database/sql: add DB.SetMaxIdleConns
Update #4805
R=golang-dev, r
CC=golang-dev
https://golang.org/cl/7634045
diff --git a/src/pkg/database/sql/sql.go b/src/pkg/database/sql/sql.go
index 556580e..8c6ffbc 100644
--- a/src/pkg/database/sql/sql.go
+++ b/src/pkg/database/sql/sql.go
@@ -197,6 +197,7 @@
dep map[finalCloser]depSet
onConnPut map[*driverConn][]func() // code (with mu held) run when conn is next returned
lastPut map[*driverConn]string // stacktrace of last conn's put; debug only
+ maxIdle int // zero means defaultMaxIdleConns; negative means 0
}
// driverConn wraps a driver.Conn with a mutex, to
@@ -332,11 +333,45 @@
return err
}
-func (db *DB) maxIdleConns() int {
- const defaultMaxIdleConns = 2
- // TODO(bradfitz): ask driver, if supported, for its default preference
- // TODO(bradfitz): let users override?
- return defaultMaxIdleConns
+const defaultMaxIdleConns = 2
+
+func (db *DB) maxIdleConnsLocked() int {
+ n := db.maxIdle
+ switch {
+ case n == 0:
+ // TODO(bradfitz): ask driver, if supported, for its default preference
+ return defaultMaxIdleConns
+ case n < 0:
+ return 0
+ default:
+ return n
+ }
+}
+
+// SetMaxIdleConns sets the maximum number of connections in the idle
+// connection pool.
+//
+// If n <= 0, no idle connections are retained.
+func (db *DB) SetMaxIdleConns(n int) {
+ db.mu.Lock()
+ defer db.mu.Unlock()
+ if n > 0 {
+ db.maxIdle = n
+ } else {
+ // No idle connections.
+ db.maxIdle = -1
+ }
+ for len(db.freeConn) > 0 && len(db.freeConn) > n {
+ nfree := len(db.freeConn)
+ dc := db.freeConn[nfree-1]
+ db.freeConn[nfree-1] = nil
+ db.freeConn = db.freeConn[:nfree-1]
+ go func() {
+ dc.Lock()
+ dc.ci.Close()
+ dc.Unlock()
+ }()
+ }
}
// conn returns a newly-opened or cached *driverConn
@@ -441,7 +476,7 @@
if putConnHook != nil {
putConnHook(db, dc)
}
- if n := len(db.freeConn); !db.closed && n < db.maxIdleConns() {
+ if n := len(db.freeConn); !db.closed && n < db.maxIdleConnsLocked() {
db.freeConn = append(db.freeConn, dc)
db.mu.Unlock()
return
