Ledgerd is a messaging system. It is broken into two primary components:

• libledger - The underlying storage library. Embeddable as a C library inside your own process
• ledgerd - a C++ GRPC interface on top of libledger, if you'd rather talk to a centralized server process.

Ledger borrows many ideas from other systems, namely Apache Kafka, jlog and other open source messaging systems. Making messaging infrastructure the central component of your data system is a powerful idea that helps build scalable data systems and topologies. Ledger aims to be a flexible tool that can help with that goal.

• No Zookeeper: Ledgerd should aim to be standalone, and avoid depedencies that are complicated.
• Scales up and down: You should be able to use the correct messaging abstractions early on in your project lifecycle. Many messaging tools are reached for too late, only because they add unecessary overhead to the development process. You should be able to embed ledger inside my process if you want to, or scale ledger up to a large distributed infrastructure as your project grows.
• Custom protocols: Ledger attempts to make all interface boundaries open and accessible: We use the GRPC RPC protocol to make interactions with the server statically typed, and usable by any client that GRPC supports.

# ledgerd_client ping

# ledgerd_client --topic my_topic --partition_count 1 --command open_topic
=> OPENED: my_topic

# ledgerd_client --topic my_topic --partition 0 --data hello --command write_partition
=> ID: 43

# ledgerd_client --topic my_topic --partition 0 --start 43 --command read_partition --nmessages 1
=> hello