Global ID - Reference models by URI
A Global ID is an app wide URI that uniquely identifies a model instance:
This is helpful when you need a single identifier to reference different classes of objects.
One example is job scheduling. We need to reference a model object rather than serialize the object itself. We can pass a Global ID that can be used to locate the model when it's time to perform the job. The job scheduler doesn't need to know the details of model naming and IDs, just that it has a global identifier that references a model.
Another example is a drop-down list of options, consisting of both Users and Groups. Normally we'd need to come up with our own ad hoc scheme to reference them. With Global IDs, we have a universal identifier that works for objects of both classes.
GlobalID::Identification into any model with a
#find(id) class method.
Support is automatically included in Active Record.
person_gid = Person.find(1).to_global_id # => #<GlobalID ... person_gid.uri # => #<URI ... person_gid.to_s # => "gid://app/Person/1" ::. person_gid # => #<Person:0x007fae94bf6298 @id="1">
Signed Global IDs
For added security GlobalIDs can also be signed to ensure that the data hasn't been tampered with.
person_sgid = Person.find(1).to_signed_global_id # => #<SignedGlobalID:0x007fea1944b410> person_sgid = Person.find(1).to_sgid # => #<SignedGlobalID:0x007fea1944b410> person_sgid.to_s # => "BAhJIh5naWQ6Ly9pZGluYWlkaS9Vc2VyLzM5NTk5BjoGRVQ=--81d7358dd5ee2ca33189bb404592df5e8d11420e" ::. person_sgid # => #<Person:0x007fae94bf6298 @id="1">
Signed Global IDs can expire some time in the future. This is useful if there's a resource people shouldn't have indefinite access to, like a share link.
expiring_sgid = Document.find(5).to_sgid(expires_in: 2.hours, for: 'sharing') # => #<SignedGlobalID:0x008fde45df8937 ...> # Within 2 hours... ::.(expiring_sgid.to_s, for: 'sharing') # => #<Document:0x007fae94bf6298 @id="5"> # More than 2 hours later... ::.(expiring_sgid.to_s, for: 'sharing') # => nil
In Rails, an auto-expiry of 1 month is set by default. You can alter that deal in an initializer with:
# config/initializers/global_id.rb Rails.application.config.global_id.expires_in = 3.months
You can assign a default SGID lifetime like so:
. = 1.month
This way any generated SGID will use that relative expiry.
It's worth noting that expiring SGIDs are not idempotent because they encode the current timestamp; repeated calls to
to_sgid will produce different results. For example, in Rails
Document.find(5).to_sgid.to_s == Document.find(5).to_sgid.to_s # => false
You need to explicitly pass
expires_in: nil to generate a permanent SGID that will not expire,
# Passing a false value to either expiry option turns off expiration entirely. never_expiring_sgid = Document.find(5).to_sgid(expires_in: nil) # => #<SignedGlobalID:0x008fde45df8937 ...> # Any time later... ::. never_expiring_sgid # => #<Document:0x007fae94bf6298 @id="5">
It's also possible to pass a specific expiry time
explicit_expiring_sgid = SecretAgentMessage.find(5).to_sgid(expires_at: Time.now.advance(hours: 1)) # => #<SignedGlobalID:0x008fde45df8937 ...> # 1 hour later... ::. explicit_expiring_sgid.to_s # => nil
Note that an explicit
:expires_at takes precedence over a relative
You can even bump the security up some more by explaining what purpose a Signed Global ID is for. In this way evildoers can't reuse a sign-up form's SGID on the login page. For example.
signup_person_sgid = Person.find(1).to_sgid(for: 'signup_form') # => #<SignedGlobalID:0x007fea1984b520 ::.(signup_person_sgid.to_s, for: 'signup_form') # => #<Person:0x007fae94bf6298 @id="1">
Locating many Global IDs
When needing to locate many Global IDs use
GlobalID::Locator.locate_many_signed for Signed Global IDs to allow loading
Global IDs more efficiently.
For instance, the default locator passes every
model_name.where(id: model_ids) versus
In the case of looking up Global IDs from a database, it's only necessary to query
model_name as shown here:
gids = users.concat(people).sort_by(&:id).map(&:to_global_id) # => [#<GlobalID:0x00007ffd6a8411a0 @uri=#<URI::GID gid://app/User/1>>, #<GlobalID:0x00007ffd675d32b8 @uri=#<URI::GID gid://app/Student/1>>, #<GlobalID:0x00007ffd6a840b10 @uri=#<URI::GID gid://app/User/2>>, #<GlobalID:0x00007ffd675d2c28 @uri=#<URI::GID gid://app/Student/2>>, #<GlobalID:0x00007ffd6a840480 @uri=#<URI::GID gid://app/User/3>>, #<GlobalID:0x00007ffd675d2598 @uri=#<URI::GID gid://app/Student/3>>] ::. gids # SELECT "users".* FROM "users" WHERE "users"."id" IN ($1, $2, $3) [["id", 1], ["id", 2], ["id", 3]] # SELECT "students".* FROM "students" WHERE "students"."id" IN ($1, $2, $3) [["id", 1], ["id", 2], ["id", 3]] # => [#<User id: 1>, #<Student id: 1>, #<User id: 2>, #<Student id: 2>, #<User id: 3>, #<Student id: 3>]
Note the order is maintained in the returned results.
Custom App Locator
A custom locator can be set for an app by calling
GlobalID::Locator.use and providing an app locator to use for that app.
A custom app locator is useful when different apps collaborate and reference each others' Global IDs.
When finding a Global ID's model, the locator to use is based on the app name provided in the Global ID url.
A custom locator can either be a block or a class.
Using a block:
::. :foo do |gid| FooRemote.const_get(gid.model_name).find(gid.model_id) end
Using a class:
::. :bar, BarLocator.new class BarLocator def locate(gid) @search_client.search name: gid.model_name, id: gid.model_id end end
After defining locators as above, URIs like "gid://foo/Person/1" and "gid://bar/Person/1" will now use the foo block locator and
Other apps will still keep using the default locator.
Contributing to GlobalID
GlobalID is work of many contributors. You're encouraged to submit pull requests, propose features and discuss issues.
GlobalID is released under the MIT License.