diff --git a/docsite/latest/rst/playbooks_acceleration.rst b/docsite/latest/rst/playbooks_acceleration.rst index 8d3777bdbd..02391fc7c0 100644 --- a/docsite/latest/rst/playbooks_acceleration.rst +++ b/docsite/latest/rst/playbooks_acceleration.rst @@ -1,999 +1,5 @@ -Advanced Playbooks -================== - -Here are some advanced features of the playbooks language. Using all of these features -is not necessary, but many of them will prove useful. If a feature doesn't seem immediately -relevant, feel free to skip it. For many people, the features documented in `playbooks` will -be 90% or more of what they use in Ansible. - -.. contents:: - :depth: 2 - -Tags -```` - -.. versionadded:: 0.6 - -If you have a large playbook it may become useful to be able to run a -specific part of the configuration. Both plays and tasks support a -"tags:" attribute for this reason. - -Example:: - - tasks: - - - yum: name={{ item }} state=installed - with_items: - - httpd - - memcached - tags: - - packages - - - template: src=templates/src.j2 dest=/etc/foo.conf - tags: - - configuration - -If you wanted to just run the "configuration" and "packages" part of a very long playbook, you could do this:: - - ansible-playbook example.yml --tags "configuration,packages" - -Playbooks Including Playbooks -````````````````````````````` - -.. versionadded:: 0.6 - -To further advance the concept of include files, playbook files can -include other playbook files. Suppose you define the behavior of all -your webservers in "webservers.yml" and all your database servers in -"dbservers.yml". You can create a "site.yml" that would reconfigure -all of your systems like this:: - - --- - - include: playbooks/webservers.yml - - include: playbooks/dbservers.yml - -This concept works great with tags to rapidly select exactly what plays you want to run, and exactly -what parts of those plays. - -Ignoring Failed Commands -```````````````````````` - -.. versionadded:: 0.6 - -Generally playbooks will stop executing any more steps on a host that -has a failure. Sometimes, though, you want to continue on. To do so, -write a task that looks like this:: - - - name: this will not be counted as a failure - command: /bin/false - ignore_errors: yes - -Overriding Changed Result -````````````````````````` - -.. versionadded:: 1.3 - -When a shell/command or other module runs it will typically report -"changed" status based on whether it thinks it affected machine state. - -Sometimes you will know, based on the return code -or output that it did not make any changes, and wish to override -the "changed" result such that it does not appear in report output or -does not cause handlers to fire:: - - tasks: - - - shell: /usr/bin/billybass --mode="take me to the river" - register: bass_result - changed_when: "bass_result.rc != 2" - - # this will never report 'changed' status - - shell: wall 'beep' - -Accessing Complex Variable Data -``````````````````````````````` - -Some provided facts, like networking information, are made available as nested data structures. To access -them a simple {{ foo }} is not sufficient, but it is still easy to do. Here's how we get an IP address:: - - {{ ansible_eth0["ipv4"]["address"] }} - -Similarly, this is how we access the first element of an array:: - - {{ foo[0] }} - -Magic Variables, and How To Access Information About Other Hosts -```````````````````````````````````````````````````````````````` - -Even if you didn't define them yourself, Ansible provides a few variables for you automatically. -The most important of these are 'hostvars', 'group_names', and 'groups'. Users should not use -these names themselves as they are reserved. 'environment' is also reserved. - -Hostvars lets you ask about the variables of another host, including facts that have been gathered -about that host. If, at this point, you haven't talked to that host yet in any play in the playbook -or set of playbooks, you can get at the variables, but you will not be able to see the facts. - -If your database server wants to use the value of a 'fact' from another node, or an inventory variable -assigned to another node, it's easy to do so within a template or even an action line:: - - {{ hostvars['test.example.com']['ansible_distribution'] }} - -Additionally, *group_names* is a list (array) of all the groups the current host is in. This can be used in templates using Jinja2 syntax to make template source files that vary based on the group membership (or role) of the host:: - - {% if 'webserver' in group_names %} - # some part of a configuration file that only applies to webservers - {% endif %} - -*groups* is a list of all the groups (and hosts) in the inventory. This can be used to enumerate all hosts within a group. -For example:: - - {% for host in groups['app_servers'] %} - # something that applies to all app servers. - {% endfor %} - -A frequently used idiom is walking a group to find all IP addresses in that group:: - - {% for host in groups['app_servers'] %} - {{ hostvars[host]['ansible_eth0']['ipv4']['address'] }} - {% endfor %} - -An example of this could include pointing a frontend proxy server to all of the app servers, setting up the correct firewall rules between servers, etc. - -Just a few other 'magic' variables are available... There aren't many. - -Additionally, *inventory_hostname* is the name of the hostname as configured in Ansible's inventory host file. This can -be useful for when you don't want to rely on the discovered hostname `ansible_hostname` or for other mysterious -reasons. If you have a long FQDN, *inventory_hostname_short* also contains the part up to the first -period, without the rest of the domain. - -Don't worry about any of this unless you think you need it. You'll know when you do. - -Also available, *inventory_dir* is the pathname of the directory holding Ansible's inventory host file, *inventory_file* is the pathname and the filename pointing to the Ansible's inventory host file. - -Variable File Separation -```````````````````````` - -It's a great idea to keep your playbooks under source control, but -you may wish to make the playbook source public while keeping certain -important variables private. Similarly, sometimes you may just -want to keep certain information in different files, away from -the main playbook. - -You can do this by using an external variables file, or files, just like this:: - - --- - - hosts: all - remote_user: root - vars: - favcolor: blue - vars_files: - - /vars/external_vars.yml - tasks: - - name: this is just a placeholder - command: /bin/echo foo - -This removes the risk of sharing sensitive data with others when -sharing your playbook source with them. - -The contents of each variables file is a simple YAML dictionary, like this:: - - --- - # in the above example, this would be vars/external_vars.yml - somevar: somevalue - password: magic - -.. note:: - It's also possible to keep per-host and per-group variables in very - similar files, this is covered in :ref:`patterns`. - -Prompting For Sensitive Data -```````````````````````````` - -You may wish to prompt the user for certain input, and can -do so with the similarly named 'vars_prompt' section. This has uses -beyond security, for instance, you may use the same playbook for all -software releases and would prompt for a particular release version -in a push-script:: - - --- - - hosts: all - remote_user: root - vars: - from: "camelot" - vars_prompt: - name: "what is your name?" - quest: "what is your quest?" - favcolor: "what is your favorite color?" - -There are full examples of both of these items in the github examples/playbooks directory. - -If you have a variable that changes infrequently, it might make sense to -provide a default value that can be overridden. This can be accomplished using -the default argument:: - - vars_prompt: - - name: "release_version" - prompt: "Product release version" - default: "1.0" - -An alternative form of vars_prompt allows for hiding input from the user, and may later support -some other options, but otherwise works equivalently:: - - vars_prompt: - - name: "some_password" - prompt: "Enter password" - private: yes - - name: "release_version" - prompt: "Product release version" - private: no - -If `Passlib `_ is installed, vars_prompt can also crypt the -entered value so you can use it, for instance, with the user module to define a password:: - - vars_prompt: - - name: "my_password2" - prompt: "Enter password2" - private: yes - encrypt: "md5_crypt" - confirm: yes - salt_size: 7 - -You can use any crypt scheme supported by 'Passlib': - -- *des_crypt* - DES Crypt -- *bsdi_crypt* - BSDi Crypt -- *bigcrypt* - BigCrypt -- *crypt16* - Crypt16 -- *md5_crypt* - MD5 Crypt -- *bcrypt* - BCrypt -- *sha1_crypt* - SHA-1 Crypt -- *sun_md5_crypt* - Sun MD5 Crypt -- *sha256_crypt* - SHA-256 Crypt -- *sha512_crypt* - SHA-512 Crypt -- *apr_md5_crypt* - Apache’s MD5-Crypt variant -- *phpass* - PHPass’ Portable Hash -- *pbkdf2_digest* - Generic PBKDF2 Hashes -- *cta_pbkdf2_sha1* - Cryptacular’s PBKDF2 hash -- *dlitz_pbkdf2_sha1* - Dwayne Litzenberger’s PBKDF2 hash -- *scram* - SCRAM Hash -- *bsd_nthash* - FreeBSD’s MCF-compatible nthash encoding - -However, the only parameters accepted are 'salt' or 'salt_size'. You can use you own salt using -'salt', or have one generated automatically using 'salt_size'. If nothing is specified, a salt -of size 8 will be generated. - -Passing Variables On The Command Line -````````````````````````````````````` - -In addition to `vars_prompt` and `vars_files`, it is possible to send variables over -the Ansible command line. This is particularly useful when writing a generic release playbook -where you may want to pass in the version of the application to deploy:: - - ansible-playbook release.yml --extra-vars "version=1.23.45 other_variable=foo" - -This is useful, for, among other things, setting the hosts group or the user for the playbook. - -Example:: - - --- - - remote_user: '{{ user }}' - hosts: '{{ hosts }}' - tasks: - - ... - - ansible-playbook release.yml --extra-vars "hosts=vipers user=starbuck" - -As of Ansible 1.2, you can also pass in extra vars as quoted JSON, like so:: - - --extra-vars '{"pacman":"mrs","ghosts":["inky","pinky","clyde","sue"]}' - -The key=value form is obviously simpler, but it's there if you need it! - -As of Ansible 1.3, extra vars can be loaded from a JSON file with the "@" syntax:: - - --extra-vars "@some_file.json" - -Also as of Ansible 1.3, extra vars can be formatted as YAML, either on the command line -or in a file as above. - -Conditional Execution -````````````````````` - -(Note: this section covers 1.2 conditionals, if you are using a previous version, select -the previous version of the documentation, `Ansible 1.1 Docs `_ . -Those conditional forms continue to be operational in 1.2, although the new mechanisms are cleaner.) - -Sometimes you will want to skip a particular step on a particular host. This could be something -as simple as not installing a certain package if the operating system is a particular version, -or it could be something like performing some cleanup steps if a filesystem is getting full. - -This is easy to do in Ansible, with the `when` clause, which contains a Jinja2 expression (see chapter -`Playbooks `_ for more info). -Don't panic -- it's actually pretty simple:: - - tasks: - - name: "shutdown Debian flavored systems" - command: /sbin/shutdown -t now - when: ansible_os_family == "Debian" - -A number of Jinja2 "filters" can also be used in when statements, some of which are unique -and provided by Ansible. Suppose we want to ignore the error of one statement and then -decide to do something conditionally based on success or failure:: - - tasks: - - command: /bin/false - register: result - ignore_errors: True - - command: /bin/something - when: result|failed - - command: /bin/something_else - when: result|success - - command: /bin/still/something_else - when: result|skipped - - -As a reminder, to see what derived variables are available, you can do:: - - ansible hostname.example.com -m setup - -Tip: Sometimes you'll get back a variable that's a string and you'll want to do a comparison on it. You can do this like so:: - - tasks: - - shell: echo "only on Red Hat 6, derivatives, and later" - when: ansible_os_family == "RedHat" and ansible_lsb.major_release|int >= 6 - -Note the above example requires the lsb_release package on the target host in order to return the ansible_lsb.major_release fact. - -Variables defined in the playbooks or inventory can also be used. - -An example may be the execution of a task based on a variable's boolean value:: - - vars: - epic: true - -Then a conditional execution with action on the boolean value of epic being True:: - - tasks: - - shell: echo "This certainly is epic!" - when: epic - -With a boolean value of False:: - - tasks: - - shell: echo "This certainly isn't epic!" - when: not epic - -If a required variable has not been set, you can skip or fail using Jinja2's -`defined` test. For example:: - - tasks: - - shell: echo "I've got '{{ foo }}' and am not afraid to use it!" - when: foo is defined - - - fail: msg="Bailing out: this play requires 'bar'" - when: bar is not defined - -This is especially useful in combination with the conditional import of vars -files (see below). - -It's also easy to provide your own facts if you want, which is covered in :doc:`moduledev`. To run them, just -make a call to your own custom fact gathering module at the top of your list of tasks, and variables returned -there will be accessible to future tasks:: - - tasks: - - name: gather site specific fact data - action: site_facts - - command: echo {{ my_custom_fact_can_be_used_now }} - -One useful trick with *when* is to key off the changed result of a last command. As an example:: - - tasks: - - template: src=/templates/foo.j2 dest=/etc/foo.conf - register: last_result - - command: echo 'the file has changed' - when: last_result.changed - -{{ last_result }} is a variable set by the register directive. This assumes Ansible 0.8 and later. - -When combining `when` with `with_items`, be aware that the `when` statement is processed separately for each item. -This is by design:: - - tasks: - - command: echo {{ item }} - with_items: [ 0, 2, 4, 6, 8, 10 ] - when: item > 5 - -Note that if you have several tasks that all share the same conditional statement, you can affix the conditional -to a task include statement as below. Note this does not work with playbook includes, just task includes. All the tasks -get evaluated, but the conditional is applied to each and every task:: - - - include: tasks/sometasks.yml - when: "'reticulating splines' in output" - -Conditional Imports -``````````````````` - -Sometimes you will want to do certain things differently in a playbook based on certain criteria. -Having one playbook that works on multiple platforms and OS versions is a good example. - -As an example, the name of the Apache package may be different between CentOS and Debian, -but it is easily handled with a minimum of syntax in an Ansible Playbook:: - - --- - - hosts: all - remote_user: root - vars_files: - - "vars/common.yml" - - [ "vars/{{ ansible_os_family }}.yml", "vars/os_defaults.yml" ] - tasks: - - name: make sure apache is running - service: name={{ apache }} state=running - -.. note:: - The variable 'ansible_os_family' is being interpolated into - the list of filenames being defined for vars_files. - -As a reminder, the various YAML files contain just keys and values:: - - --- - # for vars/CentOS.yml - apache: httpd - somethingelse: 42 - -How does this work? If the operating system was 'CentOS', the first file Ansible would try to import -would be 'vars/CentOS.yml', followed by '/vars/os_defaults.yml' if that file -did not exist. If no files in the list were found, an error would be raised. -On Debian, it would instead first look towards 'vars/Debian.yml' instead of 'vars/CentOS.yml', before -falling back on 'vars/os_defaults.yml'. Pretty simple. - -To use this conditional import feature, you'll need facter or ohai installed prior to running the playbook, but -you can of course push this out with Ansible if you like:: - - # for facter - ansible -m yum -a "pkg=facter ensure=installed" - ansible -m yum -a "pkg=ruby-json ensure=installed" - - # for ohai - ansible -m yum -a "pkg=ohai ensure=installed" - -Ansible's approach to configuration -- separating variables from tasks, keeps your playbooks -from turning into arbitrary code with ugly nested ifs, conditionals, and so on - and results -in more streamlined & auditable configuration rules -- especially because there are a -minimum of decision points to track. - -Do-Until -```````` - -Sometimes you would want to retry a task till a certain condition is met, In such conditions the Do/Until feature will help. -Here's an example which show's the syntax to be applied for the task.:: - - - action: shell /usr/bin/foo - register: result - until: register.stdout.find("all systems go") != -1 - retries: 5 - delay: 10 - -The above example run the shell module recursively till the module's result has "all systems go" in it's stdout or the task has -been retried for 5 times with a delay of 10 seconds. The default value for "retries" is 3 and "delay" is 5. - -The task returns the results returned by the last task run. The results of individual retries can be viewed by -vv option. -The results will have a new key "attempts" which will have the number of the retries for the task. - -.. Note:: - - The Do/Until does not take decision on whether to fail or pass the play when the maximum retries are completed, the user can - can do that in the next task as follows. - -Example:: - - - action: shell /usr/bin/foo - register: result - until: register.stdout.find("all systems go") != -1 - retries: 5 - delay: 10 - failed_when: result.attempts == 5 - - -Loops -````` - -To save some typing, repeated tasks can be written in short-hand like so:: - - - name: add several users - user: name={{ item }} state=present groups=wheel - with_items: - - testuser1 - - testuser2 - -If you have defined a YAML list in a variables file, or the 'vars' section, you can also do:: - - with_items: somelist - -The above would be the equivalent of:: - - - name: add user testuser1 - user: name=testuser1 state=present groups=wheel - - name: add user testuser2 - user: name=testuser2 state=present groups=wheel - -The yum and apt modules use with_items to execute fewer package manager transactions. - -Note that the types of items you iterate over with 'with_items' do not have to be simple lists of strings. -If you have a list of hashes, you can reference subkeys using things like:: - - - name: add several users - user: name={{ item.name }} state=present groups={{ item.groups }} - with_items: - - { name: 'testuser1', groups: 'wheel' } - - { name: 'testuser2', groups: 'root' } - -Nested Loops -```````````` - -Loops can be nested as well:: - - - name: give users access to multiple databases - mysql_user: name={{ item[0] }} priv={{ item[1] }}.*:ALL password=foo - with_nested: - - [ 'alice', 'bob', 'eve' ] - - [ 'clientdb', 'employeedb', 'providerdb' ] - -As with the case of 'with_items' above, you can use previously defined variables. Just specify the variable's name without templating it with '{{ }}':: - - - name: here, 'users' contains the above list of employees - mysql_user: name={{ item[0] }} priv={{ item[1] }}.*:ALL password=foo - with_nested: - - users - - [ 'clientdb', 'employeedb', 'providerdb' ] - -Lookup Plugins - Accessing Outside Data -``````````````````````````````````````` - -.. versionadded:: 0.8 - -Various *lookup plugins* allow additional ways to iterate over data. Ansible will have more of these -over time. You can write your own, as is covered in the API section. Each typically takes a list and -can accept more than one parameter. - -``with_fileglob`` matches all files in a single directory, non-recursively, that match a pattern. It can -be used like this:: - - --- - - hosts: all - - tasks: - - # first ensure our target directory exists - - file: dest=/etc/fooapp state=directory - - # copy each file over that matches the given pattern - - copy: src={{ item }} dest=/etc/fooapp/ owner=root mode=600 - with_fileglob: - - /playbooks/files/fooapp/* - -``with_file`` loads data in from a file directly:: - - - authorized_key: user=foo key={{ item }} - with_file: - - /home/foo/.ssh/id_rsa.pub - -.. note:: - - When using ``with_fileglob`` or ``with_file`` with :ref:`roles`, if you - specify a relative path (e.g., :file:`./foo`), Ansible resolves the path - relative to the :file:`roles//files` directory. - -.. versionadded:: 0.9 - -Many new lookup abilities were added in 0.9. Remember, lookup plugins are run on the *controlling* machine:: - - --- - - hosts: all - - tasks: - - - debug: msg="{{ lookup('env','HOME') }} is an environment variable" - - - debug: msg="{{ item }} is a line from the result of this command" - with_lines: - - cat /etc/motd - - - debug: msg="{{ lookup('pipe','date') }} is the raw result of running this command" - - - debug: msg="{{ lookup('redis_kv', 'redis://localhost:6379,somekey') }} is value in Redis for somekey" - - - debug: msg="{{ lookup('dnstxt', 'example.com') }} is a DNS TXT record for example.com" - - - debug: msg="{{ lookup('template', './some_template.j2') }} is a value from evaluation of this template" - -As an alternative you can also assign lookup plugins to variables or use them -elsewhere. This macros are evaluated each time they are used in a task (or -template):: - - vars: - motd_value: "{{ lookup('file', '/etc/motd') }}" - - tasks: - - debug: msg="motd value is {{ motd_value }}" - -.. versionadded:: 1.0 - -``with_sequence`` generates a sequence of items in ascending numerical order. You -can specify a start, end, and an optional step value. - -Arguments should be specified in key=value pairs. If supplied, the 'format' is a printf style string. - -Numerical values can be specified in decimal, hexadecimal (0x3f8) or octal (0600). -Negative numbers are not supported. This works as follows:: - - --- - - hosts: all - - tasks: - - # create groups - - group: name=evens state=present - - group: name=odds state=present - - # create some test users - - user: name={{ item }} state=present groups=evens - with_sequence: start=0 end=32 format=testuser%02x - - # create a series of directories with even numbers for some reason - - file: dest=/var/stuff/{{ item }} state=directory - with_sequence: start=4 end=16 stride=2 - - # a simpler way to use the sequence plugin - # create 4 groups - - group: name=group{{ item }} state=present - with_sequence: count=4 - -.. versionadded:: 1.1 - -``with_password`` and associated lookup macro generate a random plaintext password and store it in -a file at a given filepath. Support for crypted save modes (as with vars_prompt) is pending. If the -file exists previously, it will retrieve its contents, behaving just like with_file. Usage of variables like "{{ inventory_hostname }}" in the filepath can be used to set -up random passwords per host (what simplifies password management in 'host_vars' variables). - -Generated passwords contain a random mix of upper and lowercase ASCII letters, the -numbers 0-9 and punctuation (". , : - _"). The default length of a generated password is 30 characters. -This length can be changed by passing an extra parameter:: - - --- - - hosts: all - - tasks: - - # create a mysql user with a random password: - - mysql_user: name={{ client }} - password="{{ lookup('password', 'credentials/' + client + '/' + tier + '/' + role + '/mysqlpassword length=15') }}" - priv={{ client }}_{{ tier }}_{{ role }}.*:ALL - - (...) - - # dump a mysql database with a given password (this example showing the other form). - - mysql_db: name={{ client }}_{{ tier }}_{{ role }} - login_user={{ client }} - login_password={{ item }} - state=dump - target=/tmp/{{ client }}_{{ tier }}_{{ role }}_backup.sql - with_password: credentials/{{ client }}/{{ tier }}/{{ role }}/mysqlpassword length=15 - - (...) - - # create a user with a given password - - user: name=guestuser - state=present - uid=5000 - password={{ item }} - with_password: credentials/{{ hostname }}/userpassword encrypt=sha256_crypt - -Setting the Environment (and Working With Proxies) -`````````````````````````````````````````````````` - -.. versionadded:: 1.1 - -It is quite possible that you may need to get package updates through a proxy, or even get some package -updates through a proxy and access other packages not through a proxy. Ansible makes it easy for you -to configure your environment by using the 'environment' keyword. Here is an example:: - - - hosts: all - remote_user: root - - tasks: - - - apt: name=cobbler state=installed - environment: - http_proxy: http://proxy.example.com:8080 - -The environment can also be stored in a variable, and accessed like so:: - - - hosts: all - remote_user: root - - # here we make a variable named "env" that is a dictionary - vars: - proxy_env: - http_proxy: http://proxy.example.com:8080 - - tasks: - - - apt: name=cobbler state=installed - environment: "{{ proxy_env }}" - -While just proxy settings were shown above, any number of settings can be supplied. The most logical place -to define an environment hash might be a group_vars file, like so:: - - --- - # file: group_vars/boston - - ntp_server: ntp.bos.example.com - backup: bak.bos.example.com - proxy_env: - http_proxy: http://proxy.bos.example.com:8080 - https_proxy: http://proxy.bos.example.com:8080 - -Getting values from files -````````````````````````` - -.. versionadded:: 0.8 - -Sometimes you'll want to include the content of a file directly into a playbook. You can do so using a macro. -This syntax will remain in future versions, though we will also will provide ways to do this via lookup plugins (see "More Loops") as well. What follows -is an example using the authorized_key module, which requires the actual text of the SSH key as a parameter:: - - tasks: - - name: enable key-based ssh access for users - authorized_key: user={{ item }} key="{{ lookup('file', '/keys/' + item ) }}" - with_items: - - pinky - - brain - - snowball - -Selecting Files And Templates Based On Variables -```````````````````````````````````````````````` - -Sometimes a configuration file you want to copy, or a template you will use may depend on a variable. -The following construct selects the first available file appropriate for the variables of a given host, which is often much cleaner than putting a lot of if conditionals in a template. - -The following example shows how to template out a configuration file that was very different between, say, CentOS and Debian:: - - - name: template a file - template: src={{ item }} dest=/etc/myapp/foo.conf - first_available_file: - - /srv/templates/myapp/{{ ansible_distribution }}.conf - - /srv/templates/myapp/default.conf - -first_available_file is only available to the copy and template modules. - -Asynchronous Actions and Polling -```````````````````````````````` - -By default tasks in playbooks block, meaning the connections stay open -until the task is done on each node. If executing playbooks with -a small parallelism value (aka ``--forks``), you may wish that long -running operations can go faster. The easiest way to do this is -to kick them off all at once and then poll until they are done. - -You will also want to use asynchronous mode on very long running -operations that might be subject to timeout. - -To launch a task asynchronously, specify its maximum runtime -and how frequently you would like to poll for status. The default -poll value is 10 seconds if you do not specify a value for `poll`:: - - --- - - hosts: all - remote_user: root - tasks: - - name: simulate long running op (15 sec), wait for up to 45, poll every 5 - command: /bin/sleep 15 - async: 45 - poll: 5 - -.. note:: - There is no default for the async time limit. If you leave off the - 'async' keyword, the task runs synchronously, which is Ansible's - default. - -Alternatively, if you do not need to wait on the task to complete, you may -"fire and forget" by specifying a poll value of 0:: - - --- - - hosts: all - remote_user: root - tasks: - - name: simulate long running op, allow to run for 45, fire and forget - command: /bin/sleep 15 - async: 45 - poll: 0 - -.. note:: - You shouldn't "fire and forget" with operations that require - exclusive locks, such as yum transactions, if you expect to run other - commands later in the playbook against those same resources. - -.. note:: - Using a higher value for ``--forks`` will result in kicking off asynchronous - tasks even faster. This also increases the efficiency of polling. - -Local Playbooks -``````````````` - -It may be useful to use a playbook locally, rather than by connecting over SSH. This can be useful -for assuring the configuration of a system by putting a playbook on a crontab. This may also be used -to run a playbook inside a OS installer, such as an Anaconda kickstart. - -To run an entire playbook locally, just set the "hosts:" line to "hosts:127.0.0.1" and then run the playbook like so:: - - ansible-playbook playbook.yml --connection=local - -Alternatively, a local connection can be used in a single playbook play, even if other plays in the playbook -use the default remote connection type:: - - hosts: 127.0.0.1 - connection: local - -Turning Off Facts -````````````````` - -If you know you don't need any fact data about your hosts, and know everything about your systems centrally, you -can turn off fact gathering. This has advantages in scaling Ansible in push mode with very large numbers of -systems, mainly, or if you are using Ansible on experimental platforms. In any play, just do this:: - - - hosts: whatever - gather_facts: no - -Pull-Mode Playbooks -``````````````````` - -The use of playbooks in local mode (above) is made extremely powerful with the addition of `ansible-pull`. -A script for setting up ansible-pull is provided in the examples/playbooks directory of the source -checkout. - -The basic idea is to use Ansible to set up a remote copy of Ansible on each managed node, each set to run via -cron and update playbook source via git. This inverts the default push architecture of Ansible into a pull -architecture, which has near-limitless scaling potential. The setup playbook can be tuned to change -the cron frequency, logging locations, and parameters to ansible-pull. - -This is useful both for extreme scale-out as well as periodic remediation. Usage of the 'fetch' module to retrieve -logs from ansible-pull runs would be an excellent way to gather and analyze remote logs from ansible-pull. - -Register Variables -`````````````````` - -.. versionadded:: 0.7 - -Often in a playbook it may be useful to store the result of a given command in a variable and access -it later. Use of the command module in this way can in many ways eliminate the need to write site specific facts, for -instance, you could test for the existence of a particular program. - -The 'register' keyword decides what variable to save a result in. The resulting variables can be used in templates, action lines, or *when* statements. It looks like this (in an obviously trivial example):: - - - name: test play - hosts: all - - tasks: - - - shell: cat /etc/motd - register: motd_contents - - - shell: echo "motd contains the word hi" - when: motd_contents.stdout.find('hi') != -1 - -As shown previously, the registered variable's string contents are accessible with the 'stdout' value. -The registered result can be used in the "with_items" of a task if it is converted into -a list (or already is a list) as shown below. "stdout_lines" is already available on the object as -well though you could also call "home_dirs.stdout.split()" if you wanted, and could split by other -fields:: - - - name: registered variable usage as a with_items list - hosts: all - - tasks: - - - name: retrieve the list of home directories - command: ls /home - register: home_dirs - - - name: add home dirs to the backup spooler - file: path=/mnt/bkspool/{{ item }} src=/home/{{ item }} state=link - with_items: home_dirs.stdout_lines - # with_items: home_dirs.stdout.split() - -Rolling Updates -``````````````` - -.. versionadded:: 0.7 - -By default, Ansible will try to manage all of the machines referenced in a play in parallel. For a rolling updates -use case, you can define how many hosts Ansible should manage at a single time by using the ''serial'' keyword:: - - - - name: test play - hosts: webservers - serial: 3 - -In the above example, if we had 100 hosts, 3 hosts in the group 'webservers' -would complete the play completely before moving on to the next 3 hosts. - -Maximum Failure Percentage -`````````````````````````` - -.. versionadded:: 1.3 - -By default, Ansible will continue executing actions as long as there are hosts in the group that have not yet failed. -In some situations, such as with the rolling updates described above, it may be desireable to abort the play when a -certain threshold of failures have been reached. To acheive this, as of version 1.3 you can set a maximum failure -percentage on a play as follows:: - - - hosts: webservers - max_fail_percentage: 30 - serial: 10 - -In the above example, if more than 3 of the 10 servers in the group were to fail, the rest of the play would be aborted. - -.. note:: - - The percentage set must be exceeded, not equaled. For example, if serial were set to 4 and you wanted the task to abort - when 2 of the systems failed, the percentage should be set at 49 rather than 50. - -Delegation -`````````` - -.. versionadded:: 0.7 - -If you want to perform a task on one host with reference to other hosts, use the 'delegate_to' keyword on a task. -This is ideal for placing nodes in a load balanced pool, or removing them. It is also very useful for controlling -outage windows. Using this with the 'serial' keyword to control the number of hosts executing at one time is also -a good idea:: - - --- - - hosts: webservers - serial: 5 - - tasks: - - name: take out of load balancer pool - command: /usr/bin/take_out_of_pool {{ inventory_hostname }} - delegate_to: 127.0.0.1 - - - name: actual steps would go here - yum: name=acme-web-stack state=latest - - - name: add back to load balancer pool - command: /usr/bin/add_back_to_pool {{ inventory_hostname }} - delegate_to: 127.0.0.1 - - -These commands will run on 127.0.0.1, which is the machine running Ansible. There is also a shorthand syntax that -you can use on a per-task basis: 'local_action'. Here is the same playbook as above, but using the shorthand -syntax for delegating to 127.0.0.1:: - - --- - # ... - tasks: - - name: take out of load balancer pool - local_action: command /usr/bin/take_out_of_pool {{ inventory_hostname }} - - # ... - - - name: add back to load balancer pool - local_action: command /usr/bin/add_back_to_pool {{ inventory_hostname }} - -A common pattern is to use a local action to call 'rsync' to recursively copy files to the managed servers. -Here is an example:: - - --- - # ... - tasks: - - name: recursively copy files from management server to target - local_action: command rsync -a /path/to/files {{ inventory_hostname }}:/path/to/target/ - -Note that you must have passphrase-less SSH keys or an ssh-agent configured for this to work, otherwise rsync -will need to ask for a passphrase. - Accelerated Mode -```````````````` +================ .. versionadded:: 1.3 @@ -1112,219 +118,3 @@ Fedora and EPEL also have Ansible RPM subpackages available for fireball-depende Also see the module documentation section. - -Understanding Variable Precedence -````````````````````````````````` - -You have already learned about inventory variables, 'vars', and 'vars_files'. In the -event the same variable name occurs in more than one place, what happens? There are really three tiers -of precedence, and within those tiers, some minor ordering rules that you probably won't even need to remember. -We'll explain them anyway though. - -Variables that are set during the execution of the play have highest priority. This includes registered -variables and facts, which are discovered pieces of information about remote hosts. - -Descending in priority are variables defined in the playbook. 'vars_files' as defined in the playbook are next up, -followed by variables as passed to ansible-playbook via --extra-vars (-e), then variables defined in the 'vars' section. These -should all be taken to be basically the same thing -- good places to define constants about what the play does to all hosts -in the play. - -Finally, inventory variables have the least priority. Variables about hosts override those about groups. -If a variable is defined in multiple groups and one group is a child of the other, the child group variable -will override the variable set in the parent. - -This makes the 'group_vars/all' file the best place to define a default value you wish to override in another -group, or even in a playbook. For example, your organization might set a default ntp server in group_vars/all -and then override it based on a group based on a geographic region. However if you type 'ntpserver: asdf.example.com' -in a vars section of a playbook, you know from reading the playbook that THAT specific value is definitely the one -that is going to be used. You won't be fooled by some variable from inventory sneaking up on you. - -So, in short, if you want something easy to remember: facts beat playbook definitions, and -playbook definitions beat inventory variables. - -There's a little bit more if you are using roles -- roles fit in the "playbook definitions" category of scale. They are -trumped by facts, and still trump inventory variables. However, there's a bit of extra magic. - -Variables passed as parameters to the role are accesible only within that role (and dependencies of that role). You can -almost think of them like programming functions or macros. - -Variables loaded via the 'vars/' directory of a role are made available to all roles and tasks, which in older versions of Ansible -could be confusing in the case of a reused variable name. In Ansible 1.3 and later, however, vars/ directories are guaranteed to be scoped to the current role, just like roles parameters. They are still available globally though, so if you want to set a variable like "ntp_server" in a common role, other roles can still make use of it. Thus they are just like "vars_files" construct that they emulate, but they have a bit more of a "Do What I Mean" semantic to them. They are smarter. - -If there are role dependencies involved, dependent roles can set variables visible to the roles that require them, but -the requiring role is allowed to override those variables. For instance if a role "myapp" requires "apache", and -the value of "apache_port" in "apache" is 80, "myapp" could choose to set it to 8080. Thus you may think of this somewhat -like an inheritance system if you're a developer -- though it's not exactly -- and we don't require folks to think in programming terms to know how things work. - -If you want, you can choose to prefix variable names with the name of your role and be extra sure of where -data sources are coming from, but this is optional. However it can be a nice thing to do in your templates as you immediately -know where the variable was defined. - -Ultimately, the variable system may seem complex -- but it's really not. It's mostly a "Do What I Mean" kind of system, though knowing the details may help you if you get stuck or are trying to do something advanced. Feel free to experiment! - -Check Mode ("Dry Run") --check -``````````````````````````````` - -.. versionadded:: 1.1 - -When ansible-playbook is executed with --check it will not make any changes on remote systems. Instead, any module -instrumented to support 'check mode' (which contains the primary core modules, but it is not required that all modules do -this) will report what changes they would have made. Other modules that do not support check mode will also take no -action, but just will not report what changes they might have made. - -Check mode is just a simulation, and if you have steps that use conditionals that depend on the results of prior commands, -it may be less useful for you. However it is great for one-node-at-time basic configuration management use cases. - -Example:: - - ansible-playbook foo.yml --check - -Running a task in check mode -```````````````````````````` - -.. versionadded:: 1.3 - -Sometimes you may want to have a task to be executed even in check -mode. To achieve this, use the `always_run` clause on the task. Its -value is a Jinja2 expression, just like the `when` clause. In simple -cases a boolean YAML value would be sufficient as a value. - -Example:: - - tasks: - - - name: this task is run even in check mode - command: /something/to/run --even-in-check-mode - always_run: yes - -As a reminder, a task with a `when` clause evaluated to false, will -still be skipped even if it has a `always_run` clause evaluated to -true. - - -Showing Differences with --diff -``````````````````````````````` - -.. versionadded:: 1.1 - -The --diff option to ansible-playbook works great with --check (detailed above) but can also be used by itself. When this flag is supplied, if any templated files on the remote system are changed, and the ansible-playbook CLI will report back -the textual changes made to the file (or, if used with --check, the changes that would have been made). Since the diff -feature produces a large amount of output, it is best used when checking a single host at a time, like so:: - - ansible-playbook foo.yml --check --diff --limit foo.example.com - -Dictionary & Nested (Complex) Arguments -``````````````````````````````````````` - -As a review, most tasks in Ansible are of this form:: - - tasks: - - - name: ensure the cobbler package is installed - yum: name=cobbler state=installed - -However, in some cases, it may be useful to feed arguments directly in from a hash (dictionary). In fact, a very small -number of modules (the CloudFormations module is one) actually require complex arguments. They work like this:: - - tasks: - - - name: call a module that requires some complex arguments - foo_module: - fibonacci_list: - - 1 - - 1 - - 2 - - 3 - my_pets: - dogs: - - fido - - woof - fish: - - limpet - - nemo - - "{{ other_fish_name }}" - -You can of course use variables inside these, as noted above. - -If using local_action, you can do this:: - - - name: call a module that requires some complex arguments - local_action: - module: foo_module - arg1: 1234 - arg2: 'asdf' - -Which of course means that, though more verbose, this is also legal syntax:: - - - name: foo - template: { src: '/templates/motd.j2', dest: '/etc/motd' } - -Local Facts (Facts.d) -````````````````````` - -.. versionadded:: 1.3 - -As discussed in the playbooks chapter, Ansible facts are a way of getting data about remote systems for use in playbook variables. -Usually these are discovered automatically by the 'setup' module in Ansible. Users can also write custom facts modules, as described -in the API guide. However, what if you want to have a simple way to provide system or user -provided data for use in Ansible variables, without writing a fact module? For instance, what if you want users to be able to control some aspect about how their systems are managed? "Facts.d" is one such mechanism. - -If a remotely managed system has an "/etc/ansible/facts.d" directory, any files in this directory -ending in ".fact", can be JSON, INI, or executable files returning JSON, and these can supply local facts in Ansible. - -For instance assume a /etc/ansible/facts.d/preferences.fact:: - - [general] - asdf=1 - bar=2 - -This will produce a hash variable fact named "general" with 'asdf' and 'bar' as members. -To validate this, run the following:: - - ansible -m setup -a "filter=ansible_local" - -And you will see the following fact added:: - - "ansible_local": { - "preferences": { - "general": { - "asdf" : "1", - "bar" : "2" - } - } - } - -And this data can be accessed in a template/playbook as:: - - {{ ansible_local.preferences.general.asdf }} - -The local namespace prevents any user supplied fact from overriding system facts -or variables defined elsewhere in the playbook. - -Style Points -```````````` - -Ansible playbooks are colorized. If you do not like this, set the ANSIBLE_NOCOLOR=1 environment variable. - -Ansible playbooks also look more impressive with cowsay installed, and we encourage installing this package. - -.. seealso:: - - :doc:`YAMLSyntax` - Learn about YAML syntax - :doc:`playbooks` - Review the basic playbook features - :doc:`bestpractices` - Various tips about playbooks in the real world - :doc:`modules` - Learn about available modules - :doc:`moduledev` - Learn how to extend Ansible by writing your own modules - :doc:`patterns` - Learn about how to select hosts - `Github examples directory `_ - Complete playbook files from the github project source - `Mailing List `_ - Questions? Help? Ideas? Stop by the list on Google Groups - -