connectionReleaseDelay PoolOption

[julianladisch]

Close idle connections that wait in the pool for connectionReleaseDelay
milliseconds. Defaults to 0 = keep them forever.

The option name is taken from vertx-mysql-postgresql-client:
https://github.com/vert-x3/vertx-mysql-postgresql-client/blob/3.9.1/vertx-mysql-postgresql-client-jasync/src/main/java/io/vertx/ext/asyncsql/impl/pool/AsyncConnectionPool.java#L68

Implementation
If connectionReleaseDelay is > 0:
When a connection is put into the pool create a timer
that closes the connection and removes it from the pool: expire().
If a connection in the pool is acquired before the timer
fires the timer is cancelled: cancelIdleTimer().

In PoolOptions

• add connectionReleaseDelay option
• fix and unit test equals() and hashCode()

In ConnectionPool

• add constructor that takes PoolOptions to avoid long parameter lists
• add package-private allSize() for unit testing
• rename and move release(PooledConnection) to PooledConnection.addToPool()
  to avoid a name that is misleading if connectionReleaseDelay exists

[vietj]

the pool should be reimplemented before 4.0 or around, so I would rather do that in the new pool rather than adding this here

[julianladisch]

We use and will use the old pool in production and therefore would like to have this merged upstream (= in eclipse-vertx/vertx-sql-client) to avoid maintaining a fork.

[julianladisch]

@vietj Is the code quality of this pull request too low, or is the scheduled pool re-implementation the only reason?

[julianladisch]

@vietj What needs to be changed to get this merged to eclipse-vertx/vertx-sql-client?

[vietj]

at least connectionReleaseDelay that might not be part of the next options for this pool

[vietj]

it is rescheduled reimplementation based on the vertx HTTP pool but that would be in 4.1 or 4.2