//@file
## Global configuration properties

Property                                 | C/P | Range           |       Default | Description              
-----------------------------------------|-----|-----------------|--------------:|--------------------------
builtin.features                         |  *  |                 | gzip, snappy, ssl, sasl, regex, lz4, sasl_gssapi, sasl_plain, sasl_scram, plugins | Indicates the builtin features for this build of librdkafka. An application can either query this value or attempt to set it with its list of required features to check for library support. <br>*Type: CSV flags*
client.id                                |  *  |                 |       rdkafka | Client identifier. <br>*Type: string*
metadata.broker.list                     |  *  |                 |               | Initial list of brokers as a CSV list of broker host or host:port. The application may also use `rd_kafka_brokers_add()` to add brokers during runtime. <br>*Type: string*
bootstrap.servers                        |  *  |                 |               | Alias for `metadata.broker.list`
message.max.bytes                        |  *  | 1000 .. 1000000000 |       1000000 | Maximum Kafka protocol request message size. <br>*Type: integer*
message.copy.max.bytes                   |  *  | 0 .. 1000000000 |         65535 | Maximum size for message to be copied to buffer. Messages larger than this will be passed by reference (zero-copy) at the expense of larger iovecs. <br>*Type: integer*
receive.message.max.bytes                |  *  | 1000 .. 2147483647 |     100000000 | Maximum Kafka protocol response message size. This serves as a safety precaution to avoid memory exhaustion in case of protocol hickups. This value is automatically adjusted upwards to be at least `fetch.max.bytes` + 512 to allow for protocol overhead. <br>*Type: integer*
max.in.flight.requests.per.connection    |  *  | 1 .. 1000000    |       1000000 | Maximum number of in-flight requests per broker connection. This is a generic property applied to all broker communication, however it is primarily relevant to produce requests. In particular, note that other mechanisms limit the number of outstanding consumer fetch request per broker to one. <br>*Type: integer*
max.in.flight                            |  *  |                 |               | Alias for `max.in.flight.requests.per.connection`
metadata.request.timeout.ms              |  *  | 10 .. 900000    |         60000 | Non-topic request timeout in milliseconds. This is for metadata requests, etc. <br>*Type: integer*
topic.metadata.refresh.interval.ms       |  *  | -1 .. 3600000   |        300000 | Topic metadata refresh interval in milliseconds. The metadata is automatically refreshed on error and connect. Use -1 to disable the intervalled refresh. <br>*Type: integer*
metadata.max.age.ms                      |  *  | 1 .. 86400000   |            -1 | Metadata cache max age. Defaults to metadata.refresh.interval.ms * 3 <br>*Type: integer*
topic.metadata.refresh.fast.interval.ms  |  *  | 1 .. 60000      |           250 | When a topic loses its leader a new metadata request will be enqueued with this initial interval, exponentially increasing until the topic metadata has been refreshed. This is used to recover quickly from transitioning leader brokers. <br>*Type: integer*
topic.metadata.refresh.fast.cnt          |  *  | 0 .. 1000       |            10 | *Deprecated: No longer used.* <br>*Type: integer*
topic.metadata.refresh.sparse            |  *  | true, false     |          true | Sparse metadata requests (consumes less network bandwidth) <br>*Type: boolean*
topic.blacklist                          |  *  |                 |               | Topic blacklist, a comma-separated list of regular expressions for matching topic names that should be ignored in broker metadata information as if the topics did not exist. <br>*Type: pattern list*
debug                                    |  *  | generic, broker, topic, metadata, feature, queue, msg, protocol, cgrp, security, fetch, interceptor, plugin, consumer, all |               | A comma-separated list of debug contexts to enable. Detailed Producer debugging: broker,topic,msg. Consumer: consumer,cgrp,topic,fetch <br>*Type: CSV flags*
socket.timeout.ms                        |  *  | 10 .. 300000    |         60000 | Default timeout for network requests. Producer: ProduceRequests will use the lesser value of socket.timeout.ms and remaining message.timeout.ms for the first message in the batch. Consumer: FetchRequests will use fetch.wait.max.ms + socket.timeout.ms.  <br>*Type: integer*
socket.blocking.max.ms                   |  *  | 1 .. 60000      |          1000 | Maximum time a broker socket operation may block. A lower value improves responsiveness at the expense of slightly higher CPU usage. **Deprecated** <br>*Type: integer*
socket.send.buffer.bytes                 |  *  | 0 .. 100000000  |             0 | Broker socket send buffer size. System default is used if 0. <br>*Type: integer*
socket.receive.buffer.bytes              |  *  | 0 .. 100000000  |             0 | Broker socket receive buffer size. System default is used if 0. <br>*Type: integer*
socket.keepalive.enable                  |  *  | true, false     |         false | Enable TCP keep-alives (SO_KEEPALIVE) on broker sockets <br>*Type: boolean*
socket.nagle.disable                     |  *  | true, false     |         false | Disable the Nagle algorithm (TCP_NODELAY). <br>*Type: boolean*
socket.max.fails                         |  *  | 0 .. 1000000    |             1 | Disconnect from broker when this number of send failures (e.g., timed out requests) is reached. Disable with 0. NOTE: The connection is automatically re-established. <br>*Type: integer*
broker.address.ttl                       |  *  | 0 .. 86400000   |          1000 | How long to cache the broker address resolving results (milliseconds). <br>*Type: integer*
broker.address.family                    |  *  | any, v4, v6     |           any | Allowed broker IP address families: any, v4, v6 <br>*Type: enum value*
reconnect.backoff.jitter.ms              |  *  | 0 .. 3600000    |           500 | Throttle broker reconnection attempts by this value +-50%. <br>*Type: integer*
statistics.interval.ms                   |  *  | 0 .. 86400000   |             0 | librdkafka statistics emit interval. The application also needs to register a stats callback using `rd_kafka_conf_set_stats_cb()`. The granularity is 1000ms. A value of 0 disables statistics. <br>*Type: integer*
enabled_events                           |  *  | 0 .. 2147483647 |             0 | See `rd_kafka_conf_set_events()` <br>*Type: integer*
error_cb                                 |  *  |                 |               | Error callback (set with rd_kafka_conf_set_error_cb()) <br>*Type: pointer*
throttle_cb                              |  *  |                 |               | Throttle callback (set with rd_kafka_conf_set_throttle_cb()) <br>*Type: pointer*
stats_cb                                 |  *  |                 |               | Statistics callback (set with rd_kafka_conf_set_stats_cb()) <br>*Type: pointer*
log_cb                                   |  *  |                 |               | Log callback (set with rd_kafka_conf_set_log_cb()) <br>*Type: pointer*
log_level                                |  *  | 0 .. 7          |             6 | Logging level (syslog(3) levels) <br>*Type: integer*
log.queue                                |  *  | true, false     |         false | Disable spontaneous log_cb from internal librdkafka threads, instead enqueue log messages on queue set with `rd_kafka_set_log_queue()` and serve log callbacks or events through the standard poll APIs. **NOTE**: Log messages will linger in a temporary queue until the log queue has been set. <br>*Type: boolean*
log.thread.name                          |  *  | true, false     |          true | Print internal thread name in log messages (useful for debugging librdkafka internals) <br>*Type: boolean*
log.connection.close                     |  *  | true, false     |          true | Log broker disconnects. It might be useful to turn this off when interacting with 0.9 brokers with an aggressive `connection.max.idle.ms` value. <br>*Type: boolean*
socket_cb                                |  *  |                 |               | Socket creation callback to provide race-free CLOEXEC <br>*Type: pointer*
connect_cb                               |  *  |                 |               | Socket connect callback <br>*Type: pointer*
closesocket_cb                           |  *  |                 |               | Socket close callback <br>*Type: pointer*
open_cb                                  |  *  |                 |               | File open callback to provide race-free CLOEXEC <br>*Type: pointer*
opaque                                   |  *  |                 |               | Application opaque (set with rd_kafka_conf_set_opaque()) <br>*Type: pointer*
default_topic_conf                       |  *  |                 |               | Default topic configuration for automatically subscribed topics <br>*Type: pointer*
internal.termination.signal              |  *  | 0 .. 128        |             0 | Signal that librdkafka will use to quickly terminate on rd_kafka_destroy(). If this signal is not set then there will be a delay before rd_kafka_wait_destroyed() returns true as internal threads are timing out their system calls. If this signal is set however the delay will be minimal. The application should mask this signal as an internal signal handler is installed. <br>*Type: integer*
api.version.request                      |  *  | true, false     |          true | Request broker's supported API versions to adjust functionality to available protocol features. If set to false, or the ApiVersionRequest fails, the fallback version `broker.version.fallback` will be used. **NOTE**: Depends on broker version >=0.10.0. If the request is not supported by (an older) broker the `broker.version.fallback` fallback is used. <br>*Type: boolean*
api.version.request.timeout.ms           |  *  | 1 .. 300000     |         10000 | Timeout for broker API version requests. <br>*Type: integer*
api.version.fallback.ms                  |  *  | 0 .. 604800000  |       1200000 | Dictates how long the `broker.version.fallback` fallback is used in the case the ApiVersionRequest fails. **NOTE**: The ApiVersionRequest is only issued when a new connection to the broker is made (such as after an upgrade). <br>*Type: integer*
broker.version.fallback                  |  *  |                 |         0.9.0 | Older broker versions (<0.10.0) provides no way for a client to query for supported protocol features (ApiVersionRequest, see `api.version.request`) making it impossible for the client to know what features it may use. As a workaround a user may set this property to the expected broker version and the client will automatically adjust its feature set accordingly if the ApiVersionRequest fails (or is disabled). The fallback broker version will be used for `api.version.fallback.ms`. Valid values are: 0.9.0, 0.8.2, 0.8.1, 0.8.0. Any other value, such as 0.10.2.1, enables ApiVersionRequests. <br>*Type: string*
security.protocol                        |  *  | plaintext, ssl, sasl_plaintext, sasl_ssl |     plaintext | Protocol used to communicate with brokers. <br>*Type: enum value*
ssl.cipher.suites                        |  *  |                 |               | A cipher suite is a named combination of authentication, encryption, MAC and key exchange algorithm used to negotiate the security settings for a network connection using TLS or SSL network protocol. See manual page for `ciphers(1)` and `SSL_CTX_set_cipher_list(3). <br>*Type: string*
ssl.key.location                         |  *  |                 |               | Path to client's private key (PEM) used for authentication. <br>*Type: string*
ssl.key.password                         |  *  |                 |               | Private key passphrase <br>*Type: string*
ssl.certificate.location                 |  *  |                 |               | Path to client's public key (PEM) used for authentication. <br>*Type: string*
ssl.ca.location                          |  *  |                 |               | File or directory path to CA certificate(s) for verifying the broker's key. <br>*Type: string*
ssl.crl.location                         |  *  |                 |               | Path to CRL for verifying broker's certificate validity. <br>*Type: string*
ssl.keystore.location                    |  *  |                 |               | Path to client's keystore (PKCS#12) used for authentication. <br>*Type: string*
ssl.keystore.password                    |  *  |                 |               | Client's keystore (PKCS#12) password. <br>*Type: string*
sasl.mechanisms                          |  *  |                 |        GSSAPI | SASL mechanism to use for authentication. Supported: GSSAPI, PLAIN, SCRAM-SHA-256, SCRAM-SHA-512. **NOTE**: Despite the name only one mechanism must be configured. <br>*Type: string*
sasl.mechanism                           |  *  |                 |               | Alias for `sasl.mechanisms`
sasl.kerberos.service.name               |  *  |                 |         kafka | Kerberos principal name that Kafka runs as, not including /hostname@REALM <br>*Type: string*
sasl.kerberos.principal                  |  *  |                 |   kafkaclient | This client's Kerberos principal name. (Not supported on Windows, will use the logon user's principal). <br>*Type: string*
sasl.kerberos.kinit.cmd                  |  *  |                 | kinit -S "%{sasl.kerberos.service.name}/%{broker.name}" -k -t "%{sasl.kerberos.keytab}" %{sasl.kerberos.principal} | Full kerberos kinit command string, %{config.prop.name} is replaced by corresponding config object value, %{broker.name} returns the broker's hostname. <br>*Type: string*
sasl.kerberos.keytab                     |  *  |                 |               | Path to Kerberos keytab file. Uses system default if not set.**NOTE**: This is not automatically used but must be added to the template in sasl.kerberos.kinit.cmd as ` ... -t %{sasl.kerberos.keytab}`. <br>*Type: string*
sasl.kerberos.min.time.before.relogin    |  *  | 1 .. 86400000   |         60000 | Minimum time in milliseconds between key refresh attempts. <br>*Type: integer*
sasl.username                            |  *  |                 |               | SASL username for use with the PLAIN and SASL-SCRAM-.. mechanisms <br>*Type: string*
sasl.password                            |  *  |                 |               | SASL password for use with the PLAIN and SASL-SCRAM-.. mechanism <br>*Type: string*
plugin.library.paths                     |  *  |                 |               | List of plugin libaries to load (; separated). The library search path is platform dependent (see dlopen(3) for Unix and LoadLibrary() for Windows). If no filename extension is specified the platform-specific extension (such as .dll or .so) will be appended automatically. <br>*Type: string*
interceptors                             |  *  |                 |               | Interceptors added through rd_kafka_conf_interceptor_add_..() and any configuration handled by interceptors. <br>*Type: *
group.id                                 |  *  |                 |               | Client group id string. All clients sharing the same group.id belong to the same group. <br>*Type: string*
partition.assignment.strategy            |  *  |                 | range,roundrobin | Name of partition assignment strategy to use when elected group leader assigns partitions to group members. <br>*Type: string*
session.timeout.ms                       |  *  | 1 .. 3600000    |         30000 | Client group session and failure detection timeout. <br>*Type: integer*
heartbeat.interval.ms                    |  *  | 1 .. 3600000    |          1000 | Group session keepalive heartbeat interval. <br>*Type: integer*
group.protocol.type                      |  *  |                 |      consumer | Group protocol type <br>*Type: string*
coordinator.query.interval.ms            |  *  | 1 .. 3600000    |        600000 | How often to query for the current client group coordinator. If the currently assigned coordinator is down the configured query interval will be divided by ten to more quickly recover in case of coordinator reassignment. <br>*Type: integer*
enable.auto.commit                       |  C  | true, false     |          true | Automatically and periodically commit offsets in the background. Note: setting this to false does not prevent the consumer from fetching previously committed start offsets. To circumvent this behaviour set specific start offsets per partition in the call to assign(). <br>*Type: boolean*
auto.commit.interval.ms                  |  C  | 0 .. 86400000   |          5000 | The frequency in milliseconds that the consumer offsets are committed (written) to offset storage. (0 = disable). This setting is used by the high-level consumer. <br>*Type: integer*
enable.auto.offset.store                 |  C  | true, false     |          true | Automatically store offset of last message provided to application. <br>*Type: boolean*
queued.min.messages                      |  C  | 1 .. 10000000   |        100000 | Minimum number of messages per topic+partition librdkafka tries to maintain in the local consumer queue. <br>*Type: integer*
queued.max.messages.kbytes               |  C  | 1 .. 2097151    |       1048576 | Maximum number of kilobytes per topic+partition in the local consumer queue. This value may be overshot by fetch.message.max.bytes. This property has higher priority than queued.min.messages. <br>*Type: integer*
fetch.wait.max.ms                        |  C  | 0 .. 300000     |           100 | Maximum time the broker may wait to fill the response with fetch.min.bytes. <br>*Type: integer*
fetch.message.max.bytes                  |  C  | 1 .. 1000000000 |       1048576 | Initial maximum number of bytes per topic+partition to request when fetching messages from the broker. If the client encounters a message larger than this value it will gradually try to increase it until the entire message can be fetched. <br>*Type: integer*
max.partition.fetch.bytes                |  C  |                 |               | Alias for `fetch.message.max.bytes`
fetch.max.bytes                          |  C  | 0 .. 2147483135 |      52428800 | Maximum amount of data the broker shall return for a Fetch request. Messages are fetched in batches by the consumer and if the first message batch in the first non-empty partition of the Fetch request is larger than this value, then the message batch will still be returned to ensure the consumer can make progress. The maximum message batch size accepted by the broker is defined via `message.max.bytes` (broker config) or `max.message.bytes` (broker topic config). `fetch.max.bytes` is automatically adjusted upwards to be at least `message.max.bytes` (consumer config). <br>*Type: integer*
fetch.min.bytes                          |  C  | 1 .. 100000000  |             1 | Minimum number of bytes the broker responds with. If fetch.wait.max.ms expires the accumulated data will be sent to the client regardless of this setting. <br>*Type: integer*
fetch.error.backoff.ms                   |  C  | 0 .. 300000     |           500 | How long to postpone the next fetch request for a topic+partition in case of a fetch error. <br>*Type: integer*
offset.store.method                      |  C  | none, file, broker |        broker | Offset commit store method: 'file' - local file store (offset.store.path, et.al), 'broker' - broker commit store (requires Apache Kafka 0.8.2 or later on the broker). <br>*Type: enum value*
consume_cb                               |  C  |                 |               | Message consume callback (set with rd_kafka_conf_set_consume_cb()) <br>*Type: pointer*
rebalance_cb                             |  C  |                 |               | Called after consumer group has been rebalanced (set with rd_kafka_conf_set_rebalance_cb()) <br>*Type: pointer*
offset_commit_cb                         |  C  |                 |               | Offset commit result propagation callback. (set with rd_kafka_conf_set_offset_commit_cb()) <br>*Type: pointer*
enable.partition.eof                     |  C  | true, false     |          true | Emit RD_KAFKA_RESP_ERR__PARTITION_EOF event whenever the consumer reaches the end of a partition. <br>*Type: boolean*
check.crcs                               |  C  | true, false     |         false | Verify CRC32 of consumed messages, ensuring no on-the-wire or on-disk corruption to the messages occurred. This check comes at slightly increased CPU usage. <br>*Type: boolean*
queue.buffering.max.messages             |  P  | 1 .. 10000000   |        100000 | Maximum number of messages allowed on the producer queue. <br>*Type: integer*
queue.buffering.max.kbytes               |  P  | 1 .. 2097151    |       1048576 | Maximum total message size sum allowed on the producer queue. This property has higher priority than queue.buffering.max.messages. <br>*Type: integer*
queue.buffering.max.ms                   |  P  | 0 .. 900000     |             0 | Delay in milliseconds to wait for messages in the producer queue to accumulate before constructing message batches (MessageSets) to transmit to brokers. A higher value allows larger and more effective (less overhead, improved compression) batches of messages to accumulate at the expense of increased message delivery latency. <br>*Type: integer*
linger.ms                                |  P  |                 |               | Alias for `queue.buffering.max.ms`
message.send.max.retries                 |  P  | 0 .. 10000000   |             2 | How many times to retry sending a failing MessageSet. **Note:** retrying may cause reordering. <br>*Type: integer*
retries                                  |  P  |                 |               | Alias for `message.send.max.retries`
retry.backoff.ms                         |  P  | 1 .. 300000     |           100 | The backoff time in milliseconds before retrying a protocol request. <br>*Type: integer*
queue.buffering.backpressure.threshold   |  P  | 0 .. 1000000    |            10 | The threshold of outstanding not yet transmitted requests needed to backpressure the producer's message accumulator. A lower number yields larger and more effective batches. <br>*Type: integer*
compression.codec                        |  P  | none, gzip, snappy, lz4 |          none | compression codec to use for compressing message sets. This is the default value for all topics, may be overriden by the topic configuration property `compression.codec`.  <br>*Type: enum value*
compression.type                         |  P  |                 |               | Alias for `compression.codec`
batch.num.messages                       |  P  | 1 .. 1000000    |         10000 | Maximum number of messages batched in one MessageSet. The total MessageSet size is also limited by message.max.bytes. <br>*Type: integer*
delivery.report.only.error               |  P  | true, false     |         false | Only provide delivery reports for failed messages. <br>*Type: boolean*
dr_cb                                    |  P  |                 |               | Delivery report callback (set with rd_kafka_conf_set_dr_cb()) <br>*Type: pointer*
dr_msg_cb                                |  P  |                 |               | Delivery report callback (set with rd_kafka_conf_set_dr_msg_cb()) <br>*Type: pointer*


## Topic configuration properties

Property                                 | C/P | Range           |       Default | Description              
-----------------------------------------|-----|-----------------|--------------:|--------------------------
request.required.acks                    |  P  | -1 .. 1000      |             1 | This field indicates how many acknowledgements the leader broker must receive from ISR brokers before responding to the request: *0*=Broker does not send any response/ack to client, *1*=Only the leader broker will need to ack the message, *-1* or *all*=broker will block until message is committed by all in sync replicas (ISRs) or broker's `min.insync.replicas` setting before sending response.  <br>*Type: integer*
acks                                     |  P  |                 |               | Alias for `request.required.acks`
request.timeout.ms                       |  P  | 1 .. 900000     |          5000 | The ack timeout of the producer request in milliseconds. This value is only enforced by the broker and relies on `request.required.acks` being != 0. <br>*Type: integer*
message.timeout.ms                       |  P  | 0 .. 900000     |        300000 | Local message timeout. This value is only enforced locally and limits the time a produced message waits for successful delivery. A time of 0 is infinite. <br>*Type: integer*
queuing.strategy                         |  P  | fifo, lifo      |          fifo | Producer queuing strategy. FIFO preserves produce ordering, while LIFO prioritizes new messages. WARNING: `lifo` is experimental and subject to change or removal. <br>*Type: enum value*
produce.offset.report                    |  P  | true, false     |         false | Report offset of produced message back to application. The application must be use the `dr_msg_cb` to retrieve the offset from `rd_kafka_message_t.offset`. <br>*Type: boolean*
partitioner                              |  P  |                 | consistent_random | Partitioner: `random` - random distribution, `consistent` - CRC32 hash of key (Empty and NULL keys are mapped to single partition), `consistent_random` - CRC32 hash of key (Empty and NULL keys are randomly partitioned), `murmur2` - Java Producer compatible Murmur2 hash of key (NULL keys are mapped to single partition), `murmur2_random` - Java Producer compatible Murmur2 hash of key (NULL keys are randomly partitioned. This is functionally equivalent to the default partitioner in the Java Producer.). <br>*Type: string*
partitioner_cb                           |  P  |                 |               | Custom partitioner callback (set with rd_kafka_topic_conf_set_partitioner_cb()) <br>*Type: pointer*
msg_order_cmp                            |  P  |                 |               | Message queue ordering comparator (set with rd_kafka_topic_conf_set_msg_order_cmp()). Also see `queuing.strategy`. <br>*Type: pointer*
opaque                                   |  *  |                 |               | Application opaque (set with rd_kafka_topic_conf_set_opaque()) <br>*Type: pointer*
compression.codec                        |  P  | none, gzip, snappy, lz4, inherit |       inherit | Compression codec to use for compressing message sets. inherit = inherit global compression.codec configuration. <br>*Type: enum value*
compression.type                         |  P  |                 |               | Alias for `compression.codec`
auto.commit.enable                       |  C  | true, false     |          true | If true, periodically commit offset of the last message handed to the application. This committed offset will be used when the process restarts to pick up where it left off. If false, the application will have to call `rd_kafka_offset_store()` to store an offset (optional). **NOTE:** This property should only be used with the simple legacy consumer, when using the high-level KafkaConsumer the global `enable.auto.commit` property must be used instead. **NOTE:** There is currently no zookeeper integration, offsets will be written to broker or local file according to offset.store.method. <br>*Type: boolean*
enable.auto.commit                       |  C  |                 |               | Alias for `auto.commit.enable`
auto.commit.interval.ms                  |  C  | 10 .. 86400000  |         60000 | The frequency in milliseconds that the consumer offsets are committed (written) to offset storage. This setting is used by the low-level legacy consumer. <br>*Type: integer*
auto.offset.reset                        |  C  | smallest, earliest, beginning, largest, latest, end, error |       largest | Action to take when there is no initial offset in offset store or the desired offset is out of range: 'smallest','earliest' - automatically reset the offset to the smallest offset, 'largest','latest' - automatically reset the offset to the largest offset, 'error' - trigger an error which is retrieved by consuming messages and checking 'message->err'. <br>*Type: enum value*
offset.store.path                        |  C  |                 |             . | Path to local file for storing offsets. If the path is a directory a filename will be automatically generated in that directory based on the topic and partition. <br>*Type: string*
offset.store.sync.interval.ms            |  C  | -1 .. 86400000  |            -1 | fsync() interval for the offset file, in milliseconds. Use -1 to disable syncing, and 0 for immediate sync after each write. <br>*Type: integer*
offset.store.method                      |  C  | file, broker    |        broker | Offset commit store method: 'file' - local file store (offset.store.path, et.al), 'broker' - broker commit store (requires "group.id" to be configured and Apache Kafka 0.8.2 or later on the broker.). <br>*Type: enum value*
consume.callback.max.messages            |  C  | 0 .. 1000000    |             0 | Maximum number of messages to dispatch in one `rd_kafka_consume_callback*()` call (0 = unlimited) <br>*Type: integer*

### C/P legend: C = Consumer, P = Producer, * = both
