Using Apache Kafka for log aggregation
I am learning Apache Kafka from their quickstart tutorial: http://kafka.apache.org/documentation.html#quickstart. Upto now, I have done the setup as follows. A producer node, where a web server is running at port 8888. A Kafka server(broker), Consumer and Zookeeper instance on another node. And I have tested the default console/file enabled producer and consumer with 3 partitions. The setup is perfect, and I am able to see the messages I sent in the order they created (with in each partition).
Now, I want to send the logs generated from the web server to Kafka Broker. These messages will be processed by consumer later. Currently I am using syslog-ng to capture server logs to a text file. I have come up with 3 rough ideas on how to implement producer to use kafka for log aggregation
Producer Implementations
First Kind:
Listen to tcp port of syslog-ng. Fetch each message and send to kafka server. Here we have two middle processes: Producer and syslog-ng
Second Kind: Using syslog-ng as Producer. Should find a way to send messages to Kafka server instead of writing to a file. Syslog-ng, the producer is the middle process.
Third Kind: Configuring the webserver itself as producer.
Am I correct in my thinking. In the last case we don't have any middle process. But I doubt its implementation will effect server performance. Can anyone let me know the best way of using Apache Kafka(if the above 3 are not good) and guide me through appropriate configuration of server?..
P.S.: I am using node.js for my web server
Thanks,
Sarath
Answer
Since you specify that you wish to send the logs generated to kafka broker, it indeed looks as if executing a process to listen and resend messages mainly creates another point of failure with no additional value (unless you need a specific syslog-ng capability).
Syslog-ng can send messages to external applications using: http://www.balabit.com/sites/default/files/documents/syslog-ng-ose-3.4-guides/en/syslog-ng-ose-v3.4-guide-admin/html/configuring-destinations-program.html. I don't know if there are other ways to do that.
For the third option, I am not sure if kafka can easily be integrated into Node.js as it requires a c++ producer and when I last looked for one, I was not able to find. However, an easy alternative could be to have kafka read the log file created by the server and send those logs (using the console producer provided with kafka). This is usually a good way, as it completely remove dependencies between kafka and the web server (embedding the producer in would require error handling, configuration, etc). It requires the use of tail --follow and it works for us very well. If you wish more details on that, I can include them as well. Still you would need to supervise kafka execution to make sure messages are not lost (and provide a recovery option to offline send messages that failed). But, the good thing about this method is that there are no dependency between the tools.
Hope it helps...
Eran