Uploading small files is slow

[jffry]

Uploading tiny files can be very slow. Here we upload a 1081-byte JSON file, with conversion to a Google Doc explicitly disabled:

(time
  (let [auth (google-apps-clj.credentials/default-credential ["https://www.googleapis.com/auth/drive"])
        folder-id "FOLDERIDFOLDERIDFOLDERIDFOLD"
        raw-req (google-apps-clj.google-drive/upload-file folder-id "test.json" "desc" "text/plain" "/path/to/test.json" false)
        req (assoc raw-req :fields ["id"])]
    (google-apps-clj.google-drive/execute-query! auth req)))

"Elapsed time: 2312.169 msecs"

It seems that by default, the Java client library uses resumable media uploads, which will upload the file using multiple requests: https://developers.google.com/api-client-library/java/google-api-java-client/media-upload#direct

For tiny files, we don't need this. In ee4931b I added an option to support direct media uploads. For this small file I ran some tests both with and without direct upload enabled, to see the response times in ms:

without	with
943.888	1027.120
2420.539	1615.611
1102.272	624.711
800.267	625.270
2845.130	668.712
869.747	689.082
753.111	691.276
4449.890	744.944
2416.990	834.301
1096.242	908.461
----------	----------	-------
1769.808	842.949	mean
1226.861	301.284	stdev

While this is a big improvement, a mean of 842ms to upload a 1081-byte file is still a bit too large and leaves room to improve.