getPersistentSubcriptionInfo/1 ?

[kristofka]

Hi, some of the other clients implement a getPersistentSubscriptionInfo function, granted, it's easy enough to implement with Spear.request/5 eg:

iex(1)>  {:ok, conn} = Spear.Connection.start_link(connection_string: "esdb://localhost:2113")
{:ok, #PID<0.234.0>}
iex(2)> require Spear.Records.Persistent
Spear.Records.Persistent
iex(3)> require Spear.Records.Shared
Spear.Records.Shared
iex(4)> stream_id = Spear.Records.Shared.stream_identifier(stream_name: "$ce-commandedtestdadc98d0_31d8_4518_b4a2_d4a148595ec8")
{:"event_store.client.StreamIdentifier",
 "$ce-commandedtestdadc98d0_31d8_4518_b4a2_d4a148595ec8"}
iex(5)> stream_options = Spear.Records.Persistent.get_info_req_options(stream_option:  {:stream_identifier, stream_id}, group_name: "subscriber")
{:"event_store.client.persistent_subscriptions.GetInfoReq.Options",
 {:stream_identifier,
  {:"event_store.client.StreamIdentifier",
   "$ce-commandedtestdadc98d0_31d8_4518_b4a2_d4a148595ec8"}}, "subscriber"}
iex(6)> get_info_message= Spear.Records.Persistent.get_info_req(options: stream_options)
{:"event_store.client.persistent_subscriptions.GetInfoReq",
 {:"event_store.client.persistent_subscriptions.GetInfoReq.Options",
  {:stream_identifier,
   {:"event_store.client.StreamIdentifier",
    "$ce-commandedtestdadc98d0_31d8_4518_b4a2_d4a148595ec8"}}, "subscriber"}}
iex(7)> {:ok, resp} = Spear.request(conn, Spear.Records.Persistent,:GetInfo, [get_info_message])
{:ok,
 {:"event_store.client.persistent_subscriptions.GetInfoResp",
  {:"event_store.client.persistent_subscriptions.SubscriptionInfo",
   "$ce-commandedtestdadc98d0_31d8_4518_b4a2_d4a148595ec8", "subscriber",
   "Live", [], 0, 2, 0, "", "2", true, "0", 10000, false, 10, 100, 300, 100,
   3000, 1, 100, 2, 3, 1, 0, 0, "RoundRobin", 1, 0}}}
iex(8)> {_, infos} = resp
{:"event_store.client.persistent_subscriptions.GetInfoResp",
 {:"event_store.client.persistent_subscriptions.SubscriptionInfo",
  "$ce-commandedtestdadc98d0_31d8_4518_b4a2_d4a148595ec8", "subscriber", "Live",
  [], 0, 2, 0, "", "2", true, "0", 10000, false, 10, 100, 300, 100, 3000, 1,
  100, 2, 3, 1, 0, 0, "RoundRobin", 1, 0}}
iex(9)>  Spear.Records.Persistent.subscription_info(infos) |> Enum.into(%{})
%{
  average_per_second: 0,
  buffer_size: 300,
  check_point_after_milliseconds: 3000,
  connections: [],
  count_since_last_measurement: 0,
  event_source: "$ce-commandedtestdadc98d0_31d8_4518_b4a2_d4a148595ec8",
  extra_statistics: false,
  group_name: "subscriber",
  last_checkpointed_event_position: "",
  last_known_event_position: "2",
  live_buffer_count: 3,
  live_buffer_size: 100,
  max_check_point_count: 100,
  max_retry_count: 10,
  max_subscriber_count: 1,
  message_timeout_milliseconds: 10000,
  min_check_point_count: 1,
  named_consumer_strategy: "RoundRobin",
  outstanding_messages_count: 0,
  parked_message_count: 0,
  read_batch_size: 100,
  read_buffer_count: 2,
  resolve_link_tos: true,
  retry_buffer_count: 1,
  start_from: "0",
  status: "Live",
  total_in_flight_messages: 0,
  total_items: 2
}

If you think such a function could live under the Spear#utility set of functions, I'd gladly attempt a pull request.

There would be two issues to keep in mind :

• a struct Spear.PersistentSubscription.Info would probably needed;
• from a cursory look at other clients, it seems the feature may not be present on all servers, so an extra check would be needed.

If you think you'd rather have client applications handle that through Spear.request/5, feel free to close the issue.

Thanks.

[the-mikedavis]

Ah looks like these are new RPCs: https://github.com/EventStore/EventStore/commit/31454a061fbfb27a790aa7c2e3f698bf02a79fde#diff-96a3dceee570d38ca341085c4887d112c8fc3ad5bbcf3963e3a73937c7b21b87

Adding new functions for them sounds good 👍. I think they could belong in @doc api: :persistent since they're defined in the persistent.proto. And I agree, a new struct Spear.PersistentSubscription.Info is needed - that's a lot of fields in the SubscriptionInfo message. A PR would be great!

It looks like those RPCs are only implemented in the v22.10.0 tag. For now I've been adding a note to the docs for RPCs that are implemented only on some server versions (see Spear.append_batch/5). I think other clients check the server capabilities RPC on start-up (if available) and give a more helpful error message if it isn't implemented. I left that out of the Spear.Connection module for now since it adds a lot of complexity but maybe that should be added too eventually.

[kristofka]

A quick update to let you know I'm working on the PR. I'll add a note in the doc stating that the function is available only for v22.10.0 and above.

The PR should come within a couple of days.

[the-mikedavis]

Added in #76