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All the outgoing pools configured by the outgoing_pools option are hidden behind the mongoose_wpool API. Every pool is described by a tuple {Type, Host, Tag, PoolOptions, ConnectionOptions} (see outgoing pools for details about each element of the tuple).

Supervision tree

Supervision tree

  • mongoose_wpool_sup supervisor for every type of the pool. Under it there can be many children of:
    • mongoose_wpool_type_sup is started on-demand when a pool of given type is started. Many pools of the same type are supervised by the supervisor. Its children are:
      • mongoose_wpool_mgr all the pools of the same type are managed by a manager. It's responsible for starting, stopping and restarting the pool. Restarting happens when the main worker_pool process for the pool is stopped unintentionally. This usually happens when there was too many restarts of worker processes.
      • many worker_pool supervisors holding a specific pool are on the same level as the manager.

The mongoose_wpool_mgr manages the pool by setting monitor for every started pool.

Implementing new pool type

To add a new pool type, create a mongoose_wpool_NEW_TYPE module implementing the mongoose_wpool behaviour. This means that for a new type xyz we need to create a mongoose_wpool_xyz module. Then we can use the xyz type to start the pool via outgoing_pools option or directly via the mongoose_wpool API.