database/sql: add context methods

Add context methods to sql and sql/driver methods. If
the driver doesn't implement context methods the connection
pool will still handle timeouts when a query fails to return
in time or when a connection is not available from the pool
in time.

There will be a follow-up CL that will add support for
context values that specify transaction levels and modes
that a driver can use.

Fixes #15123

Change-Id: Ia99f3957aa3f177b23044dd99d4ec217491a30a7
Reviewed-on: https://go-review.googlesource.com/29381
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

1 files changed, 231 insertions, 0 deletions

diff --git a/src/database/sql/ctxutil.go b/src/database/sql/ctxutil.go
new file mode 100644
index 0000000000..65e1652657
--- /dev/null
+++ b/src/database/sql/ctxutil.go
@@ -0,0 +1,231 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package sql
+
+import (
+	"context"
+	"database/sql/driver"
+	"errors"
+)
+
+func ctxDriverPrepare(ctx context.Context, ci driver.Conn, query string) (driver.Stmt, error) {
+	if ciCtx, is := ci.(driver.ConnPrepareContext); is {
+		return ciCtx.PrepareContext(ctx, query)
+	}
+	type R struct {
+		err   error
+		panic interface{}
+		si    driver.Stmt
+	}
+
+	rc := make(chan R, 1)
+	go func() {
+		r := R{}
+		defer func() {
+			if v := recover(); v != nil {
+				r.panic = v
+			}
+			rc <- r
+		}()
+		r.si, r.err = ci.Prepare(query)
+	}()
+	select {
+	case <-ctx.Done():
+		go func() {
+			<-rc
+			close(rc)
+		}()
+		return nil, ctx.Err()
+	case r := <-rc:
+		if r.panic != nil {
+			panic(r.panic)
+		}
+		return r.si, r.err
+	}
+}
+
+func ctxDriverExec(ctx context.Context, execer driver.Execer, query string, dargs []driver.Value) (driver.Result, error) {
+	if execerCtx, is := execer.(driver.ExecerContext); is {
+		return execerCtx.ExecContext(ctx, query, dargs)
+	}
+	type R struct {
+		err   error
+		panic interface{}
+		resi  driver.Result
+	}
+
+	rc := make(chan R, 1)
+	go func() {
+		r := R{}
+		defer func() {
+			if v := recover(); v != nil {
+				r.panic = v
+			}
+			rc <- r
+		}()
+		r.resi, r.err = execer.Exec(query, dargs)
+	}()
+	select {
+	case <-ctx.Done():
+		go func() {
+			<-rc
+			close(rc)
+		}()
+		return nil, ctx.Err()
+	case r := <-rc:
+		if r.panic != nil {
+			panic(r.panic)
+		}
+		return r.resi, r.err
+	}
+}
+
+func ctxDriverQuery(ctx context.Context, queryer driver.Queryer, query string, dargs []driver.Value) (driver.Rows, error) {
+	if queryerCtx, is := queryer.(driver.QueryerContext); is {
+		return queryerCtx.QueryContext(ctx, query, dargs)
+	}
+	type R struct {
+		err   error
+		panic interface{}
+		rowsi driver.Rows
+	}
+
+	rc := make(chan R, 1)
+	go func() {
+		r := R{}
+		defer func() {
+			if v := recover(); v != nil {
+				r.panic = v
+			}
+			rc <- r
+		}()
+		r.rowsi, r.err = queryer.Query(query, dargs)
+	}()
+	select {
+	case <-ctx.Done():
+		go func() {
+			<-rc
+			close(rc)
+		}()
+		return nil, ctx.Err()
+	case r := <-rc:
+		if r.panic != nil {
+			panic(r.panic)
+		}
+		return r.rowsi, r.err
+	}
+}
+
+func ctxDriverStmtExec(ctx context.Context, si driver.Stmt, dargs []driver.Value) (driver.Result, error) {
+	if siCtx, is := si.(driver.StmtExecContext); is {
+		return siCtx.ExecContext(ctx, dargs)
+	}
+	type R struct {
+		err   error
+		panic interface{}
+		resi  driver.Result
+	}
+
+	rc := make(chan R, 1)
+	go func() {
+		r := R{}
+		defer func() {
+			if v := recover(); v != nil {
+				r.panic = v
+			}
+			rc <- r
+		}()
+		r.resi, r.err = si.Exec(dargs)
+	}()
+	select {
+	case <-ctx.Done():
+		go func() {
+			<-rc
+			close(rc)
+		}()
+		return nil, ctx.Err()
+	case r := <-rc:
+		if r.panic != nil {
+			panic(r.panic)
+		}
+		return r.resi, r.err
+	}
+}
+
+func ctxDriverStmtQuery(ctx context.Context, si driver.Stmt, dargs []driver.Value) (driver.Rows, error) {
+	if siCtx, is := si.(driver.StmtQueryContext); is {
+		return siCtx.QueryContext(ctx, dargs)
+	}
+	type R struct {
+		err   error
+		panic interface{}
+		rowsi driver.Rows
+	}
+
+	rc := make(chan R, 1)
+	go func() {
+		r := R{}
+		defer func() {
+			if v := recover(); v != nil {
+				r.panic = v
+			}
+			rc <- r
+		}()
+		r.rowsi, r.err = si.Query(dargs)
+	}()
+	select {
+	case <-ctx.Done():
+		go func() {
+			<-rc
+			close(rc)
+		}()
+		return nil, ctx.Err()
+	case r := <-rc:
+		if r.panic != nil {
+			panic(r.panic)
+		}
+		return r.rowsi, r.err
+	}
+}
+
+var errLevelNotSupported = errors.New("sql: selected isolation level is not supported")
+
+func ctxDriverBegin(ctx context.Context, ci driver.Conn) (driver.Tx, error) {
+	if ciCtx, is := ci.(driver.ConnBeginContext); is {
+		return ciCtx.BeginContext(ctx)
+	}
+	// TODO(kardianos): check the transaction level in ctx. If set and non-default
+	// then return an error here as the BeginContext driver value is not supported.
+
+	type R struct {
+		err   error
+		panic interface{}
+		txi   driver.Tx
+	}
+	rc := make(chan R, 1)
+	go func() {
+		r := R{}
+		defer func() {
+			if v := recover(); v != nil {
+				r.panic = v
+			}
+			rc <- r
+		}()
+		r.txi, r.err = ci.Begin()
+	}()
+	select {
+	case <-ctx.Done():
+		go func() {
+			<-rc
+			close(rc)
+		}()
+		return nil, ctx.Err()
+	case r := <-rc:
+		if r.panic != nil {
+			panic(r.panic)
+		}
+		return r.txi, r.err
+	}
+}