jhellerstein

Invent and Simplify: CALM

One of the more innovative and important results in my work is an idea now known as the CALM Theorem. CALM came from a desire to sidestep expensive "coordination" services whenever possible, including database transactions and consensus services (e.g., Paxos, RAFT). This desire came up naturally with web-scale data (e.g., "NoSQL" systems like Dynamo) and geo-distributed cloud computing (e.g., AWS). Unfortunately, when we abandon the familiar foundations of coordination, we risk unpredictable behavior if nodes make decisions based on stale or inconsistent data.

In this note I explain the CALM Theorem and reflect on why I think it's both important and a good example of the principle to Invent and Simplify.

Let's begin with terminology. CALM is an acronym: Consistency As Logical Monotonicity. That is a mouthful for sure, so we'll break it down.

Consistency

jhellerstein

## Invent and Simplify: CALM

One of the more innovative and important results in my work is an idea now known as the CALM Theorem. CALM came from a desire to sidestep expensive "coordination" services whenever possible, including database transactions and consensus services (e.g., Paxos, RAFT). This desire came up naturally with web-scale data (e.g., "NoSQL" systems like Dynamo) and geo-distributed cloud computing (e.g., AWS). Unfortunately, when we abandon the familiar foundations of coordination, we risk unpredictable behavior if nodes make decisions based on stale or inconsistent data.

In this note I explain the CALM Theorem and reflect on why I think it's both important and a good example of the principle to Invent and Simplify.

Let's begin with terminology. CALM is an acronym: *Consistency As Logical Monotonicity*. That is a mouthful for sure, so we'll break it down.

#### Consistency

jhellerstein

DROP TABLE IF EXISTS loops;
DROP TABLE IF EXISTS log_entries;

CREATE TABLE loops (
  loop_id integer PRIMARY KEY,
  loop_name text, 
  loop_val integer,
  parent_id integer,
  UNIQUE (loop_name, loop_val, parent_id),
  FOREIGN KEY (parent_id) REFERENCES loops

jhellerstein

hydroflow]> export CARGO_LOG=cargo::core::compiler::fingerprint=info
hydroflow]> cargo build
[2022-12-05T17:52:58Z INFO  cargo::core::compiler::fingerprint] stale: missing "/Users/jmh/.git/HEAD"
[2022-12-05T17:52:58Z INFO  cargo::core::compiler::fingerprint] fingerprint error for hydroflow v0.1.0 (/Users/jmh/Dropbox/code/hydroflow/hydroflow)/Build/TargetInner { ..: lib_target("hydroflow", ["lib"], "/Users/jmh/Dropbox/code/hydroflow/hydroflow/src/lib.rs", Edition2021) }
[2022-12-05T17:52:58Z INFO  cargo::core::compiler::fingerprint]     err: current filesystem status shows we're outdated
[2022-12-05T17:52:58Z INFO  cargo::core::compiler::fingerprint] fingerprint error for hydroflow_datalog v0.1.0 (/Users/jmh/Dropbox/code/hydroflow/hydroflow_datalog)/Build/TargetInner { for_host: true, proc_macro: true, ..: lib_target("hydroflow_datalog", ["proc-macro"], "/Users/jmh/Dropbox/code/hydroflow/hydroflow_datalog/src/lib.rs", Edition2021) }
[2022-12-05T17:52:58Z INFO  cargo::core::compiler::fingerprint]     err: curre

jhellerstein

RISELab Kicks Off

Berkeley's computer science division has an ongoing tradition of 5-year collaborative research labs. In the fall of 2016 we closed out the most recent of the series: the AMPlab. We think it was a pretty big deal, and many agreed.

One great thing about Berkeley is the endless supply of energy and ideas that

jhellerstein

#include <vector>
#include <functional>
#include "Stream.h"

using namespace stream;
using namespace stream::op;
using namespace std;

std::vector<tuple<int, string>> make_vector() {
	tuple<int, string> t1 = {1, "cgwu"};