LilyBin AWS Lambda Function

This will be used to power LilyBin, a pastebin for music based on LilyPond. It is written for AWS Lambda to allow for an unmatched on-demand scalability.

How This Works

For each version of LilyPond desired, a separate Lambda function needs to be created. The version is controlled by the version file in the root directory.

The workflow of this Lambda function is like this:

Receive event payload from LilyBin core, in the scheme of:

{
  "code": "this is the LilyPond source",
  "id"  : "this is the ID of the source"
}

cd to /tmp, the only writable storage.
Try to install LilyPond using install_lilypond.sh:
1. Detects if /tmp/ly exists. If so, assume LilyPond is already installed, and skip to #4.
2. Downloads a decompressed tarball from an S3 bucket (for now s3://lilybin-tarballs/).
3. Extracts it to /tmp/ly. PATH and LD_LIBRARY_PATH are modified.
4. The internal Ghostscript binary (gs) is monkey patched to avoid a weird error regarding Fontmaps.
Write the input file to input.ly.
Execute LilyPond on it, outputting to rendered.pdf, rendered.midi, and rendered*.png. stderr output is saved into a response object.
Do three things concurrently (uploadFiles):
1. Upload rendered.pdf if it exists.
2. Upload rendered.midi if it exists.
3. Try to stat rendered.png.
  1. If it exists, upload it to S3 as <key>-page1.png, and set pages property in response object to 1.
  2. If it doesn't, count how many pages there are, and upload them as <key>-page*.png.
Report that the run succeeded (or failed) with the response object.

Deployment

Some deployment helpers are available in deploy/. These contain some details about how my developement environment is set up so don't expect much out of it :)

make-zipball.sh makes a zipball of source files, as code.zip.
create.sh creates a new Lambda function with the generated zipball:
```
# deploy/create.sh <version>
deploy/create.sh unstable
```
deploy.sh updates the source of an existing Lambda function:
```
# deploy/deploy.sh <version>
deploy/deploy.sh unstable
```

LilyPond Tarball Generation

In tools/ there are some tools for checking and updating LilyPond tarballs.

check-new-version.sh checks for the latest version of stable and unstable LilyPond builds, output the release versions to versions.json, and prints the distribution versions.

make-tarball.sh downloads a LilyPond binary and decompresses it to a vanilla .tar archive.

#                                 recommended; renames the tarball
#                                 to a form fit for uploading
# tools/make-tarball.sh <version> [<lilybin_version>]
tools/make-tarball.sh 2.18.2-1   stable
# --> lilypond-stable.linux-64.tar

upload-tarballs.sh uploads all files matching lilypond-*.tar to S3, and versions.json if it exists.
update.sh combines all of the above.

Local and Live Tests

test/ contains some non-automated tests.

Local

When you have made some local changes, node local.js is your friend. It emulates the AWS Lambda API and tries to run your handler against a payload, in payload.json.

You might need to rm -rf /tmp/input.ly /tmp/rendered* /tmp/ly if you want a clean start.

Live

If you have AWS CLI installed and configured properly, test/live.sh can be used to test a deployed instance. You have to manually modify func variable in the file to change function to test. (PR welcome)

License

MIT licensed.

See LICENSE.md for the full license text.

LilyBin / lambda-compile

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