Scap

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thcipriani@tin:~$ scap fortune | scap say
 ------------------------------------------------
/                                                \
|   S.C.A.P.: scatter crap around production    |
\                                                /
 ------------------------------------------------
    \
     \
      \
           ___ ____
         ⎛   ⎛ ,----
          \  //==--'
     _//|,.·//==--'    ____________________________
    _OO≣=-  ︶ ᴹw ⎞_§ ______  ___\ ___\ ,\__ \/ __ \
   (∞)_, )  (     |  ______/__  \/ /__ / /_/ / /_/ /
     ¨--¨|| |- (  / ______\____/ \___/ \__^_/  .__/
         ««_/  «_/ jgs/bd808                /_/

scap is the Wikimedia deployment tool. Scap started life as a series of shell scripts written around 2004 when the code was moved from an NFS-mount ("insta-deployment") to the harddisks of the Apache servers. It was ported to python in 2013. Starting in late 2015 it was modified to support the use-case of deploying software apart from MediaWiki (formerly done using a salt-based deployment tool called Trebuchet).

Scap is used for:

Usage

As of July 2017 there are two sets of operations that can be preformed by scap:

  1. MediaWiki deployments
  2. Other software deployments

MediaWiki Deployments

Basic commands

scap pull

Performs the action only on the one server on which the command is run
  • syncs /srv/mediawiki-staging from a deployment rsync server-> /srv/mediawiki on the local server
  • This action was formerly run as sync-common

scap sync-file

This is an all-script!
  • for a single file
  • checks PHP syntax
  • syncs /srv/mediawiki-staging/(some file) -> /srv/mediawiki

scap sync-wikiversions

This is an all-script!
  • syncs /srv/mediawiki-staging/wikiversions.{json,cdb} -> /srv/mediawiki

scap sync

'scap' logo
A diagram of wikimedia 'scap' deployment tool
This is an all-script!
"sync-common-all-php"
  • lints PHP files in ./wmf-config, ./multiversion
  • Sync deploy directory (/srv/mediawiki-staging) on localhost with staging area (/srv/mediawiki)
  • for all mediawiki versions currently deployed (usually 2) it:
    • rebuilds localization caches of core and extensions
    • creates json files from localization caches for better rsync performance
  • runs scap pull on co-master servers to update /srv/mediawiki-staging
  • runs scap pull on rsync fanout servers to update /srv/mediawiki
  • runs scap pull on "all" servers to update /srv/mediawiki from nearest rsync proxy
  • rebuilds localization caches on "all" servers from json files that were synced by scap pull
    • rsync is not the optimal tool for cdb files, so json is synced and cdb files are built from those
  • compiles wikiversions.json to wikiversions.cdb on localhost
  • runs scap sync-wikiversions

SWAT deploys

SWAT_deploys are small code deployment windows that happen 3 times per day in #wikimedia-operations connect on Freenode. SWAT deploys use the commands above to merge and deploy code. For more detailed instructions there is a page that details how to run a SWAT deployment

Other Software Deployments

Scap is capable of deploying software other than MediaWiki. These commands are meant to be run from the active deployment server in the directory for the repo you are deploying. These repos are all sub-directories of /srv/deployment. For example, Parsoid is deployed from the directory /srv/deployment/parsoid/deploy

scap deploy

This is a deployment-server-script!
  • Uses git to sync deployment-server:/srv/deployment/[repo] -> targets:/srv/deployment/[repo]
  • Syncs in 5 separate stages
    1. config-deploy(optional/requires configuration) - uses templates in the /srv/deployment/[repo]/scap directory to deploy a configuration file on the targets
    2. fetch - Uses git fetch to fetch code from the deployment-server to a local cache repo (for example: target:/srv/deployment/parsoid/deploy-cache/cache)
    3. promote
      • Uses git clone to create a checkout of the current repo in the state it's in on the deployment-server (for example: it will make a checkout in target:/srv/deployment/parsoid/deploy-cache/revs/xxxxxxxxxxxxxxxxxxxxx)
      • Creates symlink on target from revision to final location (for example: it will make a symlink target:/srv/deployment/parsoid/deploy-cache/revs/xxxxxxxxxxxxxxxxxxxxx -> target:/srv/deployment/parsoid/deploy)
    4. service_restart (optional) - if a service_name is specified in scap/scap.cfg that service will be restarted
    5. finalize - removes files on targets used for rollback.

Usage

usage: scap deploy [-h] [-v] [--environment ENVIRONMENT]
                   [-r REV] [-l LIMIT_HOSTS] [-f] [--dry-run]
                   [--service-restart] [-i] [message [message ...]]

Sync new service code across cluster.

positional arguments:
message               Log message for SAL

optional arguments:
  -h, --help            show this help message and exit
  -r REV, --rev REV     Revision to deploy
  -l LIMIT_HOSTS, --limit-hosts LIMIT_HOSTS
                        Limit deploy to hosts matching expression
  -f, --force           force re-fetch and checkout
  --dry-run             Compile and deploy config files to a temp location and
                        output a diff against the previously deployed config
                        files.
  --service-restart     Restart service
  -i, --init            Setup a repo for initial deployment

Examples

# show verbose output:
scap deploy -v "Updating repo"
# deploy using configuration inside scap/environments/staging/scap.cfg
scap deploy --environtment staging
# deploy only to the scap-target-01 host
scap deploy -l 'scap-target-01'
# deploy only to the 5 hosts [scap-target-01..scap-target-05]
scap deploy -l 'scap-target-[01:05]'
# deploy to all hosts EXCEPT those in eqiad
scap deploy -l '!scap-target-*.eqiad.wmnet'
deployer@tin:/srv/deployment/foo/deploy$ scap deploy
20:46:12 Started deploy_foo/deploy
Entering 'foo'
20:46:12
== DEFAULT ==
:* scap-target-07
:* scap-target-08
:* scap-target-09
:* scap-target-04
:* scap-target-05
:* scap-target-06
:* scap-target-10
:* scap-target-01
:* scap-target-02
:* scap-target-03
deploy_foo/deploy_config_deploy: 100% (ok: 10; fail: 0; left: 0)
deploy_foo/deploy_fetch: 100% (ok: 10; fail: 0; left: 0)
deploy_foo/deploy_promote: 100% (ok: 10; fail: 0; left: 0)
20:46:42 Finished deploy_foo/deploy (duration: 00m 29s)

scap deploy --service-restart

This is a deployment-server-script!
  • If a service_name is defined in scap/scap.cfg, the --service-restart command can be used to restart a service on all targets

Usage

deployer@tin:/srv/deployment/foo/deploy$ scap deploy --service-restart -v "Restarting for Upgrade"
17:17:30 Started restart [foo_deploy/deploy@61368b4]
17:17:30 Deploying Rev: 61368b4253c9f6a5d2d62d482319d644b31791f0
17:17:30 Prepare config deploy
17:17:30 Config deploy file: /srv/deployment/foo/deploy/scap/config-files.yaml
17:17:30 Update DEPLOY_HEAD
17:17:30 Creating /srv/deployment/foo/deploy/.git/DEPLOY_HEAD
17:17:30 Update server info
Entering 'foo'
17:17:30 Started restart [foo/deploy@61368b4]: Restarting for Upgrade
17:17:30
== DEFAULT ==
:* scap-target-07
:* scap-target-08
:* scap-target-09
:* scap-target-04
:* scap-target-05
:* scap-target-06
:* scap-target-10
:* scap-target-01
:* scap-target-02
:* scap-target-03
17:17:30 Running remote deploy cmd ['scap', 'deploy-local', '-v', '--repo', 'foo/deploy', '-g', 'default', 'restart_service', '--refresh-config']
foo/deploy: restart_service stage(s): 100% (ok: 10; fail: 0; left: 0)
17:17:44
== DEFAULT ==
:* scap-target-07
:* scap-target-08
:* scap-target-09
:* scap-target-04
:* scap-target-05
:* scap-target-06
:* scap-target-10
:* scap-target-01
:* scap-target-02
:* scap-target-03
17:17:44 Running remote deploy cmd ['scap', 'deploy-local', '-v', '--repo', 'foo/deploy', '-g', 'default', 'finalize', '--refresh-config']
foo/deploy: finalize stage(s): 100% (ok: 10; fail: 0; left: 0)
17:17:55 Finished restart [foo/deploy@61368b4] (duration: 00m 24s)

scap deploy-log

scap deploy-log running
This is a deployment-server-script!

The scap deploy-log command provides powerful filters for the scap deploy logs.

The main deploy application sends all structured log output to a file under scap/log/git-tag.log. deploy-log is meant to run during or after a deploy, potentially in a separate terminal. Log entries can be filtered on one or more fields using a given free-form expression. By default scap deploy-log will periodically scan the scap/log directory for new files and immediately begin tailing any newly discovered log file.

As an alternative to the default behavior, you can either specify the log file to parse via the scap deploy-log --file option or choose the newest log file by using scap deploy-log --latest; in this case, it will simply filter the entire file for matching records and exit, rather than watching for more log files to be created.

The default behavior is convenient for monitoring an ongoing deployment from a separate terminal. Simply start scap deploy-log in a separate terminal prior to running scap deploy. Once your deployment starts, scap deploy-log will discover the new log file and immediately begin displaying relevant log messages

Usage

scap deploy-log [--file <file>] [--latest] [-v] [expr]

scap deploy-log [--file <file>] [--latest] [-v] [expr]

-f <file>, --file <file>

    Used to explicitly specify the log file to be parsed. If no file is specified then deploy-log will automatically open any newly created log files and immediately begin outputting any matching log messages.

-l, --latest

    Parse and filter the latest log file, exiting once the entire file has been processed.

-v, --verbose

    Produce verbose output

expr

    Optional filter expression which is used to match log entries in <file>

Examples

# show verbose output:
scap deploy-log -v
# tail the most recent log file:
scap deploy-log --latest
# show log messages for the host named scap-target-01
scap deploy-log 'host == scap-target-01'
# show log messages matching a regex pattern:
scap deploy-log 'msg ~ "some important (message|msg)"'
# show WARNING messages for hosts whose name begins with "scap-target-"
scap deploy-log 'levelno >= WARNING host == scap-target-*'

Deployment-server-script

A deployment-server-script is a script that is meant to be run from the active deployment server that operates on target boxes via ssh.

All-script

An all-script is a deployment-server-script that operates on mediawiki-installation boxes via ssh. These scripts performs the action on all servers.

The specific servers include:

Wholesome Fun

bd808@silver:~$ scap fortune | scap say
 ------------------------------------------------
/                                                \
|     S.C.A.P.: someone can always pontificate    |
\                                                /
 ------------------------------------------------
    \
     \
      \
           ___ ____
         ⎛   ⎛ ,----
          \  //==--'
     _//|,.·//==--'    ____________________________
    _OO≣=-  ︶ ᴹw ⎞_§ ______  ___\ ___\ ,\__ \/ __ \
   (∞)_, )  (     |  ______/__  \/ /__ / /_/ / /_/ /
     ¨--¨|| |- (  / ______\____/ \___/ \__^_/  .__/
         ««_/  «_/ jgs/bd808                /_/