The gizzard, also referred to as the ventriculus, gastric mill, and gigerium, is an organ found in the digestive tract of some animals, including archosaurs (dinosaurs, birds, pterosaurs, crocodiles and alligators), earthworms, some gastropods, some fish and some crustaceans. This specialized stomach constructed of thick muscular walls is used for grinding up food, often aided by particles of stone or grit. In certain insects and molluscs, the gizzard features chitinous plates or teeth.
The word "gizzard" comes from the Middle English giser, which derives from a similar word in Old French, which itself evolved from the Latin gigeria, meaning giblets.
Birds swallow food and store it in their crop if necessary. Then the food passes into their glandular stomach, also called the proventriculus, which is also sometimes referred to as the true stomach. This is the secretory part of the stomach. Then the food passes into the ventriculus (also known as the muscular stomach or gizzard). The gizzard can grind the food with previously-swallowed stones and pass it back to the true stomach, and vice versa. Bird gizzards are lined with a tough layer made of the carbohydrate-protein complex koilin, to protect the muscles in the gizzard.
Gizzard is an open source sharding framework to create custom fault-tolerant, distributed databases. It was initially used by Twitter and emerged from a wide variety of data storage problems. Gizzard operates as a middleware networking service that runs on the Java Virtual Machine. It manages partitioning data across arbitrary backend datastores, that allows it to be accessed efficiently. The partitioning rules are stored in a forwarding table that maps key ranges to partitions. Each partition manages its own replication through a declarative replication tree. Gizzard handles both physical and logical shards. Physical shards point to a physical database backend whereas logical shards are trees of other shards. In addition Gizzard also supports migrations and gracefully handles failures. The system is made eventually consistent by requiring that all write operations are idempotent and commutative. As operations fail they are retried at a later time. Gizzard is available at GitHub and licensed under the Apache License.