net/http: remove persistConn reference from wantConn

Transport getConn creates wantConn w, tries to obtain idle connection for it
based on the w.key and, when there is no idle connection, puts wantConn into
idleConnWait wantConnQueue.

Then getConn dials connection for w in a goroutine and blocks.
After dial succeeds getConn unblocks and returns connection to the caller.

At this point w is stored in the idleConnWait and will not be evicted
until another wantConn with the same w.key is requested or alive
connection returned into the idle pool which may not happen e.g. if
server closes the connection.

The problem is that even after tryDeliver succeeds w references
persistConn wrapper that allocates bufio.Reader and bufio.Writer and
prevents them from being garbage collected.

To fix the problem this change removes persistConn and error references
from wantConn and delivers them via channel to getConn.

This way wantConn could be kept in wantConnQueues arbitrary long.

Fixes #43966
Fixes #50798

Change-Id: I77942552f7db04c225fb40d770b3101a8cfe655d
GitHub-Last-Rev: 027a0833f98b23ddadb3ec7ee4f2e62653bc7705
GitHub-Pull-Request: golang/go#62227
Reviewed-on: https://go-review.googlesource.com/c/go/+/522095
Reviewed-by: Damien Neil <dneil@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Auto-Submit: Damien Neil <dneil@google.com>

0 files changed, 0 insertions, 0 deletions