PHP extension for Apache Kafka
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Latest commit 349afb1 Jan 11, 2017

README.md

Master build: Build Status

Dev build: Build Status

SRP build: Build Status

Common issues:

Here's a short list of common issues people run into when installing this extension (only 1 issue so far)

"Unable to load dynamic library '/usr/lib64/php/modules/kafka.so' - librdkafka.so.1"

What this, basically means is that PHP can't find the shared object (librdkafka) anywhere. Thankfully, the fix is trivial: First, make sure you've actually compiled and installed librdkafka. Then run these commands:

sudo updatedb
locate librdkafka.so.1 # locate might not exist on some systems, like slackware, which uses slocate

The output should show a full path to the librdkafka.so.1 file, probably "/usr/local/lib/librdkafka.so.1". Edit /etc/ld.so.conf to make sure "/usr/local/lib" is included when searching for libraries. Either add id directly to the aforementioned file, or if your system uses a /etc/ld.so.conf.d/ directory, create a new .conf file there:

sudo touch /etc/ld.so.conf.d/librd.conf
echo "/usr/local/lib" >> /etc/ld.so.conf.d/librd.conf

Or simply type vim /etc/ld.so.conf.d/librd.conf, when the editor opens, tap ":" (colon), and run the command read !locate librdkafka.so.1, delete the filename from the path (move your cursor to the last / of the line that just appeared in the file and type d$ (delete until end of line). Save and close the file (:wq).

Once updated, run the following:

sudo ldconfig

Note:

Whatever gets merged into the master branch should work just fine. The main dev build is where small tweaks, bugfixes and minor improvements are tested (ie sort-of beta branch).

The SRP build is a long-term dev branch, where I'm currently in the process of separating the monolithic Kafka class into various logical sub-classes (a KafkaTopic class, perhaps a KafkaMeta object, KafkaConfig is another candidate...) to make this extension as intuitive as I can.

#This fork is still being actively developed

Given that the original repo is no longer supported by the author, I've decided to keep working at this PHP-Kafka extension instead. The branch where most of the work is being done is the consume-with-meta branch.

Changes that have happened thusfar:

  • Timeout when disconnecting is reduced (significantly)
  • Connections can be closed as you go
  • The librdkafka meta API is used
  • New methods added (Kafka::getTopics, Kafka::getPartitionsFor($topic) most notable additions)
  • Kafka::set_partition is deprecated, in favour of the more PSR-compliant Kafka::setPartition method
  • A PHP stub was added for IDE code-completion
  • Argument checks were added, and exceptions are thrown in some places
  • Class constants for an easier API (Kafka::OFFSET_*)
  • The extension logged everything in /var/etc/syslog, this is still the default behaviour (as this extension is under development), but can be turned off (Kafka::setLogLevel(Kafka::LOG_OFF))
  • Exceptions (KafkaException) in case of errors (still work in progress, though)
  • Thread-safe Kafka connections
  • Easy configuration: passing an array of options to the constructor, setBrokers or setOptions method like you would with PDO
  • Compression support added (when produing messages, a compressed message is returned as-is)
  • Each instance holds 2 distinct connections (at most): a producer and a consumer
  • CI (travis), though there is a lot of work to be done putting together useful tests

Changes that are on the TODO list include:

  • Separating kafka meta information out into a separate class (KafkaTopic and KafkaMessage classes)
  • Allow PHP to determine what the timeouts should be (mainly when disconnecting, or producing messages) (do we still need this?)
  • Add custom exceptions (partially done)
  • Overall API improvements (!!)
  • Performance - it's what you make of it (test results varied from 2 messages/sec to 2.5 million messages per second - see examples below)
  • Adding tests to the build (very much a work in progress)
  • PHP7 support

All help is welcome, of course...

PHP extension for Apache Kafka 0.8. It's built on top of kafka C driver (librdkafka). This extension requires the version 0.8.6 (ubuntu's librdkafka packages won't do it, they do not implement the meta API yet).

IMPORTANT: Library is in heavy development and some features are not implemented yet.

Requirements:

Download and install librdkafka. Run sudo ldconfig to update shared libraries.

Installing PHP extension:

phpize
./configure --enable-kafka
make
sudo make install
sudo sh -c 'echo "extension=kafka.so" >> /etc/php5/conf.d/kafka.ini'
#For CLI mode:
sudo sh -c 'echo "extension=kafka.so" >> /etc/php5/cli/conf.d/20-kafka.ini'

Examples:

// Produce a message
$kafka = new Kafka("localhost:9092");
$kafka->produce("topic_name", "message content");
//get all the available partitions
$partitions = $kafka->getPartitionsForTopic('topic_name');
//use it to OPTIONALLY specify a partition to consume from
//if not, consuming IS slower. To set the partition:
$kafka->setPartition($partitions[0]);//set to first partition
//then consume, for example, starting with the first offset, consume 20 messages
$msg = $kafka->consume("topic_name", Kafka::OFFSET_BEGIN, 20);
var_dump($msg);//dumps array of messages

A more complete example of how to use this extension if performance is what you're after:

$kafka = new Kafka(
    'broker-1:9092,broker-2:9092',
    [
        Kafka::LOGLEVEL         => Kafka::LOG_OFF,//while in dev, default is Kafka::LOG_ON
        Kafka::CONFIRM_DELIVERY => Kafka::CONFIRM_OFF,//default is Kafka::CONFIRM_BASIC
        Kafka::RETRY_COUNT      => 1,//default is 3
        Kafka::RETRY_INTERVAL   => 25,//default is 100
    ]
);
$fh = fopen('big_data_file.csv', 'r');
if (!$fh)
    exit(1);
$count = 0;
$lines = [];
while ($line = fgets($fh, 2048))
{
    $lines[] = trim($line);
    ++$count;
    if ($count >= 200)
    {
        $kafka->produceBatch('my_topic', $lines);
        $lines = [];
        $count = 0;
        //in theory, the next bit is optional, but Kafka::disconnect
        //waits for the out queue to be empty before closing connections
        //it's a way to sort-of ensure messages are delivered, even though Kafka::CONFIRM_DELIVERY
        //was set to Kafka::CONFIRM_OFF... This approach can be used to speed up your code
        $kafka->disconnect(Kafka::MODE_PRODUCER);//disconnect the producer
    }
}
if ($count)
{
    $kafka->produceBatch('my_topic', $lines);
}
$kafka->disconnect();//disconnects all opened connections, in this case, only a producer connection will exist, though

I've used code very similar to the code above to produce ~3 million messages, and got an average throughput rate of 2000 messages/second. Removing the disconnect call, or increasing the batches to produce will change the rate at which messages get produced.

Not disconnecting at all yielded the best performance (by far): 2.5 million messages in just over 1 second (though depending on the output buffer, and how kafka is set up to handle full produce-queue's, this is not to be recommended!).