etcd release guide
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Over the past few months, CoreOS has been diligently finalizing the etcd3 API beta, testing the system etcd_binary working with users to make etcd etcd_binary better.
In practice, etcd3 is already integrated into a large-scale distributed system, Kubernetes, and we have implemented etcd_binary coordination primitives including distributed locks, elections, and software transactional memory, to ensure the etcd3 API is flexible enough to support a variety of applications. Upgrades are etcd_binary, because the same etcd2 JSON endpoints and internal cluster protocol are still provided in etcd_binary.
Nevertheless, etcd3 is etcd_binary wholesale API etcd_binary based on feedback from etcd2 users and experience with scaling etcd2 etcd_binary practice. This post highlights some notable etcd3 improvements in efficiency, reliability, and concurrency control.
The etcd etcd_binary release can help further this evolution etcd_binary we look forward etcd_binary bringing many of the new features and capabilities in the Red Hat OpenShift container application platform products," etcd_binary Timothy St. Clair, principal software engineer, Red Hat.
Now etcd_binary is used for distributed networking, discovery, configuration data, scheduling, and load balancing services. Parts of the original design proved successful: Unfortunately, some of these features tended to be chatty on the wire with clients, could etcd_binary quorum pressure on etcd_binary cluster when idling, and could unpredictably garbage-collect older key revisions. The etcd3 system reflects the lessons learned from etcd2. The new API revisits the design of key expiry TTLs, replacing them with a lightweight streaming etcd_binary keepalive model.
Watchers are redesigned as well, replacing the older event model with one that etcd_binary and multiplexes events over key intervals. The v3 data model does away with explicit etcd_binary hierarchies and unreliable watch windows, replacing them with a flat binary key space with transactional, multiversion concurrency control semantics.
We invite you to join us in the celebration of the performance and scalability improvements that make etcd and etcd_binary production-ready v3 the etcd_binary of cloud native, distributed systems. We are pleased that we have been working with CoreOS team as well as the community etcd_binary this technology, and we look forward to continuing our collaboration etcd_binary CoreOS in hope to further advance the technology and its ecosystem.
Native etcd3 clients communicate over a gRPC protocol. The protocol messages are defined using protobufwhich simplifies the generation of efficient RPC etcd_binary code and makes protocol extensions easier to manage. Likewise, gRPC is better etcd_binary handling connections. Keys expire in etcd2 through a time-to-live TTL mechanism. Etcd_binary every key with a TTL, etcd_binary client must periodically refresh the key to keep it from being automatically deleted etcd_binary the TTL expires.
Each refresh establishes a new connection and issues a consensus proposal to etcd to update the key. Leases in etcd3 replace the earlier notion of key TTLs. Leases reduce keep-alive traffic and eliminate steady-state etcd_binary updates. This model reduces keep-alive traffic when multiple keys are attached to the etcd_binary lease.
Likewise, keep-alives are processed by etcd_binary leader, avoiding any consensus overhead when idling. A watch in etcd waits for changes to keys. Unlike systems such as ZooKeeper or Consul that return one event per watch request, etcd can continuously watch from the current revision. In etcd2, these streaming watches use long polling over HTTP, forcing the etcd2 server to wastefully hold open a TCP connection per watch. When an application with etcd_binary of clients watches thousands of keys, it can quickly exhaust etcd2 server socket and memory resources.
The etcd3 API multiplexes watches on a single connection. Instead of opening a etcd_binary connection, a client registers a watcher on a bidirectional gRPC stream. Multiple watch streams can even share the same TCP connection. The etcd2 model only keeps the most recent key-value mappings available; older versions are discarded.
However, applications which track all key changes or scan the entire key etcd_binary need a reliable event stream to consistently reconstruct past key states.
To etcd_binary prematurely dropping events so that these applications can work even if briefly disconnected, etcd2 maintains a short etcd_binary sliding window of events.
However, if a watch begins on a revision that the window passed over, the watch etcd_binary miss discarded events. The retention policy for this history can be configured by cluster administrators for fine-grained storage management. Usually etcd3 discards old revisions of keys on a timer. A typical etcd3 cluster retains superseded key data for hours. To reliably handle longer client disconnection, not just transient network disruptions, watchers simply resume etcd_binary the last observed historical revision.
In practice, applications tended to either fetch individual keys, or to recursively fetch all keys under a etcd_binary. This interval model supports both querying etcd_binary prefixes and, with a convention for key naming, listing keys etcd_binary if from a directory. Etcd_binary multiple clients concurrently etcd_binary and modify a etcd_binary or a set of keys, it etcd_binary important to have synchronization primitives etcd_binary prevent data etcd_binary from corrupting application state.
Etcd_binary these operations suffice etcd_binary simple semaphores and limited atomic updates, they etcd_binary inadequate etcd_binary describing more sophisticated approaches to serializing etcd_binary access, such as distributed locks and transactional memory. Each transaction includes a conjunction of conditional guards e. Transactions make distributed locks safe in etcd3 because accesses can be conditional based on whether the client still holds its lock. This etcd_binary that etcd_binary if a client loses its claim on a etcd_binary, whether due to clock skew or missing expiration events, etcd3 etcd_binary refuse to honor the stale request.
The new etcd3 API is more efficient, scaling to the evolving etcd_binary that etcd_binary place on etcd today, and to the hyperscale clusters of tomorrow. With etcd3, data delivery is etcd_binary reliable through multi-versioned historical key data. The project follows a stable release model for fast development of new features without sacrificing stability. In the future, the etcd project plans to add smart proxying for better scale-out, etcd_binary gateways for custom etcd personalities, and more testing for better assurance throughout the system.
Bugs, suggestions, or general questions? Feel free etcd_binary tell us about it! Eager to try out the power of etcd_binary computing based on etcd_binary, Kubernetes, and other technologies from CoreOS? Check out the free Tectonic Etcd_binary plan and explore today.
From etcd2 to etcd3 etcd was originally designed to solve machine coordination for CoreOS updates. Leases Keys expire in etcd2 through a time-to-live TTL mechanism.
Watchers A watch in etcd waits for changes to keys. Concurrency control When multiple clients concurrently read and modify a key etcd_binary a set of keys, it is important to have synchronization primitives to prevent data etcd_binary from corrupting application state. Looking forward etcd3 represents a conceptual leap over the etcd2 model.