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use std::collections::HashMap;
use std::time::Duration;
use crate::client::{self, FetchOffset, GroupOffsetStorage, KafkaClient};
use crate::error::{Error, Result};
use super::assignment;
use super::config::Config;
use super::state::State;
use super::{Consumer, DEFAULT_FALLBACK_OFFSET, DEFAULT_RETRY_MAX_BYTES_LIMIT};
#[cfg(feature = "security")]
use crate::client::SecurityConfig;
#[cfg(not(feature = "security"))]
type SecurityConfig = ();
/// A Kafka Consumer builder easing the process of setting up various
/// configuration settings.
#[derive(Debug)]
pub struct Builder {
client: Option<KafkaClient>,
hosts: Vec<String>,
group: String,
assignments: HashMap<String, Vec<i32>>,
fallback_offset: FetchOffset,
fetch_max_wait_time: Duration,
fetch_min_bytes: i32,
fetch_max_bytes_per_partition: i32,
retry_max_bytes_limit: i32,
fetch_crc_validation: bool,
security_config: Option<SecurityConfig>,
group_offset_storage: Option<GroupOffsetStorage>,
conn_idle_timeout: Duration,
client_id: Option<String>,
}
// ~ public only to be shared inside the kafka crate; not supposed to
// be published outside the crate itself
pub fn new(client: Option<KafkaClient>, hosts: Vec<String>) -> Builder {
let mut b = Builder {
client,
hosts,
fetch_max_wait_time: Duration::from_millis(client::DEFAULT_FETCH_MAX_WAIT_TIME_MILLIS),
fetch_min_bytes: client::DEFAULT_FETCH_MIN_BYTES,
fetch_max_bytes_per_partition: client::DEFAULT_FETCH_MAX_BYTES_PER_PARTITION,
fetch_crc_validation: client::DEFAULT_FETCH_CRC_VALIDATION,
retry_max_bytes_limit: DEFAULT_RETRY_MAX_BYTES_LIMIT,
group: String::new(),
assignments: HashMap::new(),
fallback_offset: DEFAULT_FALLBACK_OFFSET,
security_config: None,
group_offset_storage: client::DEFAULT_GROUP_OFFSET_STORAGE,
conn_idle_timeout: Duration::from_millis(client::DEFAULT_CONNECTION_IDLE_TIMEOUT_MILLIS),
client_id: None,
};
if let Some(ref c) = b.client {
b.fetch_max_wait_time = c.fetch_max_wait_time();
b.fetch_min_bytes = c.fetch_min_bytes();
b.fetch_max_bytes_per_partition = c.fetch_max_bytes_per_partition();
b.fetch_crc_validation = c.fetch_crc_validation();
b.group_offset_storage = c.group_offset_storage();
b.conn_idle_timeout = c.connection_idle_timeout();
}
b
}
impl Builder {
/// Specifies the group on whose behalf to maintain consumed
/// message offsets.
///
/// The group is allowed to be the empty string, in which case the
/// resulting consumer will be group-less.
#[must_use]
pub fn with_group(mut self, group: String) -> Builder {
self.group = group;
self
}
/// Specifies a topic to consume. All of the available partitions
/// of the identified topic will be consumed unless overridden
/// later using `with_topic_partitions`.
///
/// This method may be called multiple times to assign the
/// consumer multiple topics.
///
/// This method or `with_topic_partitions` must be called at least
/// once, to assign a topic to the consumer.
#[must_use]
pub fn with_topic(mut self, topic: String) -> Builder {
self.assignments.insert(topic, Vec::new());
self
}
/// Explicitly specifies topic partitions to consume. Only the
/// specified partitions for the identified topic will be consumed
/// unless overridden later using `with_topic`.
///
/// This method may be called multiple times to subscribe to
/// multiple topics.
///
/// This method or `with_topic` must be called at least once, to
/// assign a topic to the consumer.
#[must_use]
pub fn with_topic_partitions(mut self, topic: String, partitions: &[i32]) -> Builder {
self.assignments.insert(topic, partitions.to_vec());
self
}
/// Specifies the security config to use.
/// See `KafkaClient::new_secure` for more info.
#[cfg(feature = "security")]
#[must_use]
pub fn with_security(mut self, sec: SecurityConfig) -> Builder {
self.security_config = Some(sec);
self
}
/// Specifies the offset to use when none was committed for the
/// underlying group yet or the consumer has no group configured.
///
/// Running the underlying group for the first time against a
/// topic or running the consumer without a group results in the
/// question where to start reading from the topic, since it might
/// already contain a lot of messages. Common strategies are
/// starting at the earliest available message (thereby consuming
/// whatever is currently in the topic) or at the latest one
/// (thereby staring to consume only newly arriving messages.)
/// The "fallback offset" here corresponds to `time` in
/// `KafkaClient::fetch_offsets`.
#[must_use]
pub fn with_fallback_offset(mut self, fallback_offset: FetchOffset) -> Builder {
self.fallback_offset = fallback_offset;
self
}
/// See `KafkaClient::set_fetch_max_wait_time`
#[must_use]
pub fn with_fetch_max_wait_time(mut self, max_wait_time: Duration) -> Builder {
self.fetch_max_wait_time = max_wait_time;
self
}
/// See `KafkaClient::set_fetch_min_bytes`
#[must_use]
pub fn with_fetch_min_bytes(mut self, min_bytes: i32) -> Builder {
self.fetch_min_bytes = min_bytes;
self
}
/// See `KafkaClient::set_fetch_max_bytes_per_partition`
#[must_use]
pub fn with_fetch_max_bytes_per_partition(mut self, max_bytes_per_partition: i32) -> Builder {
self.fetch_max_bytes_per_partition = max_bytes_per_partition;
self
}
/// See `KafkaClient::set_fetch_crc_validation`
#[must_use]
pub fn with_fetch_crc_validation(mut self, validate_crc: bool) -> Builder {
self.fetch_crc_validation = validate_crc;
self
}
/// See `KafkaClient::set_group_offset_storage`
#[must_use]
pub fn with_offset_storage(mut self, storage: Option<GroupOffsetStorage>) -> Builder {
self.group_offset_storage = storage;
self
}
/// Specifies the upper bound of data bytes to allow fetching from
/// a kafka partition when retrying a fetch request due to a too
/// big message in the partition.
///
/// By default, this consumer will fetch up to
/// `KafkaClient::fetch_max_bytes_per_partition` data from each
/// partition. However, when it discovers that there are messages
/// in an underlying partition which could not be delivered, the
/// request to that partition might be retried a few times with an
/// increased `fetch_max_bytes_per_partition`. The value
/// specified here defines a limit to this increment.
///
/// A value smaller than the
/// `KafkaClient::fetch_max_bytes_per_partition`, e.g. zero, will
/// disable the retry feature of this consumer. The default value
/// for this setting is `DEFAULT_RETRY_MAX_BYTES_LIMIT`.
///
/// Note: if the consumed topic partitions are known to host large
/// messages it is much more efficient to set
/// `KafkaClient::fetch_max_bytes_per_partition` appropriately
/// instead of relying on the limit specified here. This limit is
/// just an upper bound for already additional retry requests.
#[must_use]
pub fn with_retry_max_bytes_limit(mut self, limit: i32) -> Builder {
self.retry_max_bytes_limit = limit;
self
}
/// Specifies the timeout for idle connections.
/// See `KafkaClient::set_connection_idle_timeout`.
#[must_use]
pub fn with_connection_idle_timeout(mut self, timeout: Duration) -> Self {
self.conn_idle_timeout = timeout;
self
}
/// Specifies a `client_id` to be sent along every request to Kafka
/// brokers. See `KafkaClient::set_client_id`.
#[must_use]
pub fn with_client_id(mut self, client_id: String) -> Self {
self.client_id = Some(client_id);
self
}
#[cfg(not(feature = "security"))]
#[must_use]
fn new_kafka_client(hosts: Vec<String>, _: Option<SecurityConfig>) -> KafkaClient {
KafkaClient::new(hosts)
}
#[cfg(feature = "security")]
fn new_kafka_client(hosts: Vec<String>, security: Option<SecurityConfig>) -> KafkaClient {
if let Some(security) = security {
KafkaClient::new_secure(hosts, security)
} else {
KafkaClient::new(hosts)
}
}
/// Finally creates/builds a new consumer based on the so far
/// supplied settings.
///
/// Fails with the `NoTopicsAssigned` error, if neither
/// `with_topic` nor `with_topic_partitions` have been called to
/// assign at least one topic for consumption.
pub fn create(self) -> Result<Consumer> {
// ~ fail immediately if there's no topic to be consumed
if self.assignments.is_empty() {
return Err(Error::NoTopicsAssigned);
}
// ~ create the client if necessary
let (mut client, need_metadata) = match self.client {
Some(client) => (client, false),
None => (
Self::new_kafka_client(self.hosts, self.security_config),
true,
),
};
// ~ apply configuration settings
client.set_fetch_max_wait_time(self.fetch_max_wait_time)?;
client.set_fetch_min_bytes(self.fetch_min_bytes);
client.set_fetch_max_bytes_per_partition(self.fetch_max_bytes_per_partition);
client.set_group_offset_storage(self.group_offset_storage);
client.set_connection_idle_timeout(self.conn_idle_timeout);
if let Some(client_id) = self.client_id {
client.set_client_id(client_id);
}
// ~ load metadata if necessary
if need_metadata {
client.load_metadata_all()?;
}
// ~ load consumer state
let config = Config {
group: self.group,
fallback_offset: self.fallback_offset,
retry_max_bytes_limit: self.retry_max_bytes_limit,
};
let state = State::new(&mut client, &config, assignment::from_map(self.assignments))?;
debug!(
"initialized: Consumer {{ config: {:?}, state: {:?} }}",
config, state
);
Ok(Consumer {
client,
state,
config,
})
}
}