9018b3dc4d
It turns out that that learners must be allowed to cast votes.
This seems counter- intuitive but is necessary in the situation in which
a learner has been promoted (i.e. is now a voter) but has not learned
about this yet.
For example, consider a group in which id=1 is a learner and id=2 and
id=3 are voters. A configuration change promoting 1 can be committed on
the quorum `{2,3}` without the config change being appended to the
learner's log. If the leader (say 2) fails, there are de facto two
voters remaining. Only 3 can win an election (due to its log containing
all committed entries), but to do so it will need 1 to vote. But 1
considers itself a learner and will continue to do so until 3 has
stepped up as leader, replicates the conf change to 1, and 1 applies it.
Ultimately, by receiving a request to vote, the learner realizes that
the candidate believes it to be a voter, and that it should act
accordingly. The candidate's config may be stale, too; but in that case
it won't win the election, at least in the absence of the bug discussed
in:
https://github.com/etcd-io/etcd/issues/7625#issuecomment-488798263.
etcd
Note: The master branch may be in an unstable or even broken state during development. Please use releases instead of the master branch in order to get stable binaries.
etcd is a distributed reliable key-value store for the most critical data of a distributed system, with a focus on being:
- Simple: well-defined, user-facing API (gRPC)
- Secure: automatic TLS with optional client cert authentication
- Fast: benchmarked 10,000 writes/sec
- Reliable: properly distributed using Raft
etcd is written in Go and uses the Raft consensus algorithm to manage a highly-available replicated log.
etcd is used in production by many companies, and the development team stands behind it in critical deployment scenarios, where etcd is frequently teamed with applications such as Kubernetes, locksmith, vulcand, Doorman, and many others. Reliability is further ensured by rigorous testing.
See etcdctl for a simple command line client.
Community meetings
Community meeting will resume at 11:00 am on Thursday, January 10th, 2019.
etcd contributors and maintainers have monthly (every four weeks) meetings at 11:00 AM (USA Pacific) on Thursday.
An initial agenda will be posted to the shared Google docs a day before each meeting, and everyone is welcome to suggest additional topics or other agendas.
Please download and import the following iCalendar (.ics) files to calendar system.
Join Zoom Meeting https://zoom.us/j/916003437
One tap mobile
+14086380986,,916003437# US (San Jose)
+16465588665,,916003437# US (New York)
Dial by location
+1 408 638 0986 US (San Jose)
+1 646 558 8665 US (New York)
Meeting ID: 916 003 437
To Find local number: https://zoom.us/u/actX55uPfS
Getting started
Getting etcd
The easiest way to get etcd is to use one of the pre-built release binaries which are available for OSX, Linux, Windows, and Docker on the release page.
For more installation guides, please check out play.etcd.io and operating etcd.
For those wanting to try the very latest version, build the latest version of etcd from the master branch. This first needs Go installed (version 1.12+ is required). All development occurs on master, including new features and bug fixes. Bug fixes are first targeted at master and subsequently ported to release branches, as described in the branch management guide.
Running etcd
First start a single-member cluster of etcd.
If etcd is installed using the pre-built release binaries, run it from the installation location as below:
/tmp/etcd-download-test/etcd
The etcd command can be simply run as such if it is moved to the system path as below:
mv /tmp/etcd-download-test/etcd /usr/local/bin/
etcd
If etcd is built from the master branch, run it as below:
./bin/etcd
This will bring up etcd listening on port 2379 for client communication and on port 2380 for server-to-server communication.
Next, let's set a single key, and then retrieve it:
etcdctl put mykey "this is awesome"
etcdctl get mykey
etcd is now running and serving client requests. For more, please check out:
etcd TCP ports
The official etcd ports are 2379 for client requests, and 2380 for peer communication.
Running a local etcd cluster
First install goreman, which manages Procfile-based applications.
Our Procfile script will set up a local example cluster. Start it with:
goreman start
This will bring up 3 etcd members infra1, infra2 and infra3 and etcd grpc-proxy, which runs locally and composes a cluster.
Every cluster member and proxy accepts key value reads and key value writes.
Next steps
Now it's time to dig into the full etcd API and other guides.
- Read the full documentation.
- Explore the full gRPC API.
- Set up a multi-machine cluster.
- Learn the config format, env variables and flags.
- Find language bindings and tools.
- Use TLS to secure an etcd cluster.
- Tune etcd.
Contact
- Mailing list: etcd-dev
- IRC: #etcd on freenode.org
- Planning/Roadmap: milestones, roadmap
- Bugs: issues
Contributing
See CONTRIBUTING for details on submitting patches and the contribution workflow.
Reporting bugs
See reporting bugs for details about reporting any issues.
Reporting a security vulnerability
A security vulnerability can be reported as an issue, however, GitHub and mailing lists may NOT always be an appropriate place for reporting vulnerabilities. In that case, please reach out to the project MAINTAINERS to first discuss the vulnerabilities with them and take necessary action per such discussion.
Issue and PR management
See issue triage guidelines for details on how issues are managed.
See PR management for guidelines on how pull requests are managed.
etcd Emeritus Maintainers
These emeritus maintainers dedicated a part of their career to etcd and reviewed code, triaged bugs, and pushed the project forward over a substantial period of time. Their contribution is greatly appreciated.
- Fanmin Shi
- Anthony Romano
License
etcd is under the Apache 2.0 license. See the LICENSE file for details.