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About

ZipStreamer is a golang project for building and streaming zip files from a series of web links. For example, if you have 200 files on S3, and you want to download a zip file of them, you can do so in 1 request to this server.

Highlights include:

  • Low memory: the files are streamed out to the client immediately
  • Low CPU: the default server doesn't compress files, only packages them into a zip, so there's minimal CPU load (configurable)
  • High concurrency: the two properties above allow a single small server to stream hundreds of large zips simultaneous
  • It includes a HTTP server, but can be used as a library (see zip_streamer.go).

Deploy - Heroku

Deploy

Be sure to enable session afinity if you're using multiple servers and /create_download_link.

Deploy - Docker

View on Docker Hub

docker pull langboost/zipstreamer

docker run --rm -p '4008:4008' langboost/zipstreamer

HTTP Endpoints

POST /download

This endpoint takes a post, and returns a zip file.

It expects a JSON body defining which files to include in the zip. The ZipPath is the path and filename in the resulting zip file (it should be a relative path).

Example body:

{
  "entries": [
    {"Url":"https://server.com/image1.jpg","ZipPath":"image1.jpg"},
    {"Url":"https://server.com/image2.jpg","ZipPath":"in-a-sub-folder/image2.jpg"}
  ]
}

POST /create_download_link

This endpoint creates a temporary link which can be used to download a zip via a GET. This is helpful as on a webapp it can be painful to POST results, and trigger a "Save File" popup with the result. With this, you can create the link in a POST, then open the download link in a new window.

Important:

  • This stores the link in an in memory cache, so it's not suitable for deploying to a cluster. However if using heroku and requests are coming from a browser, you can use a cluster if you enable session afinity which ensures requests from a given client are routed to the same server.
  • These links are only live for 60 seconds. They are expected to be used immediately and are not long living.

It expects the same body format as /download.

Here is an example response body:

{
  "status":"ok",
  "link_id":"b4ecfdb7-e0fa-4aca-ad87-cb2e4245c8dd"
}

GET /download_link/{link_id}

Call this endpoint with a link_id generated with /create_download_link to download that zip file.

Config

These ENV vars can be used to config the server:

  • PORT - which port the HTTP server binds to. If not set defaults to 4008
  • ZS_URL_PREFIX - if set, requires that the URL of files downloaded start with this prefix. Useful to preventing others from using your server to serve their files.
  • DEFLATE - if set to 1, uses the DEFLATE algorithm in the .zip file. Otherwise, no compression is employed.

Why

I was mentoring at a "Teens Learning Code" class, but we had too many mentors, so I had some downtime.