franz-go - A complete Apache Kafka client written in Go

Franz-go is an all-encompassing Apache Kafka client fully written Go. This library aims to provide every Kafka feature from Apache Kafka v0.8.0 onward. It has support for transactions, regex topic consuming, the latest partitioning strategies, data loss detection, closest replica fetching, and more. If a client KIP exists, this library aims to support it.

This library attempts to provide an intuitive API while interacting with Kafka the way Kafka expects (timeouts, etc.).

Features

• Feature complete client (Kafka >= 0.8.0 through v3.1+)
• Full Exactly-Once-Semantics (EOS)
• Idempotent & transactional producers
• Simple (legacy) consumer
• Group consumers with eager (roundrobin, range, sticky) and cooperative (cooperative-sticky) balancers
• All compression types supported: gzip, snappy, lz4, zstd
• SSL/TLS provided through custom dialer options
• All SASL mechanisms supported (GSSAPI/Kerberos, PLAIN, SCRAM, and OAUTHBEARER)
• Low-level admin functionality supported through a simple Request function
• High-level admin package with many helper types to make cluster administration easy.
• Utilizes modern & idiomatic Go (support for contexts, variadic configuration options, ...)
• Highly performant by avoiding channels and goroutines where not necessary
• Written in pure Go (no wrapper lib for a C library or other bindings)
• Ability to add detailed log messages or metrics using hooks
• Plug-in metrics support for prometheus, zap, etc.

Works with any Kafka compatible brokers:

• Redpanda: the fastest and most efficient Kafka compatible event streaming platform
• Kafka: the original Java project
• Microsoft Event Hubs
• Amazon MSK

Getting started

Here's a basic overview of producing and consuming:

seeds := []string{"localhost:9092"}
// One client can both produce and consume!
// Consuming can either be direct (no consumer group), or through a group. Below, we use a group.
cl, err := kgo.NewClient(
	kgo.SeedBrokers(seeds...),
	kgo.ConsumerGroup("my-group-identifier"),
	kgo.ConsumeTopics("foo"),
)
if err != nil {
	panic(err)
}
defer cl.Close()

ctx := context.Background()

// 1.) Producing a message
// All record production goes through Produce, and the callback can be used
// to allow for synchronous or asynchronous production.
var wg sync.WaitGroup
wg.Add(1)
record := &kgo.Record{Topic: "foo", Value: []byte("bar")}
cl.Produce(ctx, record, func(_ *kgo.Record, err error) {
	defer wg.Done()
	if err != nil {
		fmt.Printf("record had a produce error: %v\n", err)
	}

})
wg.Wait()

// Alternatively, ProduceSync exists to synchronously produce a batch of records.
if err := cl.ProduceSync(ctx, record).FirstErr(); err != nil {
	fmt.Printf("record had a produce error while synchronously producing: %v\n", err)
}

// 2.) Consuming messages from a topic
for {
	fetches := cl.PollFetches(ctx)
	if errs := fetches.Errors(); len(errs) > 0 {
		// All errors are retried internally when fetching, but non-retriable errors are
		// returned from polls so that users can notice and take action.
		panic(fmt.Sprint(errs))
	}

	// We can iterate through a record iterator...
	iter := fetches.RecordIter()
	for !iter.Done() {
		record := iter.Next()
		fmt.Println(string(record.Value), "from an iterator!")
	}

	// or a callback function.
	fetches.EachPartition(func(p kgo.FetchTopicPartition) {
		for _, record := range p.Records {
			fmt.Println(string(record.Value), "from range inside a callback!")
		}

		// We can even use a second callback!
		p.EachRecord(func(record *kgo.Record) {
			fmt.Println(string(record.Value), "from a second callback!")
		})
	})
}

This only shows producing and consuming in the most basic sense, and does not show the full list of options to customize how the client runs, nor does it show transactional producing / consuming. Check out the examples directory for more!

API reference documentation can be found on . Supplementary information can be found in the docs directory:

docs
├── admin requests — an overview of how to issue admin requests
├── metrics and logging — a small writeup on how to enable metrics & logging in franz-go, as well as a few thoughts on latency tracking
├── package layout — describes the packages in franz-go
├── producing and consuming — descriptions of producing & consuming & the guarantees
└── transactions — a description of transactions and the safety even in a pre-KIP-447 world

Who uses this?

In alphabetical order,

• Alpaca
• Eoitek
• Kowl
• Mux
• Redpanda Data
• Unistack (Cloud Management System)

If you use this library and want on the list above, please either open a PR or comment on #142!

Version Pinning

By default, the client issues an ApiVersions request on connect to brokers and defaults to using the maximum supported version for requests that each broker supports.

Kafka 0.10.0 introduced the ApiVersions request; if you are working with brokers older than that, you must use the kversions package. Use the MaxVersions option for the client if you do so.

As well, it is recommended to set the MaxVersions to the version of your broker cluster. Until KIP-584 is implemented, it is possible that if you do not pin a max version, this client will speak with some features to one broker while not to another when you are in the middle of a broker update roll.

Metrics & logging

Note there exists plug-in packages that allow you to easily add prometheus metrics, go-metrics, zap logging, etc. to your client! See the plugin directory for more information! These plugins are provided under dedicated modules, e.g. github.com/LSparkzwz/franz-go/plugin/kprom@v0.1.0.

The franz-go client takes a neutral approach to metrics by providing hooks that you can use to plug in your own metrics.

All connections, disconnections, reads, writes, and throttles can be hooked into, as well as per-batch produce & consume metrics. If there is an aspect of the library that you wish you could have insight into, please open an issue and we can discuss adding another hook.

Hooks allow you to log in the event of specific errors, or to trace latencies, count bytes, etc., all with your favorite monitoring systems.

In addition to hooks, logging can be plugged in with a general Logger interface. A basic logger is provided if you just want to write to a given file in a simple format. All logs have a message and then key/value pairs of supplementary information. It is recommended to always use a logger and to use LogLevelInfo.

See this example for an expansive example of integrating with prometheus! Alternatively, see this example for how to use the plug-in prometheus package!

Benchmarks

This client is quite fast; it is the fastest and most cpu and memory efficient client in Go.

For 100 byte messages,

• This client is 4x faster at producing than confluent-kafka-go, and up to 10x-20x faster (at the expense of more memory usage) at consuming.

• This client is 2.5x faster at producing than sarama, and 1.5x faster at consuming.

• This client is 2.4x faster at producing than segment's kafka-go, and so much faster at consuming that I'm not sure I wrote the consuming comparison correctly here.

To check benchmarks yourself, see the bench example. This example lets you produce or consume to a cluster and see the byte / record rate. The compare subdirectory shows comparison code.

Supported KIPs

Theoretically, this library supports every (non-Java-specific) client facing KIP. Any KIP that simply adds or modifies a protocol is supported by code generation.

KIP	Kafka release	Status
KIP-1 — Disallow acks > 1	0.8.3	Supported & Enforced
KIP-4 — Request protocol changes	0.9.0 through 0.10.1	Supported
KIP-8 — Flush method on Producer	0.8.3	Supported
KIP-12 — SASL & SSL	0.9.0	Supported
KIP-13 — Throttling (on broker)	0.9.0	Supported
KIP-15 — Close with a timeout	0.9.0	Supported (via context)
KIP-19 — Request timeouts	0.9.0	Supported
KIP-22 — Custom partitioners	0.9.0	Supported
KIP-31 — Relative offsets in message sets	0.10.0	Supported
KIP-32 — Timestamps in message set v1	0.10.0	Supported
KIP-35 — ApiVersion	0.10.0	Supported
KIP-40 — ListGroups and DescribeGroups	0.9.0	Supported
KIP-41 — max.poll.records	0.10.0	Supported (via PollRecords)
KIP-42 — Producer & consumer interceptors	0.10.0	Partial support (hooks)
KIP-43 — SASL PLAIN & handshake	0.10.0	Supported
KIP-48 — Delegation tokens	1.1	Supported
KIP-54 — Sticky partitioning	0.11.0	Supported
KIP-57 — Fix lz4	0.10.0	Supported
KIP-62 — background heartbeats & improvements	0.10.1	Supported
KIP-70 — On{Assigned,Revoked}	0.10.1	Supported
KIP-74 — Fetch response size limits	0.10.1	Supported
KIP-78 — ClusterID in Metadata	0.10.1	Supported
KIP-79 — List offsets for times	0.10.1	Supported
KIP-81 — Bound fetch memory usage	WIP	Supported (through a combo of options)
KIP-82 — Record headers	0.11.0	Supported
KIP-84 — SASL SCRAM	0.10.2	Supported
KIP-86 — SASL Callbacks	0.10.2	Supported (through callback fns)
KIP-88 — OffsetFetch for admins	0.10.2	Supported
KIP-91 — Intuitive producer timeouts	2.1	Supported (as a matter of opinion)
KIP-97 — Backwards compat for old brokers	0.10.2	Supported
KIP-98 — EOS	0.11.0	Supported
KIP-101 — OffsetForLeaderEpoch v0	0.11.0	Supported
KIP-102 — Consumer close timeouts	0.10.2	Supported (via context)
KIP-107 — DeleteRecords	0.11.0	Supported
KIP-108 — CreateTopic validate only field	0.10.2	Supported
KIP-110 — zstd	2.1	Supported
KIP-112 — Broker request protocol changes	1.0	Supported
KIP-113 — LogDir requests	1.0	Supported
KIP-117 — Admin client	0.11.0	Supported (via kmsg)
KIP-124 — Request rate quotas	0.11.0	Supported
KIP-126 — Ensure proper batch size after compression	0.11.0	Supported (avoided entirely)
KIP-133 — Describe & Alter configs	0.11.0	Supported
KIP-140 — ACLs	0.11.0	Supported
KIP-144 — Broker reconnect backoff	0.11.0	Supported
KIP-152 — More SASL; SASLAuthenticate	1.0	Supported
KIP-183 — Elect preferred leaders	2.2	Supported
KIP-185 — Idempotency is default	1.0	Supported
KIP-192 — Cleaner idempotence semantics	1.0	Supported
KIP-195 — CreatePartitions	1.0	Supported
KIP-204 — DeleteRecords via admin API	1.1	Supported
KIP-207 — New error in ListOffsets	2.2	Supported
KIP-219 — Client-side throttling	2.0	Supported
KIP-222 — Group operations via admin API	2.0	Supported
KIP-226 — Describe configs v1	1.1	Supported
KIP-227 — Incremental fetch	1.1	Supported
KIP-229 — DeleteGroups	1.1	Supported
KIP-249 — Delegation tokens in admin API	2.0	Supported
KIP-255 — SASL OAUTHBEARER	2.0	Supported
KIP-266 — Fix indefinite consumer timeouts	2.0	Supported (via context)
KIP-279 — OffsetForLeaderEpoch bump	2.0	Supported
KIP-289 — Default group.id to null	2.2	Supported
KIP-294 — TLS verification	2.0	Supported (via dialer)
KIP-302 — Use multiple addrs for resolved hostnames	2.1	Supported (via dialer)
KIP-320 — Fetcher: detect log truncation	2.1	Supported
KIP-322 — DeleteTopics disabled error code	2.1	Supported
KIP-339 — IncrementalAlterConfigs	2.3	Supported
KIP-341 — Sticky group bugfix	?	Supported
KIP-342 — OAUTHBEARER extensions	2.1	Supported
KIP-345 — Static group membership	2.4	Supported
KIP-357 — List ACLs per principal via admin API	2.1	Supported
KIP-360 — Safe epoch bumping for UNKNOWN_PRODUCER_ID	2.5	Supported
KIP-361 — Allow disable auto topic creation	2.3	Supported
KIP-368 — Periodically reauthenticate SASL	2.2	Supported
KIP-369 — An always round robin produce partitioner	2.4	Supported
KIP-380 — Inter-broker protocol changes	2.2	Supported
KIP-389 — Group max size error	2.2	Supported
KIP-392 — Closest replica fetching w/ rack	2.2	Supported
KIP-394 — Require member.id for initial join request	2.2	Supported
KIP-396 — Commit offsets manually	2.4	Supported
KIP-412 — Dynamic log levels w/ IncrementalAlterConfigs	2.4	Supported
KIP-429 — Incremental rebalance (see KAFKA-8179)	2.4	Supported
KIP-430 — Authorized ops in DescribeGroups	2.3	Supported
KIP-447 — Producer scalability for EOS	2.5	Supported
KIP-455 — Replica reassignment API	2.4	Supported
KIP-460 — Leader election API	2.4	Supported
KIP-464 — CreateTopic defaults	2.4	Supported
KIP-467 — Per-record error codes when producing	2.4	Supported (and ignored)
KIP-480 — Sticky partition producing	2.4	Supported
KIP-482 — Tagged fields (KAFKA-8885)	2.4	Supported
KIP-496 — OffsetDelete admin command	2.4	Supported
KIP-497 — New AlterISR API	2.7	Supported
KIP-498 — Max bound on reads	?	Supported
KIP-511 — Client name/version in ApiVersions request	2.4	Supported
KIP-514 — Bounded Flush	2.4	Supported (via context)
KIP-516 — Topic IDs	???	Supported as it is implemented
KIP-518 — List groups by state	2.6	Supported
KIP-519 — Configurable SSL "engine"	2.6	Supported (via dialer)
KIP-525 — CreateTopics v5 returns configs	2.4	Supported
KIP-526 — Reduce metadata lookups	2.5	Supported
KIP-533 — Default API timeout (total time, not per request)	2.5	Supported (via RetryTimeout)
KIP-546 — Client Quota APIs	2.5	Supported
KIP-554 — Broker side SCRAM APIs	2.7	Supported
KIP-559 — Protocol info in sync/join	2.5	Supported
KIP-568 — Explicit rebalance triggering on the consumer	2.6	Supported
KIP-569 — Docs & type in DescribeConfigs	2.6	Supported
KIP-570 — Leader epoch in StopReplica	2.6	Supported
KIP-580 — Exponential backoff	2.6	Supported
KIP-584 — Versioning scheme for features	?	Supported (nothing to do yet)
KIP-588 — Producer recovery from txn timeout	2.7	Supported
KIP-590 — Envelope (broker only)	2.7	Supported
KIP-595 — New APIs for raft protocol	2.7	Supported
KIP-599 — Throttling on create/delete topic/partition	2.7	Supported
KIP-602 — Use all resolved addrs by default	2.6	Supported (via dialer)
KIP-651 — Support PEM	2.7	Supported (via dialer)
KIP-654 — Aborted txns with unflushed data is not fatal	2.7	Supported (default behavior)
KIP-664 — Describe producers / etc.	2.8 (mostly)	Supported
KIP-679 — Strongest producer guarantee by default	3.0	Supported (by default always)
KIP-699 — Batch FindCoordinators	3.0	Supported
KIP-700 — DescribeCluster	2.8	Supported
KIP-704 — AlterISR => AlterPartition	3.2	Supported
KIP-709 — Batch OffsetFetch	3.0	Supported
KIP-730 - AllocateProducerIDs	3.0	Supported
KIP-734 — Support MaxTimestamp in ListOffsets	3.0	Supported (simple version bump)
KIP-735 — Bump default session timeout	?	Supported
KIP-784 — Add ErrorCode to DescribeLogDirs response	3.1	Supported
KIP-800 — Reason in Join/Leave group	3.1	Supported
KIP-814 — SkipAssignment for static group leaders	3.1	Supported

Missing from above but included in librdkafka is:

• KIP-85, which does not seem relevant for franz-go
• KIP-92 for consumer lag metrics, which is better suited for an external system via the admin api
• KIP-223 for more metrics
• KIP-235, which is confusing but may be implement via a custom dialer and custom kerberos?
• KIP-359 to verify leader epoch when producing; this is easy to support but actually is not implemented in Kafka yet
• KIP-421 for dynamic values in configs; librdkafka mentions it does not support it, and neither does franz-go for the same reason (we do not use a config file)
• KIP-436 is about yet another metric
• KIP-517, more metrics