ElectrumX takes no command line arguments, instead its behaviour is controlled by environment variables. Only a few are required to be given, the rest will have sensible defaults if not specified. Many of the defaults around resource usage are conservative; I encourage you to review them.
Note: by default the server will only serve to connections from the same machine. To be accessible to other users across the internet you must set HOST appropriately; see below.
These environment variables are always required:
.. envvar:: COIN Must be a :attr:`NAME` from one of the :class:`Coin` classes in `lib/coins.py`_.
.. envvar:: DB_DIRECTORY The path to the database directory. Relative paths should be relative to the parent process working directory. This is the directory of the `run` script if you use it.
.. envvar:: DAEMON_URL
A comma-separated list of daemon URLs. If more than one is provided
ElectrumX will initially connect to the first, and failover to
subsequent ones round-robin style if one stops working.
The generic form of a daemon URL is::
http://username:password@hostname:port/
The leading ``http://`` is optional, as is the trailing slash. The
``:port`` part is also optional and will default to the standard RPC
port for :envvar:`COIN` and :envvar:`NET` if omitted.
The following are required if you use the run script:
.. envvar:: ELECTRUMX The path to the electrumx_server.py script. Relative paths should be relative to the directory of the ``run`` script.
.. envvar:: USERNAME The username the server will run as.
These environment variables are optional:
.. envvar:: LOG_FORMAT The Python logging `format string <https://docs.python.org/3/library/logging.html#logrecord-attributes>`_ to use. Defaults to ``%(levelname)s:%(name)s:%(message)s``.
.. envvar:: ALLOW_ROOT Set this environment variable to anything non-empty to allow running ElectrumX as root.
.. envvar:: NET Must be a :envvar:`NET` from one of the **Coin** classes in `lib/coins.py`_. Defaults to ``mainnet``.
.. envvar:: DB_ENGINE Database engine for the UTXO and history database. The default is ``leveldb``. The other alternative is ``rocksdb``. You will need to install the appropriate python package for your engine. The value is not case sensitive.
.. envvar:: HOST The host or IP address that the TCP and SSL servers will use when binding listening sockets. Defaults to ``localhost``. To listen on multiple specific addresses specify a comma-separated list. Set to an empty string to listen on all available interfaces (likely both IPv4 and IPv6).
.. envvar:: TCP_PORT
If set ElectrumX will serve TCP clients on
:envvar:`HOST`\::envvar:`TCP_PORT`.
.. note:: ElectrumX will not serve TCP connections until it has
fully caught up with your daemon.
.. envvar:: SSL_PORT
If set ElectrumX will serve SSL clients on
:envvar:`HOST`\::envvar:`SSL_PORT`. If set then
:envvar:`SSL_CERTFILE` and :envvar:`SSL_KEYFILE` must be defined
environment variables with values the filesystem paths to those SSL
files.
.. note:: ElectrumX will not serve SSL connections until it has
fully caught up with your daemon.
.. envvar:: RPC_HOST The host or IP address that the RPC server will listen on and defaults to ``localhost``. To listen on multiple specific addresses specify a comma-separated list. Servers with unusual networking setups might want to specify e.g. ``::1`` or ``127.0.0.1`` explicitly rather than defaulting to ``localhost``. An empty string (normally indicating all interfaces) is interpreted as ``localhost``, because allowing access to the server's RPC interface to arbitrary connections across the internet is not a good idea.
.. envvar:: RPC_PORT ElectrumX will listen on this port for local RPC connections. ElectrumX listens for RPC connections unless this is explicitly set to blank. The default depends on :envvar:`COIN` and :envvar:`NET` (e.g., 8000 for Bitcoin mainnet) if not set, as indicated in `lib/coins.py`_.
.. envvar:: DONATION_ADDRESS The server donation address reported to Electrum clients. Defaults to empty, which Electrum interprets as meaning there is none.
.. envvar:: BANNER_FILE
The path to a banner file to serve to clients in Electrum's
"Console" tab. Relative file paths must be relative to
:envvar:`DB_DIRECTORY`. The banner file is re-read for each new
client.
You can place several meta-variables in your banner file, which will be
replaced before serving to a client.
+ ``$SERVER_VERSION`` is replaced with the ElectrumX version you are
running, such as ``1.0.10``.
+ ``$SERVER_SUBVERSION`` is replaced with the ElectrumX user agent
string. For example, ``ElectrumX 1.0.10``.
+ ``$DAEMON_VERSION`` is replaced with the daemon's version as a
dot-separated string. For example ``0.12.1``.
+ ``$DAEMON_SUBVERSION`` is replaced with the daemon's user agent
string. For example, ``/BitcoinUnlimited:0.12.1(EB16; AD4)/``.
+ ``$DONATION_ADDRESS`` is replaced with the address from the
:envvar:`DONATION_ADDRESS` environment variable.
See `here <https://github.com/shsmith/electrumx-banner-updater>`_
for a script that updates a banner file periodically with useful
statistics about fees, last block time and height, etc.
.. envvar:: TOR_BANNER_FILE As for :envvar:`BANNER_FILE` (which is also the default) but shown to incoming connections believed to be to your Tor hidden service.
.. envvar:: ANON_LOGS Set to anything non-empty to replace IP addresses in logs with redacted text like ``xx.xx.xx.xx:xxx``. By default IP addresses will be written to logs.
.. envvar:: LOG_SESSIONS The number of seconds between printing session statistics to the log. The output is identical to the :ref:`sessions` RPC command except that :envvar:`ANON_LOGS` is honoured. Defaults to 3600. Set to zero to suppress this logging.
.. envvar:: REORG_LIMIT The maximum number of blocks to be able to handle in a chain reorganisation. ElectrumX retains some fairly compact undo information for this many blocks in levelDB. The default is a function of :envvar:`COIN` and :envvar:`NET`; for Bitcoin mainnet it is 200.
.. envvar:: EVENT_LOOP_POLICY The name of an event loop policy to replace the default asyncio policy, if any. At present only ``uvloop`` is accepted, in which case you must have installed the `uvloop`_ Python package. If you are not sure what this means leave it unset.
The following environment variables are all optional and help to limit server resource consumption and prevent simple DoS.
Address subscriptions in ElectrumX are very cheap - they consume about 160 bytes of memory each and are processed efficiently. I feel the two subscription-related defaults below are low and encourage you to raise them.
.. envvar:: MAX_SESSIONS The maximum number of incoming connections. Once reached, TCP and SSL listening sockets are closed until the session count drops naturally to 95% of the limit. Defaults to 1,000.
.. envvar:: MAX_SEND The maximum size of a response message to send over the wire, in bytes. Defaults to 1,000,000. Values smaller than 350,000 are taken as 350,000 because standard Electrum protocol header "chunk" requests are almost that large. The Electrum protocol has a flaw in that address histories must be served all at once or not at all, an obvious avenue for abuse. :envvar:`MAX_SEND` is a stop-gap until the protocol is improved to admit incremental history requests. Each history entry is approximately 100 bytes so the default is equivalent to a history limit of around 10,000 entries, which should be ample for most legitimate users. If you use a higher default bear in mind one client can request history for multiple addresses. Also note that the largest raw transaction you will be able to serve to a client is just under half of :envvar:`MAX_SEND`, as each raw byte becomes 2 hexadecimal ASCII characters on the wire. Very few transactions on Bitcoin mainnet are over 500KB in size.
.. envvar:: MAX_SUBS The maximum number of address subscriptions across all sessions. Defaults to 250,000.
.. envvar:: MAX_SESSION_SUBS The maximum number of address subscriptions permitted to a single session. Defaults to 50,000.
.. envvar:: BANDWIDTH_LIMIT Per-session periodic bandwidth usage limit in bytes. This is a soft, not hard, limit. Currently the period is hard-coded to be one hour. The default limit value is 2 million bytes. Bandwidth usage over each period is totalled, and when this limit is exceeded each subsequent request is stalled by sleeping before handling it, effectively giving higher processing priority to other sessions. The more bandwidth usage exceeds this soft limit the longer the next request will sleep. Sleep times are a round number of seconds with a minimum of 1. Each time the delay changes the event is logged. Bandwidth usage is gradually reduced over time by "refunding" a proportional part of the limit every now and then.
.. envvar:: SESSION_TIMEOUT An integer number of seconds defaulting to 600. Sessions with no activity for longer than this are disconnected. Properly functioning Electrum clients by default will send pings roughly every 60 seconds.
In response to the :func:`server.peers.subscribe` RPC call, ElectrumX will only return peer servers that it has recently connected to and verified basic functionality.
If you are not running a Tor proxy ElectrumX will be unable to connect to onion server peers, in which case rather than returning no onion peers it will fall back to a hard-coded list.
To give incoming clients a full range of onion servers you will need to be running a Tor proxy for ElectrumX to use.
ElectrumX will perform peer-discovery by default and announce itself to other peers. If your server is private you may wish to disable some of this.
.. envvar:: PEER_DISCOVERY This environment variable is case-insensitive and defaults to ``on``. If ``on``, ElectrumX will occasionally connect to and verify its network of peer servers. If ``off``, peer discovery is disabled and a hard-coded default list of servers will be read in and served. If set to ``self`` then peer discovery is disabled and the server will only return itself in the peers list.
.. envvar:: PEER_ANNOUNCE Set this environment variable to empty to disable announcing itself. If not defined, or non-empty, ElectrumX will announce itself to peers. If peer discovery is disabled this environment variable has no effect, because ElectrumX only announces itself to peers when doing peer discovery if it notices it is not present in the peer's returned list.
.. envvar:: FORCE_PROXY By default peer discovery happens over the clear internet. Set this to non-empty to force peer discovery to be done via the proxy. This might be useful if you are running a Tor service exclusively and wish to keep your IP address private.
.. envvar:: TOR_PROXY_HOST The host where your Tor proxy is running. Defaults to ``localhost``. If you are not running a Tor proxy just leave this environment variable undefined.
.. envvar:: TOR_PROXY_PORT The port on which the Tor proxy is running. If not set, ElectrumX will autodetect any proxy running on the usual ports 9050 (Tor), 9150 (Tor browser bundle) and 1080 (socks).
These environment variables affect how your server is advertised by peer discovery (if enabled).
.. envvar:: REPORT_HOST The clearnet host to advertise. If not set, no clearnet host is advertised.
.. envvar:: REPORT_TCP_PORT The clearnet TCP port to advertise if :envvar:`REPORT_HOST` is set. Defaults to :envvar:`TCP_PORT`. ``0`` disables publishing a TCP port.
.. envvar:: REPORT_SSL_PORT The clearnet SSL port to advertise if :envvar:`REPORT_HOST` is set. Defaults to :envvar:`SSL_PORT`. ``0`` disables publishing an SSL port.
.. envvar:: REPORT_HOST_TOR If you wish run a Tor service, this is the Tor host name to advertise and must end with ``.onion``.
.. envvar:: REPORT_TCP_PORT_TOR The Tor TCP port to advertise. The default is the clearnet :envvar:`REPORT_TCP_PORT`, unless disabled or it is ``0``, otherwise :envvar:`TCP_PORT`. ``0`` disables publishing a Tor TCP port.
.. envvar:: REPORT_SSL_PORT_TOR
The Tor SSL port to advertise. The default is the clearnet
:envvar:`REPORT_SSL_PORT`, unless disabled or it is ``0``, otherwise
:envvar:`SSL_PORT`. ``0`` disables publishing a Tor SSL port.
.. note:: Certificate-Authority signed certificates don't work over
Tor, so you should set :envvar:`REPORT_SSL_PORT_TOR` to
``0`` if yours is not self-signed.
If synchronizing from the Genesis block your performance might change by tweaking the cache size. Cache size is only checked roughly every minute, so the cache can grow beyond the specified size. Moreover, the Python process is often quite a bit fatter than the cache size, because of Python overhead and also because leveldb consumes a lot of memory when flushing. So I recommend you do not set this over 60% of your available physical RAM:
.. envvar:: CACHE_MB The amount of cache, in MB, to use. The default is 1,200. A portion of the cache is reserved for unflushed history, which is written out frequently. The bulk is used to cache UTXOs. Larger caches probably increase performance a little as there is significant searching of the UTXO cache during indexing. However, I don't see much benefit in my tests pushing this too high, and in fact performance begins to fall, probably because LevelDB already caches, and also because of Python GC. I do not recommend raising this above 2000.