Check out the successor of kash.py - kafi - including support for Confluent REST Proxy, S3, Azure Blob Storage, Pandas etc.

kash.py

kash.py is a Kafka shell based on Python, or, in other words, a Python-based client library for Kafka based on confluent-kafka-python by Magnus Edenhill, which is itself based on the native Kafka client library librdkafka by the same author.

The idea behind kash.py is to make it as easy as possible to interact with Kafka using Python, without having to know any of the implementation details of the underlying confluent-kafka-python module. To this end, not only are the functions/methods are simpler to use, but also all classes are converted to simple Python types like tuples and dictionaries. As a result, development chores that took numerous of lines of boilerplate code before can be formulated as one-liners, both in interactive mode using the Python REPL, or within convenient scripts.

kash.py has been built for Kafka users of all kinds:

• For developers and devops engineers to view and manipulate Kafka topics using familiar shell syntax (you have ls, touch, rm, cp, cat, grep, wc etc.).
• For data scientists to bridge the gap between batch and stream processing, using functions to upload/download files to/from topics, and even functional abstractions a la Databricks/Apache Spark (there are various foldls, flatmaps and maps for you to explore).

kash.py supports Avro, Protobuf and JSONSchema, Confluent Cloud, Redpanda, etc...and it will give you Kafka superpowers of a kind you have never experienced before. Honestly :)

Check out the full kashpy package documentation if you are interested in seeing the entire functionality of kash.py.

Installation

Just write...

pip install kashpy

...and off you go.

Configuration

kash.py makes use of configuration files suffixed .yaml which are being searched for in the folder clusters, starting 1) from the directory in the KASHPY_HOME environment variable, or, if that environment variable is not set, 2) from the current directory.

For the YAML-based configuration files sporting environment variable interpolation, kash.py makes use of the ingenious little library Piny from Vitaly Samigullin (see also his illustrative blog about the genesis of Piny).

A barebones configuration file looks like this (including Schema Registry):

kafka:
  bootstrap.servers: localhost:9092

schema_registry:
  schema.registry.url: http://localhost:8081

You can also set some of the defaults of kash.py in the kash section like this:

kash:
  flush.num.messages: 10000
  flush.timeout: -1.0
  retention.ms: -1
  consume.timeout: 1.0
  auto.offset.reset: earliest
  enable.auto.commit: true
  session.timeout.ms: 10000
  progress.num.messages: 1000
  block.num.retries.int: 50
  block.interval: 0.1

You can find an in-depth explanation of these settings in the kashpy package documentation, including example configuration files for connecting to Confluent Cloud, Redpanda etc.

Kafka Made Simple

For interactive use, e.g. using your local cluster configured in the file clusters/local.yaml, just do the following to list the topics:

$ python3
>>> from kashpy.kash import *
>>> c = Cluster("local")
>>> c.ls()
['__consumer_offsets', '_schemas']
>>>

Or, if you'd like to replicate the topic test holding 1000 messages from a Kafka cluster local on your local machine to a Kafka cluster ccloud on Confluent Cloud:

>>> c_local = Cluster("local")
>>> c_ccloud = Cluster("ccloud")
>>> c.cp(c_local, "test", c_ccloud, "test")
(1000, 1000)
>>>

In the following, we go a bit deeper in two short tutorials; the first demonstrating how kash.py helps you to fulfill tasks on a single cluster, and the second how to make use of your newly obtained Kafka superpowers across clusters.

Tutorial 1 (single cluster)

This is the first tutorial, showcasing the single cluster capabilities of kash.py in interactive mode.

Let's start Python, import kash.py and create a Cluster object c:

$ python3
>>> from kashpy.kash import *
>>> c = Cluster("local")
>>>

List the topics on the cluster:

>>> c.ls()
['__consumer_offsets', '_schemas']
>>>

Create a new topic snacks:

>>> c.touch("snacks")
'snacks'
>>> 

List the topics on the cluster again:

>>> c.ls()
['__consumer_offsets', '_schemas', 'snacks']
>>>

Upload the following local file snacks.txt to the topic snacks (examples inspired by the great blog Kafka with AVRO vs., Kafka with Protobuf vs., Kafka with JSON Schema by Simon Aubury):

{"name": "cookie", "calories": 500.0, "colour": "brown"}
{"name": "cake", "calories": 260.0, "colour": "white"}
{"name": "timtam", "calories": 80.0, "colour": "chocolate"}

>>> c.cp("./snacks.txt", "snacks")
(3, 3)
>>>

Show the contents of topic snacks:

>>> c.cat("snacks")
{'headers': None, 'partition': 0, 'offset': 0, 'timestamp': (1, 1678915066323), 'key': None, 'value': '{"name": "cookie", "calories": 500.0, "colour": "brown"}'}
{'headers': None, 'partition': 0, 'offset': 1, 'timestamp': (1, 1678915066323), 'key': None, 'value': '{"name": "cake", "calories": 260.0, "colour": "white"}'}
{'headers': None, 'partition': 0, 'offset': 2, 'timestamp': (1, 1678915066323), 'key': None, 'value': '{"name": "timtam", "calories": 80.0, "colour": "chocolate"}'}
3
>>> 

If you'd like to see the output of the values of the messages in an indented fashion, you can tell kash.py 1) that you'd like to pretty print the messages and 2) that the values have the type json:

>>> c.cat("snacks", foreach_function=ppretty, value_type="json")
{
  "headers": null,
  "partition": 0,
  "offset": 0,
  "timestamp": [
    1,
    1678915066323
  ],
  "key": null,
  "value": {
    "name": "cookie",
    "calories": 500.0,
    "colour": "brown"
  }
}
{
  "headers": null,
  "partition": 0,
  "offset": 1,
  "timestamp": [
    1,
    1678915066323
  ],
  "key": null,
  "value": {
    "name": "cake",
    "calories": 260.0,
    "colour": "white"
  }
}
{
  "headers": null,
  "partition": 0,
  "offset": 2,
  "timestamp": [
    1,
    1678915066323
  ],
  "key": null,
  "value": {
    "name": "timtam",
    "calories": 80.0,
    "colour": "chocolate"
  }
}
3
>>> 

Count the number of messages, words and bytes of the topic snacks:

>>> c.wc("snacks")
(3, 18, 169)
>>>

Find those messages whose values matches the regular expression .*cake.*:

>>> c.grep("snacks", ".*cake.*")
Found matching message on partition 0, offset 1.
([{'headers': None, 'partition': 0, 'offset': 1, 'timestamp': (1, 1664989815680), 'key': None, 'value': '{"name": "cake", "calories": 260.0, "colour": "white"}'}], 1, 3)
>>>

Filter the messages to only keep those where the colour is brown:

>>> c.filter("snacks", lambda x: x["value"]["colour"] == "brown", value_type="json")
([{'headers': None, 'partition': 0, 'offset': 0, 'timestamp': (1, 1666090118747), 'key': None, 'value': {'name': 'cookie', 'calories': 500.0, 'colour': 'brown'}}], 3)
>>>

Create a new topic snacks_protobuf:

>>> c.touch("snacks_protobuf")
'snacks_protobuf'
>>>

Copy the topic snacks onto another topic snacks_protobuf using Protobuf (and storing the schema in the Schema Registry):

>>> c.cp("snacks", "snacks_protobuf", target_value_type="protobuf", target_value_schema='message Snack { required string name = 1; required float calories = 2; optional string colour = 3; }')
(3, 3)
>>>

Show the contents of topic snacks_protobuf (showing the values directly as bytes):

>>> c.cat("snacks_protobuf", value_type="bytes")
{'headers': None, 'partition': 0, 'offset': 0, 'timestamp': (1, 1664989815680), 'key': None, 'value': b'\x00\x00\x00\x00\x03\x00\n\x06cookie\x15\x00\x00\xfaC\x1a\x05brown'}
{'headers': None, 'partition': 0, 'offset': 1, 'timestamp': (1, 1664989815680), 'key': None, 'value': b'\x00\x00\x00\x00\x03\x00\n\x04cake\x15\x00\x00\x82C\x1a\x05white'}
{'headers': None, 'partition': 0, 'offset': 2, 'timestamp': (1, 1664989815680), 'key': None, 'value': b'\x00\x00\x00\x00\x03\x00\n\x06timtam\x15\x00\x00\xa0B\x1a\tchocolate'}
>>>

Show the contents of the topic snacks_protobuf again (decoding the values using Protobuf and the Schema Registry):

>>> c.cat("snacks_protobuf", value_type="protobuf")
{'headers': None, 'partition': 0, 'offset': 0, 'timestamp': (1, 1664989815680), 'key': None, 'value': {'name': 'cookie', 'calories': 500.0, 'colour': 'brown'}}
{'headers': None, 'partition': 0, 'offset': 1, 'timestamp': (1, 1664989815680), 'key': None, 'value': {'name': 'cake', 'calories': 260.0, 'colour': 'white'}}
{'headers': None, 'partition': 0, 'offset': 2, 'timestamp': (1, 1664989815680), 'key': None, 'value': {'name': 'timtam', 'calories': 80.0, 'colour': 'chocolate'}}
3
>>>

Again, kash.py can give you a prettified indented output:

>>> c.cat("snacks_protobuf", foreach_function=ppretty, value_type="protobuf")
{
  "headers": null,
  "partition": 0,
  "offset": 0,
  "timestamp": [
    1,
    1678915066323
  ],
  "key": null,
  "value": {
    "name": "cookie",
    "calories": 500.0,
    "colour": "brown"
  }
}
{
  "headers": null,
  "partition": 0,
  "offset": 1,
  "timestamp": [
    1,
    1678915066323
  ],
  "key": null,
  "value": {
    "name": "cake",
    "calories": 260.0,
    "colour": "white"
  }
}
{
  "headers": null,
  "partition": 0,
  "offset": 2,
  "timestamp": [
    1,
    1678915066323
  ],
  "key": null,
  "value": {
    "name": "timtam",
    "calories": 80.0,
    "colour": "chocolate"
  }
}
3
>>>

Get a diff of the two topics snacks and snacks_protobuf, comparing the dictionaries obtained by converting the string payload in snacks to Python dictionaries, and the Protobuf payload in snacks_protobuf to Python dictionaries as well:

>>> c.diff("snacks", "snacks_protobuf", value_type1="json", value_type2="protobuf")
([], 3, 3)
>>>

Now we are getting functional - using a foldl operation to sum up the calories of the messages in snacks:

>>> c.foldl("snacks", lambda acc, x: acc + x["value"]["calories"], 0, value_type="json")
(840.0, 3)
>>>

We can also use a flatmap operation to get a list of all messages in snacks where each message is duplicated:

>>> c.flatmap("snacks", lambda x: [x, x])
([{'headers': None, 'partition': 0, 'offset': 0, 'timestamp': (1, 1664989815680), 'key': None, 'value': '{"name": "cookie", "calories": 500.0, "colour": "brown"}'}, {'headers': None, 'partition': 0, 'offset': 0, 'timestamp': (1, 1664989815680), 'key': None, 'value': '{"name": "cookie", "calories": 500.0, "colour": "brown"}'}, {'headers': None, 'partition': 0, 'offset': 1, 'timestamp': (1, 1664989815680), 'key': None, 'value': '{"name": "cake", "calories": 260.0, "colour": "white"}'}, {'headers': None, 'partition': 0, 'offset': 1, 'timestamp': (1, 1664989815680), 'key': None, 'value': '{"name": "cake", "calories": 260.0, "colour": "white"}'}, {'headers': None, 'partition': 0, 'offset': 2, 'timestamp': (1, 1664989815680), 'key': None, 'value': '{"name": "timtam", "calories": 80.0, "colour": "chocolate"}'}, {'headers': None, 'partition': 0, 'offset': 2, 'timestamp': (1, 1664989815680), 'key': None, 'value': '{"name": "timtam", "calories": 80.0, "colour": "chocolate"}'}], 3)
>>>

Next, we use a map operation to add the suffix ish to all the colours:

>>> def map_function(x):
...   x["value"]["colour"] += "ish"
...   return x
... 
>>> c.map("snacks", map_function, value_type="json")
([{'headers': None, 'partition': 0, 'offset': 0, 'timestamp': (1, 1664989815680), 'key': None, 'value': {'name': 'cookie', 'calories': 500.0, 'colour': 'brownish'}}, {'headers': None, 'partition': 0, 'offset': 1, 'timestamp': (1, 1664989815680), 'key': None, 'value': {'name': 'cake', 'calories': 260.0, 'colour': 'whiteish'}}, {'headers': None, 'partition': 0, 'offset': 2, 'timestamp': (1, 1664989815680), 'key': None, 'value': {'name': 'timtam', 'calories': 80.0, 'colour': 'chocolateish'}}], 3)
>>>

And last, but not least, we copy the topic snacks back to a local file snacks1.txt while both duplicating the messages and adding the suffix ish to all the colours:

>>> def flatmap_function(x):
...   x["value"]["colour"] += "ish"
...   return [x, x]
... 
>>> c.flatmap_to_file("snacks", "./snacks1.txt", flatmap_function, value_type="json")
(3, 6)
>>>

The resulting file snacks1.txt looks like this:

{"name": "cookie", "calories": 500.0, "colour": "brownish"}
{"name": "cookie", "calories": 500.0, "colour": "brownish"}
{"name": "cake", "calories": 260.0, "colour": "whiteish"}
{"name": "cake", "calories": 260.0, "colour": "whiteish"}
{"name": "timtam", "calories": 80.0, "colour": "chocolateish"}
{"name": "timtam", "calories": 80.0, "colour": "chocolateish"}

Tutorial 2 (cross-cluster)

This is the second tutorial, showcasing the cross-cluster capabilities of kash.py in interactive mode.

First, let's start Python, import kash.py and let's see what clusters we have defined in our clusters directory:

$ python3
>>> from kashpy.kash import *
>>> clusters()
['ccloud', 'local', 'redpanda']

Next, we create a Cluster object c1:

>>> c1 = Cluster("local")
>>>

Create a new topic snacks1 on cluster c1:

>>> c1.touch("snacks1")
'snacks1'
>>>

Upload the following local file snacks.txt to the topic snacks1 on cluster c1:

{"name": "cookie", "calories": 500.0, "colour": "brown"}
{"name": "cake", "calories": 260.0, "colour": "white"}
{"name": "timtam", "calories": 80.0, "colour": "chocolate"}

>>> c1.cp("./snacks.txt", "snacks1")
(3, 3)

Create a new Cluster object c2:

>>> c2 = Cluster("ccloud")
>>>

Create a new topic snacks2 on c2:

>>> c2.touch("snacks2")
'snacks2'
>>>

Copy the topic snacks1 from cluster c1 to topic snacks2 on cluster c2:

>>> cp(c1, "snacks1", c2, "snacks2")
(3, 3)
>>>

Get the diff from topic snacks1 on cluster c1 to a topic snacks2 on cluster c2:

>>> diff(c1, "snacks1", c2, "snacks2")
([], 3, 3)
>>>

Now let's venture into the cross-cluster functional programming domain... let's copy topic snacks1 on cluster c1 to a topic snacks2_duplicate on cluster c2, while duplicating each message using a flatmap operation:

>>> flatmap(c1, "snacks1", c2, "snacks2_duplicate", lambda x: [x, x])
(3, 6)
>>>

Next, we use a cross-cluster map operation to add the suffix ish to all the colours and produce the resulting messages to topic snacks2_ish on cluster c2:

>>> def map_function(x):
...   x["value"]["colour"] += "ish"
...   return x
... 
>>> map(c1, "snacks1", c2, "snacks2_ish", map_function, source_value_type="json")
(3, 3)
>>>

Now for the most advanced operation of the tutorials: A zip of topic snacks1 on cluster c1 and topic snacks2_ish on cluster c2 followed by a foldl accumulating pairs of those messages from both topics where the colour of the message from topic snacks2_ish ends with eish:

>>> def zip_foldl_function(acc, x1, x2):
...   return acc + [(x1, x2)] if x2["value"]["colour"].endswith("eish") else acc
... 
>>> zip_foldl(c1, "snacks1", c2, "snacks2_ish", zip_foldl_function, [], value_type2="json")
([({'headers': None, 'partition': 0, 'offset': 1, 'timestamp': (1, 1664989815680), 'key': None, 'value': b'{"name": "cake", "calories": 260.0, "colour": "white"}'}, {'headers': None, 'partition': 0, 'offset': 1, 'timestamp': (1, 1664989815680), 'key': None, 'value': {'name': 'cake', 'calories': 260.0, 'colour': 'whiteish'}}), ({'headers': None, 'partition': 0, 'offset': 2, 'timestamp': (1, 1664989815680), 'key': None, 'value': b'{"name": "timtam", "calories": 80.0, "colour": "chocolate"}'}, {'headers': None, 'partition': 0, 'offset': 2, 'timestamp': (1, 1664989815680), 'key': None, 'value': {'name': 'timtam', 'calories': 80.0, 'colour': 'chocolateish'}})], 3, 3)
>>>

kash.py and Functional Programming

As already hinted at in the tutorials above, the more advanced functionality of kash.py rests on a Functional Programming (FP) backbone. If you intend to use kash.py to ease your everyday tasks, you don't have to be aware of that - the bash-like abstractions on top of the functional backbone should already help you out a lot. However, if you are familiar with FP or you would like to become familiar with it, this functional backbone of kash.py can actually let you wield even stronger Kafka superpowers.

Single Cluster

Kafka Topic to Python Datatype

We start with functional backbone of those functions which consume a Kafka topic and return a Python datatype. Those functions are based on the foldl ("fold left") function. foldl consumes messages from a topic and then, for each message, calls a function that takes this message and an accumulator of any type, and returns the updated accumulator. foldl can be used e.g. to aggregate information from topics, such as the sum of calories of the messages of the topic snacks in the following example:

>>> c.foldl("snacks", lambda acc, x: acc + x["value"]["calories"], 0, value_type="json")
(840.0, 3)
>>>

foldl is the basis for flatmap which also consumes messages from a topic, but then calls a simpler function that takes just this message and returns a list of anything (including the empty list). flatmap can be used e.g. to duplicate the messages of a topic, as in the following example:

>>> c.flatmap("snacks", lambda x: [x, x])
([{'headers': None, 'partition': 0, 'offset': 0, 'timestamp': (1, 1664989815680), 'key': None, 'value': '{"name": "cookie", "calories": 500.0, "colour": "brown"}'}, {'headers': None, 'partition': 0, 'offset': 0, 'timestamp': (1, 1664989815680), 'key': None, 'value': '{"name": "cookie", "calories": 500.0, "colour": "brown"}'}, {'headers': None, 'partition': 0, 'offset': 1, 'timestamp': (1, 1664989815680), 'key': None, 'value': '{"name": "cake", "calories": 260.0, "colour": "white"}'}, {'headers': None, 'partition': 0, 'offset': 1, 'timestamp': (1, 1664989815680), 'key': None, 'value': '{"name": "cake", "calories": 260.0, "colour": "white"}'}, {'headers': None, 'partition': 0, 'offset': 2, 'timestamp': (1, 1664989815680), 'key': None, 'value': '{"name": "timtam", "calories": 80.0, "colour": "chocolate"}'}, {'headers': None, 'partition': 0, 'offset': 2, 'timestamp': (1, 1664989815680), 'key': None, 'value': '{"name": "timtam", "calories": 80.0, "colour": "chocolate"}'}], 3)
>>>

flatmap, in turn, is the basis for map which again consumes messages from a topic, but then calls a function that takes just this message and returns anything. map can be used e.g. to modify the messages of a topic, as in the following example:

>>> def map_function(x):
...   x["value"]["colour"] += "ish"
...   return x
... 
>>> c.map("snacks", map_function, value_type="json")
([{'headers': None, 'partition': 0, 'offset': 0, 'timestamp': (1, 1664989815680), 'key': None, 'value': {'name': 'cookie', 'calories': 500.0, 'colour': 'brownish'}}, {'headers': None, 'partition': 0, 'offset': 1, 'timestamp': (1, 1664989815680), 'key': None, 'value': {'name': 'cake', 'calories': 260.0, 'colour': 'whiteish'}}, {'headers': None, 'partition': 0, 'offset': 2, 'timestamp': (1, 1664989815680), 'key': None, 'value': {'name': 'timtam', 'calories': 80.0, 'colour': 'chocolateish'}}], 3)
>>>

Filter the messages to only keep those where the colour is brown:

>>> c.filter("snacks", lambda x: x["value"]["colour"] == "brown", value_type="json")
([{'headers': None, 'partition': 0, 'offset': 0, 'timestamp': (1, 1666090118747), 'key': None, 'value': {'name': 'cookie', 'calories': 500.0, 'colour': 'brown'}}], 3)
>>>

Here is an overview of the relations between those functions of kash.py which consume messages from Kafka topics and return a Python datatype (or nothing):

• foldl

  • flatmap, cat, foreach, wc

    • map, filter, grep, grep_fun

As explained above, foldl is the basis of it all, flatmap is based on foldland map is based on flatmap. In addition, cat, foreach and wc are also based on foldl, and filter and grep and grep_fun are based on flatmap.

Kafka Topic to Local File

We turn to those functions consuming messages from a Kafka topic and writing them to a local file, transforming or even removing messages. Here, the basis function is flatmap_to_file. Here is an example where the flatmap function is the identity function. Hence, the messages from the topic snacks are written to the local file ./snacks.txt:

>>> c.flatmap_to_file("snacks", "./snacks.txt", lambda x: [x])
(3, 3)
>>> 

map_to_file is based on flatmap_to_file and can be used to transform each message before it is written to the local file:

>>> def map_function(x):
...   x["value"]["colour"] += "ish"
...   return x
... 
>>> c.map_to_file("snacks", "./snacks.txt", map_function)
(3, 3)
>>> 

filter_to_file is also based on flatmap_to_file and writes only those messages to the local file which fulfil a condition, for example:

>>> def filter_function(message_dict):
...   return "cake" in message_dict["value"]
... 
>>> c.filter_to_file("snacks", "./snacks.txt", filter_function)
(3, 1)

Here is an overview of the relations between those functions of kash.py which consume messages from Kafka topics and write them to a local file:

• flatmap_to_file

  • map_to_file, filter_to_file, cp/download

Again, as explained above, map_to_file and filter_to_file are based on flatmap_to_file, as well as cp (with the first not being a file and the second argument being a file marked by it containing a slash /) and download.

Local File to Kafka Topic

The last set of functional functions are those reading lines/messages from a local file and producing them to a Kafka topic. Here, the basis function is flatmap_from_file. Here is an example where the flatmap function is the identity function. Hence, the messages from the local file ./snacks.txt are produced into the topic snacks:

>>> c.flatmap_from_file("./snacks.txt", "snacks", lambda x: [x])
(3, 3)
>>> 

map_from_file is based on flatmap_from_file and can be used to transform each line/message before it is written to the local file:

>>> c.map_to_file("snacks", "./snacks.txt", lambda x: x)
(3, 3)
>>> 

filter_from_file is also based on flatmap_from_file and produces only those messages to the Kafka topic which fulfil a condition. In the example below we produce only those messages which have the string cake in their value:

>>> def filter_function(xy):
...   x, y = xy
...   return "cake" in y
... 
>>> c.filter_from_file("./snacks.txt", "snacks", filter_function)
(3, 1)
>>> 

Here is an overview of the relations between those functions of kash.py which read lines/messages from a file and produce them to a Kafka topic:

• flatmap_from_file

  • map_from_file, filter_from_file, cp/download

Again, as explained above, map_from_file and filter_from_file are based on flatmap_from_file, as well as cp (with the first argument being a file marked by it containing a slash / and the second not a file) and upload.

There is also a function foldl_from_file. Here is an example where we use it to sum up the calories of the lines/messages from the file ./snacks.txt:

>> foldl_from_file("./snacks.txt", lambda acc, x: acc + json.loads(x)["calories"], 0)
(840.0, 3)
>>> 

Cross-Cluster

Kafka Topic to Kafka Topic

kash.py also offers functional functions to use across clusters, based on flatmap. In the example below, we use flatmap to copy the topic snacks1 on cluster c1 to a topic snacks2_duplicate on cluster c2, while duplicating each message using a flatmap operation:

>>> flatmap(c1, "snacks1", c2, "snacks2_duplicate", lambda x: [x, x])
(3, 6)
>>>

map is based on flatmap. In the following example, we use a cross-cluster map to add the suffix ish to all the colours and produce the resulting messages to topic snacks2_ish on cluster c2:

>>> def map_function(x):
...   x["value"]["colour"] += "ish"
...   return x
... 
>>> map(c1, "snacks1", c2, "snacks2_ish", map_function, source_value_type="json")
(3, 3)
>>>

The function filter is also based on flatmap and, in the example below, is used to only keep those messages where the colour is brown:

>>> c.filter("snacks", lambda x: x["value"]["colour"] == "brown", value_type="json")
([{'headers': None, 'partition': 0, 'offset': 0, 'timestamp': (1, 1666090118747), 'key': None, 'value': {'name': 'cookie', 'calories': 500.0, 'colour': 'brown'}}], 3)
>>>

Here is an overview of the relations between those cross-cluster functions of kash.py which consume messages from a topic on one cluster and produce them in another (or equally named) topic on another (or the same) cluster:

• flatmap

  • map, filter, cp

Consuming Two Topics At the Same Time

The diff and diff_fun functions are based on the functional abstraction zip_foldl. As an example, we show the zip of topic snacks1 on cluster c1 and topic snacks2_ish on cluster c2 followed by a foldl accumulating pairs of those messages from both topics where the colour of the message from topic snacks2_ish ends with eish:

>>> def zip_foldl_function(acc, x1, x2):
...   return acc + [(x1, x2)] if x2["value"]["colour"].endswith("eish") else acc
... 
>>> zip_foldl(c1, "snacks1", c2, "snacks2_ish", zip_foldl_function, [], value_type2="json")
([({'headers': None, 'partition': 0, 'offset': 1, 'timestamp': (1, 1664989815680), 'key': None, 'value': b'{"name": "cake", "calories": 260.0, "colour": "white"}'}, {'headers': None, 'partition': 0, 'offset': 1, 'timestamp': (1, 1664989815680), 'key': None, 'value': {'name': 'cake', 'calories': 260.0, 'colour': 'whiteish'}}), ({'headers': None, 'partition': 0, 'offset': 2, 'timestamp': (1, 1664989815680), 'key': None, 'value': b'{"name": "timtam", "calories": 80.0, "colour": "chocolate"}'}, {'headers': None, 'partition': 0, 'offset': 2, 'timestamp': (1, 1664989815680), 'key': None, 'value': {'name': 'timtam', 'calories': 80.0, 'colour': 'chocolateish'}})], 3, 3)
>>>

Here is the overview of the relations between those functions of kash.py which consume messages from two topics (on the same cluster or on different clusters):

• zip_foldl

  • diff/diff_fun