// OpenResourceForUniter returns metadata about the resource and
// a reader for the resource. The resource is associated with
// the unit once the reader is completely exhausted.
func (st resourceState) OpenResourceForUniter(unit resource.Unit, name string) (resource.Resource, io.ReadCloser, error) {
applicationID := unit.ApplicationName()
pendingID, err := newPendingID()
if err != nil {
return resource.Resource{}, nil, errors.Trace(err)
}
resourceInfo, resourceReader, err := st.OpenResource(applicationID, name)
if err != nil {
return resource.Resource{}, nil, errors.Trace(err)
}
pending := resourceInfo // a copy
pending.PendingID = pendingID
if err := st.persist.SetUnitResourceProgress(unit.Name(), pending, 0); err != nil {
resourceReader.Close()
return resource.Resource{}, nil, errors.Trace(err)
}
resourceReader = &unitSetter{
ReadCloser: resourceReader,
persist: st.persist,
unit: unit,
pending: pending,
resource: resourceInfo,
clock: clock.WallClock,
}
return resourceInfo, resourceReader, nil
}
// OpenResource returns metadata about the resource, and a reader for
// the resource.
func (st resourceState) OpenResource(unit resource.Unit, name string) (resource.Resource, io.ReadCloser, error) {
serviceID := unit.ServiceName()
id := newResourceID(serviceID, name)
resourceInfo, storagePath, err := st.persist.GetResource(id)
if err != nil {
return resource.Resource{}, nil, errors.Annotate(err, "while getting resource info")
}
if resourceInfo.IsPlaceholder() {
logger.Tracef("placeholder resource %q treated as not found", name)
return resource.Resource{}, nil, errors.NotFoundf("resource %q", name)
}
resourceReader, resSize, err := st.storage.Get(storagePath)
if err != nil {
return resource.Resource{}, nil, errors.Annotate(err, "while retrieving resource data")
}
if resSize != resourceInfo.Size {
msg := "storage returned a size (%d) which doesn't match resource metadata (%d)"
return resource.Resource{}, nil, errors.Errorf(msg, resSize, resourceInfo.Size)
}
resourceReader = unitSetter{
ReadCloser: resourceReader,
persist: st.persist,
unit: unit,
resource: resourceInfo,
}
return resourceInfo, resourceReader, nil
}