Generic offline store

Configure offline message store.

In the vanilla VerneMQ(1.11.0) on netsplit, the broker state had to be cleared before restoration which led to loss of offline messages stored in leveldb using vmq_generic_message_store plugin. Since this kind of persistence is actually not useful so no-op engine was introduced which bypass this persistence step and helped in quick recovery of broker as there was no message state to be loaded in memory.

Using offline message store, only offline messages are persisted for the offline clients. In order to use offline message store, message store plugin needs to be explicitly configured.

message_store_plugin = vmq_generic_offline_msg_store

Currently two offline store engines are available, postgres and redis sentinel.

Offline store engine

Specify the engine to be used for storage.

offline_message_store_engine = vmq_offline_storage_engine_redis

Offline store host

For redis sentinel engine, all the hosts(master and slaves) can be specified in a list format, ["host1", "host2"]

offline_message_store_opts.host = localhost

Offline store port

Specify the port on which the offline store is listening.

offline_message_store_opts.port = 6379

Offline store database

Specify the name of the database to be used as offline store.

offline_message_store_opts.database = 2

Offline store connect timeout

Specify the connect timeout (in milliseconds).

offline_message_store_opts.connect_timeout = 4000

Offline store query timeout

Specify the query timeout (in milliseconds).

offline_message_store_opts.query_timeout = 2000