Configuring and Running DVID

Before running DVID, you have to specify the various ports, storage backends, email notification address and mail server in case of crashes, and other run-time options.

Configuration via TOML file

DVID configuration is specified in a TOML file. It's an easily readable configuration format that maps unambiguously to a hash table. There is an example configuration file that comes with DVID source code.

A filled-in example might look like this:

[server]
httpAddress = ":6000"
rpcAddress = ":6001"
webClient = "/path/to/dvid-console"

# Who to send email in case of panic
[email]
notify = ["[email protected]"]
username = "[email protected]"
password = ""
server = "10.1.50.90"
port = 25

[logging]
logfile = "/path/to/dvid.log"
max_log_size = 500 # MB
max_log_age = 360  # days

[store]
    [store.mutable]
    engine = "basholeveldb"
    path = "/data/dbs/emdata1"

    [store.immutable]
    engine = "kvautobus"
    path = "http://tem-dvid.int.janelia.org:9000"

The [server] section allows you to set the RPC and HTTP ports as well as the path to a web app that comes up when you point a web browser to the root HTTP address. The httpAddress option allows for binding to unique IP addresses. This is crucial for hosting on cloud services such as AWS.

The webClient property is a path to static website code for DVID administration, etc. We suggest you download the dvid console project and set the webClient path to its location. The stock dvid console lets you browse data repos and provides nice graphical representations of the data versions.

If you've configured the [email] section and there is a catchable panic, the DVID server will try to email an admin and continue on. Here's an example email you'll hopefully never receive but could be useful during debugging new features:

Subject: DVID panic report
Date: Friday, July 17, 2015 at 3:19:06 PM Eastern Daylight Time From: [email protected]
To: DVID admin

Panic detected on request c06u27.int.janelia.org/67bmYZ78V0-10888375: runtime error: index out of range
IP: 10.8.1.45:64608, URL: /api/node/ee7dc/annotations/keyrange/0
Stack trace:
goroutine 17099711 [running]: github.com/janelia-flyem/dvid/server.func·005()
/groups/flyem/home/katzw/work/go/src/github.com/janelia-flyem/dvid/server/web.go:399 +0xd6 github.com/janelia-flyem/dvid/datatype/keyvalue.(*Data).ServeHTTP(0xc2081dc648, 0xc2081a1760, 0x20, 0xc215091788, 0x7f2504847080, 0xc2082904b0, 0xc20bd41110)
/groups/flyem/home/katzw/work/go/src/github.com/janelia- flyem/dvid/datatype/keyvalue/keyvalue.go:430 +0x2143 github.com/janelia-flyem/dvid/server.func·009(0x7f2504847080, 0xc2082904b0, 0xc20bd41110)
/groups/flyem/home/katzw/work/go/src/github.com/janelia-flyem/dvid/server/web.go:536 +0x649 net/http.HandlerFunc.ServeHTTP(0xc2243fda00, 0x7f2504847080, 0xc2082904b0, 0xc20bd41110)
...
created by net/http.(*Server).Serve
/opt/buildem/src/golang-1.4.2/src/net/http/server.go:1751 +0x35e

Sincerely,
DVID at c06u27.int.janelia.org

The [store] section is evolving. Currently, you must specify a mutable store (required by DVID's metadata) and can optionally specify immutable and metadata stores. If neither immutable or metadata stores are specified, the mutable store is used for both.

Immutable stores are for write-once data and can achieve higher performance for less money because the store doesn't have to worry about mutating data. For example, caching becomes easier and the store doesn't have to worry about distributed transactions. There is a natural match between mutable and immutable datastores and how DVID thinks of versioned data as a directed acyclic graph (DAG):

For connectomics research at Janelia (and the FlyEM research group in particular), the majority of data exists near the top of the DAG since most of our workflows involve ingesting very large image volumes and pre-generating segmentation for every voxel. So the bulk of our data can persist in immutable stores, allowing us to use smaller, faster storage solutions for the mutable portion of the DAG, namely the leaf nodes where manual editing tends to dominate.

Running DVID

Once the configuration file is set, you can run DVID using this command:

% dvid serve /path/to/config.toml

This will start DVID and have it listen on the specified HTTP and RPC ports. If the httpAddress was :8000, you can point your web browser to localhost:8000 and see whatever web app was specified in the webClient path.

When using DVID for non-trivial reasons, we suggest using the following command:

% nohup dvid serve /path/to/config.toml >> /path/to/dvid.log &

Several points can be made about the above server startup command:

• You can use "nohup" to manually start the server but it continues even if the admin user logs out. The serve command can also be added as a service if you want automatic startup.
• The standard output and error for the serve command is appended to the log file that we also have in our config.toml. We do this so any stack dump or error is in somewhat the same order as our other time-stamped logging.
• Note that we try to send logging data to a different drive system than those used for the storage engines themselves. This will decrease contention on drives between logging and actual database requests.