1. Order service based on Kafka
Distributed sorting service
The Kafka-based sorting service uses Kafka as a transaction message queue to achieve high-throughput data distribution.
Each channel corresponds to a topic of Kafka .
The ordering service node plays different roles in different stages.
1. Receiving transaction stage:
The ordering service node acts as a Kafka producer and forwards the transaction to the topic of the corresponding channel after receiving the transaction.
2. Message processing stage:
Service node acts as a sort of Kafka is a consumer (consumer), real-time monitoring messages for subsequent processing to generate a block or split transaction messages.
Second, the best practice of order based on Kafka
1. Number of nodes of Kafka and Zookeeper
The number of nodes in Kafka is K
The number of Zookeeper nodes is Z
K requires at least 4 nodes
Only after one node goes down can continue to submit transactions, sort and create new channels.
Z can choose 3, 5 or 7 nodes.
Choosing an odd number of nodes can avoid split-brain. 1 node will have a single point problem, and more than 7 nodes will be too much.
Three, the yaml file required for practice
docker-compose-cli.yaml
docker-compose-base.yaml
peer-base.yaml
docker-compose-couch.yaml
dc-orderer-kafka-base.yml
dc-orderer-kafka.yml
Fourth, data persistence
| container |
Path in the container |
Host path |
| peer |
/ var / hyperledger / production |
./p0o1 |
| orderer |
/ var / hyperledger / production / orderer |
./orderer0 |
| kafka |
/tmp/kafka-logs |
./k0 |
| couchdb |
/opt/couchdb/data |
./c0 |
Five, Kafka configuration
min.insync.relicas = 2 (M)
At least the number of written copies, and the number of written copies of a message is not less than this number to confirm that the writing is successful.
The larger the value, the more reliable the system, the smaller the higher the performance.
The reason for setting 2 here is to avoid a single point of failure.
default.relication.factor = 3 (N)
The number of copies saved when creating a theme. When creating a channel, at least N nodes must synchronize data to create a successful one.
The value of N needs to satisfy 1<M<N<K, N<K because K needs to have a node redundancy.
unclean.leader.clection.enable = false
Whether to allow nodes not in the replica synchronization set to elect as the master node, the master node is responsible for reading and writing messages.
A message is submitted successfully only when all nodes in the replica synchronization set are synchronized.
If nodes not in the synchronization set are allowed to elect as the master node, there is a risk of data loss.