util: fix retry.WithMaxAttempts context cancelled before run.

If context gets cancelled right after `retry.WithMaxAttempts` runs, the function
passed to it will never gets run. Now `retry.WithMaxAttempts` will at least run
the function once otherwise an error will be returned.

Making this change because there are places such as `show_cluster_setting.go`
require the passed in function to be run at least once. Otherwise there will
be seg fault.

Fixes: 25600, 25603, 25570, 25567, 25566, 25511, 25485.
Release note: None

pkg/util/retry/retry.go

@@ -21,6 +21,7 @@ import (
  "time"
 
  "github.com/cockroachdb/cockroach/pkg/util/timeutil"
+ "github.com/pkg/errors"
 )
 
 // Options provides reusable configuration of Retry objects.
@@ -150,7 +151,12 @@ func (r *Retry) NextCh() <-chan time.Time {
 }
 
 // WithMaxAttempts is a helper that runs fn N times and collects the last err.
+// It guarantees fn will run at least once. Otherwise, an error will be returned.
 func WithMaxAttempts(ctx context.Context, opts Options, n int, fn func() error) error {
+ if n <= 0 {
+ return errors.Errorf("max attempts should not be 0 or below, got: %d", n)
+ }
+
  opts.MaxRetries = n - 1
  var err error
  for r := StartWithCtx(ctx, opts); r.Next(); {
@@ -159,6 +165,9 @@ func WithMaxAttempts(ctx context.Context, opts Options, n int, fn func() error)
  return nil
  }
  }
+ if err == nil {
+ err = errors.Wrap(ctx.Err(), "did not run function")
+ }
  return err
 }