Using targets and rate controls to send commands to a fleet
You can send commands to tens, hundreds, or thousands of instances by using the
targets parameter (the Specify instance tags
option in the Run a command page in the console). The
targets parameter accepts a Key,Value combination
based on Amazon EC2 tags that you specified for your instances. When you run the
command,
the system locates and attempts to run the command on all instances that match
the
specified tags. For more information about Amazon EC2 tags, see Tagging your Amazon EC2 resources in the
Amazon EC2 User Guide (content applies to Windows Server and Linux
instances). You can also send commands to instances that belong to an AWS resource
group. For more information about resource groups, see What are Resource Groups? in the AWS Resource Groups User
Guide.
You can also use the targets parameter to target a list of
specific instance IDs, as described in the next section.
To control command execution across hundreds or thousands of instances, Run Command also includes parameters for restricting how many instances can simultaneously process a request and how many errors can be thrown by a command before the command is terminated.
Targeting multiple instances
You can run a command and target instances by specifying tags applied to managed instances, AWS resource group names, or instance IDs.
Sample commands in this section are truncated using [...].
For use with the AWS CLI send-command command, the
targets parameter supports the syntax demonstrated in the
following examples:
Example 1: Targeting tags
Example 2: Targeting an AWS resource group
You can specify a maximum of one resource group name per command. When you
create a resource group, we recommend including
AWS::SSM:ManagedInstance and AWS::EC2::Instance as
resource types in your grouping criteria.
In order to send commands that target a resource group, you must have been granted IAM permissions to list, or view, the resources that belong to that group. For more information, see Set Up Permissions in the AWS Resource Groups User Guide.
Example 3: Targeting instance IDs
If you tagged instances for different environments using a Key
named Environment and Values of
Development, Test, Pre-production and
Production, then you could send a command to all of the
instances in one of these environments by using the
targets parameter with the following syntax:
You could target additional instances in other environments by adding to the
Values list. Separate items using commas.
Variation: Refining your targets using
multiple Key criteria
You can refine the number of targets for your command by including multiple
Key criteria. If you include more than one Key
criteria, the system targets instances that meet all of the
criteria. The following command targets all instances tagged for the Finance
Department and tagged for the database server role.
Variation: Using multiple Key
and Value criteria
Expanding on the previous example, you can target multiple departments and
multiple server roles by including additional items in the Values
criteria.
Variation: Targeting tagged instances using
multiple Values criteria
If you tagged instances for different environments using a Key
named Department and Values of Sales and
Finance, then you could send a command to all of the instances
in these environments by using the targets parameter with the
following syntax:
You can specify a maximum of five keys, and five values for each key.
If either a tag key (the tag name) or a tag value includes spaces, then you must enclose the tag key or the value in quotation marks, as show in the following examples.
Example: Spaces in Value
tag
Example: Spaces in tag key and
Value
Example: Spaces in one item in a list of
Values
Using rate controls
You can control the rate at which commands are sent to instances in a group by using concurrency controls and error controls.
Using concurrency controls
You can control how many servers run the command at the same time by using
the max-concurrency parameter (the
Concurrecy options in the Run a
command page). You can specify either an absolute number of
instances, for example 10, or a percentage of the target set, for example
10%. The queueing system delivers the command to a single instance and waits
until the initial invocation completes before sending the command to two
more instances. The system exponentially sends commands to more instances
until the value of max-concurrency is met. The default for
value max-concurrency is 50. The following examples show you
how to specify values for the max-concurrency parameter.
Using error controls
You can also control the execution of a command to hundreds or thousands
of instances by setting an error limit using the max-errors
parameters (the Error threshold field in the
Run a command page). The parameter specifies how
many errors are allowed before the system stops sending the command to
additional instances. You can specify either an absolute number of errors,
for example 10, or a percentage of the target set,
for example 10%. If you specify
3, for example, the system stops sending the
command when the fourth error is received. If you specify
0, then the system stops sending the command to
additional instances after the first error result is returned. If you send a
command to 50 instances and set max-errors to
10%, then the system stops sending the command to
additional instances when the sixth error is received.
Invocations that are already running a command when
max-errors is reached are allowed to complete, but some of
these invocations may fail as well. If you need to ensure that there won’t
be more than max-errors failed invocations, set
max-concurrency to 1 so the
invocations proceed one at a time. The default for max-errors is 0. The
following examples show you how to specify values for the
max-errors parameter.
