Verm client library for Ruby

Verm (https://github.com/willbryant/verm) is a WORM (write-once, read-many) file store to make it easy to reliably store and replicate files. Clients talk to Verm over simple HTTP POST and GET calls.

This tiny client library adds one-line convenience methods for storing files in Verm and retrieving/streaming them back again.

Saving content

mydata = "data to store"
VERM_CLIENT = Verm::Client.new("my-verm-server")
VERM_CLIENT.store("/important_gifs/january", mydata, "text/plain") # => String

The store call will return a path like /important_gifs/january/ab/cdefgh.txt, only longer (Verm makes the filename using an URL-safe base64 encoding of the SHA-256 of the content).

Saving files

You don't need to read the whole file into memory before calling store, just pass the IO object in:

VERM_CLIENT = Verm::Client.new("my-verm-server")

File.open("example.jpg", "rb") do |f|
  VERM_CLIENT.store("/important_gifs/january", f, "image/jpeg") # => String
end

Retrieving content

VERM_CLIENT = Verm::Client.new("my-verm-server")

data, content_type = VERM_CLIENT.load("/important_gifs/january/ab/cdefgh.jpg")

This basically does the same thing as the built-in Net::HTTP get method (aside from timeouts, error handling, etc.):

Net::HTTP.get('my-verm-server:3404', '/important_gifs/january/ab/cdefgh.jpg') # => String - the file content

So you really don't need a client library for this - but it's usually more convenient to configure the Verm server somewhere central, instead of sprinkling it through your application.

Verm stores all content without touching its character encoding, but Ruby 1.9+ treats all strings as having a specific character encoding. Most applications use UTF-8 for all text, so by default, the load method will set the character encoding of text/* content returned by Verm to UTF-8. You can override this or disable it entirely:

data, content_type = VERM_CLIENT.load("/important_gifs/january/ab/cdefgh.csv", force_encoding: 'ISO-8859-1')
data, content_type = VERM_CLIENT.load("/important_gifs/january/ab/cdefgh.csv", force_encoding: nil)

Retrieving large content

If the data is large, reading it all into memory as a string is inefficient. Instead you can use stream, which will yield the file contents in chunks:

VERM_CLIENT = Verm::Client.new("my-verm-server")

File.open("out.csv", "w") do |f|
  VERM_CLIENT.stream("/big_data/ab/cdefgh.csv") do |chunk|
    f.write chunk
  end
end

Because the chunks may not be broken on a character encoding boundary, the character encoding can't be set as for load, so they will still have the default ASCII-8BIT binary encoding.

File compression

Like HTTP and web browsers, Verm treats gzip compression as being a way of making transfers smaller and faster, not a separate file type. So if you want to store gzipped files, you still get to say what content-type the actual file content has.

Saving files that are already gzip-compressed just requires one extra argument:

File.open("acme_20150101.csv.gz", "rb") do |f|
  VERM_CLIENT.store("/third_party_files/acme/2015", f, "text/csv", encoding: "gzip")
end

It's important to note that Ruby's Net::HTTP client will automatically uncompress gzip transfer-encoding on responses - so when you use load or store, you'll get the uncompressed content back, not the gzip file.

You can suppress that behavior by passing Accept-Encoding: gzip as a header (Net::HTTP would accept gzip anyway, but setting this header has the side effect of disabling uncompression):

data, content_type = VERM_CLIENT.load("/third_party_files/acme/2015/ab/cdefgh.csv", 'Accept-Encoding' => 'gzip')

Network stuff

Verm runs its HTTP server on port 3404 by default. You can override this in the client configuration:

VERM_CLIENT = Verm::Client.new("my-verm-server", port: 80)

Verm::Client defaults to a 15s timeout, which you can override:

VERM_CLIENT = Verm::Client.new("my-verm-server", timeout: 60)

Like Net::HTTP, this timeout applies to individual network operations, not the whole method.

Reusing connections

By default, Ruby's Net::HTTP client will open a new connection for each request. This makes it very safe with regards to forking or threading, but it can become a bottleneck if you are doing a bulk upload or download from Verm. You can explicitly start a connection to work around this:

VERM_CLIENT.http_client.start do
  100.times do
    VERM_CLIENT.store(...)
    VERM_CLIENT.load(...)
  end
end

If you'd like to use another gem that manages connection reuse automatically, note that you can also substitute any HTTP client class that supports the Net::HTTP API, by providing the http_class option to Verm::Client.new.