# librdkafka v2.1.0 librdkafka v2.1.0 is a feature release: * [KIP-320](https://cwiki.apache.org/confluence/display/KAFKA/KIP-320%3A+Allow+fetchers+to+detect+and+handle+log+truncation) Allow fetchers to detect and handle log truncation (#4122). * Fix a reference count issue blocking the consumer from closing (#4187). * Fix a protocol issue with ListGroups API, where an extra field was appended for API Versions greater than or equal to 3 (#4207). * Fix an issue with `max.poll.interval.ms`, where polling any queue would cause the timeout to be reset (#4176). * Fix seek partition timeout, was one thousand times lower than the passed value (#4230). * Fix multiple inconsistent behaviour in batch APIs during **pause** or **resume** operations (#4208). See **Consumer fixes** section below for more information. * Update lz4.c from upstream. Fixes [CVE-2021-3520](https://github.com/advisories/GHSA-gmc7-pqv9-966m) (by @filimonov, #4232). * Upgrade OpenSSL to v3.0.8 with various security fixes, check the [release notes](https://www.openssl.org/news/cl30.txt) (#4215). ## Enhancements * Added `rd_kafka_topic_partition_get_leader_epoch()` (and `set..()`). * Added partition leader epoch APIs: - `rd_kafka_topic_partition_get_leader_epoch()` (and `set..()`) - `rd_kafka_message_leader_epoch()` - `rd_kafka_*assign()` and `rd_kafka_seek_partitions()` now supports partitions with a leader epoch set. - `rd_kafka_offsets_for_times()` will return per-partition leader-epochs. - `leader_epoch`, `stored_leader_epoch`, and `committed_leader_epoch` added to per-partition statistics. ## Fixes ### OpenSSL fixes * Fixed OpenSSL static build not able to use external modules like FIPS provider module. ### Consumer fixes * A reference count issue was blocking the consumer from closing. The problem would happen when a partition is lost, because forcibly unassigned from the consumer or if the corresponding topic is deleted. * When using `rd_kafka_seek_partitions`, the remaining timeout was converted from microseconds to milliseconds but the expected unit for that parameter is microseconds. * Fixed known issues related to Batch Consume APIs mentioned in v2.0.0 release notes. * Fixed `rd_kafka_consume_batch()` and `rd_kafka_consume_batch_queue()` intermittently updating `app_offset` and `store_offset` incorrectly when **pause** or **resume** was being used for a partition. * Fixed `rd_kafka_consume_batch()` and `rd_kafka_consume_batch_queue()` intermittently skipping offsets when **pause** or **resume** was being used for a partition. ## Known Issues ### Consume Batch API * When `rd_kafka_consume_batch()` and `rd_kafka_consume_batch_queue()` APIs are used with any of the **seek**, **pause**, **resume** or **rebalancing** operation, `on_consume` interceptors might be called incorrectly (maybe multiple times) for not consumed messages. # librdkafka v2.0.2 librdkafka v2.0.2 is a bugfix release: * Fix OpenSSL version in Win32 nuget package (#4152). # librdkafka v2.0.1 librdkafka v2.0.1 is a bugfix release: * Fixed nuget package for Linux ARM64 release (#4150). # librdkafka v2.0.0 librdkafka v2.0.0 is a feature release: * [KIP-88](https://cwiki.apache.org/confluence/display/KAFKA/KIP-88%3A+OffsetFetch+Protocol+Update) OffsetFetch Protocol Update (#3995). * [KIP-222](https://cwiki.apache.org/confluence/display/KAFKA/KIP-222+-+Add+Consumer+Group+operations+to+Admin+API) Add Consumer Group operations to Admin API (started by @lesterfan, #3995). * [KIP-518](https://cwiki.apache.org/confluence/display/KAFKA/KIP-518%3A+Allow+listing+consumer+groups+per+state) Allow listing consumer groups per state (#3995). * [KIP-396](https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=97551484) Partially implemented: support for AlterConsumerGroupOffsets (started by @lesterfan, #3995). * OpenSSL 3.0.x support - the maximum bundled OpenSSL version is now 3.0.7 (previously 1.1.1q). * Fixes to the transactional and idempotent producer. ## Upgrade considerations ### OpenSSL 3.0.x #### OpenSSL default ciphers The introduction of OpenSSL 3.0.x in the self-contained librdkafka bundles changes the default set of available ciphers, in particular all obsolete or insecure ciphers and algorithms as listed in the OpenSSL [legacy](https://www.openssl.org/docs/man3.0/man7/OSSL_PROVIDER-legacy.html) manual page are now disabled by default. **WARNING**: These ciphers are disabled for security reasons and it is highly recommended NOT to use them. Should you need to use any of these old ciphers you'll need to explicitly enable the `legacy` provider by configuring `ssl.providers=default,legacy` on the librdkafka client. #### OpenSSL engines and providers OpenSSL 3.0.x deprecates the use of engines, which is being replaced by providers. As such librdkafka will emit a deprecation warning if `ssl.engine.location` is configured. OpenSSL providers may be configured with the new `ssl.providers` configuration property. ### Broker TLS certificate hostname verification The default value for `ssl.endpoint.identification.algorithm` has been changed from `none` (no hostname verification) to `https`, which enables broker hostname verification (to counter man-in-the-middle impersonation attacks) by default. To restore the previous behaviour, set `ssl.endpoint.identification.algorithm` to `none`. ## Known Issues ### Poor Consumer batch API messaging guarantees The Consumer Batch APIs `rd_kafka_consume_batch()` and `rd_kafka_consume_batch_queue()` are not thread safe if `rkmessages_size` is greater than 1 and any of the **seek**, **pause**, **resume** or **rebalancing** operation is performed in parallel with any of the above APIs. Some of the messages might be lost, or erroneously returned to the application, in the above scenario. It is strongly recommended to use the Consumer Batch APIs and the mentioned operations in sequential order in order to get consistent result. For **rebalancing** operation to work in sequencial manner, please set `rebalance_cb` configuration property (refer [examples/rdkafka_complex_consumer_example.c] (examples/rdkafka_complex_consumer_example.c) for the help with the usage) for the consumer. ## Enhancements * Self-contained static libraries can now be built on Linux arm64 (#4005). * Updated to zlib 1.2.13, zstd 1.5.2, and curl 7.86.0 in self-contained librdkafka bundles. * Added `on_broker_state_change()` interceptor * The C++ API no longer returns strings by const value, which enables better move optimization in callers. * Added `rd_kafka_sasl_set_credentials()` API to update SASL credentials. * Setting `allow.auto.create.topics` will no longer give a warning if used by a producer, since that is an expected use case. Improvement in documentation for this property. * Added a `resolve_cb` configuration setting that permits using custom DNS resolution logic. * Added `rd_kafka_mock_broker_error_stack_cnt()`. * The librdkafka.redist NuGet package has been updated to have fewer external dependencies for its bundled librdkafka builds, as everything but cyrus-sasl is now built-in. There are bundled builds with and without linking to cyrus-sasl for maximum compatibility. * Admin API DescribeGroups() now provides the group instance id for static members [KIP-345](https://cwiki.apache.org/confluence/display/KAFKA/KIP-345%3A+Introduce+static+membership+protocol+to+reduce+consumer+rebalances) (#3995). ## Fixes ### General fixes * Windows: couldn't read a PKCS#12 keystore correctly because binary mode wasn't explicitly set and Windows defaults to text mode. * Fixed memory leak when loading SSL certificates (@Mekk, #3930) * Load all CA certificates from `ssl.ca.pem`, not just the first one. * Each HTTP request made when using OAUTHBEARER OIDC would leak a small amount of memory. ### Transactional producer fixes * When a PID epoch bump is requested and the producer is waiting to reconnect to the transaction coordinator, a failure in a find coordinator request could cause an assert to fail. This is fixed by retrying when the coordinator is known (#4020). * Transactional APIs (except `send_offsets_for_transaction()`) that timeout due to low timeout_ms may now be resumed by calling the same API again, as the operation continues in the background. * For fatal idempotent producer errors that may be recovered by bumping the epoch the current transaction must first be aborted prior to the epoch bump. This is now handled correctly, which fixes issues seen with fenced transactional producers on fatal idempotency errors. * Timeouts for EndTxn requests (transaction commits and aborts) are now automatically retried and the error raised to the application is also a retriable error. * TxnOffsetCommitRequests were retried immediately upon temporary errors in `send_offsets_to_transactions()`, causing excessive network requests. These retries are now delayed 500ms. * If `init_transactions()` is called with an infinite timeout (-1), the timeout will be limited to 2 * `transaction.timeout.ms`. The application may retry and resume the call if a retriable error is returned. ### Consumer fixes * Back-off and retry JoinGroup request if coordinator load is in progress. * Fix `rd_kafka_consume_batch()` and `rd_kafka_consume_batch_queue()` skipping other partitions' offsets intermittently when **seek**, **pause**, **resume** or **rebalancing** is used for a partition. * Fix `rd_kafka_consume_batch()` and `rd_kafka_consume_batch_queue()` intermittently returing incorrect partitions' messages if **rebalancing** happens during these operations. # librdkafka v1.9.2 librdkafka v1.9.2 is a maintenance release: * The SASL OAUTHBEAR OIDC POST field was sometimes truncated by one byte (#3192). * The bundled version of OpenSSL has been upgraded to version 1.1.1q for non-Windows builds. Windows builds remain on OpenSSL 1.1.1n for the time being. * The bundled version of Curl has been upgraded to version 7.84.0. # librdkafka v1.9.1 librdkafka v1.9.1 is a maintenance release: * The librdkafka.redist NuGet package now contains OSX M1/arm64 builds. * Self-contained static libraries can now be built on OSX M1 too, thanks to disabling curl's configure runtime check. # librdkafka v1.9.0 librdkafka v1.9.0 is a feature release: * Added KIP-768 OUATHBEARER OIDC support (by @jliunyu, #3560) * Added KIP-140 Admin API ACL support (by @emasab, #2676) ## Upgrade considerations * Consumer: `rd_kafka_offsets_store()` (et.al) will now return an error for any partition that is not currently assigned (through `rd_kafka_*assign()`). This prevents a race condition where an application would store offsets after the assigned partitions had been revoked (which resets the stored offset), that could cause these old stored offsets to be committed later when the same partitions were assigned to this consumer again - effectively overwriting any committed offsets by any consumers that were assigned the same partitions previously. This would typically result in the offsets rewinding and messages to be reprocessed. As an extra effort to avoid this situation the stored offset is now also reset when partitions are assigned (through `rd_kafka_*assign()`). Applications that explicitly call `..offset*_store()` will now need to handle the case where `RD_KAFKA_RESP_ERR__STATE` is returned in the per-partition `.err` field - meaning the partition is no longer assigned to this consumer and the offset could not be stored for commit. ## Enhancements * Improved producer queue scheduling. Fixes the performance regression introduced in v1.7.0 for some produce patterns. (#3538, #2912) * Windows: Added native Win32 IO/Queue scheduling. This removes the internal TCP loopback connections that were previously used for timely queue wakeups. * Added `socket.connection.setup.timeout.ms` (default 30s). The maximum time allowed for broker connection setups (TCP connection as well as SSL and SASL handshakes) is now limited to this value. This fixes the issue with stalled broker connections in the case of network or load balancer problems. The Java clients has an exponential backoff to this timeout which is limited by `socket.connection.setup.timeout.max.ms` - this was not implemented in librdkafka due to differences in connection handling and `ERR__ALL_BROKERS_DOWN` error reporting. Having a lower initial connection setup timeout and then increase the timeout for the next attempt would yield possibly false-positive `ERR__ALL_BROKERS_DOWN` too early. * SASL OAUTHBEARER refresh callbacks can now be scheduled for execution on librdkafka's background thread. This solves the problem where an application has a custom SASL OAUTHBEARER refresh callback and thus needs to call `rd_kafka_poll()` (et.al.) at least once to trigger the refresh callback before being able to connect to brokers. With the new `rd_kafka_conf_enable_sasl_queue()` configuration API and `rd_kafka_sasl_background_callbacks_enable()` the refresh callbacks can now be triggered automatically on the librdkafka background thread. * `rd_kafka_queue_get_background()` now creates the background thread if not already created. * Added `rd_kafka_consumer_close_queue()` and `rd_kafka_consumer_closed()`. This allow applications and language bindings to implement asynchronous consumer close. * Bundled zlib upgraded to version 1.2.12. * Bundled OpenSSL upgraded to 1.1.1n. * Added `test.mock.broker.rtt` to simulate RTT/latency for mock brokers. ## Fixes ### General fixes * Fix various 1 second delays due to internal broker threads blocking on IO even though there are events to handle. These delays could be seen randomly in any of the non produce/consume request APIs, such as `commit_transaction()`, `list_groups()`, etc. * Windows: some applications would crash with an error message like `no OPENSSL_Applink()` written to the console if `ssl.keystore.location` was configured. This regression was introduced in v1.8.0 due to use of vcpkgs and how keystore file was read. #3554. * Windows 32-bit only: 64-bit atomic reads were in fact not atomic and could in rare circumstances yield incorrect values. One manifestation of this issue was the `max.poll.interval.ms` consumer timer expiring even though the application was polling according to profile. Fixed by @WhiteWind (#3815). * `rd_kafka_clusterid()` would previously fail with timeout if called on cluster with no visible topics (#3620). The clusterid is now returned as soon as metadata has been retrieved. * Fix hang in `rd_kafka_list_groups()` if there are no available brokers to connect to (#3705). * Millisecond timeouts (`timeout_ms`) in various APIs, such as `rd_kafka_poll()`, was limited to roughly 36 hours before wrapping. (#3034) * If a metadata request triggered by `rd_kafka_metadata()` or consumer group rebalancing encountered a non-retriable error it would not be propagated to the caller and thus cause a stall or timeout, this has now been fixed. (@aiquestion, #3625) * AdminAPI `DeleteGroups()` and `DeleteConsumerGroupOffsets()`: if the given coordinator connection was not up by the time these calls were initiated and the first connection attempt failed then no further connection attempts were performed, ulimately leading to the calls timing out. This is now fixed by keep retrying to connect to the group coordinator until the connection is successful or the call times out. Additionally, the coordinator will be now re-queried once per second until the coordinator comes up or the call times out, to detect change in coordinators. * Mock cluster `rd_kafka_mock_broker_set_down()` would previously accept and then disconnect new connections, it now refuses new connections. ### Consumer fixes * `rd_kafka_offsets_store()` (et.al) will now return an error for any partition that is not currently assigned (through `rd_kafka_*assign()`). See **Upgrade considerations** above for more information. * `rd_kafka_*assign()` will now reset/clear the stored offset. See **Upgrade considerations** above for more information. * `seek()` followed by `pause()` would overwrite the seeked offset when later calling `resume()`. This is now fixed. (#3471). **Note**: Avoid storing offsets (`offsets_store()`) after calling `seek()` as this may later interfere with resuming a paused partition, instead store offsets prior to calling seek. * A `ERR_MSG_SIZE_TOO_LARGE` consumer error would previously be raised if the consumer received a maximum sized FetchResponse only containing (transaction) aborted messages with no control messages. The fetching did not stop, but some applications would terminate upon receiving this error. No error is now raised in this case. (#2993) Thanks to @jacobmikesell for providing an application to reproduce the issue. * The consumer no longer backs off the next fetch request (default 500ms) when the parsed fetch response is truncated (which is a valid case). This should speed up the message fetch rate in case of maximum sized fetch responses. * Fix consumer crash (`assert: rkbuf->rkbuf_rkb`) when parsing malformed JoinGroupResponse consumer group metadata state. * Fix crash (`cant handle op type`) when using `consume_batch_queue()` (et.al) and an OAUTHBEARER refresh callback was set. The callback is now triggered by the consume call. (#3263) * Fix `partition.assignment.strategy` ordering when multiple strategies are configured. If there is more than one eligible strategy, preference is determined by the configured order of strategies. The partitions are assigned to group members according to the strategy order preference now. (#3818) * Any form of unassign*() (absolute or incremental) is now allowed during consumer close rebalancing and they're all treated as absolute unassigns. (@kevinconaway) ### Transactional producer fixes * Fix message loss in idempotent/transactional producer. A corner case has been identified that may cause idempotent/transactional messages to be lost despite being reported as successfully delivered: During cluster instability a restarting broker may report existing topics as non-existent for some time before it is able to acquire up to date cluster and topic metadata. If an idempotent/transactional producer updates its topic metadata cache from such a broker the producer will consider the topic to be removed from the cluster and thus remove its local partition objects for the given topic. This also removes the internal message sequence number counter for the given partitions. If the producer later receives proper topic metadata for the cluster the previously "removed" topics will be rediscovered and new partition objects will be created in the producer. These new partition objects, with no knowledge of previous incarnations, would start counting partition messages at zero again. If new messages were produced for these partitions by the same producer instance, the same message sequence numbers would be sent to the broker. If the broker still maintains state for the producer's PID and Epoch it could deem that these messages with reused sequence numbers had already been written to the log and treat them as legit duplicates. This would seem to the producer that these new messages were successfully written to the partition log by the broker when they were in fact discarded as duplicates, leading to silent message loss. The fix included in this release is to save the per-partition idempotency state when a partition is removed, and then recover and use that saved state if the partition comes back at a later time. * The transactional producer would retry (re)initializing its PID if a `PRODUCER_FENCED` error was returned from the broker (added in Apache Kafka 2.8), which could cause the producer to seemingly hang. This error code is now correctly handled by raising a fatal error. * If the given group coordinator connection was not up by the time `send_offsets_to_transactions()` was called, and the first connection attempt failed then no further connection attempts were performed, ulimately leading to `send_offsets_to_transactions()` timing out, and possibly also the transaction timing out on the transaction coordinator. This is now fixed by keep retrying to connect to the group coordinator until the connection is successful or the call times out. Additionally, the coordinator will be now re-queried once per second until the coordinator comes up or the call times out, to detect change in coordinators. ### Producer fixes * Improved producer queue wakeup scheduling. This should significantly decrease the number of wakeups and thus syscalls for high message rate producers. (#3538, #2912) * The logic for enforcing that `message.timeout.ms` is greather than an explicitly configured `linger.ms` was incorrect and instead of erroring out early the lingering time was automatically adjusted to the message timeout, ignoring the configured `linger.ms`. This has now been fixed so that an error is returned when instantiating the producer. Thanks to @larry-cdn77 for analysis and test-cases. (#3709) # librdkafka v1.8.2 librdkafka v1.8.2 is a maintenance release. ## Enhancements * Added `ssl.ca.pem` to add CA certificate by PEM string. (#2380) * Prebuilt binaries for Mac OSX now contain statically linked OpenSSL v1.1.1l. Previously the OpenSSL version was either v1.1.1 or v1.0.2 depending on build type. ## Fixes * The `librdkafka.redist` 1.8.0 package had two flaws: - the linux-arm64 .so build was a linux-x64 build. - the included Windows MSVC 140 runtimes for x64 were infact x86. The release script has been updated to verify the architectures of provided artifacts to avoid this happening in the future. * Prebuilt binaries for Mac OSX Sierra (10.12) and older are no longer provided. This affects [confluent-kafka-go](https://github.com/confluentinc/confluent-kafka-go). * Some of the prebuilt binaries for Linux were built on Ubuntu 14.04, these builds are now performed on Ubuntu 16.04 instead. This may affect users on ancient Linux distributions. * It was not possible to configure `ssl.ca.location` on OSX, the property would automatically revert back to `probe` (default value). This regression was introduced in v1.8.0. (#3566) * librdkafka's internal timers would not start if the timeout was set to 0, which would result in some timeout operations not being enforced correctly, e.g., the transactional producer API timeouts. These timers are now started with a timeout of 1 microsecond. ### Transactional producer fixes * Upon quick repeated leader changes the transactional producer could receive an `OUT_OF_ORDER_SEQUENCE` error from the broker, which triggered an Epoch bump on the producer resulting in an InitProducerIdRequest being sent to the transaction coordinator in the middle of a transaction. This request would start a new transaction on the coordinator, but the producer would still think (erroneously) it was in current transaction. Any messages produced in the current transaction prior to this event would be silently lost when the application committed the transaction, leading to message loss. This has been fixed by setting the Abortable transaction error state in the producer. #3575. * The transactional producer could stall during a transaction if the transaction coordinator changed while adding offsets to the transaction (send_offsets_to_transaction()). This stall lasted until the coordinator connection went down, the transaction timed out, transaction was aborted, or messages were produced to a new partition, whichever came first. #3571. *Note: there was no v1.8.1 librdkafka release* # librdkafka v1.8.0 librdkafka v1.8.0 is a security release: * Upgrade bundled zlib version from 1.2.8 to 1.2.11 in the `librdkafka.redist` NuGet package. The updated zlib version fixes CVEs: CVE-2016-9840, CVE-2016-9841, CVE-2016-9842, CVE-2016-9843 See https://github.com/edenhill/librdkafka/issues/2934 for more information. * librdkafka now uses [vcpkg](https://vcpkg.io/) for up-to-date Windows dependencies in the `librdkafka.redist` NuGet package: OpenSSL 1.1.1l, zlib 1.2.11, zstd 1.5.0. * The upstream dependency (OpenSSL, zstd, zlib) source archive checksums are now verified when building with `./configure --install-deps`. These builds are used by the librdkafka builds bundled with confluent-kafka-go, confluent-kafka-python and confluent-kafka-dotnet. ## Enhancements * Producer `flush()` now overrides the `linger.ms` setting for the duration of the `flush()` call, effectively triggering immediate transmission of queued messages. (#3489) ## Fixes ### General fixes * Correctly detect presence of zlib via compilation check. (Chris Novakovic) * `ERR__ALL_BROKERS_DOWN` is no longer emitted when the coordinator connection goes down, only when all standard named brokers have been tried. This fixes the issue with `ERR__ALL_BROKERS_DOWN` being triggered on `consumer_close()`. It is also now only emitted if the connection was fully up (past handshake), and not just connected. * `rd_kafka_query_watermark_offsets()`, `rd_kafka_offsets_for_times()`, `consumer_lag` metric, and `auto.offset.reset` now honour `isolation.level` and will return the Last Stable Offset (LSO) when `isolation.level` is set to `read_committed` (default), rather than the uncommitted high-watermark when it is set to `read_uncommitted`. (#3423) * SASL GSSAPI is now usable when `sasl.kerberos.min.time.before.relogin` is set to 0 - which disables ticket refreshes (by @mpekalski, #3431). * Rename internal crc32c() symbol to rd_crc32c() to avoid conflict with other static libraries (#3421). * `txidle` and `rxidle` in the statistics object was emitted as 18446744073709551615 when no idle was known. -1 is now emitted instead. (#3519) ### Consumer fixes * Automatically retry offset commits on `ERR_REQUEST_TIMED_OUT`, `ERR_COORDINATOR_NOT_AVAILABLE`, and `ERR_NOT_COORDINATOR` (#3398). Offset commits will be retried twice. * Timed auto commits did not work when only using assign() and not subscribe(). This regression was introduced in v1.7.0. * If the topics matching the current subscription changed (or the application updated the subscription) while there was an outstanding JoinGroup or SyncGroup request, an additional request would sometimes be sent before handling the response of the first. This in turn lead to internal state issues that could cause a crash or malbehaviour. The consumer will now wait for any outstanding JoinGroup or SyncGroup responses before re-joining the group. * `auto.offset.reset` could previously be triggered by temporary errors, such as disconnects and timeouts (after the two retries are exhausted). This is now fixed so that the auto offset reset policy is only triggered for permanent errors. * The error that triggers `auto.offset.reset` is now logged to help the application owner identify the reason of the reset. * If a rebalance takes longer than a consumer's `session.timeout.ms`, the consumer will remain in the group as long as it receives heartbeat responses from the broker. ### Admin fixes * `DeleteRecords()` could crash if one of the underlying requests (for a given partition leader) failed at the transport level (e.g., timeout). (#3476). # librdkafka v1.7.0 librdkafka v1.7.0 is feature release: * [KIP-360](https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=89068820) - Improve reliability of transactional producer. Requires Apache Kafka 2.5 or later. * OpenSSL Engine support (`ssl.engine.location`) by @adinigam and @ajbarb. ## Enhancements * Added `connections.max.idle.ms` to automatically close idle broker connections. This feature is disabled by default unless `bootstrap.servers` contains the string `azure` in which case the default is set to <4 minutes to improve connection reliability and circumvent limitations with the Azure load balancers (see #3109 for more information). * Bumped to OpenSSL 1.1.1k in binary librdkafka artifacts. * The binary librdkafka artifacts for Alpine are now using Alpine 3.12. OpenSSL 1.1.1k. * Improved static librdkafka Windows builds using MinGW (@neptoess, #3130). * The `librdkafka.redist` NuGet package now has updated zlib, zstd and OpenSSL versions (from vcpkg). ## Security considerations * The zlib version bundled with the `librdkafka.redist` NuGet package has now been upgraded from zlib 1.2.8 to 1.2.11, fixing the following CVEs: * CVE-2016-9840: undefined behaviour (compiler dependent) in inflate (decompression) code: this is used by the librdkafka consumer. Risk of successfully exploitation through consumed messages is eastimated very low. * CVE-2016-9841: undefined behaviour (compiler dependent) in inflate code: this is used by the librdkafka consumer. Risk of successfully exploitation through consumed messages is eastimated very low. * CVE-2016-9842: undefined behaviour in inflateMark(): this API is not used by librdkafka. * CVE-2016-9843: issue in crc32_big() which is called from crc32_z(): this API is not used by librdkafka. ## Upgrade considerations * The C++ `oauthbearer_token_refresh_cb()` was missing a `Handle *` argument that has now been added. This is a breaking change but the original function signature is considered a bug. This change only affects C++ OAuth developers. * [KIP-735](https://cwiki.apache.org/confluence/display/KAFKA/KIP-735%3A+Increase+default+consumer+session+timeout) The consumer `session.timeout.ms` default was changed from 10 to 45 seconds to make consumer groups more robust and less sensitive to temporary network and cluster issues. * Statistics: `consumer_lag` is now using the `committed_offset`, while the new `consumer_lag_stored` is using `stored_offset` (offset to be committed). This is more correct than the previous `consumer_lag` which was using either `committed_offset` or `app_offset` (last message passed to application). * The `librdkafka.redist` NuGet package is now built with MSVC runtime v140 (VS 2015). Previous versions were built with MSVC runtime v120 (VS 2013). ## Fixes ### General fixes * Fix accesses to freed metadata cache mutexes on client termination (#3279) * There was a race condition on receiving updated metadata where a broker id update (such as bootstrap to proper broker transformation) could finish after the topic metadata cache was updated, leading to existing brokers seemingly being not available. One occurrence of this issue was query_watermark_offsets() that could return `ERR__UNKNOWN_PARTITION` for existing partitions shortly after the client instance was created. * The OpenSSL context is now initialized with `TLS_client_method()` (on OpenSSL >= 1.1.0) instead of the deprecated and outdated `SSLv23_client_method()`. * The initial cluster connection on client instance creation could sometimes be delayed up to 1 second if a `group.id` or `transactional.id` was configured (#3305). * Speed up triggering of new broker connections in certain cases by exiting the broker thread io/op poll loop when a wakeup op is received. * SASL GSSAPI: The Kerberos kinit refresh command was triggered from `rd_kafka_new()` which made this call blocking if the refresh command was taking long. The refresh is now performed by the background rdkafka main thread. * Fix busy-loop (100% CPU on the broker threads) during the handshake phase of an SSL connection. * Disconnects during SSL handshake are now propagated as transport errors rather than SSL errors, since these disconnects are at the transport level (e.g., incorrect listener, flaky load balancer, etc) and not due to SSL issues. * Increment metadata fast refresh interval backoff exponentially (@ajbarb, #3237). * Unthrottled requests are no longer counted in the `brokers[].throttle` statistics object. * Log CONFWARN warning when global topic configuration properties are overwritten by explicitly setting a `default_topic_conf`. ### Consumer fixes * If a rebalance happened during a `consume_batch..()` call the already accumulated messages for revoked partitions were not purged, which would pass messages to the application for partitions that were no longer owned by the consumer. Fixed by @jliunyu. #3340. * Fix balancing and reassignment issues with the cooperative-sticky assignor. #3306. * Fix incorrect detection of first rebalance in sticky assignor (@hallfox). * Aborted transactions with no messages produced to a partition could cause further successfully committed messages in the same Fetch response to be ignored, resulting in consumer-side message loss. A log message along the lines `Abort txn ctrl msg bad order at offset 7501: expected before or at 7702: messages in aborted transactions may be delivered to the application` would be seen. This is a rare occurrence where a transactional producer would register with the partition but not produce any messages before aborting the transaction. * The consumer group deemed cached metadata up to date by checking `topic.metadata.refresh.interval.ms`: if this property was set too low it would cause cached metadata to be unusable and new metadata to be fetched, which could delay the time it took for a rebalance to settle. It now correctly uses `metadata.max.age.ms` instead. * The consumer group timed auto commit would attempt commits during rebalances, which could result in "Illegal generation" errors. This is now fixed, the timed auto committer is only employed in the steady state when no rebalances are taking places. Offsets are still auto committed when partitions are revoked. * Retriable FindCoordinatorRequest errors are no longer propagated to the application as they are retried automatically. * Fix rare crash (assert `rktp_started`) on consumer termination (introduced in v1.6.0). * Fix unaligned access and possibly corrupted snappy decompression when building with MSVC (@azat) * A consumer configured with the `cooperative-sticky` assignor did not actively Leave the group on unsubscribe(). This delayed the rebalance for the remaining group members by up to `session.timeout.ms`. * The current subscription list was sometimes leaked when unsubscribing. ### Producer fixes * The timeout value of `flush()` was not respected when delivery reports were scheduled as events (such as for confluent-kafka-go) rather than callbacks. * There was a race conditition in `purge()` which could cause newly created partition objects, or partitions that were changing leaders, to not have their message queues purged. This could cause `abort_transaction()` to time out. This issue is now fixed. * In certain high-thruput produce rate patterns producing could stall for 1 second, regardless of `linger.ms`, due to rate-limiting of internal queue wakeups. This is now fixed by not rate-limiting queue wakeups but instead limiting them to one wakeup per queue reader poll. #2912. ### Transactional Producer fixes * KIP-360: Fatal Idempotent producer errors are now recoverable by the transactional producer and will raise a `txn_requires_abort()` error. * If the cluster went down between `produce()` and `commit_transaction()` and before any partitions had been registered with the coordinator, the messages would time out but the commit would succeed because nothing had been sent to the coordinator. This is now fixed. * If the current transaction failed while `commit_transaction()` was checking the current transaction state an invalid state transaction could occur which in turn would trigger a assertion crash. This issue showed up as "Invalid txn state transition: .." crashes, and is now fixed by properly synchronizing both checking and transition of state. # librdkafka v1.6.1 librdkafka v1.6.1 is a maintenance release. ## Upgrade considerations * Fatal idempotent producer errors are now also fatal to the transactional producer. This is a necessary step to maintain data integrity prior to librdkafka supporting KIP-360. Applications should check any transactional API errors for the is_fatal flag and decommission the transactional producer if the flag is set. * The consumer error raised by `auto.offset.reset=error` now has error-code set to `ERR__AUTO_OFFSET_RESET` to allow an application to differentiate between auto offset resets and other consumer errors. ## Fixes ### General fixes * Admin API and transactional `send_offsets_to_transaction()` coordinator requests, such as TxnOffsetCommitRequest, could in rare cases be sent multiple times which could cause a crash. * `ssl.ca.location=probe` is now enabled by default on Mac OSX since the librdkafka-bundled OpenSSL might not have the same default CA search paths as the system or brew installed OpenSSL. Probing scans all known locations. ### Transactional Producer fixes * Fatal idempotent producer errors are now also fatal to the transactional producer. * The transactional producer could crash if the transaction failed while `send_offsets_to_transaction()` was called. * Group coordinator requests for transactional `send_offsets_to_transaction()` calls would leak memory if the underlying request was attempted to be sent after the transaction had failed. * When gradually producing to multiple partitions (resulting in multiple underlying AddPartitionsToTxnRequests) subsequent partitions could get stuck in pending state under certain conditions. These pending partitions would not send queued messages to the broker and eventually trigger message timeouts, failing the current transaction. This is now fixed. * Committing an empty transaction (no messages were produced and no offsets were sent) would previously raise a fatal error due to invalid state on the transaction coordinator. We now allow empty/no-op transactions to be committed. ### Consumer fixes * The consumer will now retry indefinitely (or until the assignment is changed) to retrieve committed offsets. This fixes the issue where only two retries were attempted when outstanding transactions were blocking OffsetFetch requests with `ERR_UNSTABLE_OFFSET_COMMIT`. #3265 # librdkafka v1.6.0 librdkafka v1.6.0 is feature release: * [KIP-429 Incremental rebalancing](https://cwiki.apache.org/confluence/display/KAFKA/KIP-429%3A+Kafka+Consumer+Incremental+Rebalance+Protocol) with sticky consumer group partition assignor (KIP-54) (by @mhowlett). * [KIP-480 Sticky producer partitioning](https://cwiki.apache.org/confluence/display/KAFKA/KIP-480%3A+Sticky+Partitioner) (`sticky.partitioning.linger.ms`) - achieves higher throughput and lower latency through sticky selection of random partition (by @abbycriswell). * AdminAPI: Add support for `DeleteRecords()`, `DeleteGroups()` and `DeleteConsumerGroupOffsets()` (by @gridaphobe) * [KIP-447 Producer scalability for exactly once semantics](https://cwiki.apache.org/confluence/display/KAFKA/KIP-447%3A+Producer+scalability+for+exactly+once+semantics) - allows a single transactional producer to be used for multiple input partitions. Requires Apache Kafka 2.5 or later. * Transactional producer fixes and improvements, see **Transactional Producer fixes** below. * The [librdkafka.redist](https://www.nuget.org/packages/librdkafka.redist/) NuGet package now supports Linux ARM64/Aarch64. ## Upgrade considerations * Sticky producer partitioning (`sticky.partitioning.linger.ms`) is enabled by default (10 milliseconds) which affects the distribution of randomly partitioned messages, where previously these messages would be evenly distributed over the available partitions they are now partitioned to a single partition for the duration of the sticky time (10 milliseconds by default) before a new random sticky partition is selected. * The new KIP-447 transactional producer scalability guarantees are only supported on Apache Kafka 2.5 or later, on earlier releases you will need to use one producer per input partition for EOS. This limitation is not enforced by the producer or broker. * Error handling for the transactional producer has been improved, see the **Transactional Producer fixes** below for more information. ## Known issues * The Transactional Producer's API timeout handling is inconsistent with the underlying protocol requests, it is therefore strongly recommended that applications call `rd_kafka_commit_transaction()` and `rd_kafka_abort_transaction()` with the `timeout_ms` parameter set to `-1`, which will use the remaining transaction timeout. ## Enhancements * KIP-107, KIP-204: AdminAPI: Added `DeleteRecords()` (by @gridaphobe). * KIP-229: AdminAPI: Added `DeleteGroups()` (by @gridaphobe). * KIP-496: AdminAPI: Added `DeleteConsumerGroupOffsets()`. * KIP-464: AdminAPI: Added support for broker-side default partition count and replication factor for `CreateTopics()`. * Windows: Added `ssl.ca.certificate.stores` to specify a list of Windows Certificate Stores to read CA certificates from, e.g., `CA,Root`. `Root` remains the default store. * Use reentrant `rand_r()` on supporting platforms which decreases lock contention (@azat). * Added `assignor` debug context for troubleshooting consumer partition assignments. * Updated to OpenSSL v1.1.1i when building dependencies. * Update bundled lz4 (used when `./configure --disable-lz4-ext`) to v1.9.3 which has vast performance improvements. * Added `rd_kafka_conf_get_default_topic_conf()` to retrieve the default topic configuration object from a global configuration object. * Added `conf` debugging context to `debug` - shows set configuration properties on client and topic instantiation. Sensitive properties are redacted. * Added `rd_kafka_queue_yield()` to cancel a blocking queue call. * Will now log a warning when multiple ClusterIds are seen, which is an indication that the client might be erroneously configured to connect to multiple clusters which is not supported. * Added `rd_kafka_seek_partitions()` to seek multiple partitions to per-partition specific offsets. ## Fixes ### General fixes * Fix a use-after-free crash when certain coordinator requests were retried. * The C++ `oauthbearer_set_token()` function would call `free()` on a `new`-created pointer, possibly leading to crashes or heap corruption (#3194) ### Consumer fixes * The consumer assignment and consumer group implementations have been decoupled, simplified and made more strict and robust. This will sort out a number of edge cases for the consumer where the behaviour was previously undefined. * Partition fetch state was not set to STOPPED if OffsetCommit failed. * The session timeout is now enforced locally also when the coordinator connection is down, which was not previously the case. ### Transactional Producer fixes * Transaction commit or abort failures on the broker, such as when the producer was fenced by a newer instance, were not propagated to the application resulting in failed commits seeming successful. This was a critical race condition for applications that had a delay after producing messages (or sendings offsets) before committing or aborting the transaction. This issue has now been fixed and test coverage improved. * The transactional producer API would return `RD_KAFKA_RESP_ERR__STATE` when API calls were attempted after the transaction had failed, we now try to return the error that caused the transaction to fail in the first place, such as `RD_KAFKA_RESP_ERR__FENCED` when the producer has been fenced, or `RD_KAFKA_RESP_ERR__TIMED_OUT` when the transaction has timed out. * Transactional producer retry count for transactional control protocol requests has been increased from 3 to infinite, retriable errors are now automatically retried by the producer until success or the transaction timeout is exceeded. This fixes the case where `rd_kafka_send_offsets_to_transaction()` would fail the current transaction into an abortable state when `CONCURRENT_TRANSACTIONS` was returned by the broker (which is a transient error) and the 3 retries were exhausted. ### Producer fixes * Calling `rd_kafka_topic_new()` with a topic config object with `message.timeout.ms` set could sometimes adjust the global `linger.ms` property (if not explicitly configured) which was not desired, this is now fixed and the auto adjustment is only done based on the `default_topic_conf` at producer creation. * `rd_kafka_flush()` could previously return `RD_KAFKA_RESP_ERR__TIMED_OUT` just as the timeout was reached if the messages had been flushed but there were now no more messages. This has been fixed. # librdkafka v1.5.3 librdkafka v1.5.3 is a maintenance release. ## Upgrade considerations * CentOS 6 is now EOL and is no longer included in binary librdkafka packages, such as NuGet. ## Fixes ### General fixes * Fix a use-after-free crash when certain coordinator requests were retried. * Coordinator requests could be left uncollected on instance destroy which could lead to hang. * Fix rare 1 second stalls by forcing rdkafka main thread wakeup when a new next-timer-to-be-fired is scheduled. * Fix additional cases where broker-side automatic topic creation might be triggered unexpectedly. * AdminAPI: The operation_timeout (on-broker timeout) previously defaulted to 0, but now defaults to `socket.timeout.ms` (60s). * Fix possible crash for Admin API protocol requests that fail at the transport layer or prior to sending. ### Consumer fixes * Consumer would not filter out messages for aborted transactions if the messages were compressed (#3020). * Consumer destroy without prior `close()` could hang in certain cgrp states (@gridaphobe, #3127). * Fix possible null dereference in `Message::errstr()` (#3140). * The `roundrobin` partition assignment strategy could get stuck in an endless loop or generate uneven assignments in case the group members had asymmetric subscriptions (e.g., c1 subscribes to t1,t2 while c2 subscribes to t2,t3). (#3159) * Mixing committed and logical or absolute offsets in the partitions passed to `rd_kafka_assign()` would in previous released ignore the logical or absolute offsets and use the committed offsets for all partitions. This is now fixed. (#2938) # librdkafka v1.5.2 librdkafka v1.5.2 is a maintenance release. ## Upgrade considerations * The default value for the producer configuration property `retries` has been increased from 2 to infinity, effectively limiting Produce retries to only `message.timeout.ms`. As the reasons for the automatic internal retries vary (various broker error codes as well as transport layer issues), it doesn't make much sense to limit the number of retries for retriable errors, but instead only limit the retries based on the allowed time to produce a message. * The default value for the producer configuration property `request.timeout.ms` has been increased from 5 to 30 seconds to match the Apache Kafka Java producer default. This change yields increased robustness for broker-side congestion. ## Enhancements * The generated `CONFIGURATION.md` (through `rd_kafka_conf_properties_show())`) now include all properties and values, regardless if they were included in the build, and setting a disabled property or value through `rd_kafka_conf_set()` now returns `RD_KAFKA_CONF_INVALID` and provides a more useful error string saying why the property can't be set. * Consumer configs on producers and vice versa will now be logged with warning messages on client instantiation. ## Fixes ### Security fixes * There was an incorrect call to zlib's `inflateGetHeader()` with unitialized memory pointers that could lead to the GZIP header of a fetched message batch to be copied to arbitrary memory. This function call has now been completely removed since the result was not used. Reported by Ilja van Sprundel. ### General fixes * `rd_kafka_topic_opaque()` (used by the C++ API) would cause object refcounting issues when used on light-weight (error-only) topic objects such as consumer errors (#2693). * Handle name resolution failures when formatting IP addresses in error logs, and increase printed hostname limit to ~256 bytes (was ~60). * Broker sockets would be closed twice (thus leading to potential race condition with fd-reuse in other threads) if a custom `socket_cb` would return error. ### Consumer fixes * The `roundrobin` `partition.assignment.strategy` could crash (assert) for certain combinations of members and partitions. This is a regression in v1.5.0. (#3024) * The C++ `KafkaConsumer` destructor did not destroy the underlying C `rd_kafka_t` instance, causing a leak if `close()` was not used. * Expose rich error strings for C++ Consumer `Message->errstr()`. * The consumer could get stuck if an outstanding commit failed during rebalancing (#2933). * Topic authorization errors during fetching are now reported only once (#3072). ### Producer fixes * Topic authorization errors are now properly propagated for produced messages, both through delivery reports and as `ERR_TOPIC_AUTHORIZATION_FAILED` return value from `produce*()` (#2215) * Treat cluster authentication failures as fatal in the transactional producer (#2994). * The transactional producer code did not properly reference-count partition objects which could in very rare circumstances lead to a use-after-free bug if a topic was deleted from the cluster when a transaction was using it. * `ERR_KAFKA_STORAGE_ERROR` is now correctly treated as a retriable produce error (#3026). * Messages that timed out locally would not fail the ongoing transaction. If the application did not take action on failed messages in its delivery report callback and went on to commit the transaction, the transaction would be successfully committed, simply omitting the failed messages. * EndTxnRequests (sent on commit/abort) are only retried in allowed states (#3041). Previously the transaction could hang on commit_transaction() if an abortable error was hit and the EndTxnRequest was to be retried. *Note: there was no v1.5.1 librdkafka release* # librdkafka v1.5.0 The v1.5.0 release brings usability improvements, enhancements and fixes to librdkafka. ## Enhancements * Improved broker connection error reporting with more useful information and hints on the cause of the problem. * Consumer: Propagate errors when subscribing to unavailable topics (#1540) * Producer: Add `batch.size` producer configuration property (#638) * Add `topic.metadata.propagation.max.ms` to allow newly manually created topics to be propagated throughout the cluster before reporting them as non-existent. This fixes race issues where CreateTopics() is quickly followed by produce(). * Prefer least idle connection for periodic metadata refreshes, et.al., to allow truly idle connections to time out and to avoid load-balancer-killed idle connection errors (#2845) * Added `rd_kafka_event_debug_contexts()` to get the debug contexts for a debug log line (by @wolfchimneyrock). * Added Test scenarios which define the cluster configuration. * Added MinGW-w64 builds (@ed-alertedh, #2553) * `./configure --enable-XYZ` now requires the XYZ check to pass, and `--disable-XYZ` disables the feature altogether (@benesch) * Added `rd_kafka_produceva()` which takes an array of produce arguments for situations where the existing `rd_kafka_producev()` va-arg approach can't be used. * Added `rd_kafka_message_broker_id()` to see the broker that a message was produced or fetched from, or an error was associated with. * Added RTT/delay simulation to mock brokers. ## Upgrade considerations * Subscribing to non-existent and unauthorized topics will now propagate errors `RD_KAFKA_RESP_ERR_UNKNOWN_TOPIC_OR_PART` and `RD_KAFKA_RESP_ERR_TOPIC_AUTHORIZATION_FAILED` to the application through the standard consumer error (the err field in the message object). * Consumer will no longer trigger auto creation of topics, `allow.auto.create.topics=true` may be used to re-enable the old deprecated functionality. * The default consumer pre-fetch queue threshold `queued.max.messages.kbytes` has been decreased from 1GB to 64MB to avoid excessive network usage for low and medium throughput consumer applications. High throughput consumer applications may need to manually set this property to a higher value. * The default consumer Fetch wait time has been increased from 100ms to 500ms to avoid excessive network usage for low throughput topics. * If OpenSSL is linked statically, or `ssl.ca.location=probe` is configured, librdkafka will probe known CA certificate paths and automatically use the first one found. This should alleviate the need to configure `ssl.ca.location` when the statically linked OpenSSL's OPENSSLDIR differs from the system's CA certificate path. * The heuristics for handling Apache Kafka < 0.10 brokers has been removed to improve connection error handling for modern Kafka versions. Users on Brokers 0.9.x or older should already be configuring `api.version.request=false` and `broker.version.fallback=...` so there should be no functional change. * The default producer batch accumulation time, `linger.ms`, has been changed from 0.5ms to 5ms to improve batch sizes and throughput while reducing the per-message protocol overhead. Applications that require lower produce latency than 5ms will need to manually set `linger.ms` to a lower value. * librdkafka's build tooling now requires Python 3.x (python3 interpreter). ## Fixes ### General fixes * The client could crash in rare circumstances on ApiVersion or SaslHandshake request timeouts (#2326) * `./configure --LDFLAGS='a=b, c=d'` with arguments containing = are now supported (by @sky92zwq). * `./configure` arguments now take precedence over cached `configure` variables from previous invocation. * Fix theoretical crash on coord request failure. * Unknown partition error could be triggered for existing partitions when additional partitions were added to a topic (@benesch, #2915) * Quickly refresh topic metadata for desired but non-existent partitions. This will speed up the initial discovery delay when new partitions are added to an existing topic (#2917). ### Consumer fixes * The roundrobin partition assignor could crash if subscriptions where asymmetrical (different sets from different members of the group). Thanks to @ankon and @wilmai for identifying the root cause (#2121). * The consumer assignors could ignore some topics if there were more subscribed topics than consumers in taking part in the assignment. * The consumer would connect to all partition leaders of a topic even for partitions that were not being consumed (#2826). * Initial consumer group joins should now be a couple of seconds quicker thanks expedited query intervals (@benesch). * Fix crash and/or inconsistent subscriptions when using multiple consumers (in the same process) with wildcard topics on Windows. * Don't propagate temporary offset lookup errors to application. * Immediately refresh topic metadata when partitions are reassigned to other brokers, avoiding a fetch stall of up to `topic.metadata.refresh.interval.ms`. (#2955) * Memory for batches containing control messages would not be freed when using the batch consume APIs (@pf-qiu, #2990). ### Producer fixes * Proper locking for transaction state in EndTxn handler. # librdkafka v1.4.4 v1.4.4 is a maintenance release with the following fixes and enhancements: * Transactional producer could crash on request timeout due to dereferencing NULL pointer of non-existent response object. * Mark `rd_kafka_send_offsets_to_transaction()` CONCURRENT_TRANSACTION (et.al) errors as retriable. * Fix crash on transactional coordinator FindCoordinator request failure. * Minimize broker re-connect delay when broker's connection is needed to send requests. * Proper locking for transaction state in EndTxn handler. * `socket.timeout.ms` was ignored when `transactional.id` was set. * Added RTT/delay simulation to mock brokers. *Note: there was no v1.4.3 librdkafka release* # librdkafka v1.4.2 v1.4.2 is a maintenance release with the following fixes and enhancements: * Fix produce/consume hang after partition goes away and comes back, such as when a topic is deleted and re-created. * Consumer: Reset the stored offset when partitions are un-assign()ed (fixes #2782). This fixes the case where a manual offset-less commit() or the auto-committer would commit a stored offset from a previous assignment before a new message was consumed by the application. * Probe known CA cert paths and set default `ssl.ca.location` accordingly if OpenSSL is statically linked or `ssl.ca.location` is set to `probe`. * Per-partition OffsetCommit errors were unhandled (fixes #2791) * Seed the PRNG (random number generator) by default, allow application to override with `enable.random.seed=false` (#2795) * Fix stack overwrite (of 1 byte) when SaslHandshake MechCnt is zero * Align bundled c11 threads (tinycthreads) constants to glibc and musl (#2681) * Fix return value of rd_kafka_test_fatal_error() (by @ckb42) * Ensure CMake sets disabled defines to zero on Windows (@benesch) *Note: there was no v1.4.1 librdkafka release* # Older releases See https://github.com/edenhill/librdkafka/releases