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Cachews - Caching for AWSCLI

cachews is a zero-config caching proxy for awscli.

Reducing request time by around 90% may also reduce:

  • cycle time when constructing commands or scripts that use awscli
  • your resistance to running a query across 500 accounts
  • how often you put the kettle on

Cache of Cachews

It supports the following arguments (and ignores the rest):

--query : JMESPath querys as found in awscli (and azcli)
--output : json or text (tab separated values)

Installation

cachews comes included with bash-my-aws which is installed as follows:

  1. Clone the repo
git clone https://github.com/bash-my-aws/bash-my-aws.git ${BMA_HOME:-$HOME/.bash-my-aws}
  1. Put the following in your shell's startup file:
export PATH="$PATH:${BMA_HOME:-$HOME/.bash-my-aws}/bin"
source ${BMA_HOME:-$HOME/.bash-my-aws}/aliases

# For ZSH users, uncomment the following two lines:
# autoload -U +X compinit && compinit
# autoload -U +X bashcompinit && bashcompinit

source ${BMA_HOME:-$HOME/.bash-my-aws}/bash_completion.sh
  1. [Optional] Set CACHEWS_DIR environment variable.

Usage

Choose from two commands two suit your needs:

  • cachews: A drop in replacement for aws command
  • cachews-replace: Runs any command, replacing aws with cachews executable

As a bonus, you can set BMA_AWSCLI=cashews to enable for all bash-my-aws commands.

See below for real world examples.

cachews - Replace aws command with cachews

The simplest use case is to substitute aws for cachews in your command.

Start a fresh cachedir for this demo:

$ export CACHEWS_DIR="$(mktemp -d)"

AWS command takes ~1s:

$ time aws ec2 describe-instances | wc -l
844

real    0m1.113s
user    0m0.823s
sys     0m0.076s

cachews takes ~1s but caches the response:

$ time cachews ec2 describe-instances | wc -l
844

real    0m1.147s
user    0m0.861s
sys     0m0.088s

cachews takes ~0.08 seconds the second time:

$ time cachews ec2 describe-instances | wc -l
844

real    0m0.081s
user    0m0.061s
sys     0m0.023s

cachews-replace - avoids need to change code

This could be a script with AWSCLI calls or even this crazy example.

$ time cachews-replace aws ec2 describe-instances | wc -l
844

real    0m0.083s
user    0m0.065s
sys 0m0.020s

bash-my-aws commands can use $BMA_AWSCLI env var

The bma command exports a function called aws that calls the command in BMA_AWSCLI=cachews if one is set.

$ time bma instances | wc -l
4

real    0m1.200s
user    0m0.834s
sys   0m0.098s

$ time BMA_AWSCLI=cachews bma instances | wc -l
4

real    0m0.099s
user    0m0.079s
sys   0m0.026s

bash-my-aws added $BMA_AWSCLI support back in 2020 to assist testing breaking changes in aws-cli-v2. Almost four years later when I wrote cachews it was a nice surprise to rediscover it.

commit 17376e63222033fef2a1005be6bccb0123263629
Author: Mike Bailey <mike@bailey.net.au>
Date:   Sun Mar 8 12:25:00 2020 +1100

    Set $BMA_AWSCLI to specify which awscli to use

    Added while testing breaking changes in aws-cli-v2

    Also useful for testing with
    [localstack](https://github.com/localstack/localstack)

      e.g. `$ BMA_AWSCLI=awslocal stacks`

    Also, print AWSCLI version when BMA_DEBUG=true