Code Quality Rank: L3
Programming language: Java
Tags: Utility    
Latest version: v0.9.23

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What's Embulk?

Embulk is a parallel bulk data loader that helps data transfer between various storages, databases, NoSQL and cloud services.

Embulk supports plugins to add functions. You can share the plugins to keep your custom scripts readable, maintainable, and reusable.

Embulk Embulk, an open-source plugin-based parallel bulk data loader at Slideshare


Embulk documents: http://www.embulk.org/docs/

Mailing list

  • Embulk-announce: Embulk core members post important updates such as key releases, compatibility information, and feedback requests to users.

Quick Start

Linux & Mac & BSD

Embulk is a Java application. Please make sure that Java SE Runtime Environment (JRE) is installed. Embulk v0.8 series runs on Java 7, and Embulk v0.9 series runs on Java 8. Java 9 is not supported in any version for the time being.

Following 4 commands install embulk to your home directory:

curl --create-dirs -o ~/.embulk/bin/embulk -L "https://dl.embulk.org/embulk-latest.jar"
chmod +x ~/.embulk/bin/embulk
echo 'export PATH="$HOME/.embulk/bin:$PATH"' >> ~/.bashrc
source ~/.bashrc

Next step: Running example in 4 commands


Embulk is a Java application. Please make sure that Java SE Runtime Environment (JRE) is installed. Embulk v0.8 series runs on Java 7, and Embulk v0.9 series runs on Java 8. Java 9 is not supported in any version for the time being.

You can download embulk.bat using this command on cmd.exe or PowerShell.exe.

Bintray no longer supports TLS 1.1 since June, 2018 although PowerShell's Invoke-WebRequest uses only SSL 3.0 and TLS 1.1 by default. You'll need a tweak for PowerShell to use TLS 1.2, such as:

PowerShell -Command "& {[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::TLS12; Invoke-WebRequest http://dl.embulk.org/embulk-latest.jar -OutFile embulk.bat}"

Next step: Running example in 4 commands

Running example

embulk example command generates a sample CSV file so that you can try embulk quickly:

embulk example ./try1
embulk guess   ./try1/seed.yml -o config.yml
embulk preview config.yml
embulk run     config.yml

Next step: Using plugins

Using plugins

You can use plugins to load data from/to various systems and file formats. Here is the list of publicly released plugins: list of plugins by category.

An example is embulk-output-command plugin. It executes an external command to output the records.

To install plugins, you can use embulk gem install <name> command:

embulk gem install embulk-output-command
embulk gem list

Embulk bundles some built-in plugins such as embulk-encoder-gzip or embulk-formatter-csv. You can use those plugins with following configuration file:

  type: file
  path_prefix: "./try1/csv/sample_"
  type: command
  command: "cat - > task.$INDEX.$SEQID.csv.gz"
    - {type: gzip}
    type: csv

Resuming a failed transaction

Embulk supports resuming failed transactions. To enable resuming, you need to start transaction with -r PATH option:

embulk run config.yml -r resume-state.yml

If the transaction fails, embulk stores state some states to the yaml file. You can retry the transaction using exactly same command:

embulk run config.yml -r resume-state.yml

If you give up on resuming the transaction, you can use embulk cleanup subcommand to delete intermediate data:

embulk cleanup config.yml -r resume-state.yml

Using plugin bundle

embulk mkbundle subcommand creates a isolated bundle of plugins. You can install plugins (gems) to the bundle directory instead of ~/.embulk directory. This makes it easy to manage versions of plugins. To use the bundle, add -b <bundle_dir> option to guess, preview, or run subcommand. embulk mkbundle also generates some example plugins to <bundle_dir>/embulk/*.rb directory.

See the generated <bundle_dir>/Gemfile file how to plugin bundles work.

embulk mkbundle ./embulk_bundle  # please edit ./embulk_bundle/Gemfile to add plugins. Detailed usage is written in the Gemfile
embulk guess -b ./embulk_bundle ...
embulk run   -b ./embulk_bundle ...

Use cases

For further details, visit Embulk documentation.

Upgrading to the latest version

Following command updates embulk itself to the latest released version.

embulk selfupdate

Following command updates embulk itself to the specific released version.

embulk selfupdate x.y.z

Older versions are available at dl.embulk.org.

Embulk Development


./gradlew cli  # creates pkg/embulk-VERSION.jar

You can see JaCoCo's test coverage report at ${project}/build/reports/tests/index.html You can see Findbug's report at ${project}/build/reports/findbug/main.html # FIXME coverage information is not included somehow

You can use classpath task to use bundle exec ./bin/embulk for development:

./gradlew -t classpath  # -x test: skip test

To deploy artifacts to your local maven repository at ~/.m2/repository/:

./gradlew install

To compile the source code of embulk-core project only:

./gradlew :embulk-core:compileJava

Task dependencies shows dependency tree of embulk-core project:

./gradlew :embulk-core:dependencies

Update JRuby

Modify jrubyVersion in build.gradle to update JRuby of Embulk.


Embulk uses Sphinx, YARD (Ruby API) and JavaDoc (Java API) for document generation.

brew install python
pip install sphinx
./gradlew site
# documents are: embulk-docs/build/html


You need to add your bintray account information to ~/.gradle/gradle.properties

bintray_user=(bintray user name)
bintray_api_key=(bintray api key)

Modify version in build.gradle at a detached commit to bump Embulk version up.

git checkout --detach master
(Remove "-SNAPSHOT" in "version" in build.gradle.)
git add build.gradle
git commit -m "Release vX.Y.Z"
git tag -a vX.Y.Z
(Write the release note for vX.Y.Z in the tag annotation.)
./gradlew clean && ./gradlew release
git push -u origin vX.Y.Z

See also: