Consul Template Generator
Consul-Template is an immensely valuable tool
for translating services registered with Consul into
system configurations. One potential pitfall with it, though, is the potential for large,
distributed systems to DDoS their Consul
cluster. This work can be mitigated to some degree with carefully crafted templates, but can
also be avoided by the use of consul-template-generator
The function of consul-template-generator is to delegate template generation to a single process
in a fault-tolerant fashion. The consul-template-generator "master" takes a consul lock on a
specified session K/V store key to allow redundant deployments of any given configuration to be
active simultaneously. A given consul-template-generator configuration can include an arbitrary
number ctmpl files which will be evaluated using consul-template. When updates to a ctmpl
are found consul-template-generator will update specified keys in Consul's K/V store with the
consul-template rendered templates. This allows downstream instances of consul-template to
watch a single key in Consul K/V instead of multiple Consul registered services, thus reducing
the load on the underlying Consul cluster significantly.
Usage
consul-template-generator <command> [options]
Commands
| Command | Description |
|---|---|
| once | Run once and exit. On success, the rendered template will be inserted into the KV store whether or not it has changed. |
| run | Run continually, uploading the rendered template when a change is detected. |
Options
| required | short flag | long flag | Description |
|---|---|---|---|
| No | -c HOSTNAME |
--consul HOSTNAME |
Hostname/port used to connect to consul [default: 127.0.0.1:8500] |
| Yes | -t TEMPLATES |
--templates TEMPLATES |
(required) Comma separated list of consul-template ctmpl file and keys to monitor, tmple.ctmpl:tmple-key,tmple2.ctmpl:templ-key2. If --graphite-host is supplied, target graphite path must also be supplied, e.g. tmple.ctmpl:tmple-key:consul.template.<HOSTNAME>.<template name>. |
| No | -s SESSION_KEY |
--session-key SESSION_KEY |
Key used to lock template generation session [default: consul-template-generator] |
| No | --session-ttl SESSION_TTL |
Set a TTL for consul sessions (sets an implicit ttl on locks created by consul-template-generator [default: 30s] | |
| No | --unset-proxy |
Use if 'http_proxy' is set in your environment, but you don't want to use it... | |
| No | --diff-changes |
Log diff'ed template prior to upload | |
| No | -l |
--log-level LOG_LEVEL |
Log level, options are 'debug', 'info', 'error' [default: info] |
| No | --cycle-sleep CYCLE_SLEEP |
Sleep interval in seconds between each template rendering [default: 0.5] | |
| No | --lock-sleep LOCK_SLEEP |
Sleep interval in seconds between each attempt to obtain a session lock [default: 1.0] | |
| No | -g GRAPHITE_HOST |
--graphite-host GRAPHITE_HOST |
Graphite host to post template update events to (optional) |