Mozilla Sync 1.5 Storage Server in Go

Go-syncstorage is the next generation sync storage server. It was built to solve the data degradation problem with the python+mysql implementation. Logical separation of data is now physical separation of data. In go-syncstorage each user gets their own sqlite database. Many indexes were harmed in the making of this product.

Installing and Running it

The server is distributed as a Docker container. Latest builds and releases can be found on Dockerhub.

Running the server is easy:

$ docker pull mozilla/go-syncstorage:latest
$ docker run -it \
  -e "PORT=8000" \                           [1]
  -e "SECRETS=secret0,secret1,secret2" \     [2]
  -e "DATA_DIR=/data" \                      [3]
  -v "/host/data/path:/data" \               [4]
  mozilla/go-syncstorage

Only three configurations are required: PORT, SECRETS and DATA_DIR.

1. PORT - where to listen for HTTP requests
2. SECRETS - CSV of secrets preshared with the token service
3. DATA_DIR - where to save files (relative to inside the container)
4. A volume mount so data is saved on the docker host machine

More Configuration

The server has a few knobs that can be tweaked.

Advanced Configuration

Things that probably shouldn't be touched:

go-syncstorage limits the number of open SQLite database files to keep memory usage constant. This allows a small server to handle thousands of users for a small performance hit.

Multiplying POOL_NUM x POOL_SIZE gives the maximum number of open files.

A low level lock is used in each pool when opening and closing files. Having a larger POOL_NUM decreases lock contention.

When a pool reaches POOL_SIZE number of open files it will close the least recently used database. Having a larger POOL_SIZE reduces open/close disk IO. It also increases memory usage.

Tweaking these values from default won't provide significant performance gains in production. However, a POOL_NUM=1 and POOL_SIZE=1 is useful for testing the overhead of opening and closing databases files.

Data Storage

When deploying choose the EXT4 filesystem. EXT4 is an extent based filesystem and may help improve performance for magnetic storage media.

go-syncstorage gives each user gets their own sqlite database. On a production server that enough files to be a real burden for a human when troubleshooting. Thus, files are created into a directory structure like this:

/data-dir/
   00/
   01/
   34/
     21/
       100001234.db
   ...
   99/

• Two levels of subdirectories, each with 100 subdirectories for total of 10,000 sub-directories.
• The user, 100001234, is located at 34/21/100001234.db. The path starts at the reverse of their id. Their id is used for the actual database name.
• Using the reverse order helps evenly balance the number of files per directory.

Using this scheme, one million users will only have 10,000 files per directory. This is a relatively low number that CLI tools like ls will have no trouble with. Always optimize for the proper care and feed of your sysadmins.

Other Releases

A linux binary is also available as build artifacts from Circle CI.

License

See LICENSE.