GCE(f1-micro)のdocker-composeでCannot allocate memory

背景

GCP(Google Cloud Platform)いいですよね！AWSより取っつきやすいので最近よく使っています。
その中にGCEというssh接続できるコンピューティングリソースあるんですが、無料枠のf1-microで
以下のGitHubの内容をdocker-compose upしたところ以下のエラーが出たのでシェアです！
https://github.com/koyo-miyamura/latestgram

ちなみにf1.microのスペックはこちら

エラー内容

Installing ffi 1.9.25 with native extensions
Gem::Ext::BuildError: ERROR: Failed to build gem native extension.

    current directory: /usr/local/bundle/gems/ffi-1.9.25/ext/ffi_c
/usr/local/bin/ruby -r ./siteconf20180729-6-5nocr2.rb extconf.rb
Cannot allocate memory - /usr/local/bin/ruby -r ./siteconf20180729-6-5nocr2.rb
extconf.rb 2>&1

エラーメッセージ全文（クリックで展開）

Building web
Step 1/6 : FROM ruby:2.5.1
 ---> 1d8640b852eb
Step 2/6 : WORKDIR /app
 ---> Using cache
 ---> 2b92751173b0
Step 3/6 : ADD Gemfile /app/Gemfile
 ---> Using cache
 ---> 64d4e0189481
Step 4/6 : ADD Gemfile.lock /app/Gemfile.lock
 ---> Using cache
 ---> c0a4503d04ac
Step 5/6 : RUN bundle install
 ---> Running in 15c608884196
Fetching gem metadata from https://rubygems.org/..........
Using bundler 1.16.3
Fetching ffi 1.9.25
Installing ffi 1.9.25 with native extensions
Gem::Ext::BuildError: ERROR: Failed to build gem native extension.

    current directory: /usr/local/bundle/gems/ffi-1.9.25/ext/ffi_c
/usr/local/bin/ruby -r ./siteconf20180729-6-5nocr2.rb extconf.rb
Cannot allocate memory - /usr/local/bin/ruby -r ./siteconf20180729-6-5nocr2.rb
extconf.rb 2>&1

Gem files will remain installed in /usr/local/bundle/gems/ffi-1.9.25 for
inspection.
Results logged to
/usr/local/bundle/extensions/x86_64-linux/2.5.0/ffi-1.9.25/gem_make.out

An error occurred while installing ffi (1.9.25), and Bundler cannot continue.
Make sure that `gem install ffi -v '1.9.25' --source 'https://rubygems.org/'`
succeeds before bundling.

In Gemfile:
  rerun was resolved to 0.13.0, which depends on
    listen was resolved to 3.1.5, which depends on
      rb-inotify was resolved to 0.9.10, which depends on
        ffi
ERROR: Service 'web' failed to build: The command '/bin/sh -c bundle install' returned a non-zero code: 5

解決策

エラーメッセージよく見るとメモリが足りないと言われているので、(有料になっちゃいますが)g1-smallにすれば動きました！

流石にメモリ600MBは限界ある場面も出てくるみたいですね><