Ecto: tcp recv: closed (the connection was closed by the pool with PostgreSQL 11

[xdays]

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Environment

• Elixir version (elixir -v): 1.9.1
• Database and version (PostgreSQL 9.4, MongoDB 3.2, etc.): PostgreSQL 11.5(AWS RDS)
• Ecto version (mix deps): 3.3.1
• Database adapter and version (mix deps): postgrex 0.15.3
• Operating system: Debian

Current behavior

After I upgrade to postgresql 11, I got this error on one table, but sql queries against other tables are ok.

** (DBConnection.ConnectionError) tcp recv: closed (the connection was closed by the pool, possibly due to a timeout or because the pool has been terminated)
    (ecto_sql) lib/ecto/adapters/sql.ex:629: Ecto.Adapters.SQL.raise_sql_call_error/1
    (ecto_sql) lib/ecto/adapters/sql.ex:562: Ecto.Adapters.SQL.execute/5
    (ecto) lib/ecto/repo/queryable.ex:181: Ecto.Repo.Queryable.execute/4
    (ecto) lib/ecto/repo/queryable.ex:17: Ecto.Repo.Queryable.all/3
    (naboo) lib/naboo/feeds/feeds.ex:689: anonymous fn/1 in Naboo.Feeds.views_list/1
    (naboo) lib/cache/redis_store.ex:117: Cache.RedisStore.fetch/3
    (naboo) lib/naboo/feeds/feeds.ex:634: Naboo.Feeds.push_view/2
    (naboo) lib/naboo/media/media.ex:852: Naboo.Media.create_view/3
2020-02-08 06:19:04.590 [info] {%DBConnection.ConnectionError{
   message: "tcp recv: closed (the connection was closed by the pool, possibly due to a timeout or because the pool has been terminated)",
   severity: :error
 },

and it's bad to normal after I rollback to postgresql 10.

our timeout setting for repo is default.

config :naboo, Naboo.Repo,
  adapter: Ecto.Adapters.Postgres,
  types: Naboo.PostgresTypes,
  username: System.fetch_env!("DB_USERNAME"),
  password: System.fetch_env!("DB_PASSWORD"),
  database: System.fetch_env!("DB_NAME"),
  hostname: System.fetch_env!("DB_HOST"),
  pool_size: 50

[josevalim]

Can you please provide a sample app that reproduces the error? Thank you!

[xdays]

Sorry, I've figured out it's db server side problem, thanks for your effort.

[rm-rf-etc]

Sorry, I've figured out it's db server side problem, thanks for your effort.

Would be great if you would include details of what the problem was. Your description sounds like the problem I'm encountering.

[sreecodeslayer]

@xdays Can you describe what the problem on the server side was or how you debugged this one?

[xdays]

Sorry guys, I can't remember how I fixed it from the db server side. This is a common error, you need pay attends to:

1. ecto pool_size
2. postgres server max_connections