mod_mam

Module Description

This module implements XEP-0313: Message Archive Management. It enables a service to store all user messages for one-to-one chats as well as group chats (MUC, MultiUser Chat). It uses XEP-0059: Result Set Management for paging. It is a highly customizable module, that requires some skill and knowledge to operate properly and efficiently.

MongooseIM is compatible with MAM 0.4-0.6.

Configure MAM with different storage backends:

• RDBMS (databases like MySQL, PostgreSQL, MS SQL Server)
• Cassandra (NoSQL)
• ElasticSearch (NoSQL)

mod_mam is a meta-module that ensures all relevant mod_mam_* modules are loaded and properly configured.

Message retraction

This module supports XEP-0424: Message Retraction with RDBMS storage backends. When a retraction message is received, the MAM module finds the message to retract and replaces it with a tombstone.

The following criteria are used to find the original message:

• The id attribute specified in the apply-to element of the retraction message has to be the same as the id attribute of the origin-id (or stanza-id when configured, see below) element of the original message.
• Both messages need to originate from the same user.
• Both messages need to be addressed to the same user.

If more than one message matches the criteria, only the most recent one is retracted. To avoid this case, it is recommended to use a unique identifier (UUID) as the origin ID.

Retraction on the stanza-id

This module also implements an extension to the XEP, where it allows to specify the stanza-id as created by the server's MAM, instead of the origin-id that the original XEP-0424 specifies. It announces this capability under the namespace urn:esl:message-retract-by-stanza-id:0. This is specially useful in groupchats where the stanza-id of a message is shared and known for all participants.

In this case, to use such functionality,

<apply-to id="origin-id-1" xmlns="urn:xmpp:fasten:0">
  <retract xmlns='urn:xmpp:message-retract:0'/>
</apply-to>

turns into

<apply-to id="stanza-id-1" xmlns="urn:xmpp:fasten:0">
  <retract xmlns='urn:esl:message-retract-by-stanza-id:0'/>
</apply-to>

and likewise, the answer would be tagged by the mentioned esl namespace.

Full Text Search

This module allows message filtering by their text body (if enabled, see Common backend options). This means that an XMPP client, while requesting messages from the archive may not only specify standard form fields (with, start, end), but also full-text-search (of type text-single). If this happens, the client will receive only messages that contain words specified in the request.

The exact behaviour, like whether word ordering matters, may depend on the storage backend in use. For now rdbms backend has very limited support for this feature, while cassandra does not support it at all. elasticsearch backend, on the other hand, should provide you with the best results when it comes to text filtering.

mod_mam_rdbms_arch returns all messages that contain all search words, order of words does not matter. Messages are sorted by timestamp (not by relevance).

Note on full text search with ElasticSearch backend

When using ElasticSearch MAM backend, the value provided in full-text-search form field will be passed to ElasticSearch as Simple Search Query. If you're using our official ElasticSearch mappings from priv/elasticsearch then the query analyzer is set to english. Also note that the default separator for the search query is AND (which roughly means that ElasticSearch will search for messages containing all the terms provided in the query string).

Options

modules.mod_mam.backend

• Syntax: string, one of "rdbms", "cassandra" and "elasticsearch"
• Default: "rdbms"
• Example: backend = "elasticsearch"

Database backend to use.

modules.mod_mam.no_stanzaid_element

• Syntax: boolean
• Default: false
• Example: no_stanzaid_element = true

Do not add a <stanza-id/> element from MAM v0.6.

modules.mod_mam.is_archivable_message

• Syntax: non-empty string
• Default: "mod_mam_utils"
• Example: is_archivable_message = "mod_mam_utils"

Name of a module implementing is_archivable_message/3 callback that determines if the message should be archived.

modules.mod_mam.send_message

• Syntax: non-empty string
• Default: "mod_mam_utils"
• Example: send_message = "mod_mam_utils"

Name of a module implementing send_message/4 callback that routes a message during lookup operation. Consult with mod_mam_utils:send_message/4 code for more information.

Check big_tests/tests/mam_send_message_SUITE_data/mam_send_message_example.erl file in the MongooseIM repository for the usage example.

modules.mod_mam.archive_chat_markers

• Syntax: boolean
• Default: false
• Example: archive_chat_markers = true

If set to true, XEP-0333 chat markers will be archived. See more details here.

modules.mod_mam.message_retraction

• Syntax: boolean
• Default: true
• Example: message_retraction = false

Enables XEP-0424: Message Retraction. This functionality is currently implemented only for the rdbms backend. Retraction messages are always archived regardless of this option.

backend, no_stanzaid_element, is_archivable_message and message_retraction will be applied to both pm and muc (if they are enabled), unless overridden explicitly (see example below).

Enable one-to-one message archive

Archive for one-to-one messages can be enabled in one of two ways:

• Specify [mod_mam.pm] section

[modules.mod_mam]
[modules.mod_mam.pm] # defining this section enables PM support

• Define any PM related option

[modules.mod_mam]
  pm.backend = "rdbms" # enables PM support and overrides its backend

Disable one-to-one message archive

To disable archive for one-to-one messages please remove PM section or any PM related option from the config file.

PM-specific options

modules.mod_mam.pm.archive_groupchats

• Syntax: boolean
• Default: false
• Example: modules.mod_mam.pm.archive_groupchats = true

When enabled, MAM will store groupchat messages in recipients' individual archives. USE WITH CAUTION! May increase archive size significantly. Disabling this option for existing installation will neither remove such messages from MAM storage, nor will filter out them from search results.

modules.mod_mam.pm.same_mam_id_for_peers

• Syntax: boolean
• Default: false
• Example: modules.mod_mam.pm.same_mam_id_for_peers = true

When enabled, MAM will set the same MAM ID for both sender and recipient. This can be useful in combination with retraction on the stanza-id. Note that this might not work with clients across federation, as the recipient might not implement the same retraction, nor the same IDs.

Enable MUC message archive

Archive for MUC messages can be enabled in one of two ways:

• Specify [mod_mam.muc] section

[modules.mod_mam]
[modules.mod_mam.muc] # defining this section enables MUC support

• Define any MUC related option

[modules.mod_mam]
  muc.backend = "rdbms" # enables MUC support and overrides its backend

Disable MUC message archive

To disable archive for MUC messages please remove MUC section or any MUC related option from the config file.

MUC-specific options

modules.mod_mam.muc.host

• Syntax: string
• Default: "conference.@HOST@"
• Example: modules.mod_mam.muc.host = "conference.@HOST@"

The MUC host that will be archived if MUC archiving is enabled.

Warning

If you are using MUC Light, make sure this option is set to the MUC Light domain

Example

The example below presents how to override common option for muc module specifically. Please note that you can override all common options (except cache) in a similar way.

[modules.mod_mam]
  backend = "rdbms"
  async_writer.enabled = true # this option enables async writer for RDBMS backend
  muc.async_writer.enabled = false # disable async writer for MUC archive only

RDBMS backend options

These options will only have effect when the rdbms backend is used:

modules.mod_mam.cache_users

• Syntax: boolean
• Default: true
• Example: modules.mod_mam.cache_users = false

Enables Archive ID to integer mappings cache.

If caching is enabled, by default it will spawn its own segmented cache cache, with defaults as in mod_cache_users. To change these defaults, the same config can be accessed within the cache key. To see details about the meaning of each flag, see mod_cache_users. To reuse the cache already created by mod_cache_users, see the option below.

modules.mod_mam.cache.strategy
modules.mod_mam.cache.time_to_live
modules.mod_mam.cache.number_of_segments

modules.mod_mam.cache.module

• Syntax: string, one of "mod_cache_users" or "internal"
• Default: internal
• Example: modules.mod_mam.cache.module = "mod_cache_users"

Configures which cache to use, either start an internal instance, or reuse the cache created by mod_cache_users, if such module was enabled. Note that if reuse is desired – that is, cache.module = "mod_cache_users", other cache configuration parameters will be ignored.

modules.mod_mam.async_writer.enabled

• Syntax: boolean
• Default: true
• Example: modules.mod_mam.async_writer.enabled = false

Enables an asynchronous writer that is faster than the synchronous one but harder to debug. The async writers store batches of messages that will be flush on a timeout (see flush_interval) or when the batch reaches a size (see batch_size), so the results of the lookup operations executed right after message routing may be incomplete until the configured time passes or the queue is full.

modules.mod_mam.async_writer.flush_interval

• Syntax: non-negative integer
• Default: 2000
• Example: modules.mod_mam.async_writer.flush_interval = 2000

How often (in milliseconds) the buffered messages are flushed to DB.

modules.mod_mam.async_writer.batch_size

• Syntax: non-negative integer
• Default: 30
• Example: modules.mod_mam.async_writer.batch_size = 30

Max size of the batch for an async writer before the queue is considered full and flushed. If the buffer is full, messages are flushed to a database immediately and the flush timer is reset.

modules.mod_mam.async_writer.pool_size

• Syntax: non-negative integer
• Default: 4 * erlang:system_info(schedulers_online)
• Example: modules.mod_mam.async_writer.pool_size = 32

Number of workers in the pool. More than the number of available schedulers is recommended, to minimise lock contention on the message queues, and more than the number of DB workers, to fully utilise the DB capacity. How much more than these two parameters is then a good fine-tuning for specific deployments.

Common backend options

modules.mod_mam.user_prefs_store

• Syntax: one of "rdbms", "cassandra", "mnesia"
• Default: not set
• Example: modules.mod_mam.user_prefs_store = "rdbms"

Leaving this option unset will prevent users from setting their archiving preferences. It will also increase performance. The possible values are:

• "rdbms" (RDBMS backend only) - User archiving preferences saved in RDBMS. Slow and not recommended, but might be used for simplicity (keeping everything in RDBMS).
• "cassandra" (Cassandra backend only) - User archiving preferences are saved in Cassandra.
• "mnesia" (recommended) - User archiving preferences saved in Mnesia and accessed without transactions. Recommended in most deployments, could be overloaded with lots of users updating their preferences at once. There's a small risk of an inconsistent (in a rather harmless way) state of the preferences table.

modules.mod_mam.full_text_search

• Syntax: boolean
• Default: true
• Example: modules.mod_mam.full_text_search = false

Enables full text search in message archive (see Full Text Search paragraph). Please note that the full text search is currently only implemented for "rdbms" backend. Also, full text search works only for messages archived while this option is enabled.

is_archivable_message/3 callback

is_archivable_message option has to name a module exporting is_archivable_message/3 function conforming to the spec:

-spec is_archivable_message(Mod :: module(), Dir :: incoming | outgoing,
                          Packet :: exml:element()) -> boolean().

Servers SHOULD NOT archive messages that do not have a <body/> child tag. Servers SHOULD NOT archive delayed messages.

By default, all messages that hold meaningful content, rather than state changes such as Chat State Notifications, are archived.

Archiving chat markers

Archiving chat markers can be enabled by setting archive_chat_markers option to true. However it only works if is_archivable_message callback module is set to mod_mam_utils or isn't set at all.

When performing full text search chat markers are treated as if they had empty message body.

Cassandra backend

Please consult Outgoing connections page to learn how to properly configure Cassandra connection pool. By default, mod_mam Cassandra backend requires global pool with default tag.

ElasticSearch backend

First, make sure that your ElasticSearch cluster has expected indexes and mappings in place. Please consult Outgoing connections page to learn how to properly configure ElasticSearch connection pool.

Low-level options

These options allow for fine-grained control over MAM behaviour.

modules.mod_mam.default_result_limit

• Syntax: non-negative integer
• Default: 50
• Example: modules.mod_mam.default_result_limit = 100

This sets the default page size of returned results.

modules.mod_mam.max_result_limit

• Syntax: non-negative integer
• Default: 50
• Example: modules.mod_mam.max_result_limit = 100

This sets the maximum page size of returned results.

modules.mod_mam.enforce_simple_queries

• Syntax: boolean
• Default: false
• Example: modules.mod_mam.enforce_simple_queries = true

This enforces all mam lookups to be "simple", i.e., they skip the RSM count. See Message Archive Management extensions.

modules.mod_mam.delete_domain_limit

• Syntax: non-negative integer or the string "infinity"
• Default: "infinity"
• Example: modules.mod_mam.delete_domain_limit = 10000

Domain deletion can be an expensive operation, as it requires to delete potentially many thousands of records from the DB. By default, the delete operation deletes everything in a transaction, but it might be desired, to handle timeouts and table locks more gracefully, to delete the records in batches. This limit establishes the size of the batch.

Note

Not supported by MSSQL.

modules.mod_mam.db_jid_format

• Syntax: string, one of "mam_jid_rfc", "mam_jid_rfc_trust", "mam_jid_mini" or a module implementing mam_jid behaviour
• Default: "mam_jid_rfc" for MUC archive, "mam_jid_mini" for PM archive
• Example: modules.mod_mam.db_jid_format = "mam_jid_mini"

Sets the internal MAM jid encoder/decoder module for RDBMS.

Warning

Archive MUST be empty to change this option

modules.mod_mam.db_message_format

• Syntax: string, one of "mam_message_xml", "mam_message_eterm", "mam_message_compressed_eterm" or a module implementing mam_message behaviour
• Default: "mam_message_compressed_eterm" for RDBMS, "mam_message_xml" for Cassandra
• Example: modules.mod_mam.db_message_format = "mam_message_compressed_eterm"

Sets the internal MAM message encoder/decoder module.

Warning

Archive MUST be empty to change this option

modules.mod_mam.extra_fin_element

• Syntax: string, a module implementing the extra_fin_element/3 callback
• Default: none
• Example: modules.mod_mam.extra_fin_element = "example_mod"

This module can be used to add subelements to the <fin> element of the MAM lookup query response. It can be useful to be able to add information to a mam query, that doesn't belong to any specific message but to all of them.

modules.mod_mam.extra_lookup_params

• Syntax: string, a module implementing the extra_lookup_params/2 callback
• Default: none
• Example: modules.mod_mam.extra_lookup_params = "example_mod"

This module can be used to add extra lookup parameters to MAM lookup queries.

Example configuration

[modules.mod_mam]
  backend = "rdbms"
  no_stanzaid_element = true

  pm.user_prefs_store = "rdbms"

  muc.host = "muc.example.com"
  muc.db_message_format = "mam_message_xml"
  muc.async_writer.enabled = false
  muc.user_prefs_store = "mnesia"

Metrics

If you'd like to learn more about metrics in MongooseIM, please visit MongooseIM metrics page.

Name	Type	Description (when it gets incremented)
[HostType, modMamArchiveRemoved]	spiral	User's entire archive is removed.
[HostType, modMamArchived]	spiral	A message is stored in user's archive.
[HostType, modMamDropped]	spiral	A message couldn't be stored in the DB (and got dropped).
[HostType, modMamDroppedIQ]	spiral	MAM IQ has been dropped due to: high query frequency/invalid syntax or type.
[HostType, modMamFlushed]	spiral	Message was stored in a DB asynchronously.
[HostType, modMamForwarded]	spiral	A message is sent to a client as a part of a MAM query result.
[HostType, modMamLookups]	spiral	A MAM lookup is performed.
[HostType, modMamPrefsGets]	spiral	Archiving preferences have been requested by a client.
[HostType, modMamPrefsSets]	spiral	Archiving preferences have been updated by a client.
[HostType, modMucMamArchiveRemoved]	spiral	Room's entire archive is removed.
[HostType, modMucMamArchived]	spiral	A message is stored in room's archive.
[HostType, modMucMamForwarded]	spiral	A message is sent to a client as a part of a MAM query result from MUC room.
[HostType, modMucMamLookups]	spiral	A MAM lookup in MUC room is performed.
[HostType, modMucMamPrefsGets]	spiral	MUC archiving preferences have been requested by a client.
[HostType, modMucMamPrefsSets]	spiral	MUC archiving preferences have been updated by a client.
[HostType, mod_mam_rdbms_async_pool_writer, per_message_flush_time]	histogram	Average time per message insert measured in an async MAM worker.
[HostType, mod_mam_rdbms_async_pool_writer, flush_time]	histogram	Average time per flush of all buffered messages measured in an async MAM worker.
[HostType, mod_mam_muc_rdbms_async_pool_writer, per_message_flush_time]	histogram	Average time per message insert measured in an async MUC MAM worker.
[HostType, mod_mam_muc_rdbms_async_pool_writer, flush_time]	histogram	Average time per flush of all buffered messages measured in an async MUC MAM worker.

Backend action	Description (when it gets incremented)
lookup	A lookup in an archive.
archive	One message is saved in an archive.