kafka
Connects to Kafka brokers and consumes one or more topics.
- Common
- Advanced
# Common config fields, showing default values
input:
label: ""
kafka:
addresses: [] # No default (required)
topics: [] # No default (required)
target_version: 2.1.0 # No default (optional)
consumer_group: ""
checkpoint_limit: 1024
auto_replay_nacks: true
# All config fields, showing default values
input:
label: ""
kafka:
addresses: [] # No default (required)
topics: [] # No default (required)
target_version: 2.1.0 # No default (optional)
tls:
enabled: false
skip_cert_verify: false
enable_renegotiation: false
root_cas: ""
root_cas_file: ""
client_certs: []
sasl:
mechanism: none
user: ""
password: ""
access_token: ""
token_cache: ""
token_key: ""
consumer_group: ""
client_id: bento
rack_id: ""
start_from_oldest: true
checkpoint_limit: 1024
auto_replay_nacks: true
commit_period: 1s
max_processing_period: 100ms
extract_tracing_map: root = @ # No default (optional)
group:
session_timeout: 10s
heartbeat_interval: 3s
rebalance_timeout: 60s
fetch_buffer_cap: 256
multi_header: false
batching:
count: 0
byte_size: 0
period: ""
check: ""
processors: [] # No default (optional)
Offsets are managed within Kafka under the specified consumer group, and partitions for each topic are automatically balanced across members of the consumer group.
The Kafka input allows parallel processing of messages from different topic partitions, and messages of the same topic partition are processed with a maximum parallelism determined by the field checkpoint_limit
.
In order to enforce ordered processing of partition messages set the checkpoint_limit
to 1
and this will force partitions to be processed in lock-step, where a message will only be processed once the prior message is delivered.
Batching messages before processing can be enabled using the batching
field, and this batching is performed per-partition such that messages of a batch will always originate from the same partition. This batching mechanism is capable of creating batches of greater size than the checkpoint_limit
, in which case the next batch will only be created upon delivery of the current one.
Metadata
This input adds the following metadata fields to each message:
- kafka_key
- kafka_topic
- kafka_partition
- kafka_offset
- kafka_lag
- kafka_timestamp_unix
- kafka_tombstone_message
- All existing message headers (version 0.11+)
The field kafka_lag
is the calculated difference between the high water mark offset of the partition at the time of ingestion and the current message offset.
You can access these metadata fields using function interpolation.
Ordering
By default messages of a topic partition can be processed in parallel, up to a limit determined by the field checkpoint_limit
. However, if strict ordered processing is required then this value must be set to 1 in order to process shard messages in lock-step. When doing so it is recommended that you perform batching at this component for performance as it will not be possible to batch lock-stepped messages at the output level.
Troubleshooting
If you're seeing issues writing to or reading from Kafka with this component then it's worth trying out the newer kafka_franz
input.
- I'm seeing logs that report
Failed to connect to kafka: kafka: client has run out of available brokers to talk to (Is your cluster reachable?)
, but the brokers are definitely reachable.
Unfortunately this error message will appear for a wide range of connection problems even when the broker endpoint can be reached. Double check your authentication configuration and also ensure that you have enabled TLS if applicable.
Fields
addresses
A list of broker addresses to connect to. If an item of the list contains commas it will be expanded into multiple addresses.
Type: array
# Examples
addresses:
- localhost:9092
addresses:
- localhost:9041,localhost:9042
addresses:
- localhost:9041
- localhost:9042
topics
A list of topics to consume from. Multiple comma separated topics can be listed in a single element. Partitions are automatically distributed across consumers of a topic. Alternatively, it's possible to specify explicit partitions to consume from with a colon after the topic name, e.g. foo:0
would consume the partition 0 of the topic foo. This syntax supports ranges, e.g. foo:0-10
would consume partitions 0 through to 10 inclusive.
Type: array
Requires version 1.0.0 or newer
# Examples
topics:
- foo
- bar
topics:
- foo,bar
topics:
- foo:0
- bar:1
- bar:3
topics:
- foo:0,bar:1,bar:3
topics:
- foo:0-5
target_version
The version of the Kafka protocol to use. This limits the capabilities used by the client and should ideally match the version of your brokers. Defaults to the oldest supported stable version.
Type: string
# Examples
target_version: 2.1.0
target_version: 3.1.0
tls
Custom TLS settings can be used to override system defaults.
Type: object
tls.enabled
Whether custom TLS settings are enabled.
Type: bool
Default: false
tls.skip_cert_verify
Whether to skip server side certificate verification.
Type: bool
Default: false
tls.enable_renegotiation
Whether to allow the remote server to repeatedly request renegotiation. Enable this option if you're seeing the error message local error: tls: no renegotiation
.
Type: bool
Default: false
Requires version 1.0.0 or newer
tls.root_cas
An optional root certificate authority to use. This is a string, representing a certificate chain from the parent trusted root certificate, to possible intermediate signing certificates, to the host certificate.
This field contains sensitive information that usually shouldn't be added to a config directly, read our secrets page for more info.
Type: string
Default: ""
# Examples
root_cas: |-
-----BEGIN CERTIFICATE-----
...
-----END CERTIFICATE-----
tls.root_cas_file
An optional path of a root certificate authority file to use. This is a file, often with a .pem extension, containing a certificate chain from the parent trusted root certificate, to possible intermediate signing certificates, to the host certificate.
Type: string
Default: ""
# Examples
root_cas_file: ./root_cas.pem
tls.client_certs
A list of client certificates to use. For each certificate either the fields cert
and key
, or cert_file
and key_file
should be specified, but not both.
Type: array
Default: []
# Examples
client_certs:
- cert: foo
key: bar
client_certs:
- cert_file: ./example.pem
key_file: ./example.key
tls.client_certs[].cert
A plain text certificate to use.
Type: string
Default: ""
tls.client_certs[].key
A plain text certificate key to use.
This field contains sensitive information that usually shouldn't be added to a config directly, read our secrets page for more info.
Type: string
Default: ""
tls.client_certs[].cert_file
The path of a certificate to use.
Type: string
Default: ""
tls.client_certs[].key_file
The path of a certificate key to use.
Type: string
Default: ""
tls.client_certs[].password
A plain text password for when the private key is password encrypted in PKCS#1 or PKCS#8 format. The obsolete pbeWithMD5AndDES-CBC
algorithm is not supported for the PKCS#8 format. Warning: Since it does not authenticate the ciphertext, it is vulnerable to padding oracle attacks that can let an attacker recover the plaintext.
This field contains sensitive information that usually shouldn't be added to a config directly, read our secrets page for more info.
Type: string
Default: ""
# Examples
password: foo
password: ${KEY_PASSWORD}
sasl
Enables SASL authentication.
Type: object
sasl.mechanism
The SASL authentication mechanism, if left empty SASL authentication is not used.
Type: string
Default: "none"
Option | Summary |
---|---|
OAUTHBEARER | OAuth Bearer based authentication. |
PLAIN | Plain text authentication. NOTE: When using plain text auth it is extremely likely that you'll also need to enable TLS. |
SCRAM-SHA-256 | Authentication using the SCRAM-SHA-256 mechanism. |
SCRAM-SHA-512 | Authentication using the SCRAM-SHA-512 mechanism. |
none | Default, no SASL authentication. |
sasl.user
A PLAIN username. It is recommended that you use environment variables to populate this field.
Type: string
Default: ""
# Examples
user: ${USER}
sasl.password
A PLAIN password. It is recommended that you use environment variables to populate this field.
This field contains sensitive information that usually shouldn't be added to a config directly, read our secrets page for more info.
Type: string
Default: ""
# Examples
password: ${PASSWORD}
sasl.access_token
A static OAUTHBEARER access token
Type: string
Default: ""
sasl.token_cache
Instead of using a static access_token
allows you to query a cache
resource to fetch OAUTHBEARER tokens from
Type: string
Default: ""
sasl.token_key
Required when using a token_cache
, the key to query the cache with for tokens.
Type: string
Default: ""
consumer_group
An identifier for the consumer group of the connection. This field can be explicitly made empty in order to disable stored offsets for the consumed topic partitions.
Type: string
Default: ""
client_id
An identifier for the client connection.
Type: string
Default: "bento"
rack_id
A rack identifier for this client.
Type: string
Default: ""
start_from_oldest
Determines whether to consume from the oldest available offset, otherwise messages are consumed from the latest offset. The setting is applied when creating a new consumer group or the saved offset no longer exists.
Type: bool
Default: true
checkpoint_limit
The maximum number of messages of the same topic and partition that can be processed at a given time. Increasing this limit enables parallel processing and batching at the output level to work on individual partitions. Any given offset will not be committed unless all messages under that offset are delivered in order to preserve at least once delivery guarantees.
Type: int
Default: 1024
Requires version 1.0.0 or newer
auto_replay_nacks
Whether messages that are rejected (nacked) at the output level should be automatically replayed indefinitely, eventually resulting in back pressure if the cause of the rejections is persistent. If set to false
these messages will instead be deleted. Disabling auto replays can greatly improve memory efficiency of high throughput streams as the original shape of the data can be discarded immediately upon consumption and mutation.
Type: bool
Default: true
commit_period
The period of time between each commit of the current partition offsets. Offsets are always committed during shutdown.
Type: string
Default: "1s"
max_processing_period
A maximum estimate for the time taken to process a message, this is used for tuning consumer group synchronization.
Type: string
Default: "100ms"
extract_tracing_map
EXPERIMENTAL: A Bloblang mapping that attempts to extract an object containing tracing propagation information, which will then be used as the root tracing span for the message. The specification of the extracted fields must match the format used by the service wide tracer.
Type: string
Requires version 1.0.0 or newer
# Examples
extract_tracing_map: root = @
extract_tracing_map: root = this.meta.span
group
Tuning parameters for consumer group synchronization.
Type: object
group.session_timeout
A period after which a consumer of the group is kicked after no heartbeats.
Type: string
Default: "10s"
group.heartbeat_interval
A period in which heartbeats should be sent out.
Type: string
Default: "3s"
group.rebalance_timeout
A period after which rebalancing is abandoned if unresolved.
Type: string
Default: "60s"
fetch_buffer_cap
The maximum number of unprocessed messages to fetch at a given time.
Type: int
Default: 256
multi_header
Decode headers into lists to allow handling of multiple values with the same key
Type: bool
Default: false
batching
Allows you to configure a batching policy.
Type: object
# Examples
batching:
byte_size: 5000
count: 0
period: 1s
batching:
count: 10
period: 1s
batching:
check: this.contains("END BATCH")
count: 0
period: 1m
batching.count
A number of messages at which the batch should be flushed. If 0
disables count based batching.
Type: int
Default: 0
batching.byte_size
An amount of bytes at which the batch should be flushed. If 0
disables size based batching.
Type: int
Default: 0
batching.period
A period in which an incomplete batch should be flushed regardless of its size.
Type: string
Default: ""
# Examples
period: 1s
period: 1m
period: 500ms
batching.check
A Bloblang query that should return a boolean value indicating whether a message should end a batch.
Type: string
Default: ""
# Examples
check: this.type == "end_of_transaction"
batching.processors
A list of processors to apply to a batch as it is flushed. This allows you to aggregate and archive the batch however you see fit. Please note that all resulting messages are flushed as a single batch, therefore splitting the batch into smaller batches using these processors is a no-op.
Type: array
# Examples
processors:
- archive:
format: concatenate
processors:
- archive:
format: lines
processors:
- archive:
format: json_array