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diff --git a/src/_posts/2021-07-18-radix-v4.md b/src/_posts/2021-07-18-radix-v4.md deleted file mode 100644 index bb0d04d..0000000 --- a/src/_posts/2021-07-18-radix-v4.md +++ /dev/null @@ -1,248 +0,0 @@ ---- -title: >- - V4 of Radix, a Golang Redis Driver -description: >- - What's new, what's improved, and where we're going from here. -tags: tech ---- - -Radix is a Go driver for the [Redis][redis] database. The current stable release -is v3, the docs for which can be found [here][v3]. Over the past year -(perhaps longer) I've been working on a new version, v4, with the aim of -addressing some of the shortcomings of v3 and distilling the API a bit better. - -At this point v4 is in beta. While there's still some internal bugs and QoL -improvements which need to be made, the API is roughly stable and I wouldn't -discourage anyone from using it for a non-critical project. In the coming months -I intend on finishing the polish and tagging a `v4.0.0` release, but in the -meantime let's go over the major changes and improvements in v4! - -You can see the v4 documentation [here][v4], if you'd like to follow along with -any of the particulars, and you can see the full CHANGELOG [here][changelog]. - -## Shoutouts - -Before continuing I want to give to give a huge shoutout to -[nussjustin][nussjustin]. Since before v3 was even stable Justin has been -contributing to radix in every way possible, from running benchmarks and making -very low-level performance improvements to building whole user-facing features -and responding to github issues when I get lost in the woods. Thank you Justin! - -## RESP3 - -Starting at the lowest level, v4 supports new redis's new wire protocol, -[RESP3][resp3]. This new protocol is (mostly) backwards compatible with the -previous wire protocol, and is really more an extension than anything. The [new -resp3 sub-package][resp3pkg] is capable of marshaling and unmarshaling all new -wire types, including the streamed aggregates and streamed strings. - -A major improvement made on the API level is addition of the -[resp.Opts][respOpts] type, which is used to propagate things like byte buffers -and buffered readers. Doing this allows the resp3 package to reduce memory -allocations without relying on something like `sync.Pool`, which introduces -locking overhead. - -There's still some question to be answered regarding the best way for the main -radix package to deal with the new push and attribute types, but the resp3 -package is general-purpose enough to handle most strategies in the future. - -In fact, the RESP3 protocol as a whole (and therefore v4's associated resp3 -sub-package) is totally usable outside of redis. If you're looking for a -human-readable, binary safe, fast, and simple wire protocol which already has -great tooling and libraries across multiple programming languages, I highly -recommend checking out RESP3. - -## Conn - -Arguably one of the biggest design warts of v3, in my eyes, is the -[CmdAction][cmdaction] type. This type required to allow for pipelining, which -is a feature of redis where you can write new commands to a redis connection -prior to previous ones returning their results. The major upside of pipelining -is that N pipelined commands will only result in 2 system calls (a network write -then a network read), rather than 2N system calls (N writes and N reads) if each -command was performed independently. - -The normal v3 Action type is fairly opaque, and would perform both the write and -read internally without exposing any way to do some other action in between -(such as performing writes/reads for other commands in a pipeline). CmdAction -extends Action to allow the write and read to be performed independently, and -then leaves it to the Pipeline type to deal with the batching. - -v4 gets rid of the need for CmdAction, while allowing even more Action types to -be pipeline-able than before (e.g. [EvalScript][evalscript]). This was done by -coalescing the Encode and Decode methods on the [Conn][conn] type into a single -method: EncodeDecode. By doing this we allow Actions to perform the write/read -steps in a way which groups the two together, but leaves it to Conn to actually -perform the steps in its own way. - -Because Conn now has knowledge of which read/write steps go together, it's -possible to perform pipelining in nearly all cases. Aside from using the -Pipeline type manually, the v4 Conn is able to automatically pipeline most -Actions when they are performed concurrently on the same Conn. v3 had a similar -feature, called "implicit pipelining", but v4 rebrands the feature as -"connection sharing" since the mechanism is slightly different and the -applicability is broader. - -Despite the apparent simplicity of the change (combining Encode and Decode -methods), this resulted in probably the largest code difference between v3 and -v4, involving the most complex new logic and package-wide refactorings. But the -end result is a simpler, smaller API which can be applied to more use-cases. A -great win! - -## Pool - -In v3 the connection pool, the Pool type, was implemented with the assumption -that each Action (or CmdAction) would borrow a Conn for the duration of the -Action. As such the Pool expects to be creating and destroying connections as -load increases and decreases; if number of concurrent commands goes up then -number of connections required to handle them goes up as well, and vice-versa. - -Down the road the Pool became responsible for performing implicit pipelining as -well. This allowed for grouping together many commands on the same connection, -reducing pressure on connection creation greatly, but nevertheless the Pool kept -that same general pattern of dynamic connection pool sizing. - -In v4 there is no longer the assumption that each command gets its own -connection, and in fact that assumption is flipped: each connection is expected -to handle multiple commands concurrently in almost all cases. This means the -Pool can get rid of the dynamism, and opt instead for a simple static connection -pool size. There is still room in the API for some dynamic connection sizing to -be implemented later, but it's mostly unnecessary now. - -Some care should be used with commands which _can't_ be pipelined, for example -blocking commands like BRPOPLPUSH and XREAD. These commands, ideally, should be -performed on an individual Conn created just for that purpose. Pool _will_ -properly handle them if needed, but with the caveat that the Action which will -essentially remove a Conn from the Pool for its duration. - -[The new Pool][pool] is _vastly_ simpler in implementation than the old, as most -of the complexity has been moved into Conn. Really this whole section is an -extension of the refactoring which was started by the changes to Conn. - -## MultiClient - -In v3 there was a single Client type which was used to encompass Conn, Pool, -Sentinel, and Cluster, with the aim that users could just use Client in their -code and easily swap out the underlying implementation as needed. - -In practice this didn't work out. The original Client type only had a Do method -for performing Actions, which would always perform the Actions against the -primary instance in the case of Cluster and Sentinel. Cluster and Sentinel ended -up being extended with DoSecondary methods, and Cluster required its own -constructor for Scanner, so if you used any of those features you would not be -able to use Client. - -v4 improves this situation by introducing the [MultiClient][multiclient] -interface, which is implemented by both Cluster and Sentinel, while Conn and -Pool only implement [Client][client]. Client is intended for clients which -interact with only a single redis instance, while MultiClient is intended for -use by clients which encompass multiple redis instances, and makes the -distinction between primary and secondary instances. - -In general, users will want to use MultiClient in their code and swap the -underlying implementation as their infrastructure evolves. When using only a -single Pool, one can make it into a MultiClient using the new -[ReplicaSet][replicaset]. - -One can also implement their own MultiClient's fairly easily, to handle their -own custom sharding or failover systems. It's not a common use-case, but it's -cool that existing types like Scanner will still continue to work. - -## Contexts - -A common feature request of v3 was for support for Go's [Contexts][context], -which would allow callers to unblock blocked operations in a dynamic way. There -wasn't a clear way to incorporate Contexts into v3 without greatly expanding the -API (something the Go standard library has had to do), and so I saved them for -v4. - -In v4 all operations which might potentially block accept a Context argument. -This takes the place of timeout options and some trace events which were used in -v3, and in general simplifies things for the user. - -This was a change for which there is not much to talk about, but which required -a _lot_ of work internally. Go's Contexts do not play nicely with its networking -primitives, and making this all work alongside connection sharing and pipelining -is a really hairy puzzle (for which there's a few open bugs still). I may one -day write a blog post just about this topic, if I can figure out how to explain -it in a way which isn't completely mind-numbing. - -## Configuration - -Constructors in v3 took advantage of the [functional options pattern][opts] for -accepting optional parameters. While this pattern _looks_ nice, I've since -grown out of love with it. The implementation is a lot more complex, its -behavior is more ambiguous to users in certain cases (what happens if the same -option is passed in twice?), it makes documentation more complex, and a slice of -option functions isn't inspectable or serializable like a struct is. - -v4 uses a config struct pattern, but in a different way than I've generally seen -it. See [Pool's constructor][pool] for an example. This pattern is functionally -the same as passing the config struct as an argument to the constructor, but I -think it results in a nicer grouping in the documentation. - -## Smaller Changes - -There's some smaller sets of changes which are worth mentioning. These didn't -result in huge, package-wide changes, but will be useful for users of specific -functionality. - -### Action Properties - -[v4's Action type][action] has a Properties method which returns a struct -containing various fields which are useful for client's performing the Action. -This is an improvement over v3's Action, which had no such method, in that it's -more extensible going forward. Those implementing their own custom Actions -should take care to understand the Action properties. - -### PubSub - -The v4 [PubSubConn][pubsub] has been completely redesigned from v3's -implementation. The old design tried to do too much, and resulted in weird -edge-cases when trying to tear down a connection that a user would have to -handle themselves. The new design is simple both in implementation and usage. - -### Tracing - -The v4 [trace][trace] sub-package has been extended to support tracing Sentinel -events, but at the same time has been cleaned out of all events which could be -otherwise inferred by using Context values or wrapping an interface like Conn, -Action, etc... - -## What's Next - -Obviously the most immediate goal is to get v4 stable and tagged. Once that's -done I'm sure there will be many small bugs, feature requests, etc... which come -up over time, and I'll do my best to address those as quickly as I can. I'm -very excited to start using v4 in my own day-to-day work like I currently do for -v3; it has a lot of great improvements and new flexibility that will make using -Go and redis together an even better experience than it already is. - -That all said, I don't expect there to be a radix v5. I have a lot of other -projects I'd like to work on, and radix is a huge time-sink. As time goes on v4 -will stabilize further and further, until all that's left is for it to gain -additional support for whatever new crazy features redis comes up with. My hope -is that the existing API is flexibile enough to allow others to fill in those -gaps without any major changes to the existing code, and radix v4 can be the -final major radix version. - -[redis]: https://redis.io -[v3]: https://pkg.go.dev/github.com/mediocregopher/radix/v3#section-documentation -[v4]: https://pkg.go.dev/github.com/mediocregopher/radix/v4#section-documentation -[nussjustin]: https://github.com/nussjustin -[resp3]: https://github.com/antirez/RESP3 -[resp3pkg]: https://pkg.go.dev/github.com/mediocregopher/radix/v4/resp/resp3 -[respOpts]: https://pkg.go.dev/github.com/mediocregopher/radix/v4/resp#Opts -[changelog]: https://github.com/mediocregopher/radix/blob/v4/CHANGELOG.md -[cmdaction]: https://pkg.go.dev/github.com/mediocregopher/radix/v3#CmdAction -[evalscript]: https://pkg.go.dev/github.com/mediocregopher/radix/v4#EvalScript -[conn]: https://pkg.go.dev/github.com/mediocregopher/radix/v4#Conn -[pool]: https://pkg.go.dev/github.com/mediocregopher/radix/v4#PoolConfig.New -[multiclient]: https://pkg.go.dev/github.com/mediocregopher/radix/v4#MultiClient -[client]: https://pkg.go.dev/github.com/mediocregopher/radix/v4#Client -[replicaset]: https://pkg.go.dev/github.com/mediocregopher/radix/v4#ReplicaSet -[context]: https://blog.golang.org/context -[opts]: https://dave.cheney.net/2014/10/17/functional-options-for-friendly-apis -[action]: https://pkg.go.dev/github.com/mediocregopher/radix/v4#Action -[pubsub]: https://pkg.go.dev/github.com/mediocregopher/radix/v4#PubSubConn -[trace]: https://pkg.go.dev/github.com/mediocregopher/radix/v4/trace |