18.6. Kafka Command-Line Tools¶
The GeoMesa Kafka distribution includes a set of command-line tools for feature management, ingest, export and debugging.
To install the tools, see Setting up the Kafka Command Line Tools.
Once installed, the tools should be available through the command geomesa-kafka:
$ geomesa-kafka
INFO Usage: geomesa-kafka [command] [command options]
Commands:
...
Commands that are common to multiple back ends are described in Command-Line Tools. The commands here are Kafka-specific.
18.6.1. General Arguments¶
Most commands require you to specify the connection to Kafka. This generally includes the list of
Kafka brokers, specified with --brokers (or -b). Connection properties can be specified with
--producer-config for producers, --consumer-config for consumers, or --config which will
be applied to both. See the official Kafka documentation for the available
producer and
consumer configs.
When using Zookeeper to store GeoMesa metadata, the Zookeeper servers must be specified with --zookeepers (or -z).
The Zookeeper path for storing metadata can be specified with --zkpath (or -p). See Zookeeper-less Usage for
details on when to use Zookeeper.
When not using Zookeeper, the GeoMesa catalog topic for storing metadata may be specified with --catalog (or -c).
A catalog or path can be thought of as a namespace for feature types.
To connect to Confluent Schema Registry topics, use --schema-registry
to provide the registry URL.
18.6.2. Commands¶
18.6.2.1. create-schema¶
See create-schema for an overview of this command.
In addition to the regular options, Kafka allows the number of partitions and the replication factor of the Kafka topic to be specified.
Argument |
Description |
|---|---|
|
The number of partitions used for the Kafka topic |
|
The replication factor for the Kafka topic |
18.6.2.2. export¶
See export for an overview of this command.
Unlike the standard export, this command will not not terminate until it is cancelled (through a shell interrupt)
or until --max-features have been read. Thus, it can be used to monitor a topic.
This command differs from the listen command (below) in that it allows filtering and output in various formats.
It will also ignore drop and clear messages generated by feature deletion.
In addition to the regular options, Kafka allows control over the consumer behavior:
Argument |
Description |
|---|---|
|
Start reading messages from the beginning of the Kafka topic, instead of the end |
|
Number of consumers used to read the topic |
The --num-consumers argument can be used to increase read speed. However, there can be at most one
consumer per topic partition.
The --from-beginning argument can be used to start reading the Kafka topic from the start. Otherwise,
only new messages that are sent after this command is invoked will be read.
18.6.2.3. ingest¶
See ingest for an overview of this command.
In addition to the regular options, Kafka allows the number of partitions and the replication factor of the Kafka topic to be specified. In addition, an artificial delay can be inserted to simulate a live data stream.
Argument |
Description |
|---|---|
|
The number of partitions used for the Kafka topic |
|
The replication factor for the Kafka topic |
|
The serialization format to use |
|
The delay inserted between messages |
The --delay argument should be specified as a duration, in plain language. For example, 100 millis
or 1 second. The ingest will pause after creating each SimpleFeature for the specified delay.
This can be used to simulate a live data stream.
18.6.2.4. playback¶
The playback command can simulate a data stream by replaying features from a file directly on to a Kafka Data Store. Features are returned based on a date attribute in the feature. For example, if replaying three features that have dates that are each one second apart, each feature will be emitted after a delay of one second. The rate of export can be modified to speed up or slow down the original time differences.
Argument |
Description |
|---|---|
|
The catalog table containing schema metadata |
|
The name of the schema |
|
Date attribute to base playback on. If not specified, will use the default schema date field |
|
Rate multiplier to speed-up (or slow down) features being returned, as a float |
|
Will modify the returned dates to match the current time |
|
Properties file used to configure the Kafka producer |
|
SimpleFeatureType specification as a GeoTools spec string, SFT config, or file with either |
|
GeoMesa converter specification as a config string, file name, or name of an available converter |
|
File format of input files (shp, csv, tsv, avro, etc). Optional, auto-detection will be attempted |
|
Input files are text files with lists of files, one per line, to ingest. |
|
The number of partitions used for the Kafka topic |
|
The replication factor for the Kafka topic |
|
The serialization format to use |
|
URL to a Confluent Schema Registry |
|
Input files to ingest |
The playback command is an extension of the ingest command, and accepts all the parameters outlined there. However, playback cannot run in distributed mode.
Also, note that the input files (specified in --src-list or <files>...) must be time-ordered by the --dtg
attribute before ingest or the playback will not work as expected.
The --rate parameter can be used to speed up or slow down the replay. It is specified as a floating point
number. For example --rate 10 will make replay ten times faster, while --rate 0.1 will make replay
ten times slower.
The --src-list argument is useful when you have more files to ingest than the command line will allow you to
specify. This file instructs GeoMesa to treat input files as new-line-separated file lists. As this makes it very
easy to run ingest jobs that can take days it’s recommended to split lists into reasonable chunks that can be completed
in a couple hours.
The --force argument can be used to suppress any confirmation prompts (generally from converter inference),
which can be useful when scripting commands.
The <files>... argument specifies the files to be ingested. * may be used as a wild card in file paths.
GeoMesa can handle gzip, bzip and xz file compression as long as the file extensions match the
compression type. GeoMesa supports ingesting files from local disks or HDFS. In addition, Amazon’s S3
and Microsoft’s Azure file systems are supported with a few configuration changes. See
Remote File System Support for details. Note: The behavior of this argument is changed by the --src-list argument.
By using a single - for the input files, input data may be piped directly to the ingest command using standard
shell redirection. Note that this will only work in local mode, and will only use a single thread for ingestion.
Schema inference is disabled in this case, and progress indicators may not be entirely accurate, as the total size
isn’t known up front.
For example:
$ cat foo.csv | geomesa-accumulo ingest ... -
$ geomesa-accumulo ingest ... - <foo.csv
18.6.2.5. listen¶
This command behaves similarly to the export command (above), but it does not provide options
for filtering or output format. It will show each message on the Kafka topic, including drop and
clear messages generated from feature deletion.
This command will not not terminate until it is cancelled (through a shell interrupt).
Argument |
Description |
|---|---|
|
The name of the schema |
|
Start reading messages from the beginning of the Kafka topic, instead of the end |
|
Number of consumers used to read the topic |
The --num-consumers argument can be used to increase read speed. However, there can be at most one
consumer per topic partition.
The --from-beginning argument can be used to start reading the Kafka topic from the start. Otherwise,
only new messages that are sent after this command is invoked will be read.
18.6.2.6. migrate-zookeeper-metadata¶
This command will migrate schema metadata out of Zookeeper. For additional information, see Zookeeper-less Usage.
Argument |
Description |
|---|---|
|
Delete the metadata out of Zookeeper after migrating it |