How to run a module in erlang - erlang

Question

I have a module helloworld.erl in ejabberd/src
-module(helloworld).
%% API
-export([start/0]).
start() ->
% Chat
ejabberd_auth:try_register(<<"username">>, <<"example.com">>, <<"secret_password">>).
How do I go about registering it into /etc/ejabberd/ejabberd.yml? What's the syntax?
The following attempts:
erl
c(helloworld).
hellworld:start().
Throws the error:
** exception error: undefined function jid:nodeprep/1
in function ejabberd_auth:validate_credentials/3 (src/ejabberd_auth.erl, line 796)
in call from ejabberd_auth:try_register/3 (src/ejabberd_auth.erl, line 251)
How can I fix it? What is the right way to do it so that I can call ejabberd_auth:try_register successfully?
Thank you all in advance.
ejabberd.yml
###
### ejabberd configuration file
###
###
### The parameters used in this configuration file are explained in more detail
### in the ejabberd Installation and Operation Guide.
### Please consult the Guide in case of doubts, it is included with
### your copy of ejabberd, and is also available online at
### http://www.process-one.net/en/ejabberd/docs/
### The configuration file is written in YAML.
### Refer to http://en.wikipedia.org/wiki/YAML for the brief description.
### However, ejabberd treats different literals as different types:
###
### - unquoted or single-quoted strings. They are called "atoms".
### Example: dog, 'Jupiter', '3.14159', YELLOW
###
### - numeric literals. Example: 3, -45.0, .0
###
### - quoted or folded strings.
### Examples of quoted string: "Lizzard", "orange".
### Example of folded string:
### > Art thou not Romeo,
### and a Montague?
### =======
### LOGGING
##
## loglevel: Verbosity of log files generated by ejabberd.
## 0: No ejabberd log at all (not recommended)
## 1: Critical
## 2: Error
## 3: Warning
## 4: Info
## 5: Debug
##
loglevel: 4
##
## rotation: Describe how to rotate logs. Either size and/or date can trigger
## log rotation. Setting count to N keeps N rotated logs. Setting count to 0
## does not disable rotation, it instead rotates the file and keeps no previous
## versions around. Setting size to X rotate log when it reaches X bytes.
## To disable rotation set the size to 0 and the date to ""
## Date syntax is taken from the syntax newsyslog uses in newsyslog.conf.
## Some examples:
## $D0 rotate every night at midnight
## $D23 rotate every day at 23:00 hr
## $W0D23 rotate every week on Sunday at 23:00 hr
## $W5D16 rotate every week on Friday at 16:00 hr
## $M1D0 rotate on the first day of every month at midnight
## $M5D6 rotate on every 5th day of the month at 6:00 hr
##
log_rotate_size: 10485760
log_rotate_date: ""
log_rotate_count: 1
##
## overload protection: If you want to limit the number of messages per second
## allowed from error_logger, which is a good idea if you want to avoid a flood
## of messages when system is overloaded, you can set a limit.
## 100 is ejabberd's default.
log_rate_limit: 100
##
## watchdog_admins: Only useful for developers: if an ejabberd process
## consumes a lot of memory, send live notifications to these XMPP
## accounts.
##
## watchdog_admins:
## - "bob#example.com"
### ================
### SERVED HOSTNAMES
##
## hosts: Domains served by ejabberd.
## You can define one or several, for example:
## hosts:
## - "example.net"
## - "example.com"
## - "example.org"
##
hosts:
- "localhost"
##
## route_subdomains: Delegate subdomains to other XMPP servers.
## For example, if this ejabberd serves example.org and you want
## to allow communication with an XMPP server called im.example.org.
##
## route_subdomains: s2s
### ===============
### LISTENING PORTS
##
## listen: The ports ejabberd will listen on, which service each is handled
## by and what options to start it with.
##
listen:
-
port: 5222
module: ejabberd_c2s
##
## If TLS is compiled in and you installed a SSL
## certificate, specify the full path to the
## file and uncomment these lines:
##
## certfile: "/path/to/ssl.pem"
## starttls: true
##
## To enforce TLS encryption for client connections,
## use this instead of the "starttls" option:
##
## starttls_required: true
##
## Custom OpenSSL options
##
## protocol_options:
## - "no_sslv3"
## - "no_tlsv1"
max_stanza_size: 65536
shaper: c2s_shaper
access: c2s
-
port: 5269
module: ejabberd_s2s_in
##
## ejabberd_service: Interact with external components (transports, ...)
##
## -
## port: 8888
## module: ejabberd_service
## access: all
## shaper_rule: fast
## ip: "127.0.0.1"
## hosts:
## "icq.example.org":
## password: "secret"
## "sms.example.org":
## password: "secret"
##
## ejabberd_stun: Handles STUN Binding requests
##
## -
## port: 3478
## transport: udp
## module: ejabberd_stun
##
## To handle XML-RPC requests that provide admin credentials:
##
## -
## port: 4560
## module: ejabberd_xmlrpc
-
port: 5280
module: ejabberd_http
## request_handlers:
## "/pub/archive": mod_http_fileserver
web_admin: true
http_poll: true
http_bind: true
## register: true
captcha: true
##
## s2s_use_starttls: Enable STARTTLS + Dialback for S2S connections.
## Allowed values are: false optional required required_trusted
## You must specify a certificate file.
##
## s2s_use_starttls: optional
##
## s2s_certfile: Specify a certificate file.
##
## s2s_certfile: "/path/to/ssl.pem"
## Custom OpenSSL options
##
## s2s_protocol_options:
## - "no_sslv3"
## - "no_tlsv1"
##
## domain_certfile: Specify a different certificate for each served hostname.
##
## host_config:
## "example.org":
## domain_certfile: "/path/to/example_org.pem"
## "example.com":
## domain_certfile: "/path/to/example_com.pem"
##
## S2S whitelist or blacklist
##
## Default s2s policy for undefined hosts.
##
## s2s_access: s2s
##
## Outgoing S2S options
##
## Preferred address families (which to try first) and connect timeout
## in milliseconds.
##
## outgoing_s2s_families:
## - ipv4
## - ipv6
## outgoing_s2s_timeout: 10000
### ==============
### AUTHENTICATION
##
## auth_method: Method used to authenticate the users.
## The default method is the internal.
## If you want to use a different method,
## comment this line and enable the correct ones.
##
auth_method: internal
##
## Store the plain passwords or hashed for SCRAM:
## auth_password_format: plain
## auth_password_format: scram
##
## Define the FQDN if ejabberd doesn't detect it:
## fqdn: "server3.example.com"
##
## Authentication using external script
## Make sure the script is executable by ejabberd.
##
## auth_method: external
## extauth_program: "/path/to/authentication/script"
##
## Authentication using ODBC
## Remember to setup a database in the next section.
##
## auth_method: odbc
##
## Authentication using PAM
##
## auth_method: pam
## pam_service: "pamservicename"
##
## Authentication using LDAP
##
## auth_method: ldap
##
## List of LDAP servers:
## ldap_servers:
## - "localhost"
##
## Encryption of connection to LDAP servers:
## ldap_encrypt: none
## ldap_encrypt: tls
##
## Port to connect to on LDAP servers:
## ldap_port: 389
## ldap_port: 636
##
## LDAP manager:
## ldap_rootdn: "dc=example,dc=com"
##
## Password of LDAP manager:
## ldap_password: "******"
##
## Search base of LDAP directory:
## ldap_base: "dc=example,dc=com"
##
## LDAP attribute that holds user ID:
## ldap_uids:
## - "mail": "%u#mail.example.org"
##
## LDAP filter:
## ldap_filter: "(objectClass=shadowAccount)"
##
## Anonymous login support:
## auth_method: anonymous
## anonymous_protocol: sasl_anon | login_anon | both
## allow_multiple_connections: true | false
##
## host_config:
## "public.example.org":
## auth_method: anonymous
## allow_multiple_connections: false
## anonymous_protocol: sasl_anon
##
## To use both anonymous and internal authentication:
##
## host_config:
## "public.example.org":
## auth_method:
## - internal
## - anonymous
### ==============
### DATABASE SETUP
## ejabberd by default uses the internal Mnesia database,
## so you do not necessarily need this section.
## This section provides configuration examples in case
## you want to use other database backends.
## Please consult the ejabberd Guide for details on database creation.
##
## MySQL server:
##
## odbc_type: mysql
## odbc_server: "server"
## odbc_database: "database"
## odbc_username: "username"
## odbc_password: "password"
##
## If you want to specify the port:
## odbc_port: 1234
##
## PostgreSQL server:
##
## odbc_type: pgsql
## odbc_server: "server"
## odbc_database: "database"
## odbc_username: "username"
## odbc_password: "password"
##
## If you want to specify the port:
## odbc_port: 1234
##
## If you use PostgreSQL, have a large database, and need a
## faster but inexact replacement for "select count(*) from users"
##
## pgsql_users_number_estimate: true
##
## ODBC compatible or MSSQL server:
##
## odbc_type: odbc
## odbc_server: "DSN=ejabberd;UID=ejabberd;PWD=ejabberd"
##
## Number of connections to open to the database for each virtual host
##
## odbc_pool_size: 10
##
## Interval to make a dummy SQL request to keep the connections to the
## database alive. Specify in seconds: for example 28800 means 8 hours
##
## odbc_keepalive_interval: undefined
### ===============
### TRAFFIC SHAPERS
shaper:
##
## The "normal" shaper limits traffic speed to 1000 B/s
##
normal: 1000
##
## The "fast" shaper limits traffic speed to 50000 B/s
##
fast: 50000
##
## This option specifies the maximum number of elements in the queue
## of the FSM. Refer to the documentation for details.
##
max_fsm_queue: 1000
###. ====================
###' ACCESS CONTROL LISTS
acl:
##
## The 'admin' ACL grants administrative privileges to XMPP accounts.
## You can put here as many accounts as you want.
##
## admin:
## user:
## - "aleksey": "localhost"
## - "ermine": "example.org"
##
## Blocked users
##
## blocked:
## user:
## - "baduser": "example.org"
## - "test"
## Local users: don't modify this.
##
local:
user_regexp: ""
##
## More examples of ACLs
##
## jabberorg:
## server:
## - "jabber.org"
## aleksey:
## user:
## - "aleksey": "jabber.ru"
## test:
## user_regexp: "^test"
## user_glob: "test*"
##
## Loopback network
##
loopback:
ip:
- "127.0.0.0/8"
##
## Bad XMPP servers
##
## bad_servers:
## server:
## - "xmpp.zombie.org"
## - "xmpp.spam.com"
##
## Define specific ACLs in a virtual host.
##
## host_config:
## "localhost":
## acl:
## admin:
## user:
## - "bob-local": "localhost"
### ============
### ACCESS RULES
access:
## Maximum number of simultaneous sessions allowed for a single user:
max_user_sessions:
all: 10
## Maximum number of offline messages that users can have:
max_user_offline_messages:
admin: 5000
all: 100
## This rule allows access only for local users:
local:
local: allow
## Only non-blocked users can use c2s connections:
c2s:
blocked: deny
all: allow
## For C2S connections, all users except admins use the "normal" shaper
c2s_shaper:
admin: none
all: normal
## All S2S connections use the "fast" shaper
s2s_shaper:
all: fast
## Only admins can send announcement messages:
announce:
admin: allow
## Only admins can use the configuration interface:
configure:
admin: allow
## Admins of this server are also admins of the MUC service:
muc_admin:
admin: allow
## Only accounts of the local ejabberd server can create rooms:
muc_create:
local: allow
## All users are allowed to use the MUC service:
muc:
all: allow
## Only accounts on the local ejabberd server can create Pubsub nodes:
pubsub_createnode:
local: allow
## In-band registration allows registration of any possible username.
## To disable in-band registration, replace 'allow' with 'deny'.
register:
all: allow
## Only allow to register from localhost
trusted_network:
loopback: allow
## Do not establish S2S connections with bad servers
## s2s:
## bad_servers: deny
## all: allow
## By default the frequency of account registrations from the same IP
## is limited to 1 account every 10 minutes. To disable, specify: infinity
## registration_timeout: 600
##
## Define specific Access Rules in a virtual host.
##
## host_config:
## "localhost":
## access:
## c2s:
## admin: allow
## all: deny
## register:
## all: deny
### ================
### DEFAULT LANGUAGE
##
## language: Default language used for server messages.
##
language: "en"
##
## Set a different default language in a virtual host.
##
## host_config:
## "localhost":
## language: "ru"
### =======
### CAPTCHA
##
## Full path to a script that generates the image.
##
## captcha_cmd: "/lib/ejabberd/priv/bin/captcha.sh"
##
## Host for the URL and port where ejabberd listens for CAPTCHA requests.
##
## captcha_host: "example.org:5280"
##
## Limit CAPTCHA calls per minute for JID/IP to avoid DoS.
##
## captcha_limit: 5
### =======
### MODULES
##
## Modules enabled in all ejabberd virtual hosts.
##
modules:
mod_adhoc: {}
## mod_admin_extra: {}
mod_announce: # recommends mod_adhoc
access: announce
mod_blocking: {} # requires mod_privacy
mod_caps: {}
mod_carboncopy: {}
mod_client_state:
queue_chat_states: true
queue_presence: false
mod_configure: {} # requires mod_adhoc
mod_disco: {}
## mod_echo: {}
mod_irc: {}
mod_http_bind: {}
## mod_http_fileserver:
## docroot: "/var/www"
## accesslog: "/var/log/ejabberd/access.log"
mod_last: {}
mod_muc:
## host: "conference.#HOST#"
access: muc
access_create: muc_create
access_persistent: muc_create
access_admin: muc_admin
## mod_muc_log: {}
mod_offline:
access_max_user_messages: max_user_offline_messages
mod_ping: {}
## mod_pres_counter:
## count: 5
## interval: 60
mod_privacy: {}
mod_private: {}
## mod_proxy65: {}
mod_pubsub:
access_createnode: pubsub_createnode
## reduces resource comsumption, but XEP incompliant
ignore_pep_from_offline: true
## XEP compliant, but increases resource comsumption
## ignore_pep_from_offline: false
last_item_cache: false
plugins:
- "flat"
- "hometree"
- "pep" # pep requires mod_caps
mod_register:
##
## Protect In-Band account registrations with CAPTCHA.
##
## captcha_protected: true
##
## Set the minimum informational entropy for passwords.
##
## password_strength: 32
##
## After successful registration, the user receives
## a message with this subject and body.
##
welcome_message:
subject: "Welcome!"
body: |-
Hi.
Welcome to this XMPP server.
##
## When a user registers, send a notification to
## these XMPP accounts.
##
## registration_watchers:
## - "admin1#example.org"
##
## Only clients in the server machine can register accounts
##
ip_access: trusted_network
##
## Local c2s or remote s2s users cannot register accounts
##
## access_from: deny
access: register
mod_roster: {}
mod_shared_roster: {}
mod_stats: {}
mod_time: {}
mod_vcard: {}
mod_version: {}
##
## Enable modules with custom options in a specific virtual host
##
## host_config:
## "localhost":
## modules:
## mod_echo:
## host: "mirror.localhost"
##
## Enable modules management via ejabberdctl for installation and
## uninstallation of public/private contributed modules
## (enabled by default)
##
allow_contrib_modules: true
### Local Variables:
### mode: yaml
### End:
### vim: set filetype=yaml tabstop=8

Answer 1

Old question. But let me try and explain your problem. As your shell error reported,
exception error: undefined function jid:nodeprep/1
in function ejabberd_auth:validate_credentials/3 (src/ejabberd_auth.erl, line 796)
in call from ejabberd_auth:try_register/3 (src/ejabberd_auth.erl, line 251)
This happened because erlang could find the jid module in any code path. Code path I mean, directories where erlang searches to load modules(beam files) when starting. When your ordinarily execute erl, erlang adds the current directory (from where the command was called), to its code path. Since jid.beam which is linked to ejabberd_auth is not there or any other, that exception is thrown.
Now to your questions:
How do I go about registering it into /etc/ejabberd/ejabberd.yml? What's the syntax?
Add your module to the modules list field as:
modules: mod_adhoc: {}
Make sure to follow the same indentation rule. I'm sure the YAML file parser will throw error if that's not obeyed.
How can I fix it? What is the right way to do it so that I can call ejabberd_auth:try_register successfully?
To fix that, the ejabberd_auth module and all the modules that it directly or transitively access via the call to try_register/3 must be added to the code path. You can do that with -pa flag of the erl command as:
erl -pa ./path-to-ejabberd-ebin-folder
See more at erl
However, ejabberd is an application not just a library. It has lots of other dependecies it require and states to setup(mnesia tables,...).
Even if the jid module is resolved, other problems could happened. I advise to start ejabberd as application. If you do it this way, ejabberd will auto start your module since you registered in the *ejabberd.yml** config file