State requisites and declarations#

ID vs. name#

Technically speaking, the component of the high data that determines the name argument that is passed to the state function is not called name in the high data, it is called ID.

The ID is copied into the name argument unless the name argument is explicitly declared by specifying a name value (or names values). The following example shows the declaration of both an ID and name:

/srv/salt/dns/init.sls#
push_dns_conf:                  # The ID which identifies the state
  file.managed:
    - name: /etc/named.conf     # The name passed to file.managed function
    - source: salt://dns/files/named.conf

Taking into account that the ID could be copied into the name argument, the example could also be written to only use ID:

/srv/salt/dns/init.sls#
/etc/named.conf:
  file.managed:
    - source: salt://dns/files/named.conf

ID must be unique across the entire state tree. If the same ID declaration is used twice, only the first one matched will be used. All subsequent ID declarations with the same name will be ignored.

Note

Salt Best Practices recommend always using a unique, descriptive value for the state ID

One ID to many names#

The names argument allows for one ID to become many names.

/srv/salt/py3.sls#
python-pkgs:
  pkg.installed:
    - names:
      - python
      - pypy
      - python-mako

Another example using directories:

/srv/salt/deploy_code.sls#
deploy_dirs:
  file.directory:
    - makedirs: True
    - names:
      - /opt/code/docs
      - /opt/code/config
      - /opt/code/images

State execution order#

The following sections of this chapter outline declarations that will set the order of execution as high data is processed and compiled into low data.

Tools exist in Salt to modify state ordering. These tools consist of requisite declarations and order options. When Salt States are executed, they are first ordered in a list (called low data), and then the list is iterated over.

  • This differs from other configuration management tools which execute everything within an event loop or execute raw code.
  • The approach of setting up a finite list of executions means that the code can be defined in a truly declarative way, and still execute in a completely predictable manner.

Implicit ordering#

States will always execute in the order that they are defined in your SLS files.

dns_install:
  pkg.installed:
    - name: bind

dns_service:
  service.running:
    - name: named
    - enable: True

dns_conf:
  file.managed:
    - name: /etc/named.conf
    - source: salt://dns/files/named.conf

What would be the outcome of executing this state based on implicit ordering?

The order declaration#

The order option is used by adding an order number to a state:

install_app:
  pkg.installed:
    - name: app

prestage_application_data:
  file.recurse:
    - name: /app/production
    - source: salt://app/source
    - order: 1

By setting the order option to 1 this ensures that the /app/production directory will be populated before any other states that are executed.

Any state declared without an order option will be executed after all states with the order option are executed in the order they are present in the State File. This construct can only handle ordering states from the beginning. Sometimes you may want to send a state to the end of the execution - to do this, set order: last

update_status:
  module.function:
   - name: http.query
   - args:
     - 'https://example.org/update-status'
   - kwargs:
     - method: POST
   - params: 'keyA=valA&keyB=valB'
   - order: last

install_app:
  pkg.installed:
    - name: app

prestage_application_data:
  file.recurse:
    - name: /app/production
    - source: salt://app/source
    - order: 1

Before using the order option, remember that the majority of state ordering should be done using other Requisite Declarations. A requisite declaration will override an order option so a state with an order option defined should not require or be required by other states.

Requisite declarations#

Often when setting up states any single action will require or depend on another action. Salt allows you to build relationships between states with requisite declarations.

A requisite declaration ensures that the named state is evaluated before the state requiring it. Failures can also be accounted for when completing the states defined in the SLS file.

Referencing state declarations#

Requisites can match either the ID declaration or the name parameter. A requisite references another part of a state file (SLS) in the form of: state_module: [id | name]

For example, consider the previous example:

dns_install:
  pkg.installed:
    - name: bind

dns_service:
  service.running:
    - name: named
    - enable: True

dns_conf:
  file.managed:
    - name: /etc/named.conf
    - source: salt://dns/files/named.conf

A reference to the package installation would be: pkg: dns_install (by ID) or pkg: bind (by name)

A reference to the service running would be: service: dns_service (by ID) or service: named (by name)

It is recommended as a Salt best practice to always refer to the state ID when adding requisites.

State failure behavior#

The default behavior when a state fails is to continue to execute the remainder of the defined states. This is called a soft fail, meaning that execution of the state continues after a failure.

The situation may exist where you would want all state execution to stop if a single state execution fails. This can be done in states with requisite definitions. The capability to do this is called failing hard. A hard failure can be implemented in two ways:

  • Defined in a state declaration
  • Defined globally in the minion configuration

The failhard option defined within a state declaration:

dns_install:
  pkg.installed:
    - name: bind
    - failhard: True

If the state fails to install the package, then no other states will be executed. Globally, this can be set in the minion configuration:

/etc/salt/minion.d/failhard.conf#
failhard: True

Standard requisites#

A requisite statement ensures that the named state is evaluated before the state requiring it. There are several direct requisite statements that can be used in Salt that inherently implement failing hard behavior:

  • require
  • watch
  • onfail
  • onchanges
  • use
  • prereq

The two most common types of requisites in Salt are require and watch

The require requisite#

The requisite system works by finding the states that are required, and executing them before the state that requires them. Then the required states can be evaluated to see if they have executed correctly.

The foundation of the requisite system is the require requisite declaration.

  • The require requisite ensures that the required states are executed before the state declaring the require
  • The state declaring the require will only be executed if the required state returns True
dns_install:
  pkg.installed:
    - name: bind

dns_service:
  service.running:
    - name: named
    - enable: True

dns_conf:
  file.managed:
    - name: /etc/named.conf
    - source: salt://dns/files/named.conf
    - require:
      - pkg: dns_install

In the previous example, we use a require to make sure the bind package is successfully installed before attempting to copy the configuration file to the minion. We’ll deal with the service when we describe the watch requisite.

Circular references#

Salt will detect circular references and not allow them. If a circular reference is detected Salt will return an error such as:

Data failed to compile:
----------
A recursive requisite was found, SLS "named" ID "dns_install" ID "dns_conf"

In this example, dns_install required dns_conf and dns_conf required dns_install, thus creating a circular reference. Salt must be able to evaluate which state to test first to decide order and if execution is needed based on the requirements.

The watch requisite#

The watch requisite is more advanced than the require requisite. The watch requisite executes the same logic as require:

  • If a state is being watched, it does not need to also be required. This logic is built into watch to evaluate the watched states as True
  • The watch requisite also checks if the watched states have returned any changes

If the watched states returned changes, and the watched states execute successfully, then the state declaring the watch will execute a function that reacts to the changes in the watched states:

/srv/salt/dns/init.sls#
dns_install:
  pkg.installed:
    - name: bind

dns_service:
  service.running:
    - name: named
    - enable: True
    - watch:
      - file: dns_conf

dns_conf:
  file.managed:
    - name: /etc/named.conf
    - source: salt://dns/files/named.conf
    - require:
      - pkg: dns_install

Running the previous state file execution will produce the following output if the /etc/named.conf is updated:

rebel_01:
----------
          ID: /etc/named.conf
    Function: file.managed
      Result: True
     Comment: File /etc/named.conf updated
     Started: 22:40:34.126006
    Duration: 34.006 ms
     Changes:
               ----------
              diff:
                   ---
                  +++
                  @@ -10,38 +10,37 @@
                   -     listen-on port 53 { 127.0.0.1; };
                  +     listen-on port 53 { 0.0.0.0; };
                  +zone "my.domain" IN {
                  +       type master;
                  +       file "master/master.my.domain";
                  +       // enable slaves only
                  +       allow-transfer {192.0.2.1;192.0.2.2;);
                  +};
----------
          ID: start_dns
    Function: service.running
        Name: named
      Result: True
     Comment: Started Service named
     Started: 23:10:36.318223
    Duration: 400.123 ms
     Changes:
               ----------
              named:
                  True
Summary for rebel_01
------------
Succeeded: 1 (changed=1)
Failed:    0
------------
Total states run:     1
Total run time:  34.006 ms

In this example the named service will be started (or restarted) since the file /etc/named.conf is changed (new or updated). The watch requisite is based on the mod_watch function. Salt Python state modules can include a function called mod_watch which is then called if the watch call is invoked.

  • In the case of the service state the underlying service is restarted.
  • In the case of the cmd state the command is executed.

The watch requisite only works if the state that is watching has a mod_watch function written. If the watching state where the watch is set does not have a mod_watch function (like pkg), then the listed states will behave only as if they were under a require statement.

Multiple requisites#

The requisite declaration is passed as a list, allowing for the easy addition of multiple requisites. Multiple requisite types can also be separately declared:

dns_install:
  pkg.installed:
    - name: bind

create_user:
  user.present:
    - name: bind
    - require:
    - pkg: dns_install

create_group:
 group.present:
   - name: bind
   - require:
   - pkg: dns_install

dns_service:
  service.running:
    - name: named
    - enable: True
    - require:
      - pkg: dns_install     # Technically not needed since "watch" is on dns_conf
      - user: create_user    # dns_conf has a "require" defined for dns_install
      - group: create_group  # Cascading require as "watch" is also a require
    - watch:
      - file: dns_conf

dns_conf:
  file.managed:
    - name: /etc/named.conf
    - source: salt://dns/files/named.conf
    - require:
      - pkg: dns_install

It is important to understand the flow of the state file execution.

The onfail declaration#

The onfail requisite allows for reactions to happen strictly as a response to the failure of another state.

This can be used in a number of ways, such as executing a second attempt to set up a service or begin to execute a separate thread of states because of a failure. The onfail requisite is applied in the same way as require as watch:

httpd_service:
  service.running:
    - name: httpd

report_failure:
  module.run:
    - name: slack_notify.call_hook
    - kwargs:
        message: Apache failed to start
    - onfail:
      - service: httpd_service

The onchanges declaration#

The onchanges requisite makes a state only apply if the required states generate changes, and if the watched state’s result is True.

Unlike watch, the onchange requisite does not execute if there are no detected changes, where a watch does. For example, in a watch:

dns_service:
  service.running:
    - name: named
    - enable: True
    - watch:
      - file: dns_conf

dns_conf:
  file.managed:
    - name: /etc/named.conf
    - source: salt://dns/files/named.conf

In the case of using a watch, even if there are no changes in the watch file, the Salt state system will execute this function to put the service in a running state, or at least check to see if it is running.

When using the onchanges the behavior changes:

dns_service:
  service.running:
    - name: named
    - enable: True
    - onchanges:
      - file: dns_conf

dns_conf:
  file.managed:
    - name: /etc/named.conf
    - source: salt://dns/files/named.conf

If an onchanges is declared instead of a watch, and if there are no changes, the service is not set to run if currently stopped. The logic is that the service will not be started if it is currently not running and there are no changes to the file.

This can be a useful way to execute a post hook after changing aspects of a system. An example of using an onchanges is if you only want salt-cloud updated if there is a new bootstrap script available:

deploy_bootstrap:
  file.managed:
    - name: /etc/salt/cloud.deploy.d/bootstrap-salt.sh
    - source: salt://conf/boostrap-salt.sh

install_salt_cloud:
  pkg.latest:
    - name: salt-cloud
    - onchanges:
      - file: deploy_bootstrap

The use requisite#

The use requisite declarations allow for the transparent duplication of data between states.

When a state “uses” another state, it copies the other state’s arguments as defaults. A simple example of the use declaration:

manage_eth0:
  network.managed:
    - name: eth0
    - enabled: True
    - type: eth
    - proto: static
    - ipaddr: 192.0.2.7
    - netmask: 255.255.255.0
    - gateway: 192.0.2.1
    - enable_ipv6: true
    - ipv6proto: static
    - ipv6ipaddrs:
      - 2001:db8:dead:beef::3/64
      - 2001:db8:dead:beef::7/64
    - ipv6gateway: 2001:db8:dead:beef::1
    - ipv6netmask: 64
    - dns:
      - 198.51.100.8
      - 203.0.113.4

manage_eth1:
  network.managed:
    - name: eth1
    - ipaddr: 203.0.113.120
    - gateway: 203.0.113.1
    - ipv6ipaddr: 2001:db8:dead:c0::3
    - ipv6gateway: 2001:db8:dead:c0::1
    - use:
      - network: manage_eth0

The use statement was developed primarily for the networking states but can be used on any states in Salt. This makes sense for the network state because it can define a long list of options that need to be applied to multiple network interfaces.

The prereq requisite#

The prereq requisite allows for actions to be taken based on the expected results of a state that has not yet been executed.

The state containing the prereq requisite is defined as the pre-requiring state. When a prereq requisite is evaluated, the pre-required state reports if it expects to have any changes. It does this by running the pre-required single state as a test-run by enabling test=True.

The best way to define how prereq operates is displayed in the following practical example:

gracefulRestart:
  module.run:
    - name: service.restart
    - m_names:
      - httpd
    - prereq:
      - file: site-code

siteCode:
  file.recurse:
    - name: /opt/site_code
    - source: salt://site/code

When the apache service should be shut down because underlying code is going to change, the service should be off-line while the update occurs. In this example, gracefulRestart is the pre-requiring state and siteCode is the pre-required state.

Including other SLS files#

The include declaration is a top level declaration that defines a list of SLS files to bring into the current SLS file.

An include can be used to bring in data from another SLS file for many reasons.

  • If you want to combine many states into one.
  • If the SLS file needs to require or watch components found in another SLS file.
  • If components of another SLS file need to be extended, or if a shortcut SLS file needs to be made.
  • If another SLS file needs to be read-only in another environment, but allowed to be included, used, or extended

This example includes all core states for the infrastructure:

/srv/salt/core.sls#
include:
  - ssh
  - sudo
  - edit.vim
  - edit.emacs
  - ntp

Included state files are relative to the file_roots.

Including for requisites#

Require kvm before starting libvirt. Here is the basic kvm state file:

/srv/salt/kvm/init.sls#
install_qemu:
  pkg.installed:
    - name: qemu-kvm

load_kvm:
  kmod.present:
    - name: kvm_intel

Here is the libvirt state file including the kvm state requiring it:

/srv/salt/libvirt/init.sls#
include:
  - kvm

install_libvirt:
  - pkg.installed:
    - name: libvirt

start_libvirt:
  - service.running:
    - name: libvirt
    - require:
      - kmod: load_kvm
      - pkg: install_qemu

Extending external SLS data#

Sometimes a state defined in one SLS file will need to be modified from a separate SLS file.

A good example of this is when an argument needs to be overwritten or when a service needs to watch an additional state.

The extend declaration#

The extend declaration is a top level declaration like include and encapsulates ID declaration data included from other SLS files.

Using the following Salt State file as a starting point:

/srv/salt/ssh/init.sls#
install_ssh:
  pkg.latest:
    - name: openssh

ssh_server:
  service.running:
    - name: sshd
    - enable: True
    - watch:
      - pkg: install_ssh
    - file: sshd_conf

sshd_conf:
  file.managed:
    - name: /etc/ssh/sshd_config
    - source: salt://ssh/files/sshd_config

We can use the ssh state file as a base, and then build upon it to suit specific needs:

/srv/salt/ssh/dmz.sls#
include:
  - ssh

extend:
  sshd_conf:
    file:
      - name: /etc/ssh/sshd_config
      - source: salt://ssh/files/dmz_sshd_config

  ssh_server:
    service:
      - watch:
        - file: add_banner

add_banner:
  file.managed:
    - name: /etc/ssh/banner
    - source: salt:/ssh/files/banner

A few critical things happened here. First off, the SLS files that are going to be extended are included, then the extend declaration is defined. Under the extend declaration, two ids are extended: the ssh_conf file state is overwritten with a new name and source, then ssh_server is extended to watch the banner file in addition to anything it is already watching.

Extend rules and regulation#

The extend declaration is a top-level declaration. This means that extend can only be called once in an SLS file. If it is declared more than once, then only the second extend block will be used.

The following example is wrong:

include:
  - http
  - ssh

extend:
  apache:
    file:
      - name: /etc/httpd/conf/httpd.conf
      - source: salt://http/httpd2.conf

# Second overwrites first
extend:
  ssh-server:
    service:
      - watch:
        - file: /etc/ssh/banner

Note

If the second extend is removed or commented, then the state file will work as intended.

Things to remember when extending states:

  • Always include the SLS files being extended with an include declaration
  • Requisites watch and require are appended to, everything else is overwritten
  • extend is a top level declaration. Like the state ID, it cannot be declared more than once in a single SLS
  • Many state IDs can be extended using the extend declaration

The requisite _in declarations#

Each requisite also has a corresponding _in counterpart:

  • require_in
  • watch_in
  • prereq_in
  • use_in
  • onchanges_in
  • onfail_in

The corresponding _in requisites basically allow the logic of rendering to do the reverse of the declaration.

An example using require_in and watch_in could look like this:

install_ssh:
  pkg.latest:
    - name: openssh
    - watch_in:
      - service: ssh_server
    - require_in:
      - file: sshd_conf

ssh_server:
  service.running:
    - name: sshd
    - enable: True

sshd_conf:
  file.managed:
    - name: /etc/ssh/sshd_config
    - source: salt://ssh/files/sshd_config
    - watch_in:
      - service: ssh_server

An alternate way to extend a state declaration:

include:
  - ssh

add_banner:
  file.managed:
    - name: /etc/ssh/banner
    - source: salt:/ssh/files/banner
    - watch_in:
      - service: ssh_server

Here’s our networking example with the use_in declaration taken a bit further:

manage_eth0:
  network.managed:
    - name: eth0
    - enabled: True
    - type: eth
    - proto: static
    - ipaddr: 192.0.2.7
    - netmask: 255.255.255.0
    - gateway: 192.0.2.1
    - enable_ipv6: true
    - ipv6proto: static
    - ipv6ipaddrs:
      - 2001:db8:dead:beef::3/64
      - 2001:db8:dead:beef::7/64
    - ipv6gateway: 2001:db8:dead:beef::1
    - ipv6netmask: 64
    - dns:
      - 198.51.100.8
      - 203.0.113.4
    - use_in:
      - network: manage_eth1
      - network: manage_eth2

manage_eth1:
  network.managed:
    - name: eth1
    - ipaddr: 203.0.113.120
    - gateway: 203.0.113.1
    - ipv6ipaddr: 2001:db8:dead:c0::3
    - ipv6gateway: 2001:db8:dead:c0::1

manage_eth2:
  network.managed:
    - name: eth2
    - ipaddr: 203.0.113.121
    - gateway: 203.0.113.1
    - ipv6ipaddr: 2001:db8:dead:c0::4
    - ipv6gateway: 2001:db8:dead:c0::1

Altering states#

The state altering system is used to make sure that states are evaluated exactly as the user expects. It can be used to double check that a state performed exactly how it was expected to, or to make 100% sure that a state only runs under certain conditions.

The use of unless or onlyif options help make states even more stateful.

Note

Under the hood, these altering states declarations call cmd.retcode with python_shell=True. This means the commands referenced by these declarations will be parsed by a shell. So be aware of side-effects as this shell will be run with the same privileges as the Salt Minion.

The onlyif requisite#

The onlyif requisite is used if all of the commands defined return True. Then the state will be run.

If any of the specified commands return False, the state will not run. This example creates a new MySQL database user only if the projectDB database exists.

create_db_user:
  mysql_user.present:
    - name: jdoe
    - host: localhost
    - password: p@ssw0rd
    - onlyif:
      - mysql -u ro_user -e 'use projectDB'

The unless requisite#

The unless requisite specifies that a state should only run when any of the specified commands return False.

The unless requisite operates as NAND where it produces a value of True, if, and only if, at least one of the propositions is False. It is useful in giving more granular control over when a state should execute. In the example below, the state will only run if either the vim-enhanced package is not installed (returns False) or if /usr/bin/vim does not exist (returns False). The state will run if both commands return False.

However, the state will not run if both commands return True.

install_vim:
  pkg.installed:
    - name: vim
    - unless:
      - rpm -q vim-enhanced
      - ls /usr/bin/vim

The unless requisite checks are resolved for each name to which they are associated.

The check_cmd requisite#

Check Command is used for determining that a state did or did not run as expected.

  • This will attempt to do a replace on all enabled=0 in the .repo file, and replace them with enabled=1.
comment-repo:
  file.replace:
    - name: /etc/yum.repos.d/fedora.repo
    - pattern: ^enabled=0
    - repl: enabled=1
    - check_cmd:
      - grep '^enabled=1' /etc/yum.repos.d/fedora.repo
      # or
      - grep '^enabled=0' /etc/yum.repos.d/fedora.repo && return 1 || return 0

The check_cmd is just a bash command.

  • It will do a grep for enabled=0 in the file, and if it finds any, it will return a 0, which will prompt the && portion of the command to return a 1, causing check_cmd to set the state as failed.
  • If it returns a 1, meaning it didn’t find any enabled=0 it will hit the || portion of the command, returning a 0, and declaring the function succeeded.

The listen requisite#

listen and its counterpart listen_in trigger mod_watch functions for states when those states succeed and result in changes, similar to how watch and its counterpart watch_in. Unlike watch and watch_in, listen, and listen_in will not modify the order of states and can be used to ensure your states are executed in the order they are defined. All listen/listen_in actions will occur at the end of a state run, after all states have completed.

/srv/salt/httpd/restart_last.sls#
restart_apache2:
  service.running:
    - name: apache2
    - listen:
      - file: /etc/apache2/apache2.conf

configure_apache2:
  file.managed:
    - name: /etc/apache2/apache2.conf
    - source: salt://apache2/apache2.conf