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. It's unlikely that you'll interact with the hub directly unless you're
writing an integration or you want to create or destroy scopes. Scopes, on the
other hand are more user facing. You can call
configure_scope at any point in
time to modify data stored on the scope. This is useful for doing things like
modifying 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
configure_scope function. It can be used to reconfigure the current scope.
You can, for instance, add custom tags or inform Sentry about the currently authenticated user.
Sentry.configure_scope do |scope| scope.set_tags(key: "value") scope.set_user(id: 1) end
You can also apply this configuration when unsetting a user at logout:
To learn what useful information can be associated with scopes see the context documentation.
We also support pushing and configuring a scope within a single call. This is typically
push_scope or implemented as a function parameter on the capture methods, depending on the SDK. It's very helpful if
you only want to send data for one specific event.
In the following example we use
with_scope to attach a
level and a
tag to only one specific error:
Sentry.with_scope do |scope| scope.set_tags(my_tag: "my value") Sentry.capture_message("test") # will be tagged with `my_tag: "my value"` end Sentry.capture_message("test 2") # will not be tagged
While this example looks similar to
configure_scope, it is actually very different.
configure_scope change the current active scope; all successive calls to
configure_scope will maintain previously set changes unless they are explicitly unset.
On the other hand,
with_scope creates a clone of the current scope, and the changes
made will stay isolated within the
with_scope callback function. This allows you to
more easily isolate pieces of context information to specific locations in your code or
clear to briefly remove all context information.
Our documentation is open source and available on GitHub. Your contributions are welcome, whether fixing a typo (drat!) to suggesting an update ("yeah, this would be better").