Sending Commands to a Fleet
You can send commands to tens, hundreds, or thousands of instances by using the
targets parameter (the Select Targets by Specifying a
Tag option in the Amazon EC2 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 and Linux instances).
Note
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 either Amazon EC2 tags or
instance IDs. The targets parameter uses the following syntax in
the AWS CLI:
Example 1: Targeting Tags
aws ssm send-command --document-namename--targets Key=tag:tag_name,Values=tag_value[...]
Note
Example commands in this section are truncated using [...].
Example 2: Targeting Instance IDs
aws ssm send-command --document-namename--targets Key=instanceids,Values=ID1,ID2,ID3[...]
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:
aws ssm send-command --document-namename--targets Key=tag:Environment,Values=Development[...]
You could target additional instances in other environments by adding to the
Values list. Separate items using commas.
aws ssm send-command - -document-namename--targets Key=tag:Environment,Values=Development,Test,Pre-production[...]
Example: 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.
aws ssm send-command --document-namename--targets Key=tag:Department,Values=FinanceKey=tag:ServerRole,Values=Database[...]
Example: 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.
aws ssm send-command --document-namename--targets Key=tag:Department,Values=Finance,MarketingKey=tag:ServerRole,Values=WebServer,Database[...]
Example: Targeting tagged instances using multipleValues
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:
aws ssm send-command --document-namename--targets Key=tag:Department,Values=Sales,Finance[...]
Note
You can specify a maximum of 5 keys, and 5 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 1: Spaces in Value tag.
aws ssm send-command --document-namename--targets Key=tag:OS,Values="Windows Server 2016 Nano"[...]
Example 2: Spaces in tag key and Value.
aws ssm send-command --document-namename--targets Key="tag:Operating System",Values="Windows Server 2016 Nano"[...]
Example 3: Spaces in one item in a list of Values.
aws ssm send-command --document-namename--targets Key=tag:Department,Values="Sales","Finance","Systems Mgmt"[...]
Using Concurrency Controls
You can control how many servers run the command at the same time by using the
max-concurrency parameter (the Execute on
field in the Amazon EC2 console). 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:
aws ssm send-command --document-namename--max-concurrency10--targets Key=tag:Environment,Values=Development[...]
aws ssm send-command --document-namename--max-concurrency10% --targets Key=tag:Department,Values=Finance,MarketingKey=tag:ServerRole,Values=WebServer,Database[...]
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 Stop after __ errors field in the Amazon EC2 console). 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:
aws ssm send-command --document-namename--max-errors10--targets Key=tag:Database,Values=Development[...]
aws ssm send-command --document-namename--max-errors10% --targets Key=tag:Environment,Values=Development[...]
aws ssm send-command --document-namename--max-concurrency1--max-errors1--targets Key=tag:Environment,Values=Production[...]
