kafka
The kafka output type writes a batch of messages to Kafka brokers and waits for acknowledgement before propagating it back to the input.
- Common
- Advanced
# Common config fields, showing default values
output:
label: ""
kafka:
addresses: [] # No default (required)
topic: "" # No default (required)
target_version: 2.1.0 # No default (optional)
key: ""
partitioner: fnv1a_hash
compression: none
static_headers: {} # No default (optional)
metadata:
exclude_prefixes: []
max_in_flight: 64
batching:
count: 0
byte_size: 0
period: ""
check: ""
# All config fields, showing default values
output:
label: ""
kafka:
addresses: [] # No default (required)
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: ""
topic: "" # No default (required)
client_id: bento
target_version: 2.1.0 # No default (optional)
rack_id: ""
key: ""
partitioner: fnv1a_hash
partition: ""
custom_topic_creation:
enabled: false
partitions: -1
replication_factor: -1
compression: none
static_headers: {} # No default (optional)
metadata:
exclude_prefixes: []
inject_tracing_map: meta = @.merge(this) # No default (optional)
max_in_flight: 64
idempotent_write: false
ack_replicas: false
max_msg_bytes: 1000000
timeout: 5s
retry_as_batch: false
batching:
count: 0
byte_size: 0
period: ""
check: ""
processors: [] # No default (optional)
max_retries: 0
backoff:
initial_interval: 3s
max_interval: 10s
max_elapsed_time: 30s
The config field ack_replicas
determines whether we wait for acknowledgement from all replicas or just a single broker.
Both the key
and topic
fields can be dynamically set using function interpolations described here.
Metadata will be added to each message sent as headers (version 0.11+), but can be restricted using the field metadata
.
Strict Ordering and Retries
When strict ordering is required for messages written to topic partitions it is important to ensure that both the field max_in_flight
is set to 1
and that the field retry_as_batch
is set to true
.
You must also ensure that failed batches are never rerouted back to the same output. This can be done by setting the field max_retries
to 0
and backoff.max_elapsed_time
to empty, which will apply back pressure indefinitely until the batch is sent successfully.
However, this also means that manual intervention will eventually be required in cases where the batch cannot be sent due to configuration problems such as an incorrect max_msg_bytes
estimate. A less strict but automated alternative would be to route failed batches to a dead letter queue using a fallback
broker, but this would allow subsequent batches to be delivered in the meantime whilst those failed batches are dealt with.
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
output.
- 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.
Performance
This output benefits from sending multiple messages in flight in parallel for improved performance. You can tune the max number of in flight messages (or message batches) with the field max_in_flight
.
This output benefits from sending messages as a batch for improved performance. Batches can be formed at both the input and output level. You can find out more in this doc.
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
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: ""
topic
The topic to publish messages to. This field supports interpolation functions.
Type: string
client_id
An identifier for the client connection.
Type: string
Default: "bento"
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
rack_id
A rack identifier for this client.
Type: string
Default: ""
key
The key to publish messages with. This field supports interpolation functions.
Type: string
Default: ""
partitioner
The partitioning algorithm to use.
Type: string
Default: "fnv1a_hash"
Options: fnv1a_hash
, murmur2_hash
, random
, round_robin
, manual
.
partition
The manually-specified partition to publish messages to, relevant only when the field partitioner
is set to manual
. Must be able to parse as a 32-bit integer.
This field supports interpolation functions.
Type: string
Default: ""
custom_topic_creation
If enabled, topics will be created with the specified number of partitions and replication factor if they do not already exist.
Type: object
custom_topic_creation.enabled
Whether to enable custom topic creation.
Type: bool
Default: false
custom_topic_creation.partitions
The number of partitions to create for new topics. Leave at -1 to use the broker configured default. Must be >= 1.
Type: int
Default: -1
custom_topic_creation.replication_factor
The replication factor to use for new topics. Leave at -1 to use the broker configured default. Must be an odd number, and less then or equal to the number of brokers.
Type: int
Default: -1
compression
The compression algorithm to use.
Type: string
Default: "none"
Options: none
, snappy
, lz4
, gzip
, zstd
.
static_headers
An optional map of static headers that should be added to messages in addition to metadata.
Type: object
# Examples
static_headers:
first-static-header: value-1
second-static-header: value-2
metadata
Specify criteria for which metadata values are sent with messages as headers.
Type: object
metadata.exclude_prefixes
Provide a list of explicit metadata key prefixes to be excluded when adding metadata to sent messages.
Type: array
Default: []
inject_tracing_map
EXPERIMENTAL: A Bloblang mapping used to inject an object containing tracing propagation information into outbound messages. The specification of the injected fields will match the format used by the service wide tracer.
Type: string
Requires version 1.0.0 or newer
# Examples
inject_tracing_map: meta = @.merge(this)
inject_tracing_map: root.meta.span = this
max_in_flight
The maximum number of messages to have in flight at a given time. Increase this to improve throughput.
Type: int
Default: 64
idempotent_write
Enable the idempotent write producer option. This requires the IDEMPOTENT_WRITE
permission on CLUSTER
and can be disabled if this permission is not available.
Type: bool
Default: false
ack_replicas
Ensure that messages have been copied across all replicas before acknowledging receipt.
Type: bool
Default: false
max_msg_bytes
The maximum size in bytes of messages sent to the target topic.
Type: int
Default: 1000000
timeout
The maximum period of time to wait for message sends before abandoning the request and retrying.
Type: string
Default: "5s"
retry_as_batch
When enabled forces an entire batch of messages to be retried if any individual message fails on a send, otherwise only the individual messages that failed are retried. Disabling this helps to reduce message duplicates during intermittent errors, but also makes it impossible to guarantee strict ordering of messages.
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
max_retries
The maximum number of retries before giving up on the request. If set to zero there is no discrete limit.
Type: int
Default: 0
backoff
Control time intervals between retry attempts.
Type: object
backoff.initial_interval
The initial period to wait between retry attempts.
Type: string
Default: "3s"
# Examples
initial_interval: 50ms
initial_interval: 1s
backoff.max_interval
The maximum period to wait between retry attempts
Type: string
Default: "10s"
# Examples
max_interval: 5s
max_interval: 1m
backoff.max_elapsed_time
The maximum overall period of time to spend on retry attempts before the request is aborted. Setting this value to a zeroed duration (such as 0s
) will result in unbounded retries.
Type: string
Default: "30s"
# Examples
max_elapsed_time: 1m
max_elapsed_time: 1h