The Backend API is deprecated as of March 13, 2014. Although Google will
continue to support the Backend API in accordance with our
terms of service
, it is strongly recommended that all new applications
use the
Modules API
instead.
For information on converting existing apps using the Backend API to the
Modules API, see
Converting Apps to
Modules
Backends are designed for applications that need faster performance, large amounts of addressable memory, and continuous or long-running background processes. They are exempt from request deadlines and have access to more memory (up to 1GB) and CPU (up to 4.8GHz) than normal instances. Unlike normal instances, backends are billed for uptime rather than CPU usage.
A backend may be configured as either resident or dynamic . Resident backends run continuously, allowing you to rely on the state of their memory over time and perform complex initialization. Dynamic backends come into existence when they receive a request and are turned down when idle. Dynamic backends are ideal for work that is intermittent or driven by user activity. For more information about the differences between resident and dynamic backends, see Types of Backends and also the discussion of Startup and Shutdown .
Backends do not automatically scale in response to request volume. Instead, you must specify
the number of backend instances you require and change this number by performing
an
update
or
configure
command
. The number of instances
is usually set in proportion to the size of a dataset, the degree of processing power required, and your budget for your application.
Backends are
configured
using
backends.yaml
. You can list each backend and specify its properties, such as the number of instances, the memory and CPU class, whether it is
public or private
, and other options. Backends share the handlers defined in
app.yaml
with the main application version. You can place your backends in a separate application root directory if you want to avoid sharing code or handlers, or simply mark the relevant handlers with
login: admin
.
- Properties of backends
- Commands
- Backend states
- Backend uptime
- Addressing backends
- Public and private backends
- Background threads
- Monitoring resource usage
- Periodic logging
- Fetching request logs and application logs
- Administering backends
- Billing, quotas, and limits
Properties of backends
The following table compares backend instances to default App Engine instances.
Feature |
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