key

client$create(key = "/mykey", value = "this is awesome")
#> $action
#> [1] "set"
#> 
#> $node
#> $node$key
#> [1] "/mykey"
#> 
#> $node$value
#> [1] "this is awesome"
#> 
#> $node$modifiedIndex
#> [1] 16
#> 
#> $node$createdIndex
#> [1] 16

Use ttl parameter to make it dissappear after x seconds

client$create(key = "/stuff", value = "tables", ttl = 5)
#> $action
#> [1] "set"
#> 
#> $node
#> $node$key
#> [1] "/stuff"
#> 
#> $node$value
#> [1] "tables"
#> 
#> $node$expiration
#> [1] "2016-09-02T21:40:59.617130434Z"
#> 
#> $node$ttl
#> [1] 5
#> 
#> $node$modifiedIndex
#> [1] 17
#> 
#> $node$createdIndex
#> [1] 17

And the key will be gone after 5 seconds, see:

client$key("/stuff")
#> Error in etcd_GET(sprintf("%s%s/%s/", etcdbase(), "keys", key), ...) :
#>   client error: (404) Not Found

Update a key

Create a key

client$create(key = "/foo", value = "bar")
#> $action
#> [1] "set"
#> 
#> $node
#> $node$key
#> [1] "/foo"
#> 
#> $node$value
#> [1] "bar"
#> 
#> $node$modifiedIndex
#> [1] 19
#> 
#> $node$createdIndex
#> [1] 19

Then update the key

client$update(key = "/foo", value = "bar stool")
#> $action
#> [1] "set"
#> 
#> $node
#> $node$key
#> [1] "/foo"
#> 
#> $node$value
#> [1] "bar stool"
#> 
...

Create in-order keys

client$create_inorder("/queue", "thing1")
#> $action
#> [1] "create"
#> 
#> $node
#> $node$key
#> [1] "/queue/00000000000000000021"
#> 
#> $node$value
#> [1] "thing1"
#> 
#> $node$modifiedIndex
#> [1] 21
#> 
#> $node$createdIndex
#> [1] 21

client$create_inorder("/queue", "thing2")
#> $action
#> [1] "create"
#> 
#> $node
#> $node$key
#> [1] "/queue/00000000000000000022"
#> 
#> $node$value
#> [1] "thing2"
#> 
#> $node$modifiedIndex
#> [1] 22
#> 
#> $node$createdIndex
#> [1] 22

client$create_inorder("/queue", "thing3")
#> $action
#> [1] "create"
#> 
#> $node
#> $node$key
#> [1] "/queue/00000000000000000023"
#> 
#> $node$value
#> [1] "thing3"
#> 
#> $node$modifiedIndex
#> [1] 23
#> 
#> $node$createdIndex
#> [1] 23

List keys

client$keys()
#> $action
#> [1] "get"
#> 
#> $node
#> $node$dir
#> [1] TRUE
#> 
#> $node$nodes
#> $node$nodes[[1]]
#> $node$nodes[[1]]$key
...

List a key

client$key("/mykey")
#> $action
#> [1] "get"
#> 
#> $node
#> $node$key
#> [1] "/mykey"
#> 
#> $node$value
#> [1] "this is awesome"
#> 
#> $node$modifiedIndex
#> [1] 16
#> 
#> $node$createdIndex
#> [1] 16