Redistance NPM

Redis-Tance

he's going the redistance
he's going for speed
she's all alone (all alone)
all alone in her time of need

Redis-Tance is a wrapper around redis that's mostly for the sake of convenience.

It promisifies the entire library, and provides a function that automatically caches functions passed through it.

Basic Usage

Getting Started

Because this is a wrapper around redis, you will need to construct a valid redis client and pass it to Tance.

const redis = require('redis');
const Tance = require('redistance').Tance;

const redisClient = redis.createClient();
const tance = new Tance(redisClient);

Gets & Sets

Every command against Tance is just a redis command (i.e. "set"), but it returns a promise that resolves when the command completes.

async function doThings(){
    await tance.set("argle", "bargle");
    let margle = await tance.get("argle");
    
    console.log("argle? ", margle); // argle? bargle
};

Commands that have many arguments just lay out those arguments one at a time.

async function doThings(){
    await tance.set("slappy", "pappy", "EX", 180);
    let pappy = await tance.get("slappy");
    
    console.log("slappy? ", pappy); // slappy? pappy
};

Some redis commands call for a long list of arguments. If you have these as an array, you can provide them with the spread operator.

async function getABunchOfIds(){
    let ids = ["key1", "key2", "key3"];
    return tance.mget(...ids);
}

Cache

Tance provides a cache wrapper that provides a sane-but-not-comprehensive default cache behavior for asynchronous functions.

It might struggle if given a function with very complex inputs.

    async function _rng(){
        return uuid();
    }

    const rng = tance.cache(_rng, 100);

    let rng1 = await rng();
    let rng2 = await rng();
    
    // rng2 should be the same as rng1, even though the 
    // function would otherwise produce a random value every time

    assert.equal(rng1, rng2);

Caching Functions With Arguments

Tance will only cache functions if their arguments exactly match.

    async function _rng({x, y, z}){
        return uuid();
    }

    let rng = tance.cache(_rng, 100);

    let rng1 = await rng({x: 1, y: 1, z: 1});
    let rng2 = await rng({x: 1, y: 2, z: 2});
    let rng3 = await rng({x: 1, y: 1, z: 1});

    // rng1 and rng3 should be the same, because they share arguments
    assert.equal(rng1, rng3);
    
    // rng1 and rng2 should not be the same, because they don't
    assert.notEqual(rng1, rng2);

Clearing the Cache

tance.clearCache will clear the cache of any cached items that exactly match the parameters they've been provided.

    async function _rng(){
        return uuid();
    }
    let rng = tance.cache(_rng, 100);

    let rng1 = await rng({x: 1, y: 1, z: 1});
    let rng2 = await rng({x: 2, y: 2, z: 2});

    await tance.clearCache({x: 1, y: 1, z: 1}, "_rng5");
    let rng3 = await rng({x: 1, y: 1, z: 1});
    let rng4 = await rng({x: 2, y: 2, z: 2});


    assert.notEqual(rng1, rng3);
    assert.equal(rng2, rng4);

This stuff won't work when caching functions that don't take named parameters - the only way to clear the cache for these functions is to completely clear the cache.

tance.clearCache with a null argument will completely clear the cache.

    async function _rng(){
        return uuid();
    }

    let rng = tance.cache(_rng, 100);

    let rng1 = await rng();
    await tance.clearCache(null, "_rng2");

    let rng2 = await rng();

    assert.notEqual(rng1, rng2);

Caching Stuff With a Non-String Return Value

Because everything that gets returned is pushed through Redis, it's hard to cache a function that returns a non-string value, unless you first pass it through a serializer and deserializer.

Here, we create tance.cache with JSON.stringify as the serializer and JSON.parse as the deserializer, which allows us to cache a function that returns an object.

async function _rng({x, y, z}){
    return {
        'gargle': 'margle',
        'bargle': 'fargle',
        'targle': 'chargle',
        'rng': uuid(),
    };
}

let rng = tance.cache(_rng, 100, '_rng', JSON.stringify, JSON.parse);

let rng1 = await rng({x: 1, y: 1, z: 1});
let rng2 = await rng({x: 1, y: 1, z: 1});

assert.deepEqual(rng1, rng2);
assert.isObject(rng1);
assert.isObject(rng2);

Cache Indexing

Normally, clearing the cache only works on sets of arguments that are an exact match - so, for example, if I wanted to clear {x: 1, y: 1, z:1}, I'd have to call clearCache with exactly {x: 1, y: 1, z:1}.

It's not, however, always possible to know exactly which cache entries we want to clear — but clearing the entire cache for the function wouldn't be granular enough.

That's why we have cache indexing: a way to define a subset of arguments that we can clear all at once.

async function _rng({x, y, z}){
    return uuid();
}

let rng = tance.cache(_rng, 100);
tance.cacheIndex(['x'], '_rng');

let rng1 = await rng({x: 1, y: 1, z: 1});
let rng2 = await rng({x: 1, y: 2, z: 3});
let rng3 = await rng({x: 2, y: 2, z: 3});
// this should clear everything with x=1
await tance.clearCache({'x': 1}, '_rng');
// whereas this would ONLY clear {x: 1, y: 2, z: 3}
await tance.clearCache({'x': 1, 'y': 2, 'z': 3}, '_rng');
let rng4 = await rng({x: 1, y: 1, z: 1});
let rng5 = await rng({x: 1, y: 2, z: 3});
let rng6 = await rng({x: 2, y: 2, z: 3});

assert.notEqual(rng1, rng4);
assert.notEqual(rng2, rng5);
assert.equal(rng3, rng6);

Mock Tables

What's a database got that Redis don't got?

Well, schema validation and secondary indexes, for one.

But there's nothing stopping us from cramming this stuff in, ourselves.

Creation

Here's an example of creating a Table with a Schema:

const table = require("redis-tance").Table;
const migratingSchema = require("redis-tance").MigratingSchema;

class WidgetTable extends Table{
    constructor({tance, namespace=""}){
        let widgetSchemaV1 = {
            "type": "object",
            "properties": {
                // these three properties are mandatory for every object
                "id": {"type": "string"},
                "type": {"type": "string"},
                "version": {"type": "integer"},
                // these are our real properties:
                "widgetName": {"type": "string", "index": "simple"},
                // note that widgetOptional isn't in "required"
                "widgetOptional": {"type": "string", "index": "simple"},
                "widgetTags": {"type": "array", "index": "simple"},
                "widgetInteger": {"type": "integer", "index": "integer"},
                "created_at_timestamp": {"type": "integer", "minimum": 0, "index": "integer"},
                "created_at_iso": {"type": "string"},
            },
            "additionalProperties": false,
            "required": ["id", "type", "version", "widgetOwnerId", "widgetName", "widgetTags", "widgetInteger", "created_at_timestamp", "created_at_iso"]
        };

        let schema = new MigratingSchema({type: "Widget", v1: widgetSchemaV1});

        super({tance, schema, namespace});
    };
}

let table = new WidgetTable({tance});

Every instance of WidgetTable will point to the same database:

// table1 and table2 both refer to the same table; data entered in one will be available in the other
let table1 = new WidgetTable({tance});
let table2 = new WidgetTable({tance});

It's possible to create separate WidgetTables with the namespace parameter

// table1, table2 and table3 now refer to different tables
let table1 = new WidgetTable({tance});
let table2 = new WidgetTable({tance, namespace="spargharg"});
let table3 = new WidgetTable({tance, namespace="daaaaaang"});
let table4 = new WidgetTable({tance, namespace="daaaaaang"});
// table3 and table4 refer to the same table

Schema & MigratingSchema

The Schema used to create the table is written in the language of json-schema. Our json schema validating library assures us that it can deal with schema up to draft-v4.

Tance provides both a Schema and a MigratingSchema.

If you're building a table there's a good chance you'll want to use MigratingSchema — it comes with tools for upgrading and modifying the schema against live data.

Migrating with MigratingSchema

Let's imagine we have data that looks like:

class WidgetTable extends Table{
    constructor({tance, namespace=""}){
        let widgetSchemaV1 = {
            "type": "object",
            "properties": {
                // these three properties are mandatory for every object
                "id": {"type": "string"},
                "type": {"type": "string"},
                "version": {"type": "integer"},
                // these are our real properties:
                "widgetName": {"type": "string", "index": "simple"},
                // note that widgetOptional isn't in "required"
                "widgetOptional": {"type": "string", "index": "simple"},
                "widgetTags": {"type": "array", "index": "simple"},
                "widgetInteger": {"type": "integer", "index": "integer"},
                "created_at_timestamp": {"type": "integer", "minimum": 0, "index": "integer"},
                "created_at_iso": {"type": "string"},
            },
            "additionalProperties": false,
            "required": ["id", "type", "version", "widgetOwnerId", "widgetName", "widgetTags", "widgetInteger", "created_at_timestamp", "created_at_iso"]
        };

        let schema = new MigratingSchema({type: "Widget", v1: widgetSchemaV1});

        super({tance, schema, namespace});
    };
}

we want to upgrade the WidgetTable to have a new mandatory field, widgetNameUppercase, as well as remove the field widgetInteger

We do that by adding another version to the schema, as well as an versionX => versionY function responsible for taking an object of the previous version and updating it to an object of the new version.

class WidgetTable extends Table{
    constructor({tance, namespace=""}){
        let widgetSchemaV1 = {
            "type": "object",
            "properties": {
                // these three properties are mandatory for every object
                "id": {"type": "string"},
                "type": {"type": "string"},
                "version": {"type": "integer"},
                // these are our real properties:
                "widgetName": {"type": "string", "index": "simple"},
                // note that widgetOptional isn't in "required"
                "widgetOptional": {"type": "string", "index": "simple"},
                "widgetTags": {"type": "array", "index": "simple"},
                "widgetInteger": {"type": "integer", "index": "integer"},
                "created_at_timestamp": {"type": "integer", "minimum": 0, "index": "integer"},
                "created_at_iso": {"type": "string"},
            },
            "additionalProperties": false,
            "required": ["id", "type", "version", "widgetOwnerId", "widgetName", "widgetTags", "widgetInteger", "created_at_timestamp", "created_at_iso"]
        };
        
        // added widgetNameUppercase, removed widgetInteger
        let widgetSchemaV2 = {
            "type": "object",
            "properties": {
                "id": {"type": "string"},
                "type": {"type": "string"},
                "version": {"type": "integer"},
                "widgetName": {"type": "string", "index": "simple"},
                "widgetNameUppercase": {"type": "string"},
                "widgetOptional": {"type": "string", "index": "simple"},
                "widgetTags": {"type": "array", "index": "simple"},
                "created_at_timestamp": {"type": "integer", "minimum": 0, "index": "integer"},
                "created_at_iso": {"type": "string"},
            },
            "additionalProperties": false,
            "required": ["id", "type", "version", "widgetOwnerId", "widgetName", "widgetNameUppercase", "widgetTags", "created_at_timestamp", "created_at_iso"]
        };
        let v1ToV2 = (object) =>{
            object.widgetNameUppercase = object.widgetName.toUpperCase();
            delete object.widgetInteger;
            return object;
        };

        let schema = new MigratingSchema({type: "Widget", v1: widgetSchemaV1});
        
        schema.addVersion(widgetSchemaV2, v1ToV2);

        super({tance, schema, namespace});
    };
}

This schema now contains both types of Widget, v1 widgets and v2 widgets. Any time the codebase encounters a v1 widget in the database, it will upgrade it to a v2 widget using the v1ToV2 function before returning it.

We can addVersion as many times as we update the object.

Schema

For situations where migration is not likely to be an issue, we can also create a regular Schema.

class WidgetTable extends Table{
    constructor({tance, namespace=""}){
        let widgetSchemaV1 = {
            "type": "object",
            "properties": {
                // these three properties are mandatory for every object
                "id": {"type": "string"},
                "type": {"type": "string"},
                "version": {"type": "integer"},
                // these are our real properties:
                "widgetName": {"type": "string", "index": "simple"},
                // note that widgetOptional isn't in "required"
                "widgetOptional": {"type": "string", "index": "simple"},
                "widgetTags": {"type": "array", "index": "simple"},
                "widgetInteger": {"type": "integer", "index": "integer"},
                "created_at_timestamp": {"type": "integer", "minimum": 0, "index": "integer"},
                "created_at_iso": {"type": "string"},
            },
            "additionalProperties": false,
            "required": ["id", "type", "version", "widgetOwnerId", "widgetName", "widgetTags", "widgetInteger", "created_at_timestamp", "created_at_iso"]
        };

        let schema = new Schema({type: "Widget", schema: widgetSchemaV1});

        super({tance, schema, namespace});
    };
}

Schema Expiry

Passing the expirySeconds argument to Schema creates a Schema for an object that will expire.

Any objects, tables, and indexes created for this Schema will also expire in that many seconds.

class ExpiringWidgetTable extends Table{
    constructor({tance, namespace=""}){
        let widgetSchemaV1 = {
            ...
        };

        let schema = new Schema({type: "Widget", schema: widgetSchemaV1, expirySeconds: 10});

        super({tance, schema, namespace});
    };
}

Static Schema

The Schema class also comes with a bunch of Schema baked in for really common data types:

let schemaForJustIds = Schema.Id();
let schemaForJustNumbers = Schema.Number();
let schemaForJustInts = Schema.Int();

These aren't that useful in a table (they don't represent objects, which we store) — they're useful when we're working with RedisSet, which we haven't talked about yet.

Schema automatic indexes

The JSON Schema format doesn't have any mention of these crazy index things:

"widgetTags": {"type": "array", "index": "simple"},
"widgetInteger": {"type": "integer", "index": "integer"},
}

These are special instructions that instruct the Table to automatically create Indexes for these fields.

The two available types of index are simple and integer (for now).

More details on that when we get to find.

insert

Now that we have a table, we can put stuff in it!

const luxon = require('luxon').DateTime;

let createdObject = await table.insert({
    "widgetName": "Widgeotto",
    "widgetTags": ["bippity", "boppity", "boo"],
    "widgetInteger": 7,
    "created_at_timestamp": luxon.local().valueOf(),
    "created_at_iso": luxon.local().toString(),
});

console.log(createdObject.id); // each object is automatically given an id, if we don't create it with one already

It will fail if we try to put stuff in that doesn't match the Schema that we created earlier.

// this will throw an error! 
let createdObject = await table.insert({
    "NOOOOOOOOOOOOOO": "nooooo?",
    "widgetName": "Widgeotto",
    "widgetTags": ["bippity", "boppity", "boo"],
    "widgetInteger": 7,
    "created_at_timestamp": luxon.local().valueOf(),
    "created_at_iso": luxon.local().toString(),
});

The object created by the insert operation will have an id automatically generated for it. It's possible to choose your own ID:

let createdObject = await table.insert({
    "id": "7",
    "widgetName": "Widgeotto",
    "widgetTags": ["bippity", "boppity", "boo"],
    "widgetInteger": 7,
    "created_at_timestamp": luxon.local().valueOf(),
    "created_at_iso": luxon.local().toString(),
});

This insert is an UPSERT — that means it'll insert if the ID doesn't already exist, and UPDATE if the ID does already exist.

Table objects will be automatically serialized to JSON.

get

Use table.get(id) to get stuff.

Table objects will automatically be deserialized from JSON.

let createdObject = await table.insert({
    "widgetName": "Widgeotto",
    "widgetTags": ["bippity", "boppity", "boo"],
    "widgetInteger": 7,
    "created_at_timestamp": luxon.local().valueOf(),
    "created_at_iso": luxon.local().toString(),
});

let id = createdObject.id;

let widgeotto = await table.get(id);

// poof, widgeotto is (deep) equal to createdObject

delete

Use table.delete(id) to delete stuff.

await table.delete(id);

modify

While it's entirely possible to modify an object by get-ing it, then insert-ing it again, this can cause a problem where data is read-then-written out of order, causing data inconsistency.

The table.modify(id, changeFn) function wraps this operation in a lock — only one operation can modify this document at a time.

The changeFn expected by this is an async object=>object — it expects to receive an object and produce a modified version of that object.

If the changeFn takes more than 500ms to resolve (an eternity!) the lock will expire and the write will fail. If you have something really complicated to calculate, it might be best to do it outside of this critical path.

let widgey = await table.modify(widgeotto.id, (object)=>{
    object.widgetName = "bestWidget";
    return object;
});

clear

Wanna be incredibly destructive? Of course you do!

// this empties the entire table
table.clear()

find

Now it's time to find some things in the table!

Getting everything in the entire table is as easy as:

let everythingInTheWholeDamnTable = find({});

We probably, uh, don't want to do that so often.

While it's possible to limit the results of this query with .find({'$n': 10}), that will start by loading every single ID in the entire table — it's a bad idea. The $n and $offset parameters are best when working with an already restricted set size (under 1000).

One important note about Tance Tables is that they just don't support full table searches.

IMPORTANT NOTE: Full Table Search is something to work on for the future!

In Mongo you can search on an unindexed field — it'll just take a really long time.

In Tance, if you search on an unindexed field, it'll just treat that like an empty search.

`simple` and the SimpleSetIndex

On any fields with index: 'simple', we can perform a search for exact matches only.

let createdObject = await table.insert({
    "widgetName": "Widgeotto",
    "widgetTags": ["bippity", "boppity", "boo"],
    "widgetInteger": 7,
    "created_at_timestamp": luxon.local().valueOf(),
    "created_at_iso": luxon.local().toString(),
});

let results = await table.find({widgetName: "Widgeotto"})

// results is now an array containing the one object we just created.

Arrays are configured to match if the search matches anything in the array, so:

let createdObject = await table.insert({
    "widgetName": "Widgeotto",
    "widgetTags": ["bippity", "boppity", "boo"],
    "widgetInteger": 7,
    "created_at_timestamp": luxon.local().valueOf(),
    "created_at_iso": luxon.local().toString(),
});

let results = await table.find({widgetTags: "bippity"})

// results is still an array containing the one object we just created.

It's possible to combine these search parameters to create compound AND searches:

let createdObject = await table.insert({
    "widgetName": "Widgeotto",
    "widgetTags": ["bippity", "boppity", "boo"],
    "widgetInteger": 7,
    "created_at_timestamp": luxon.local().valueOf(),
    "created_at_iso": luxon.local().toString(),
});

let results = await table.find({widgetTags: "bippity", widgetName: "Widgeotto"});

// results is *still* an array containing the one object we just created.

IntegerIndex

On fields with index: 'integer' we have more options for searching!

We can search for any values $gt (greater than), $gte (greater than or equal), $lt (less than), or $lte (less than or equal) an integer value.

let table = new WidgetTable({tance});
await table.insert({
    "widgetName": "three",
    "widgetNumber": 3,
    "created_at_timestamp": luxon.local().valueOf(),
    "created_at_iso": luxon.local().toString(),
});

await table.insert({
    "widgetName": "four",
    "widgetNumber": 4,
    "created_at_timestamp": luxon.local().valueOf(),
    "created_at_iso": luxon.local().toString(),
});

await table.insert({
    "widgetName": "five",
    "widgetNumber": 5,
    "created_at_timestamp": luxon.local().valueOf(),
    "created_at_iso": luxon.local().toString(),
});

await table.insert({
    "widgetName": "six",
    "widgetNumber": 6,
    "created_at_timestamp": luxon.local().valueOf(),
    "created_at_iso": luxon.local().toString(),
});

let fiveAndSix = await table.find({widgetNumber: {"$gte": 5}});
let justSix = await table.find({widgetNumber: {"$gt": 5}});
let threeFourFive = await table.find({widgetNumber: {"$lte": 5}});
let threeFour = await table.find({widgetNumber: {"$lt": 5}});
let justFive = await table.find({widgetNumber: {"$gt": 4, "$lt": 6}});
let alsoJustFive = await table.find({widgetNumber: {"$gt": 4, "$lt": 6}, widgetName: "five"});

We can also use $top and $bottom to get the top and bottom-ranked values against a table.

let fiveAndSix = await table.find({widgetNumber: {"$top": 2}});
let threeAndFour = await table.find({widgetNumber: {"$bottom": 2}});
let justFour = await table.find({widgetNumber: {"$gt": 0, "$n": 1, "$offset": 1}});
let justThree = await table.find({widgetNumber: {"$bottom": 2, "$n": 1}});

If we only want to get a few items from a table, creating a created_timestamp integer parameter and then querying $top on it is one way to reliably and efficiently get a few objects.

recalculateIndexes

If we, as the result of a Migration (above) add indexes to a Table, new objects will be created according to the new indexes, but old objects will not be in the newly-created indexes.

table.recalculateIndexes takes the nuclear step of deleting and recreating all indexes. Yikes!

IMPORTANT NOTE: More granular index recalculation is something to work on for the future!

RedisSet

The RedisSet object works a lot like a Table - it allows for objects to have a Schema and handles automatic serialization and deserialization, but it doesn't have indexes — it's just a plain ol' Redis Set.

let set = tance.redisSet({id: "12345", schema: Schema.Integer()});

// "set" and "add" are interchangeable operations for putting things in the set
await set.set(1);
await set.add(2);
await set.set(3);
await set.add(4);
await set.set(5);

let getThreeItemsFromTheSet = await set.randmember(3);
let thisShouldBeTrue = await set.has(3);
let thisShouldBeFalse = await set.has(9);

// "get" and "members" are interchangeable operations for getting things from the set
let everythingFromTheSet = await set.get();
let alsoEverything = await set.members();

let probablyAboutFive = await set.count();

// remove an item from the set
await set.rem(2);

let probablyAboutFour = await set.count();

// clear the whole set
await set.delete()

let probablyAboutZero = await set.count();

assert.equal(response.length, 3);

Intersect, Diff, and Union

RedisSet can perform Intersections, Diffs, and Unions.

Here's an example using union and unionStore but it works the same way for intersect and intersectStore, as well as diff and diffStore:

let set = tance.redisSet({id: "12345", schema: Schema.Integer()});

await set.set(1);
await set.set(2);
await set.set(3);
await set.set(4);
await set.set(5);

let set2 = tance.redisSet({id: "34567", schema: Schema.Integer()});

await set2.set(3);
await set2.set(4);
await set2.set(5);
await set2.set(6);
await set2.set(7);

let oneToSeven = await set.union(set2);

assert.deepEqual(oneToSeven, [1,2,3,4,5,6,7]);

let oneToSevenButAsARedisSet = await set.unionStore(set2);

assert.deepEqual(await unionObj.members(), [1,2,3,4,5,6,7]);