bigchaindb/docs/server/source/server-reference/configuration.md

# Configuration Settings

The value of each BigchainDB Server configuration setting is determined according to the following rules:

* If it's set by an environment variable, then use that value
* Otherwise, if it's set in a local config file, then use that value
* Otherwise, use the default value

For convenience, here's a list of all the relevant environment variables (documented below):

`BIGCHAINDB_KEYPAIR_PUBLIC`<br>
`BIGCHAINDB_KEYPAIR_PRIVATE`<br>
`BIGCHAINDB_KEYRING`<br>
`BIGCHAINDB_DATABASE_HOST`<br>
`BIGCHAINDB_DATABASE_PORT`<br>
`BIGCHAINDB_DATABASE_NAME`<br>
`BIGCHAINDB_SERVER_BIND`<br>
`BIGCHAINDB_SERVER_WORKERS`<br>
`BIGCHAINDB_SERVER_THREADS`<br>
`BIGCHAINDB_STATSD_HOST`<br>
`BIGCHAINDB_STATSD_PORT`<br>
`BIGCHAINDB_STATSD_RATE`<br>
`BIGCHAINDB_CONFIG_PATH`<br>
`BIGCHAINDB_BACKLOG_REASSIGN_DELAY`<br>

The local config file is `$HOME/.bigchaindb` by default (a file which might not even exist), but you can tell BigchainDB to use a different file by using the `-c` command-line option, e.g. `bigchaindb -c path/to/config_file.json start`
or using the `BIGCHAINDB_CONFIG_PATH` environment variable, e.g. `BIGHAINDB_CONFIG_PATH=.my_bigchaindb_config bigchaindb start`.
Note that the `-c` command line option will always take precedence if both the `BIGCHAINDB_CONFIG_PATH` and the `-c` command line option are used.

You can read the current default values in the file [bigchaindb/\_\_init\_\_.py](https://github.com/bigchaindb/bigchaindb/blob/master/bigchaindb/__init__.py). (The link is to the latest version.)

Running `bigchaindb -y configure` will generate a local config file in `$HOME/.bigchaindb` with all the default values, with two exceptions: It will generate a valid private/public keypair, rather than using the default keypair (`None` and `None`).


## keypair.public & keypair.private

The [cryptographic keypair](../appendices/cryptography.html) used by the node. The public key is how the node idenifies itself to the world. The private key is used to generate cryptographic signatures. Anyone with the public key can verify that the signature was generated by whoever had the corresponding private key.

**Example using environment variables**
```text
export BIGCHAINDB_KEYPAIR_PUBLIC=8wHUvvraRo5yEoJAt66UTZaFq9YZ9tFFwcauKPDtjkGw
export BIGCHAINDB_KEYPAIR_PRIVATE=5C5Cknco7YxBRP9AgB1cbUVTL4FAcooxErLygw1DeG2D
```

**Example config file snippet**
```js
"keypair": {
  "public": "8wHUvvraRo5yEoJAt66UTZaFq9YZ9tFFwcauKPDtjkGw",
  "private": "5C5Cknco7YxBRP9AgB1cbUVTL4FAcooxErLygw1DeG2D"
}
```

Internally (i.e. in the Python code), both keys have a default value of `None`, but that's not a valid key. Therefore you can't rely on the defaults for the keypair. If you want to run BigchainDB, you must provide a valid keypair, either in the environment variables or in the local config file. You can generate a local config file with a valid keypair (and default everything else) using `bigchaindb -y configure`.


## keyring

A list of the public keys of all the nodes in the cluster, excluding the public key of this node. 

**Example using an environment variable**
```text
export BIGCHAINDB_KEYRING=BnCsre9MPBeQK8QZBFznU2dJJ2GwtvnSMdemCmod2XPB:4cYQHoQrvPiut3Sjs8fVR1BMZZpJjMTC4bsMTt9V71aQ
```

Note how the keys in the list are separated by colons.

**Example config file snippet**
```js
"keyring": ["BnCsre9MPBeQK8QZBFznU2dJJ2GwtvnSMdemCmod2XPB", 
            "4cYQHoQrvPiut3Sjs8fVR1BMZZpJjMTC4bsMTt9V71aQ"]
```

**Default value (from a config file)**
```js
"keyring": []
```


## database.host, database.port & database.name

The RethinkDB database hostname, port and name.

**Example using environment variables**
```text
export BIGCHAINDB_DATABASE_HOST=localhost
export BIGCHAINDB_DATABASE_PORT=28015
export BIGCHAINDB_DATABASE_NAME=bigchain
```

**Example config file snippet**
```js
"database": {
    "host": "localhost",
    "port": 28015,
    "name": "bigchain"
}
```

**Default values (a snippet from `bigchaindb/__init__.py`)**
```python
'database': {
    'host': os.environ.get('BIGCHAINDB_DATABASE_HOST', 'localhost'),
    'port': 28015,
    'name': 'bigchain',
}
```


## server.bind, server.workers & server.threads

These settings are for the [Gunicorn HTTP server](http://gunicorn.org/), which is used to serve the [HTTP client-server API](../drivers-clients/http-client-server-api.html).

`server.bind` is where to bind the Gunicorn HTTP server socket. It's a string. It can be any valid value for [Gunicorn's bind setting](http://docs.gunicorn.org/en/stable/settings.html#bind). If you want to allow IPv4 connections from anyone, on port 9984, use '0.0.0.0:9984'. In a production setting, we recommend you use Gunicorn behind a reverse proxy server. If Gunicorn and the reverse proxy are running on the same machine, then use 'localhost:PORT' where PORT is _not_ 9984 (because the reverse proxy needs to listen on port 9984). Maybe use PORT=9983 in that case because we know 9983 isn't used. If Gunicorn and the reverse proxy are running on different machines, then use 'A.B.C.D:9984' where A.B.C.D is the IP address of the reverse proxy. There's [more information about deploying behind a reverse proxy in the Gunicorn documentation](http://docs.gunicorn.org/en/stable/deploy.html). (They call it a proxy.)

`server.workers` is [the number of worker processes](http://docs.gunicorn.org/en/stable/settings.html#workers) for handling requests. If `None` (the default), the value will be (cpu_count * 2 + 1). `server.threads` is [the number of threads-per-worker](http://docs.gunicorn.org/en/stable/settings.html#threads) for handling requests. If `None` (the default), the value will be (cpu_count * 2 + 1). The HTTP server will be able to handle `server.workers` * `server.threads` requests simultaneously.

**Example using environment variables**
```text
export BIGCHAINDB_SERVER_BIND=0.0.0.0:9984
export BIGCHAINDB_SERVER_WORKERS=5
export BIGCHAINDB_SERVER_THREADS=5
```

**Example config file snippet**
```js
"server": {
    "bind": "0.0.0.0:9984",
    "workers": 5,
    "threads": 5
}
```

**Default values (from a config file)**
```js
"server": {
    "bind": "localhost:9984",
    "workers": null,
    "threads": null
}
```


## statsd.host, statsd.port & statsd.rate

These settings are used to configure where, and how often, [StatsD](https://github.com/etsy/statsd) should send data for [cluster monitoring](../clusters-feds/monitoring.html) purposes. `statsd.host` is the hostname of the monitoring server, where StatsD should send its data. `stats.port` is the port. `statsd.rate` is the fraction of transaction operations that should be sampled. It's a float between 0.0 and 1.0.

**Example using environment variables**
```text
export BIGCHAINDB_STATSD_HOST="http://monitor.monitors-r-us.io"
export BIGCHAINDB_STATSD_PORT=8125
export BIGCHAINDB_STATSD_RATE=0.01
```

**Example config file snippet: the default**
```js
"statsd": {"host": "localhost", "port": 8125, "rate": 0.01}
```

## backlog_reassign_delay

Specifies how long, in seconds, transactions can remain in the backlog before being reassigned.  Long-waiting transactions must be reassigned because the assigned node may no longer be responsive.  The default duration is 120 seconds.

**Example using environment variables**
```text
export BIGCHAINDB_BACKLOG_REASSIGN_DELAY=30
``` 

**Default value (from a config file)**
```js
"backlog_reassign_delay": 120 
```