FAQ

Where can I get started?

Take a look at our https://github.com/concord/getting-started repository.

What is a zookeeper path?

A ZookeeperPath is modeled as a filesystem path. It's the same as a path to a file on your local computer. The only difference is that the contents are safely stored and replicated. When we refer to a zookeeper path we refer to a 'folder' where either concord or mesos stores the metadata.

An example would be /bolt. Notice the leading /. All paths must be absolute paths

How do I get data into the system?

You will need to create a computation that ingests your stream of data. This computation is known as a source as it contains no input streams. Most source computations will continuously poll some source for data, or act as a server and respond when data comes its way. The polling is controlled by setting a timer using the setTimer(int) method, and calling it again upon every processTimer callback. In this fashion you can ingest data at a configurable rate, passing records downstream to other sinks. We currently have our own special computations that allow users to stream data from Kafka or Kinesis. They will be open sourced in the near future, check back soon!

I launched a computations via concord deploy but nothing happens?

Typically, it means that the VM (VirtualBox / Vagrant) or your computer (Docker) has ran out of some resource. Either memory, or cpus (cpu shares).

Please visit the <mesos-master-node>:5050 and see if there are resources still available.

We're working on a visualization layer for this. Please check back in soon :)

I see computation with a status LOST what does that mean?

It means that the process exited abruptly for some reason. Check the mesos stderr/stdout logs. They offer tremendous insights.

I get the error bolt_executor.sh not found, how can I fix this?

This means that the Mesos Agents in your cluster haven't been properly provisioned to run Concord. The error happens when Mesos attempts to exec the Concord proxy, but can't find the binary. Adding "docker_container":"concord/runtime_executor:<concord_version>" to your operators manifest file will launch the operator in our dockerized runtime environment.

I see some type of "Internal error" reported in stderr, how can I resolve this?

This issue may arise when using an older version of a particular Concord client library. Uninstalling the library and re-installing it should fix the issue.

TNonblockingServer transport error in process()

if you see something along the lines of

Thrift: Wed Sep 9 17:35:54 2015 TNonblockingServer transport error in process(): No more data to read.

It probably means that there is an incompatible version of thrift installed.

Try upgrading the gems/pip/header files for your language.