Service discovery tool
pip install empusa==0.0.3
Empusa is a trivial tool to build a service registry on top of etcd. etcd alone serves as a key/value store, while empusa handles the keys, their structure, and values to implement the functionality of a trivial service registry.
Main command, empusa, provides several subcommands, dedicated to different aspects of the service registry operation.
$ empusa --help
Usage: empusa [OPTIONS] COMMAND [ARGS]...
Options:
--etcd-endpoint HOST:PORT [required]
--etcd-protocol TEXT
--tree-root TEXT [required]
--help Show this message and exit.
Commands:
serviceTwo bits of information are always required:
etcd endpoint - host and port where etcd listens for client connections. Use --etcd-endpoint command-line option, or EMPUSA_ETCD_ENDPOINT environment variable.
|
Note
|
At this moment, only the first |
tree root - path in the key hierarchy under which empusa would store it’s data. empusa --tree-root /foo will not read nor modify data empusa --tree-root /bar created. Use --tree-root command-line option, or EMPUSA_TREE_ROOT environment variable.
Services come in different types, e.g. HTTP server, SMTP server, Prometheus exporter, internal directory service, and so on. Of each type, usualy multiple instances exist, each having a different name and location. emposa treats service types as directories to which each instance, identified by its name, is added together with its location.
To register a service, execute following command:
$ empusa service register --service-type type-of-service --service-name name-of-the-service-instance --service-location baz:1235It is possible to use environment variables instead of command-line options:
$ EMPUSA_SERVICE_TYPE=type-of-service \
EMPUSA_SERVICE_NAME=name-of-the-service-instance \
EMPUSA_SERVICE_LOCATION=baz:1235 \
empusa service registerThe service can be unregistered as well:
$ empusa service unregister --service-type type-of-service --service-name name-of-the-service-instanceA service remains registered until explicitly removed. This may not be always possible, e.g. sometimes the services dies without any chance to perform teardown actions including update to the service registry. To help with this situation, a TTL can be set during registration, in seconds. After that time, the service is removed from the registry.
$ empusa service register ... --ttl 30The service must then periodicaly update the registry, updating its record and extending the TTL before it expires. You can either have your own scripts to perform this, or you can use empusa’s `--refresh-every option:
$ empusa service register ... --ttl 30 --refresh-every 20Every 20 seconds, empusa would update the registry, setting the TTL to 30 seconds. Should the service die unexpectedly, empusa would not have an opportunity to prolong the TTL, and etcd would remove service’s key.
start an etcd instance in Docker container:
$ docker run --rm \
-p 2379:2379 \
-p 2380:2380 \
--volume /tmp/etcd-data.tmp:/etcd-data:Z \
--name etcd-gcr-v3.3.18 \
gcr.io/etcd-development/etcd:v3.3.18 \
/usr/local/bin/etcd \
--name s1 \
--data-dir /etcd-data \
--listen-client-urls http://0.0.0.0:2379 \
--advertise-client-urls http://0.0.0.0:2379 \
--listen-peer-urls http://0.0.0.0:2380 \
--initial-advertise-peer-urls http://0.0.0.0:2380 \
--initial-cluster s1=http://0.0.0.0:2380 \
--initial-cluster-token tknset variables telling empusa where to find etcd:
$ export EMPUSA_TREE_ROOT=/foo
$ EMPUSA_ETCD_ENDPOINT=localhost:2379register a service:
$ empusa service register --service-type dummy-type \
--service-name dummy-service-1 \
--service-location baz:1235
INFO:root:service dummy-service-1 (dummy-type) registeredlist registered services:
$ empusa service list --service-type dummy-type
+----------------------------+------------+-------+
| Service | Location | TTL |
|----------------------------+------------+-------|
| dummy-type/dummy-service-1 | baz:1235 | |
+----------------------------+------------+-------+unregister the service:
$ empusa service unregister --service-type dummy-type \
--service-name dummy-service-1
INFO:root:service dummy-service-1 (dummy-type) unregisteredlist registered services:
$ empusa service list --service-type dummy-type
+-------------------------+------------+-------+
| Service | Location | TTL |
|-------------------------+------------+-------|
+-------------------------+------------+-------+service list can emit the services in JSON format instead of the table, that should be easier to process by other utilities:
$ empusa service list --service-type dummy-type --format json | jq
[
{
"service": "/foo/service/dummy-type/dummy-service-1",
"location": "baz:1235",
"ttl": null
}
]set (feature) switch:
$ empusa switch set features/super-cool-feature enabled
INFO:root:switch features/super-cool-feature set to enabledlist switches:
$ empusa switch list
+-----------------------------+----------+-------+
| Switch | Value | TTL |
|-----------------------------+----------+-------|
| features/super-cool-feature | enabled | |
+-----------------------------+----------+-------+toggle the switch:
$ empusa switch toggle feature/super-cool-feature
INFO:root:switch feature/super-cool-feature set to noAgain, switch list can emit the list of switches in JSON format instead of the table.
The Tidelift Subscription provides access to a continuously curated stream of human-researched and maintainer-verified data on open source packages and their licenses, releases, vulnerabilities, and development practices.
Learn more →Something wrong with this page? Make a suggestion
Export .ABOUT file for this package
Last synced: 2021-02-15 02:34:03 UTC
Login to resync this project