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The following environment variables are required:
DB_DIRECTORY - path to the database directory (if relative, to `run` script)
USERNAME - the username the server will run as, if using `run` script
ELECTRUMX - path to the electrumx_server.py script (if relative,
to `run` script)
DAEMON_URL - A comma-separated list of daemon URLS. If more than one is
provided ElectrumX will failover to the next when one stops
working. The generic form 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 COIN if omitted.
The other environment variables are all optional and will adopt
sensible defaults if not specified.
COIN - see lib/coins.py, must be a coin NAME. Defaults to Bitcoin.
NETWORK - see lib/coins.py, must be a coin NET. Defaults to mainnet.
DB_ENGINE - database engine for the transaction database. Default is
leveldb. Supported alternatives are rocksdb and lmdb.
You will need to install the appropriate python packages.
Not case sensitive.
REORG_LIMIT - 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.
Default is 200.
HOST - the host that the TCP and SSL servers will use. Defaults to
localhost. Set to blank to listen on all addresses (IPv4
and IPv6).
TCP_PORT - if set will serve Electrum TCP clients on that HOST:TCP_PORT
SSL_PORT - if set will serve Electrum SSL clients on that HOST:SSL_PORT
If set, SSL_CERTFILE and SSL_KEYFILE must be filesystem paths.
RPC_PORT - Listen on this port for local RPC connections, defaults to
8000.
BANNER_FILE - a path to a banner file to serve to clients. The banner file
is re-read for each new client. The string $VERSION in your
banner file will be replaced with the ElectrumX version you
are runnning, such as 'ElectrumX 0.7.11'.
LOG_SESSIONS - the number of seconds between printing session statistics to
the log. Defaults to 3600. Set to zero to suppress this
logging.
ANON_LOGS - set to anything non-empty to remove IP addresses from
logs. By default IP addresses will be logged.
DONATION_ADDRESS - server donation address. Defaults to none.
These following environment variables are to help limit server
resource consumption and to prevent simple DoS. Address subscriptions
in ElectrumX are very cheap - they consume about 100 bytes of memory
each and are processed efficiently. I feel the defaults are low and
encourage you to raise them.
MAX_SESSIONS - maximum number of sessions. Once reached, TCP and SSL
listening sockets are closed until the session count drops
naturally to 95% of the limit. Defaults to 1,000.
MAX_SEND - maximum size of a response message to send over the wire,
in bytes. Defaults to 1,000,000 and will treat values
smaller than 350,000 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. MAX_SEND is a
stop-gap until the protocol is improved to admit
incremental history requests. Each history entry
is appoximately 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 increase this bear in mind one client
can request history for multiple addresses. Also,
the largest raw transaction you will be able to serve
to a client is just under half of MAX_SEND, as each raw
byte becomes 2 hexadecimal ASCII characters on the wire.
MAX_SUBS - maximum number of address subscriptions across all
sessions. Defaults to 250,000.
MAX_SESSION_SUBS - maximum number of address subscriptions permitted to a
single session. Defaults to 50,000.
BANDWIDTH_LIMIT - per-session periodic bandwith usage limit in 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 yielding processing resources to other
sessions. Each time this happens the event is
logged. The more bandwidth usage exceeds the limit
the longer the next request will sleep. Each sleep
is a round number of seconds with a minimum of one.
The bandwith usage counter is reset to zero at the
end of each period. Currently the period is
hard-coded to be one hour. The default limit value
is 2 million bytes.
SESSION_TIMEOUT - an integer number of seconds defaulting to 600.
Sessions with no activity for longer than this are
disconnected.
If you want IRC connectivity to advertise your node:
IRC - set to anything non-empty
IRC_NICK - the nick to use when connecting to IRC. The default is a
hash of REPORT_HOST. Either way 'E_' will be prepended.
REPORT_HOST - the host to advertise. Defaults to HOST.
REPORT_TCP_PORT - the TCP port to advertise. Defaults to TCP_PORT.
'0' disables publishing the port.
REPORT_SSL_PORT - the SSL port to advertise. Defaults to SSL_PORT.
'0' disables publishing the port.
REPORT_HOST_TOR - Tor .onion address to advertise. Appends '_tor" to nick.
REPORT_TCP_PORT_TOR - the TCP port to advertise for Tor. Defaults to
REPORT_TCP_PORT, unless it is '0', then use TCP_PORT.
'0' disables publishing the port.
REPORT_SSL_PORT_TOR - the SSL port to advertise for Tor. Defaults to
REPORT_SSL_PORT, unless it is '0', then use SSL_PORT.
'0' disables publishing the port.
If synchronizing from the Genesis block your performance might change
by tweaking the following cache variables. Cache size is only checked
roughly every minute, so the caches can grow beyond the specified
size. Also the Python process is often quite a bit fatter than the
combined cache size, because of Python overhead and also because
leveldb consumes a lot of memory during UTXO flushing. So I recommend
you set the sum of these to nothing over half your available physical
RAM:
HIST_MB - amount of history cache, in MB, to retain before flushing to
disk. Default is 300; probably no benefit being much larger
as history is append-only and not searched.
UTXO_MB - amount of UTXO and history cache, in MB, to retain before
flushing to disk. Default is 1000. This may be too large
for small boxes or too small for machines with lots of RAM.
Larger caches generally perform better 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. My
machine has 24GB RAM; the slow down is probably because of
leveldb caching and Python GC effects. However this may be
very dependent on hardware and you may have different
results.
The following are for debugging purposes.
FORCE_REORG - if set to a positive integer, it will simulate a reorg
of the blockchain for that number of blocks on startup.
Although it should fail gracefully if set to a value
greater than REORG_LIMIT, I do not recommend it as I have
not tried it and there is a chance your DB might corrupt.

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=====================
Environment Variables
=====================
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.
Required
--------
These environment variables are always required:
* **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.
* **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 **COIN** and **NETWORK** if omitted.
For the `run` script
--------------------
The following are required if you use the `run` script:
* **ELECTRUMX**
The path to the electrumx_server.py script. Relative paths should
be relative to the directory of the `run` script.
* **USERNAME**
The username the server will run as.
Miscellaneous
-------------
These environment variables are optional:
* **COIN**
Must be a *NAME* from one of the **Coin** classes in
`lib/coins.py`_. Defaults to `Bitcoin`.
* **NETWORK**
Must be a *NET* from one of the **Coin** classes in `lib/coins.py`_.
Defaults to `mainnet`.
* **DB_ENGINE**
Database engine for the transaction database. The default is
`leveldb`. Supported alternatives are `rocksdb` and `lmdb`. You
will need to install the appropriate python package for your engine.
The value is not case sensitive. Note that the current way
ElectrumX uses LMDB gives poor performance .
* **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 **COIN** and **NETWORK**; for Bitcoin mainnet it is 200.
* **HOST**
The host that the TCP and SSL servers will use. Defaults to
`localhost`. Set to blank to listen on all addresses (IPv4 and IPv6).
* **TCP_PORT**
If set ElectrumX will serve TCP clients on **HOST**:**TCP_PORT**.
* **SSL_PORT**
If set ElectrumX will serve SSL clients on **HOST**:**SSL_PORT**.
If set SSL_CERTFILE and SSL_KEYFILE must be defined and be
filesystem paths to those SSL files.
* **RPC_PORT**
ElectrumX will listen on this port for local RPC connections.
ElectrumX listens for RPC connections unless this is explicity set
to blank. It defaults appropriately for **COIN** and **NETWORK**
(e.g., 8000 for Bitcoin mainnet) if not set.
* **DONATION_ADDRESS**
The server donation address reported to Electrum clients. Defaults
to empty, which Electrum interprets as meaning there is none.
* **BANNER_FILE**
The path to a banner file to serve to clients. Relative file paths
must be relative to **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.
+ **$VERSION** is replaced with the ElectrumX version you are
runnning, such as *ElectrumX 0.9.22*.
+ **$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
**DONATION_ADDRESS** environment variable.
* **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.
* **LOG_SESSIONS**
The number of seconds between printing session statistics to the
log. The output is identical to the **sessions** RPC command except
that **ANON_LOGS** is honoured. Defaults to 3600. Set to zero to
suppress this logging.
Resource Usage Limits
---------------------
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
100 bytes of memory each (160 bytes from version 0.10.0) and are
processed efficiently. I feel the two subscription-related defaults
below are low and encourage you to raise them.
* **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.
* **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.
**MAX_SEND** is a stop-gap until the protocol is improved to admit
incremental history requests. Each history entry is appoximately
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
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.
* **MAX_SUBS**
The maximum number of address subscriptions across all sessions.
Defaults to 250,000.
* **MAX_SESSION_SUBS**
The maximum number of address subscriptions permitted to a single
session. Defaults to 50,000.
* **BANDWIDTH_LIMIT**
Per-session periodic bandwith 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. Each time this happens the event is logged.
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.
Bandwidth usage is gradually reduced over time by "refunding" a
proportional part of the limit every now and then.
* **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.
IRC
---
Use the following environment variables if you want to advertise
connectivity on IRC:
* **IRC**
Set to anything non-empty to advertise on IRC
* **IRC_NICK**
The nick to use when connecting to IRC. The default is a hash of
**REPORT_HOST**. Either way a prefix will be prepended depending on
**COIN** and **NETWORK**.
* **REPORT_HOST**
The host to advertise. Defaults to **HOST**.
* **REPORT_TCP_PORT**
The TCP port to advertise. Defaults to **TCP_PORT**. '0' disables
publishing the port.
* **REPORT_SSL_PORT**
The SSL port to advertise. Defaults to **SSL_PORT**. '0' disables
publishing the port.
* **REPORT_HOST_TOR**
The tor .onion address to advertise. If set, an additional
connection to IRC happens with '_tor" appended to **IRC_NICK**.
* **REPORT_TCP_PORT_TOR**
The TCP port to advertise for Tor. Defaults to **REPORT_TCP_PORT**,
unless it is '0', otherwise **TCP_PORT**. '0' disables publishing
the port.
* **REPORT_SSL_PORT_TOR**
The SSL port to advertise for Tor. Defaults to **REPORT_SSL_PORT**,
unless it is '0', otherwise **SSL_PORT**. '0' disables publishing
the port.
Cache
-----
If synchronizing from the Genesis block your performance might change
by tweaking the following cache variables. Cache size is only checked
roughly every minute, so the caches can grow beyond the specified
size. Also the Python process is often quite a bit fatter than the
combined cache size, because of Python overhead and also because
leveldb consumes a lot of memory during UTXO flushing. So I recommend
you set the sum of these to nothing over half your available physical
RAM:
* **HIST_MB**
The amount of history cache, in MB, to retain before flushing to
disk. Default is 300; probably no benefit being much larger as
history is append-only and not searched.
I do not recommend setting this above 500.
* **UTXO_MB**
The amount of UTXO and history cache, in MB, to retain before
flushing to disk. Default is 1000. This may be too large for small
boxes or too small for machines with lots of RAM. Larger caches
generally perform better 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.
My machine has 24GB RAM; the slow down is probably because of
leveldb caching and Python GC effects.
I do not recommend setting this above 2000.
Debugging
---------
The following are for debugging purposes:
* **FORCE_REORG**
If set to a positive integer, it will simulate a reorg of the
blockchain for that number of blocks on startup. Although it should
fail gracefully if set to a value greater than **REORG_LIMIT**, I do
not recommend it as I have not tried it and there is a chance your
DB might corrupt.
.. _lib/coins.py: https://github.com/kyuupichan/electrumx/blob/master/lib/coins.py