Scopes and Hubs
When an event is captured and sent to Sentry, SDKs will merge that event data with extra information from the current scope. SDKs will typically automatically manage the scopes for you in the framework integrations and you don't need to think about them. However, you should know what a scope is and how you can use it for your advantage.
You can think of the hub as the central point that our SDKs use to route an
event to Sentry. When you call
init() a hub is created and a client and a
blank scope are created on it. That hub is then associated with the current
thread and will internally hold a stack of scopes.
The scope will hold useful information that should be sent along with the event. For instance contexts or breadcrumbs are stored on the scope. When a scope is pushed, it inherits all data from the parent scope and when it pops all modifications are reverted.
The default SDK integrations will push and pop scopes intelligently. For instance web framework integrations will create and destroy scopes around your routes or controllers.
As you start using an SDK a scope and hub are automatically created for you out
of the box. The hub you are unlikely to be interacting with directly unless you
are writing an integration or you want to create or destroy scopes. Scopes on the
other hand are more user facing. You can at any point in time call
configure-scope to modify data stored on the scope. This is for instance
used to modify the context.
When you call a global function such as
capture_event internally Sentry
discovers the current hub and asks it to capture an event. Internally the hub will
then merge the event with the topmost scope's data.
The most useful operation when working with scopes is the
It can be used to reconfigure the current scope. This for instance can be used to
add custom tags or to inform sentry about the currently authenticated user.
import 'package:sentry/sentry.dart'; Sentry.configureScope((scope) => scope ..setTag('my-tag', 'my value') ..user = User(id: '42', email: 'firstname.lastname@example.org'));
This can also be applied when unsetting a user at logout:
import 'package:sentry/sentry.dart'; Sentry.configureScope((scope) => scope.user = null);
To learn what useful information can be associated with scopes see the context documentation.
We also have support for pushing and configuring a scope in one go. This is
push-scope which is also very helpful
if you only want to send data with one specific event. In the following example we are using
that function to attach a
level and a
tag to only one specific error:
While this example looks similar to
configure-scope it's very different, in the sense that
configure-scope actually changes the current active scope, all successive calls to
will keep the changes.
While on the other hand using
with-scope creates a clone of the current scope
and will stay isolated until the function call is completed. So you can either
set context information in there that you don't want to be somewhere else or not
attach any context information at all by calling
clear on the scope, while the
"global" scope remains unchanged.