RPC (gRPC, Thrift, Apache Avro)
RPC (gRPC, Thrift, Apache Avro) in Distributed Systems: implementation patterns, named pitfalls, and the autograder cases that catch them.
Computer Science Foundations
Raft and Paxos consensus protocols with explicit state-machine traces, CAP theorem tradeoffs per workload, microservice decomposition with Docker plus Kubernetes deployment, message queue patterns with Kafka and RabbitMQ, and 2PC plus saga distributed transactions. A common consensus-lab failure is a Raft leader election that double-votes during a network partition, the safety violation our tutors catch with explicit term-checking. Verified CS graduates, starting at $20 per task, 12-hour average turnaround.
Why Distributed Systems
Raft and Paxos consensus protocols with explicit state-machine traces, CAP theorem tradeoffs per workload, microservice decomposition with Docker plus Kubernetes deployment, message queue patterns with Kafka and RabbitMQ, and 2PC plus saga distributed transactions. A common consensus-lab failure is a Raft leader election that double-votes during a network partition, the safety violation our tutors catch with explicit term-checking. Verified CS graduates, starting at $20 per task, 12-hour average turnaround.
Topics covered
RPC (gRPC, Thrift, Apache Avro) in Distributed Systems: implementation patterns, named pitfalls, and the autograder cases that catch them.
Message Queues (Kafka, RabbitMQ, NATS) in Distributed Systems: implementation patterns, named pitfalls, and the autograder cases that catch them.
Lamport Timestamps and Vector Clocks in Distributed Systems: implementation patterns, named pitfalls, and the autograder cases that catch them.
Linearizability and Sequential Consistency in Distributed Systems: implementation patterns, named pitfalls, and the autograder cases that catch them.
Causal Consistency and CRDTs in Distributed Systems: implementation patterns, named pitfalls, and the autograder cases that catch them.
Eventual Consistency (Dynamo Style) in Distributed Systems: implementation patterns, named pitfalls, and the autograder cases that catch them.
Full overview
Distributed systems are how the largest technology companies serve billions of requests per second across thousands of machines that fail independently and communicate over networks that lose messages. Distributed systems courses cover 8 named topic areas: communication models (RPC with gRPC or Thrift, message passing with TCP or RDMA, message queues with Kafka or RabbitMQ or NATS), consistency models (linearizability, sequential consistency, causal consistency, eventual consistency, snapshot isolation), consensus protocols (Paxos and its variants Multi-Paxos and EPaxos, Raft with leader election and log replication, Byzantine fault-tolerant protocols like PBFT and HotStuff), replication strategies (primary-backup, chain replication, quorum-based, state-machine replication), distributed transactions (2PC, 3PC, Percolator-style with Paxos, sagas with compensating actions), fault tolerance (timeout-based failure detection, gossip-based membership, repair via anti-entropy), distributed storage (Dynamo-style with consistent hashing plus quorums, Bigtable-style with chunked tablets, Spanner-style with TrueTime plus 2PC), and modern orchestration (Docker containers, Kubernetes pods plus deployments plus services, service meshes with Envoy or Linkerd). A typical distributed systems course spends 13 to 15 weeks on these topics with reading lists pulling from SOSP, OSDI, NSDI, SIGMOD, and VLDB conferences.
The canonical paper list includes Lamport 1978 (Time, Clocks, and the Ordering of Events), Brewer 2000 (CAP Theorem), Ongaro-Ousterhout 2014 (Raft), Corbett et al 2012 (Spanner), Dean-Ghemawat 2004 (MapReduce), DeCandia et al 2007 (Dynamo). Hands-on courses ship a multi-lab Raft implementation in Go: MapReduce on top of Raft, Raft itself with leader election plus log replication, a fault-tolerant key-value service using Raft, and a sharded version with reconfiguration. The assessment landscape is 70-30 projects over written work because distributed systems correctness requires extensive testing under simulated failure (partitions, slow nodes, message reordering) which is hard to assess without runnable code.
CSHH tutor matching for this subject draws from CS graduates with production distributed-systems experience: former engineers who built or operated large-scale services, plus PhD researchers from distributed-systems labs. Our tutors deliver Raft implementations passing the course test suite (including the linearizability checker), consensus-protocol proofs with explicit safety and liveness arguments, microservice architectures with Docker Compose for local development plus Kubernetes manifests for production deployment, message-queue producer-consumer code with explicit at-least-once vs exactly-once semantic handling, and distributed-transaction implementations with explicit rollback and compensation logic. Languages supported: Go (the lingua franca for distributed systems including Kubernetes, etcd, CockroachDB), Java (for Kafka and Cassandra ecosystem), Python (for prototyping plus scripting), C++ (for performance-critical large-scale services).
Where Students Get Stuck
A candidate must receive votes from a majority of nodes within an election timeout. Each node votes for at most 1 candidate per term, prefers candidates with longer logs (last-log-index plus last-log-term comparison). Forgetting the log-up-to-date check leads to committed entries being overwritten by a leader with a shorter log. We implement with explicit RequestVote RPC handling per Raft Figure 2.
Leader replicates log entries via AppendEntries RPC. An entry is committed when replicated to a majority of nodes. The leader cannot directly mark entries from previous terms as committed (Figure 8 scenario in the Raft paper) without first committing a new entry from its own term. We implement with explicit term-checking on commit and the nextIndex plus matchIndex tracking per follower.
Partition tolerance is mandatory in any networked system. The choice is between consistency and availability during a partition. We pick CP for transactions requiring strong consistency (banking, inventory), AP for high-availability stores (shopping carts, social-network feeds with bounded staleness). Spanner is CP for transactions but AP for stale reads.
Linearizability requires operations to appear instantaneous between invocation and response, with a single global order consistent with real time. Sequential consistency requires a single global order but does not require real-time ordering. We test for linearizability with Jepsen Knossos checker on the operation history.
TCP gives at-most-once at the connection level but exactly-once requires application-level idempotency. Kafka exactly-once requires idempotent producers (enable.idempotence=true) plus transactional consumers. We use idempotency keys on every state-changing operation, plus deduplication on the consumer side via a processed-message cache.
Coordinator failure between PREPARE and COMMIT leaves participants holding locks. Recovery requires a new coordinator to query all participants for their PREPARE-or-COMMIT state and complete the transaction. 3PC adds an extra round to avoid blocking but rarely used due to latency. We implement 2PC with explicit timeout-based recovery for the common case plus an out-of-band coordinator-failure procedure.
Assignment Types
Leader election, log replication, and persistence in Go passing the linearizability checker under partition tests. Named pitfall: granting a vote to a candidate with a shorter log, which lets a new leader overwrite already-committed entries.
Basic Paxos, Multi-Paxos, and EPaxos with explicit Prepare-Promise and Accept-Accepted phases. Named pitfall: a proposer that reuses a proposal number already seen by an acceptor, which violates the single-value safety guarantee.
Primary-backup, chain, and quorum replication plus Dynamo-style consistent hashing with anti-entropy. Named pitfall: read and write quorums that do not overlap (R plus W not greater than N), which serves stale reads.
Two-phase commit, saga compensations, and Percolator-style cross-shard transactions with explicit recovery. Named pitfall: a coordinator that fails between PREPARE and COMMIT, leaving participants holding locks indefinitely.
Linearizability, sequential, causal, and eventual consistency with CAP and PACELC tradeoff reasoning per workload. Named pitfall: treating partition tolerance as optional, when any networked system must tolerate partitions.
gRPC services and Kafka or RabbitMQ producer-consumer code with explicit delivery-semantic handling. Named pitfall: assuming exactly-once delivery by default, when it requires idempotency keys and consumer-side deduplication.
Domain-bounded service decomposition with Docker, Kubernetes manifests, and circuit breakers. Named pitfall: a circular call chain across services where per-hop timeouts cascade into a full-architecture failure.
Tutors Who Cover This Subject
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