kafka¶
Connects to Kafka brokers and consumes one or more topics.
YAML Configurations¶
Common Config¶
# Common config fields, showing default values
input:
label: ""
kafka:
addresses: []
topics: []
target_version: 2.0.0
consumer_group: ""
checkpoint_limit: 1024
Advanced Config¶
# All config fields, showing default values
input:
label: ""
kafka:
addresses: []
topics: []
target_version: 2.0.0
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: benthos
rack_id: ""
start_from_oldest: true
checkpoint_limit: 1024
commit_period: 1s
max_processing_period: 100ms
extract_tracing_map: ""
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: []
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, but by default, messages of the same topic partition are processed in lockstep in order to enforce ordered processing. This protection often means that batching messages at the output level can stall, in which case it can be tuned by increasing the field checkpoint_limit, ideally to a value greater than the number of messages you expect to batch.
Alternatively, if you perform batching at the input level using the batching field, it is done per partition and therefore avoids stalling.
Metadata¶
This input adds the following metadata fields to each message:
- kafka_key
- kafka_topic
- kafka_partition
- kafka_offset
- kafka_lag
- kafka_timestamp_unix
- All existing message headers (version 0.11+)
The field kafka_lag is the calculated difference between the high watermark 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
Default: []
# 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 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
Default: []
# 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.
Type: string
Default: "2.0.0"
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
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.
🗣 SECRET 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.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: ""
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.
🗣 SECRET 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.
🗣 SECRET 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: ""
sasl¶
Enables SASL authentication.
Type: object
sasl.mechanism¶
The SASL authentication mechanism, if left empty SASL authentication is not used. Warning: SCRAM-based methods within Benthos have not received a security audit.
Type: string
Default: "none"
| Option | Summary |
|---|---|
| none | Default, no SASL authentication. |
| PLAIN | Plain text authentication. NOTE: When using plain text auth it is extremely likely that you'll also need to enable TLS. |
| OAUTHBEARER | OAuth Bearer-based authentication. |
| SCRAM-SHA-256 | Authentication using the SCRAM-SHA-256 mechanism. |
| SCRAM-SHA-512 | Authentication using the SCRAM-SHA-512 mechanism. |
sasl.user¶
A PLAIN username. It is recommended that you use environment variables to populate this field.
Type: string
Default: ""
sasl.password¶
A PLAIN password. It is recommended that you use environment variables to populate this field.
🗣 SECRET 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: ""
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: "benthos"
rack_id¶
A rack identifier for this client.
Type: string
Default: ""
start_from_oldest¶
If an offset is not found for a topic partition, determines whether to consume from the oldest available offset; otherwise, messages are consumed from the latest offset.
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
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
Default: ""
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 the 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: ""
batching.check¶
A Bloblang query that should return a boolean value indicating whether a message should end a batch.
Type: string
Default: ""
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
Default: []