Region ID
The REGION_ID
is an abbreviated code that Google assigns
based on the region you select when you create your app. The code does not
correspond to a country or province, even though some region IDs may appear
similar to commonly used country and province codes. For apps created after
February 2020, REGION_ID
.r
is included in
App Engine URLs. For existing apps created before this date, the
region ID is optional in the URL.
Learn more about region IDs .
You configure your App Engine app's settings in the app.yaml
file.
This file specifies how URL paths correspond to request handlers and
static files.
The app.yaml
file also contains information about your
app's code, such as the runtime and the latest version
identifier.
Each service
in your app has its own app.yaml
file, which acts as a descriptor for its
deployment. You must first create the app.yaml
file for the default
service
before you can create and deploy app.yaml
files for additional services within
your app.
Directory structure
To learn more about structuring multiple services in your app, see Structuring Web Services in App Engine .Example
The following is an example of an app.yaml
file for a PHP 5
application:
runtime : php55 api_version : 1 handlers : # Serve images as static resources. - url : /(.+\.(gif|png|jpg))$ static_files : \1 upload : .+\.(gif|png|jpg)$ application_readable : true # Serve php scripts. - url : /(.+\.php)$ script : \1
The above example will serve files with extension of gif
, png
, or jpg
as
static resources. The files have been configured to be readable by the
application code at runtime.
The example will also serve all PHP scripts. You can restrict the script handler
to root-level scripts by using the url: /([^/]+\.php)
expression. Existing
applications might find it useful to simulate Apache mod_rewrite $_GET['q']
routing
.
A more extensive app.yaml
configuration is provided below:
runtime : php55 api_version : 1 handlers : - url : / script : home.php - url : /index\.html script : home.php - url : /stylesheets static_dir : stylesheets - url : /(.*\.(gif|png|jpg))$ static_files : static/\1 upload : static/.*\.(gif|png|jpg)$ - url : /admin/.* script : admin.php login : admin - url : /.* script : not_found.php
Syntax
The syntax of app.yaml
is the YAML format
.
The YAML format supports comments. A line that begins with a pound ( #
)
character is ignored:
# This is a comment.
URL and file path patterns use POSIX extended regular expression
syntax
, excluding collating
elements and collation classes. Back-references to grouped matches (e.g. \1
)
are supported, as are these Perl extensions: \w \W \s \S \d \D
.
Runtime and app elements
application
The recommended approach is to remove the application
element from your app.yaml
file and instead, use a
command-line flag to specify your application ID:
- To use the
gcloud app deploy
command, you must specify the--project
flag:gcloud app deploy --project [ YOUR_PROJECT_ID ]
For more information about using these commands, see Deploying Your App .
The application ID is the Google Cloud console project ID that you specified when you created the application in the Google Cloud console .
api_version
Required. The version of the API in the given runtime environment that is used by your app.
This field is deprecated in newer App Engine runtimes .
When Google announces support for a new version of a
runtime environment's API, your deployed app will continue to use the
one for which it was written. To upgrade your app to a new version of
the API, you change this value and then redeploy your app to App
Engine. When you specify the 1
value, the latest supported runtime environment is used each time you
deploy that app (currently
).
At this time, App Engine has one version of the php
runtime environment: 1
default_expiration
Optional. Sets a global default cache period for all static
file handlers for an application. You can also configure a cache duration for specific static file
handlers
. The value is a string of numbers and units, separated by
spaces, where units can be d for days, h for hours, m for minutes, and
s for seconds. For example, "4d 5h"
sets cache expiration
to 4 days and 5 hours after the file is first requested. If omitted,
the production server sets the expiration to 10 minutes.
runtime : php55 api_version : 1 default_expiration : "4d 5h" handlers : # ...
For more information, see Cache expiration .
Optional.
You can define environment variables in your app.yaml
file to make them available to your app. Ensure that the key in Environment variable(s) matches the expression '[a-zA-Z_][a-zA-Z0-9_]*' (start with alphabet or "_" followed by any alphanumeric or "_").
Environment variables that are prefixed with GAE
are reserved for system use and not allowed in the app.yaml
file.
env_variables : MY_VAR : "my value"
MY_VAR
and my value
are the name and
value of the environment variable that you want to define and each
environment variable entry is indented two spaces under the env_variables
element. Environment variables not assigned
a value default to "None"
. You can then retrieve the value of these variables by using either getenv()
or $_SERVER
, but not $_ENV
. The following
commands echo the value of the environment variable MY_VAR
:
echo getenv('MY_VAR');
echo $_SERVER['MY_VAR'];
error_handlers
Optional. Used to configure custom error pages that are returned for different error types.
This element can contain the following elements:
-
error_code
- Optional. The
error_code
can be one of the following:-
over_quota
- Indicates the app has exceeded a resource quota
-
timeout
- Served if a deadline is reached before there is a response from your app.
The error_code is optional; if it's not specified, the given file is the default error response for your app.
-
-
file
- Each file entry indicates a static file that should be served in
place of the generic error response. If you specify a
file
element without a correspondingerror_code
element, the static file will be the default error page for your app. The custom error data must be less than 10 kilobytes.
error_handlers : - file : default_error.html - error_code : over_quota file : over_quota.html
handlers
Required. A list of URL patterns and descriptions of how they should be handled. App Engine can handle URLs by executing application code, or by serving static files uploaded with the code, such as images, CSS, or JavaScript.
inbound_services
Optional.
Applications must enable those services before it can receive inbound
requests. You can enable the service for a PHP 5 app
by including an inbound_services
section in the app.yaml
file.
The following inbound services are available:
-
mail
- Allows your application to receive mail .
-
warmup
- Enables warmup requests. See Configuring Warmup Requests .
inbound_services : - mail - warmup
instance_class
Optional. The instance class for this service.
The following values are available depending on your service's scaling :
- Automatic scaling
-
F1
,F2
,F4
,F4_1G
- Default:
F1
Optionally use the
automatic_scaling
element to change default settings for automatic scaling, such as minimum and maximum number of instances, latency, and concurrent connections.Note:If
instance_class
is set toF2
or higher, you can optimize your instances by settingmax_concurrent_requests
to a value higher than the default value of 10. To determine the optimal value, gradually increase it and monitor the performance of your application. - Basic and manual scaling
-
B1
,B2
,B4
,B4_1G
,B8
- Default:
B2
Basic and manual instance classes require you to specify either the
basic_scaling
element or themanual_scaling
element.
module
Note:Modules are now named Services.
To manage your app with the gcloud CLI, use the service element instead.
runtime
Required. The name of the runtime environment that is used by your app. For example, to specify PHP 5, use:
runtime : php55
service
Services were formerly known as Modules.
Supported only by the gcloud CLI or gcloud CLI-based
plugins, for example: gcloud app deploy
.
Required if creating a service
.
Optional for the default
service. Each service and each version must have a name. A name can
contain numbers, letters, and hyphens. The combined length of VERSION-dot-SERVICE-dot-PROJECT_ID
, where VERSION
is the name of
your version, SERVICE
is the name of your service, and PROJECT_ID
is your project ID, cannot be longer than 63 characters and cannot
start or end with a hyphen. Choose a unique name for each service
and each version. Don't reuse names between services and versions.
service : service-name
Note:The gcloud app
deploy
command is backwards
compatible and supports existing app.yaml
files that
include services declared as modules, for example:
module : service-name
service_account
Optional. The service_account
element lets you specify a user-managed service account
as the identity for the version. The specified service account is used when accessing other Google Cloud services and executing tasks.
service_account : [ SERVICE_ACCOUNT_NAME ] @ [ PROJECT_ID ] . iam.gserviceaccount.com
skip_files
Optional.
The skip_files
element specifies which files in the
application directory are not to be uploaded to App Engine.
The value is either a regular expression, or a list of regular
expressions. Any filename that matches any of the regular expressions
is omitted from the list of files to upload when the application is
uploaded. Filenames are relative to the project directory.
The skip_files
has the following default:
skip_files : - ^(.*/)?#.*#$ - ^(.*/)?.*~$ - ^(.*/)?.*\.py[co]$ - ^(.*/)?.*/RCS/.*$ - ^(.*/)?\..*$
The default pattern excludes Emacs backup files with names of the form #...#
and ...~
, .pyc
and .pyo
files, files in an RCS
revision control
directory, and Unix hidden files with names beginning with a dot
( .
).
To extend the above regular expression list, copy and paste the above
list into your app.yaml
and add your own regular
expressions. For example, to skip files whose names end in .bak
in addition to the default patterns, add an entry
like this for skip_files
:
skip_files : - ^(.*/)?#.*#$ - ^(.*/)?.*~$ - ^(.*/)?.*\.py[co]$ - ^(.*/)?.*/RCS/.*$ - ^(.*/)?\..*$ - ^(.*/)?.*\.bak$
To skip a full directory, add the directory name to
the list. For example, to skip a directory named logs
,
add the following line to the previously described ones:
skip_files : - logs/
version
The recommended approach is to remove the version
element from your app.yaml
file and instead, use a
command-line flag to specify your version ID:
- To use the
gcloud app deploy
command, you specify the-v
flag:gcloud app deploy -v [YOUR_VERSION_ID]
For more information about using this command, see Deploying Your App .
An identifier for the version of your application code that you deploy to App Engine.
The version ID can contain lowercase letters, digits, and hyphens. It
cannot begin with the prefix ah-
and the names default
and latest
are reserved and cannot
be used.
Note: Version names should begin with a letter, to distinguish them
from numeric instances which are always specified by a number. This
avoids the ambiguity with URLs like 123-dot-my-service.uc.r.appspot.com
, which can be interpreted
two ways: If version "123" exists, the target will be version "123"
of the given service. If that version does not exist, the target will
be instance number 123 of the default version of the service.
Each version of an application retains its own copy of app.yaml
. When an application is uploaded, the version
mentioned in the app.yaml
file being uploaded is the
version that gets created or replaced by the upload. An administrator
can change which version of the application is serving traffic by
using the Google Cloud console
, and can also test
other versions before configuring them to receive traffic
.
Handlers element
The handlers
element is a required element in the app.yaml
configuration file. The element provides a list of URL
patterns and descriptions of how they should be handled. App Engine can
handle URLs by executing application code, or by serving static files uploaded
with the code, such as images, CSS, or JavaScript.
Patterns are evaluated in the order they appear in the app.yaml
file, from
top to bottom. The first mapping whose pattern matches the URL is the one used
to handle the request.
The following table lists the subelements of the handlers
element that control
the behavior for scripts, static files,
static directories, and other settings.
application_readable
This field is deprecated in newer App Engine runtimes .
d
for days, h
for hours, m
for
minutes, and s
for seconds. For example, "4d 5h"
sets cache expiration to 4 days and 5 hours after
the file is first requested. If omitted, the application's default_expiration
is used. See Cache
expiration
for more details.http_headers
Optional. You can set HTTP
headers
for responses of your static file or directory
handlers. If you need to set HTTP headers
in your script
handlers, you should instead do that in your app's
code. For information about which response headers influence caching,
see Caching
static content
.
handlers : - url : /images static_dir : static/images http_headers : X-Foo-Header : foo X-Bar-Header : bar value vary : Accept-Encoding # ...
CORS Support
One important use of this feature is to support cross-origin resource sharing (CORS), such as accessing files hosted by another App Engine app.
For example, you could have a game app mygame.uc.r.appspot.com
that accesses assets hosted by myassets.uc.r.appspot.com
.
However, if mygame
attempts to make a JavaScript XMLHttpRequest
to myassets
, it will not
succeed unless the handler for myassets
returns an Access-Control-Allow-Origin:
response header containing
the value http://mygame.uc.r.appspot.com
.
Here is how you would make your static file handler return that required response header value:
handlers : - url : /images static_dir : static/images http_headers : Access-Control-Allow-Origin : https://mygame.uc.r.appspot.com # ...
Note: if you wanted to allow everyone to access your assets, you could
use the wildcard '*'
, instead of https://mygame.uc.r.appspot.com
.
mime_type
Optional. If specified, all files served by this handler will be served using the specified MIME type. If not specified, the MIME type for a file will be derived from the file's filename extension. If the same file is uploaded with multiple extensions, the resulting extension can depend on the order in which the uploads occurred.
For more information about the possible MIME media types, see the IANA MIME Media Types website
redirect_http_response_code
Optional. redirect_http_response_code
is used with the secure
setting to set the HTTP response code returned
when performing a redirect required by how the secure
setting is configured. redirect_http_response_code
element has the following
possible values:
-
301
- Moved Permanently response code.
-
302
- Found response code.
-
303
- See Other response code.
-
307
- Temporary Redirect response code.
handlers : - url : /youraccount/.* script : accounts.php secure : always redirect_http_response_code : 301
When a user's request is redirected, the HTTP status code will be set
to the value of the redirect_http_response_code
parameter. If the parameter is not present, 302 will be returned.
script
Optional. Specifies the path to the script from the application root directory:
... handlers : - url : /profile/(.*)/(.*) script : /employee/\2/\1.php # specify a script
In newer App Engine runtimes, the the behavior of this field has changed .
secure
secure
setting,
including script handlers and
static file handlers. The secure
element has the following
possible values: -
optional
- Both HTTP and HTTPS requests with URLs that match the handler
succeed without redirects. The application can examine the request
to determine which protocol was used, and respond accordingly. This
is the default when
secure
is not provided for a handler. -
never
- Requests for a URL that match this handler that use HTTPS are automatically redirected to the HTTP equivalent URL. When a user's HTTPS request is redirected to be an HTTP request, the query parameters are removed from the request. This prevents a user from accidentally submitting query data over a non-secure connection that was intended for a secure connection.
-
always
- Requests for a URL that match this handler that do not use HTTPS are automatically redirected to the HTTPS URL with the same path. Query parameters are preserved for the redirect.
handlers : - url : /youraccount/.* script : accounts.php secure : always
The development web server does not support HTTPS connections. It
ignores the secure
parameter, so paths intended for use
with HTTPS can be tested using regular HTTP connections to the
development web server.
To target a specific version of your app
using the REGION_ID
.r.appspot.com
domain, you replace the periods that would usually separate the
subdomain components of the URL with the string " -dot-
",
for example:
https:// VERSION_ID
-dot-default-dot- PROJECT_ID
. REGION_ID
.r.appspot.com
To use custom domains with HTTPS, you must first activate and configure SSL certificates for that domain .
Google Accounts sign-in and sign-out are always performed using a secure connection, unrelated to how the application's URLs are configured.
Optional. The path to the directory containing the static files, from
the application root directory. Everything after the end of the
matched url
pattern is appended to static_dir
to form the full path to the requested file.
Each file in the static directory is served using the MIME type that
corresponds with its filename extension unless overridden by the
directory's mime_type
setting. All of the files in the
given directory are uploaded as static files, and
none of them can be run as scripts.
All files in this directory are uploaded with your app as static
files. App Engine stores and serves static files separately
from your app's files. Static files are not available in the app's
file system by default. This can be changed by setting the application_readable
option to true.
handlers : # All URLs beginning with /stylesheets are treated as paths to # static files in the stylesheets/ directory. - url : /stylesheets static_dir : stylesheets # ...
static_files
Optional. A static file pattern handler associates a URL pattern with
paths to static files uploaded with the application. The URL pattern
regular expression can define regular expression groupings to be used
in the construction of the file path. You can use this instead of static_dir
to map to specific files in a directory
structure without mapping the entire directory.
handlers : # All URLs ending in .gif .png or .jpg are treated as paths to # static files in the static/ directory. The URL pattern is a # regular expression, with a grouping that is inserted into the # path to the file. - url : /(.*\.(gif|png|jpg))$ static_files : static/\1 upload : static/.*\.(gif|png|jpg)$ # ...
App Engine stores and serves static files separately
from application files. Static files are not available in the
application's file system by default. This can be changed by setting
the application_readable
option to true.
Static files cannot be the same as application code files. If a static file path matches a path to a script used in a dynamic handler, the script will not be available to the dynamic handler.
upload
Optional. A regular expression that matches the file paths for all
files that will be referenced by this handler. This is necessary
because the handler cannot determine which files in your application
directory correspond with the given url
and static_files
patterns. Static files are uploaded and
handled separately from application files. The example
above might use the following upload
pattern: archives/(.*)/items/(.*)
url
Required element under handlers
. The URL pattern, as a
regular expression. The expression can contain groupings that can be
referred to in the file path to the script with regular expression
back-references. For example, /profile/(.*)/(.*)
would match the URL /profile/edit/manager
and use edit
and manager
as the first and second
groupings.
The URL pattern has some differences in behavior when used with the following elements:
-
static_dir
- Uses a URL prefix. The regular express pattern should not contain
groupings when used with the
static_dir
element. All URLs that begin with this prefix are handled by this handler, using the portion of the URL after the prefix as part of the file path. -
static_files
- A static file pattern handler associates a URL pattern with paths to
static files uploaded with the application. The URL pattern regular
expression can define regular expression groupings to be used in the
construction of the file path. You can use this instead of
static_dir
to map to specific files in a directory structure without mapping the entire directory.
Scaling elements
The elements in following table configure how your application scales. To learn more about how App Engine apps scale, see Scaling types .
automatic_scaling
Optional. Applicable only for applications that use an instance class of F1 or higher.
Specify this element to change default settings for automatic scaling, such as setting minimum and maximum levels for number of instances, latency, and concurrent connections for a service.
This element can contain the following elements:
-
max_instances
- Optional. Specify a value between 0 and 2147483647, where zero
disables the setting.
This parameter specifies the maximum number of instances for App Engine to create for this module version. This is useful to limit the costs of a module.
-
min_instances
-
Optional. The minimum number of instances for App Engine to
create for this module version. These instances serve traffic when
requests arrive, and continue to serve traffic even when
additional instances are started up as required to handle traffic.
Specify a value from 0 to 1000. You can set the parameter to the value 0 to allow scaling to 0 instances to lower costs when no requests are being served. Note that you are charged for the number of instances specified whether they are receiving traffic or not.
-
max_idle_instances
-
Optional. The maximum number of idle instances that App Engine should maintain for this version. Specify a value from 1 to 1000. If not specified, the default value is
automatic
, which means App Engine will manage the number of idle instances. Keep the following in mind:- A high maximum reduces the number of idle instances more gradually when load levels return to normal after a spike. This helps your application maintain steady performance through fluctuations in request load, but also raises the number of idle instances (and consequent running costs) during such periods of heavy load.
- A low maximum keeps running costs lower, but can degrade performance in the face of volatile load levels.
Note:When settling back to normal levels after a load spike, the number of idle instances can temporarily exceed your specified maximum. However, you will not be charged for more instances than the maximum number you've specified.
-
min_idle_instances
-
Optional: The number of additional instances to be kept running and ready to serve traffic for this version.
App Engine calculates the number of instances necessary to serve your current application traffic based on scaling settings such as
target_cpu_utilization
andtarget_throughput_utilization
. Settingmin_idle_instances
specifies the number of instances to run in addition to this calculated number. For example, if App Engine calculates that 5 instances are necessary to serve traffic, andmin_idle_instances
is set to 2, App Engine will run 7 instances (5, calculated based on traffic, plus 2 additional permin_idle_instances
).Note that you are charged for the number of instances specified whether they are receiving traffic or not. Keep the following in mind:
- A low minimum helps keep your running costs down during idle periods, but means that fewer instances might be immediately available to respond to a sudden load spike.
-
A high minimum allows you to prime the application for rapid spikes in request load. App Engine keeps the minimum number of instances running to serve incoming requests. You are charged for the number of instances specified, whether or not they are handling requests.
If you set a minimum number of idle instances, pending latency will have less effect on your application's performance.
-
target_cpu_utilization
- Optional. Specify a value between 0.5 and 0.95. The default is
0.6
.This parameter specifies the CPU usage threshold at which new instances will be started to handle traffic, enabling you to balance between performance and cost, with lower values increasing performance and increasing cost, and higher values decreasing performance but also decreasing cost. For example, a value of 0.7 means that new instances will be started after CPU usage reaches 70 percent.
-
target_throughput_utilization
- Optional. Specify a value from 0.5 to 0.95. The default is
0.6
.Used with
max_concurrent_requests
to specify when a new instance is started due to concurrent requests. When the number of concurrent requests reaches a value equal tomax_concurrent_requests
timestarget_throughput_utilization
, the scheduler tries to start a new instance. -
max_concurrent_requests
-
Optional. The number of concurrent requests an automatic scaling instance can accept before the scheduler spawns a new instance (Default: 5, Maximum: 1000).
Used with
target_throughput_utilization
to specify when a new instance is started due to concurrent requests. When the number of concurrent requests reaches a value equal tomax_concurrent_requests
timestarget_throughput_utilization
, the scheduler tries to start a new instance.We recommend you do not set
max_concurrent_requests
to less than 10 unless you need single threading. A value of less than 10 is likely to result in more instances being created than you need for a threadsafe app, and that may lead to unnecessary cost.If this setting is too high, you might experience increased API latency. Note that the scheduler might spawn a new instance before the actual maximum number of requests is reached.
-
max_pending_latency
-
The maximum amount of time that App Engine should allow a request to wait in the pending queue before starting additional instances to handle requests so that pending latency is reduced. When this threshold is reached, it is a signal to scale up, and results in an increase in the number of instances. If not specified, the default value is
automatic
. This means requests can remain in the pending queue for up to 10s, the maximum pending request time limit , before new instance starts are triggered.A low maximum means App Engine will start new instances sooner for pending requests, improving performance but raising running costs.
A high maximum means users might wait longer for their requests to be served (if there are pending requests and no idle instances to serve them), but your application will cost less to run.
-
min_pending_latency
-
An optional element you can set to specify the minimum amount of time that App Engine should allow a request to wait in the pending queue before starting a new instance to handle it. Specifying a value can lower running costs but increase the time users must wait for their requests to be served.
For free apps, the default value is
500ms
. For paid apps, the default value is0
.This element works together with the
max_pending_latency
element to determine when App Engine creates new instances. If pending requests are in the queue:- Less than the
min_pending_latency
you specify, App Engine will not create new instances. - More than
max_pending_latency
, App Engine will try to create a new instance. - Between the time specified by
min_pending_latency
andmax_pending_latency
, App Engine will try to reuse an existing instance. If no instances are able to process the request beforemax_pending_latency
, App Engine will create a new instance.
- Less than the
automatic_scaling : target_cpu_utilization : 0.65 min_instances : 5 max_instances : 100 min_pending_latency : 30ms max_pending_latency : automatic max_concurrent_requests : 50
basic_scaling
Applications that use an instance
class
of B1 or higher must specify either this element or manual_scaling
.
This element enables basic scaling of instance classes B1 and higher, can contain the following elements:
-
max_instances
- Required. The maximum number of instances for App Engine to create for this service version. This is useful to limit the costs of a service.
-
idle_timeout
- Optional. The instance will be shut down this amount of time after
receiving its last request. The default is 5 minutes
(
5m
).
basic_scaling : max_instances : 11 idle_timeout : 10m
manual_scaling
Applications that use an instance
class
of B1 or higher must specify either this element or basic_scaling
.
This element enables manual scaling of instance classes B1 and higher, and can contain the following element:
-
instances
- The number of instances to assign to the service at the start.
manual_scaling : instances : 5