[DRILL-8307] Ensure thread safety in the Druid plugin HTTP client

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.20.2
• Fix Version/s: 1.20.3
• Component/s: Storage - Other
• Assignee: Unassigned
• Reporter: James Turton
• Created: 15/Sep/22 12:13
• Updated: 22/Sep/22 11:12
• Resolved: 22/Sep/22 11:12

Description

When multiple concurrent queries are run against a single Druid storage plugin then an error such as is shown below is reported by the Apache HttpClient used in that plugin. The Druid storage plugin uses a single static HttpClient instance which should be replaced with something like PoolingHttpClientConnectionManager or the OkHttp3 library for multithreaded access.

[1cdd2b75-1310-xxxx-xxxx-5a638567ed07:foreman] INFO
o.a.d.e.s.d.s.DruidSchemaFactory

User Error Occurred: Failure while loading druid datasources for database
'druid-egsmd300'. (Invalid use of BasicClientConnManager: connection still
allocated.
Make sure to release the connection before allocating another one.)
org.apache.drill.common.exceptions.UserException: DATA_READ ERROR: Failure
while loading druid datasources for database '<connection name>'.