make sender configuerable

apps/explorer/config/config.exs

@@ -16,7 +16,11 @@ config :explorer,
   include_uncles_in_average_block_time:
     if(System.get_env("UNCLES_IN_AVERAGE_BLOCK_TIME") == "true", do: true, else: false),
   healthy_blocks_period: System.get_env("HEALTHY_BLOCKS_PERIOD") || :timer.minutes(5),
-  realtime_events_sender: Explorer.Chain.Events.DBSender
+  realtime_events_sender:
+    if(System.get_env("DISABLE_WEBAPP") != "true",
+      do: Explorer.Chain.Events.SimpleSender,
+      else: Explorer.Chain.Events.DBSender
+    )
 
 average_block_period =
   case Integer.parse(System.get_env("AVERAGE_BLOCK_CACHE_PERIOD", "")) do

docs/env-variables.md

@@ -59,7 +59,7 @@ $ export NETWORK=POA
 | `UNCLES_IN_AVERAGE_BLOCK_TIME` | Include or exclude nonconsensus blocks in avg block time calculation. Exclude if `false`. | false | v2.0.1+ | | |
 | `AVERAGE_BLOCK_CACHE_PERIOD` | | Update of average block cache, in seconds | 30 minutes | v2.0.2+ | |
 | `MARKET_HISTORY_CACHE_PERIOD` | | Update of market history cache, in seconds | 6 hours | v2.0.2+ | |
-| `DISABLE_WEBAPP` | | If `true`, endpoints to webapp are hidden (compile-time) | `false` | v2.0.3+ | :white_check_mark: | |
+| `DISABLE_WEBAPP` | | If `true`, endpoints to webapp are hidden (compile-time). Also, enabling it makes notifications go through `db_notify` | `false` | v2.0.3+ | :white_check_mark: | |
 | `DISABLE_READ_API` | | If `true`, read-only endpoints to API are hidden (compile-time) | `false` | v2.0.3+ | :white_check_mark: | |
 | `DISABLE_WRITE_API` | | If `true`, write endpoints to API are hidden (compile-time) | `false` | v2.0.3+ | :white_check_mark: | |
 | `DISABLE_INDEXER` | | If `true`, indexer application doesn't run | `false` | v2.0.3+ | :white_check_mark: | |