T3C

t3c is a transliteration of traffic_ops_ort.pl script to the go language. It is designed to replace the traffic_ops_ort.pl perl script and it is used to apply configuration from Traffic Control, stored in Traffic Ops, to the cache.

Typical usage is to install T3C on the cache machine, and then run it periodically via a CRON job.

NOTE T3C requires and uses /opt/ort/atstccfg

Options

T3C has the following command-line options:

long option	short	default	description
--cache-hostname=[hostname]	-H	""	override the short hostname of the OS for config generation.
--dispersion=[seconds]	-D	300	wait a random number of seconds between 0 and [seconds] before starting.
--login-dispersion=[seconds]	-l	0	wait a random number of seconds between 0 and [seconds] before login.
--log-location-debug=[value]	-d	stdout	Where to log debugs. May be a file path, stdout, stderr, or null
--log-location-error=[value]	-e	stdout	Where to log errors. May be a file path, stdout, stderr, or null
--log-location-info=[value]	-i	stdout	Where to log info messages. May be a file path, stdout, stderr, or null
--log-location-warn=[value]	-w	stdout	Where to log warning messages. May be a file path, stdout, stderr, or null
--num-retries=[number]	-r	3	retry connection to Traffic Ops URL [number] times.
--rev-proxy-disable=[‘true’ or ‘false’]	-p	false	bypass the reverse proxy even if one has been configured.
--reval-wait-time=[seconds]	-T	60	wait a random number of seconds between 0 and [seconds] before revlidation
--run-mode=[mode]	-m	report	The mode of operation, where mode is [badass
--skip-os-check=[‘true’ or ‘false’]	-s	false	bypass the check for a supported CentOS version.
--traffic-ops-timeout-milliseconds=[ms]	-t	30000	The Traffic Ops request timeout in milliseconds.
--traffic-ops-password=[password]	-P	""	TrafficOps password. Required if not set with the environment variable TO_PASS
--traffic-ops-url=[url]	-u	""	TrafficOps URL. Required if not set with the environment variable TO_URL
--traffic-ops-user=[username]	-U	""	TrafficOps username. Required if not set with the environment variable TO_USER
--trafficserver-home=[directory]	-R	""	Used to specify an alternate install location for ATS, otherwise its set from the RPM.
--wait-for-parents=[‘true’ or ‘false’]	-W	true	do not update if parent_pending = 1 in the update json.

Modes

T3C can be run in a number of modes.

The syncds mode is the normal mode of operation, which should typically be run periodically via cron or a similar tool.

The badass mode is typically an emergency-fix mode, which will override and replace all files with the configuration generated from the current Traffic Ops data, regardless whether T3C (presumably incorrectly) thinks the files need updating or not. It is recommended to run this mode when something goes wrong, and the configuration on the cache is incorrect, and the data in Traffic Ops and config generation is believed to be correct. It is not recommended to run this in normal operation; use syncds mode for normal operation.

The revalidate mode will apply Revalidations from Traffic Ops (regex_revalidate.config) but no other configuration. This mode was intended to quickly apply revalidations when T3C took a long time to run. It is less relevant with T3C's current speed, but may still be useful on slow networks or very large deployments.

mode	description
report	prints config differences and exits (default)
badass	attempts to fix all config differences that it can
syncds	syncs delivery services with what is configured in Traffic Ops
revalidate	checks for updated revalidations in Traffic Ops and applies them

Behavior

When T3C is run, it will:

Delete all of its temporary directories over a week old. Currently, the base temp directory is hard-coded to /tmp/ort.
Determine if Updates have been Queued on the server (by checking the Server's Update Pending or Revalidate Pending flag in Traffic Ops).
1. If Updates were not queued and the script is running in syncds mode (the normal mode), exit.
Get the config files from Traffic Ops, via atstccfg.
Process CentOS Yum packages.
1. These are specified via Parameters on the Server's Profile, with the Config File ‘package’, where the Parameter Name is the package name, and the Parameter Value is the package version.
2. Uninstall any packages which are installed but whose version does not match.
3. Install all packages in the Server Profile.
Process chkconfig directives.
1. These are specified via Parameters on the Server's Profile, with the Config File ‘chkconfig’, where the Parameter Name is the package name, and the Parameter Value is the chkconfig directive line.
2. All chkconfig directives in the Server's Profile are applied to the CentOS chkconfig.
3. NOTE the default profiles distributed by Traffic Control have an ATS chkconfig with a runlevel before networking is enabled, which is likely incorrect.
4. NOTE this is not used by CentOS 7+ and ATS 7+. SystemD does not use chkconfig, and ATS 7+ uses a SystemD script not an init script.
Process each config file
1. If T3C is in revalidate mode, this will only be regex_revalidate.config
2. Perform any special processing. See Special Processing.
3. If a file exists at the path of the file, load it from disk and compare the two.
4. If there are no changes, don't apply the new file.
5. If there are changes, backup the existing file in the temp directory, and write the new file.
If configuration was changed which requires an ATS reload to apply, perform a service reload of ATS.
If configuration was changed which requires an ATS restart to apply, and T3C is in badass mode, perform a service restart of ATS.
If a sysctl.conf config file was changed, and T3C is in badass mode, run sysctl -p.
If a ntpd.conf config file was changed, and T3C is in badass mode, perform a service restart of ntpd.
Update Traffic Ops to unset the Update Pending or Revalidate Pending flag of this Server.

Special Processing

Certain config files perform extra processing.

Global replacements

All config files have certain text directives replaced. This is done by the atstccfg config generator before the file is returned to T3C.

__SERVER_TCP_PORT__ is replaced with the Server‘s Port from Traffic Ops; unless the server’s port is 80, 0, or null, in which case any occurrences preceded by a colon are removed.
__CACHE_IPV4__ is replaced with the Server's IP address from Traffic Ops.
__HOSTNAME__ is replaced with the Server's (short) HostName from Traffic Ops.
__FULL_HOSTNAME__ is replaced with the Server‘s HostName, a dot, and the Server’s DomainName from Traffic Ops (i.e. the Server's Fully Qualified Domain Name).
__RETURN__ is replaced with a newline character, and any whitespace before or after it is removed.

remap.config

T3C processes ##OVERRIDE## directives in the remap.config file.

The ##OVERRIDE## template string allows the Delivery Service Raw Remap Text field to override to fully override the Delivery Service’s line in the remap.config ATS configuration file, generated by Traffic Ops. The end result is the original, generated line commented out, prepended with ##OVERRIDDEN## and the ##OVERRIDE## rule is activated in its place. This behavior is used to incrementally deploy plugins used in this configuration file. Normally, this entails cloning the Delivery Service that will have the plugin, ensuring it is assigned to a subset of the cache servers that serve the Delivery Service content, then using this ##OVERRIDE## rule to create a remap.config rule that will use the plugin, overriding the normal rule. Simply grow the subset over time at the desired rate to slowly deploy the plugin. When it encompasses all cache servers that serve the original Delivery Service’s content, the “override Delivery Service” can be deleted and the original can use a non-##OVERRIDE## Raw Remap Text to add the plugin.

50-ats.rules

This is presumed to be a udev file for devices which are block devices to be used as disk storage by ATS.

T3C verifies all devices in the file are owned by the owner listed in the file, and logs errors otherwise.

T3C verifies all devices in the file do not have filesystems. If any device has a filesystem, T3C assumes it was a mistake to assign as an ATS storage device, and logs a fatal error.

Trivia

T3C stands for “TrafficOps Cache Control and Configuration.”, 3 C's.