Merge branch 'main' of https://github.com/flowerinthenight/hedge

README.md

@@ -3,35 +3,35 @@
 [![Go Reference](https://pkg.go.dev/badge/github.com/flowerinthenight/hedge.svg)](https://pkg.go.dev/github.com/flowerinthenight/hedge)
 
 ## hedge
-A library built on top of [`spindle`](https://github.com/flowerinthenight/spindle) and [Cloud Spanner](https://cloud.google.com/spanner) that provides rudimentary distributed computing facilities to Kubernetes [Deployments](https://kubernetes.io/docs/concepts/workloads/controllers/deployment/). Features include a consistent, append-only, Spanner-backed distributed key/value storage, a distributed locking/leader election mechanism through `spindle`, a simple member-to-leader communication channel, a broadcast (send-to-all) mechanism, and a distributed semaphore. It also works even on single-pod deployments.
+A library built on top of [spindle](https://github.com/flowerinthenight/spindle) and [Cloud Spanner](https://cloud.google.com/spanner) that provides rudimentary distributed computing facilities to Kubernetes [Deployments](https://kubernetes.io/docs/concepts/workloads/controllers/deployment/). Features include a consistent, append-only, Spanner-backed distributed key/value storage, a distributed locking/leader election mechanism through spindle, a simple member-to-leader communication channel, a broadcast (send-to-all) mechanism, and a distributed semaphore. It also works even on single-pod deployments.
 
 <p align="center">
   <img src="./assets/hedge.png" width="560" title="hedge">
 </p>
 
-At the moment, `hedge` is heavily used in [Alphaus](https://www.alphaus.cloud/) production with services that scale from single digit pods to hundreds.
+At the moment, **hedge** is heavily used in [Alphaus](https://www.alphaus.cloud/) production with services that scale from single digit pods to hundreds.
 
 ## Why?
-First, I wanted a cluster coordinator that can work within k8s Deployments as a library, not as an external service (like [ZooKeeper](https://zookeeper.apache.org/)). So far, our efforts in making [Raft](https://raft.github.io/) play well with bursty, frequently scaling up/down deployments as a library is not that reliable yet (though we have an ongoing multi-[Paxos](https://en.wikipedia.org/wiki/Paxos_(computer_science))-based experiment [here](https://github.com/alphauslabs/juno) as well). I also wanted an easily-accessible storage that is a bit decoupled from the code (easier to query, edit, debug, backup, etc). We are already a heavy Spanner user, and `spindle` has been in our production for many years now: these two should be able to do it; StatefulSets or DaemonSets shouldn't be a requirement. Since then, additional features have been added, such as the `Send()` API.
+First, I wanted a cluster coordinator that can work within k8s Deployments as a library, not as an external service (like [ZooKeeper](https://zookeeper.apache.org/)). So far, our efforts in making [Raft](https://raft.github.io/) play well with bursty, frequently scaling up/down deployments as a library is not that reliable yet (though we have an ongoing multi-[Paxos](https://en.wikipedia.org/wiki/Paxos_(computer_science))-based experiment [here](https://github.com/alphauslabs/juno) as well). I also wanted an easily-accessible storage that is a bit decoupled from the code (easier to query, edit, debug, backup, etc). We are already a heavy Spanner user, and spindle has been in our production for many years now: these two should be able to do it; StatefulSets or DaemonSets shouldn't be a requirement. Since then, additional features have been added, such as the `Send()` API.
 
 ## What does it do?
-Leader election is handled by [`spindle`](https://github.com/flowerinthenight/spindle). Two APIs are provided for storage: `Put()` and `Get()`. All pods can serve the `Get()` calls, while only the leader handles the `Put()` API. If a non-leader pod calls `Put()`, that call is forwarded to the leader, who will do the actual write. All `Put()`'s are append-only.
+Leader election is handled by [spindle](https://github.com/flowerinthenight/spindle). Two APIs are provided for storage: `Put()` and `Get()`. All pods can serve the `Get()` calls, while only the leader handles the `Put()` API. If a non-leader pod calls `Put()`, that call is forwarded to the leader, who will do the actual write. All `Put()`'s are append-only.
 
-`spindle`'s `HasLock()` function is also available for distributed locking due to struct embedding, although you can use `spindle` separately for that, if you prefer.
+Spindle's `HasLock()` function is also available for distributed locking due to struct embedding, although you can use spindle separately for that, if you prefer.
 
 A `Send()` API is also provided for members to be able to send simple request/reply-type messages to the current leader at any time. A streaming equivalent (gRPC) is also available.
 
-A `Broadcast()` API is also available for all pods. Note that due to the nature of k8s deployments (pods come and go) and the internal heartbeat delays, some pods might not receive the broadcast message at call time, although all pods will have the complete broadcast target list eventually. `hedge` uses a combination of heartbeats and broadcasts to propagate member information to all pods; non-leaders send liveness heartbeats to the leader while the leader broadcasts active members to all pods. A streaming equivalent (gRPC) is also available.
+A `Broadcast()` API is also available for all pods. Note that due to the nature of k8s deployments (pods come and go) and the internal heartbeat delays, some pods might not receive the broadcast message at call time, although all pods will have the complete broadcast target list eventually. Hedge uses a combination of heartbeats and broadcasts to propagate member information to all pods; non-leaders send liveness heartbeats to the leader while the leader broadcasts active members to all pods. A streaming equivalent (gRPC) is also available.
 
-An experimental linked storage is also supported. It's currently used in bursty, quick load-process-discard type of data processing. A linked storage is simply a combined memory area and a disk area between pods. For example, a pod can define a linked storage of 1GB memory and 1GB disk. If there are 100 pods running under `hedge`, that's a combined storage of (1GB + 1GB) * 100. During writes, `hedge` handles the data distribution between local RAM, disk, and between pods.
+An experimental linked storage is also supported. It's currently used in bursty, quick load-process-discard type of data processing. A linked storage in hedge is simply a combined memory area and a disk area between pods. For example, a pod can define a linked storage of 1GB memory and 1GB disk. If there are 100 pods running under hedge, that's a combined storage of (1GB + 1GB) * 100. During writes, hedge handles the data distribution between local RAM, disk, and between pods.
 
 Finally, a distributed semaphore is also provided through the `NewSemaphore()`, `[Try]Acquire()`, and `Release()` APIs.
 
 ## Prerequisites
 * All pods within the group should be able to contact each other via TCP (address:port).
-* Each `hedge`'s instance id should be set using the pod's cluster IP address:port. You can use [downward API](https://kubernetes.io/docs/concepts/workloads/pods/downward-api/) to get the pod's IP address, or you can use the ":port" format in which case the IP address will be resolved internally.
-* For now, `spindle`'s lock table and `hedge`'s log table are within the same database.
-* Tables for `spindle` and `hedge` need to be created beforehand. See [here](https://github.com/flowerinthenight/spindle#usage) for `spindle`'s DDL. For `hedge`, see below:
+* Each hedge's instance id should be set using the pod's cluster IP address:port. You can use [downward API](https://kubernetes.io/docs/concepts/workloads/pods/downward-api/) to get the pod's IP address, or you can use the ":port" format in which case the IP address will be resolved internally.
+* For now, spindle's lock table and hedge's log table are within the same database.
+* Tables for spindle and hedge need to be created beforehand. See [here](https://github.com/flowerinthenight/spindle#usage) for spindle's DDL. For hedge, see below:
 
 ```sql
 -- 'logtable' name is just an example