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 Elastic Compute Cloud (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 Tag your
Amazon EC2 resources in the Amazon EC2 User Guide for Linux Instances (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 how commands run across hundreds or thousands of instances, Run Command, a capability of AWS Systems Manager, 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 canceled.
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.
For use with the AWS Command Line Interface (AWS CLI ) send-command
command, the targets parameter supports the syntax demonstrated in
the following examples. Sample commands in this section are truncated using
[...].
Example 1: Targeting tags
Example 2: Targeting an AWS resource group by name
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 AWS Identity and Access Management (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 an AWS resource group by resource type
You can specify a maximum of five resource group types 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 4: 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 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, enclose the tag key or the value in quotation marks, as shown 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 the number of servers that run the command simultaneously
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 system
acknowledges the initial invocation before sending the command to two more
instances. The system exponentially sends commands to more instances until
the system meets the value of max-concurrency. 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 might 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.
