Data

Ampt provides a super fast, automatically scalable K/V datastore that's built in to our runtime. Using the @ampt/data package, developers can manage massive collections of complex objects that can be queried on multiple dimensions, sorted, and paginated. With single-digit millisecond response times, it provides enough power to cover your most common needs and use cases.

Your data is just there as part of your application's runtime. You don’t need to think about the connection strings, credentials, capacity planning, or database maintenance. You can  get, set, and remove data whenever you need access to state.

Plus, Ampt provides isolated databases to each ENVIRONMENT, enabling developers to have independent copies of application data in each sandbox, preview and permanent environment of every app.

Overview #

Ampt makes API calls in order to set and retrieve records, so any route/function that uses the data interface must use async/await.

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import { data } from "@ampt/data";
import { api } from "@ampt/api";

api("my-api")
  .router("/test-data")
  .get("/", async (event) => {
    // Set and get data
    await data.set("foo", "bar");
    let results = await data.get("foo");
  });

Setting Items #

Setting data can be accomplished using the set method. You provide a key as the first argument and a value (either a string, boolean, number, array, or object) as the second parameter. Keys are case sensitive, can be a string of up to 256 bytes each, and can contain any valid utf8 character including spaces. By default, the set command will return the updated item.

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await data.set("foo", "bar");
await data.set("fooNum", 123456);
await data.set("foo-Bool", true);
await data.set("foo_Array", ["val1", "val2", "val3"]);
await data.set("foo Obj", { key1: "some val", key2: "some other val" });

An options object can be passed as third argument. The following options are supported:

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await data.set("foo", "bar", {
  meta: true,
  overwrite: true,
  ttl: 3600,
  label1: "baz",
  label2: "baz:bat",
});

Above is an example of using options object while setting data.

Setting Multiple Items #

To set multiple items at the same time, you can specify an array of objects that each contain a key and value as well as any additional meta data (e.g. labels and a ttl value) as the first argument of the set method. You can specify up to 25 items in each request. The second parameter must be an options object with the overwrite flag set to true. This is for future compatibility to support batch updates. You can also add a meta: true flag to return the metadata of your items.

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let results = await data.set(
	[
		{ key: "key1", value: "string value" },
		{ key: "someOtherKey", value: 123, ttl: 1000 },
		{ key: "namespacedKey:keyX", value: { foo: "bar" }, label1: "foo:baz" }
	],
	{ overwrite: true }
);

Updating with atomic counters #

Atomic counters allow numeric items or numeric item object values to be atomically updated. Atomic updates ensure that addition and subtraction operations are processed in order, giving users the ability to maintain the integrity of counters even if there are multiple simultaneous requests.

Updating a single value atomically #

If you only need to update a single value, Ampt provides the add method to help you do that. If the item is a simple numeric value (e.g. { key: "myCounter", value: 10 }, you provide the full key name (including collection namespace) as the first parameter and the numeric value you want to "add" to the existing value as the second parameter. Numbers can be positive or negative, and atomic counters support both integers and float values.

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let results = await data.add("myCounter", 1);
let results = await data.add("myNegativeCounter", -1);

The add method will return the updated value by default. You can specify an optional third parameter of true to return the item's metadata, or pass in an options object like { meta: true }.

If the value you want to atomically update is nested within an object, you specify the full key name as the first parameter, the name of the nested object key you want to update as the second parameter, and a numeric value as the third parameter.

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let results = await data.add("myObjectKey", "nestedCounter", 5);

The add method will return the updated object by default. You can specify an optional fourth parameter of true to return the item's metadata, or pass in an options object like { meta: true }.

Updating multiple values atomically #

You may want to atomically update several fields with a single item and potentially update other values as well. You can achieve this using the standard set method along with a special $add keyword. You set an item like you normally would, but for any numeric value that you'd like to atomically update, you specify a value of { $add: 1 }, where 1 is whatever value you wish to add. For example:

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let results = await data.set("myObject", {
  nestedCounter: { $add: 1 },
  anotherCounter: { $add: 5 },
  someOtherValue: "foo",
});

In the example above, nestedCounter will be atomically increased by 1 on every call and anotherCounter will be atomically increased by 5.

Getting Items #

Items can be retrieved using the get method. This method takes the key as the first argument, and an optional options object as the second argument. By default, the get method will return the value stored in the item.

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const result = await data.get("foo");

In addition to retrieving a single key, you can also retrieve items by providing the namespace name with a colon and a * as a wildcard.

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const result = await data.get("my-namespace:*");

This will return an items array with all keys in the namespaced collection. By default, the items will be limited to 100 and the keys will be sorted in ascending lexicographical order. These defaults can be changed by providing an options object as the second argument.

The following options are supported:

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const users = await data.get("users:*", { limit: 10, reverse: true });

If the only option you need to pass is { meta: true }, you can simply pass true as the second argument to the get method.

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const results = await data.get("foo", true);
const results = await data.get("*", true);

Ampt either returns a single item or an array of multiple items. Any get request that specifies an exact key match will return a single item. Any request that could return more than one item will return an object with an items array that contains keys and values:

{
  items: [
    { key: "foo:bar", value: "item1" },
    { key: "foo:bat", value: { some: "value" } },
    { key: "foo:baz", value: 1234 },
  ];
}

Pagination #

The total number of items returned by a single get() call is limited to the value specified by the limit parameter (default 100). If additional items are available, a lastKey will be returned. This value can be passed into a subsequent call to get() as the start parameter. A .next() convenience function will also be returned which can be called directly instead of constructing the additional call.

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const result = await data.get("foo:*", { limit: 3 });

{
	items: [
		{ key: "foobar", value: "item1" },
		{ key: "foobat", value: true" },
		{ key: "foobaz", value: 1234 },
	],
	lastKey: "foobaz",
	next: [Function: next]
}

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const nextResult = await data.get("foo:*", { limit: 3, start: "foobaz" });

To paginate through all items using next():

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let result = await data.get("foo:*", { limit: 3 });

while (result) {
  // do something with result.items
  result = result.next ? await result.next() : null;
}

Querying with conditionals #

Partial matches #

You've already seen the * wildcard used to retrieve all items, but you can also use the wildcard to retrieve items with partially matching keys as well.

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// Retrieve all keys from the `user123` collection
let results = await data.get("user123:*");

// Retrieve all keys from the `user123` collection that start with 'orders'
let results = await data.get("user123:orders*", true);

Greater than and Less than #

Keys in collections are sorted in lexicographical order, so you can retrieve all items from a collection that are greater than, greater than or equal to, less than, or less than or equal to a supplied key. Use the standard symbols (>, >=, <, <=) after the collection name and colon to filter the return items.

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// Retrieve all keys from the `user123` collection greater than 2021-05-18
let results = await data.get("user123:>2021-05-18");

// Retrieve all keys from the `user123` collection greater than or equal to 2021-05-18
let results = await data.get("user123:>=2021-05-18");

// Retrieve all keys from the `user123` collection less than 2021-05-18
let results = await data.get("user123:<2021-05-18");

// Retrieve all keys from the `user123` collection less than or equal to 2021-05-18
let results = await data.get("user123:<=2021-05-18");

Retrieving items between two keys #

If you want to retrieve items that are lexicographically between two keys, specify the two partial keys between a |.

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// Retrieve all keys between 2021-05-01 and 2021-05-31
let results = await data.get("user123:2021-05-01|2021-05-31");

Getting items by their labels #

You can get items by their labels using the get method and the { label: 'labeln' } option, or you can use the getByLabel convenience method. This method takes the label as the first parameter (e.g. label3), the key as the second parameter, and then an optional third parameter that accepts all the same options as the get method.

Labels support collections as well as simple keys. Since they behave the same way, you can also use collection querying methods like * and >= on labels as well.

Labels are incredibly powerful, allowing you to pivot and access your data in multiple "views". For example, if you store orders in a "user" collection (e.g. user-1234), then you can store their order date and number as the key (e.g. user-1234:ORDER_2021-05-18_9321). This would let you list all (or some) of their orders and sort them by date. But if you wanted to access this same information by the unique order number (9321), a simple key-value store wouldn't let you. You can set label1 to something like ORDER-9321. Now you can either get the orders BY USER or BY ORDER ID:

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// Set the order
let newOrder = await data.set(
 'user-1234:ORDER_2021-05-18_9321', // the key
 { ...the-order-data-here... }, // the details of the order
 { label1: 'ORDER-9321' } // our order id label
)

// Get all orders for user-1234
let user_orders = await data.get('user-1234:ORDER_*');

// Get ORDER 9321
let order = await data.getByLabel('label1','ORDER-9321');

Getting multiple items by their key #

If you'd like to retrieve multiple items that aren't part of the same collection, you can specify an array of keys as the first argument in the get method. Keys must be the complete key as wildcards and other conditionals are not supported in batch operations. You can specify up to 25 keys in each request.

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let results = await data.get(["key1", "someOtherKey", "namespacedKey:keyX"]);

Removing items #

You can remove items by providing and item's key or an array of keys to the remove() method. Keys must be the complete key as wildcards and other conditionals are not supported in the remove operation. You can specify up to 25 keys in each request.

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let results = await data.remove("foo");
let results = await data.remove("foo:bar");
let results = await data.remove(["key1", "someOtherKey", "namespacedKey:keyX"]);

Reacting to changes in data #

Ampt runtime emits an event every time a record is created, updated, or deleted, which you can react to by writing an event handler. This lets you decouple your application and process changes to your data asynchronously. For example, your API could set data and then immediately send a response, while your event handler can do some data aggregation or send a request to an outside app.

Defining event handlers #

You define an event handler using the data.on() method.

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data.on("created", async (event) => {
  // an item has been created
});

The first argument is the event name: created, updated, or deleted. The second argument is your handler function, which receives a single "event" argument.

You can also react to more than one event using an array of event names, or * to react to any event:

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data.on(["created", "updated"], async (event) => {
  // an item has been created or updated
});

data.on("*", async (event) => {
  // an item has been created, updated, or deleted
});

It's possible for more than one handler to be called for a given change to a data item, in which case the handlers are called in the order they were defined. In the example above, the first handler will always be called before the second handler when an item is created or updated, and only the second handler will be called when an item is deleted.

Event format #

The event passed to your handler has the following properties:

• name: the event name, which is one of created, updated, or deleted
• item: the item, including metadata and the value of the item in the value property
• previous: the previous state of the item when the event is updated

Filtering by key #

You can define a handler that is only called when specific keys are affected by adding namespace and key filters to the event name.

To add a filter you can use one of these formats:

• <event-name>:<key-filter>
• <event-name>:<namespace-filter>:<key-filter>

Each filter can either be an exact string or a prefix by adding * to the end of the filter.

For example, to filter using a specific simple key:

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data.on("*:global-item", (event) => {
  // called when the item with key `global-item` is created, updated or deleted
});

To filter using a simple key prefix:

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data.on("created:order_*", (event) => {
  // called when an item with a simple key starting with `order_` is created
});

To filter using both a namespace and key prefix:

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data.on("created:order_*:item_*", (event) => {
  // called when an item is created that has a namespace starting with `order_`
  // and a key starting with `item_`
});

Event ordering #

Data events are processed in the order that the changes were applied to your data items, within an item namespace. It's possible for multiple handlers to be invoked in parallel, but for different namespaces.

Handling errors #

If a handler throws an error, it will be retried with exponential backoff for up to 24 hours until it succeeds. After 24 hours the event will be dropped.

It's important to handle errors in your handler, since a failing handler will prevent new events from being processed.

Handlers should only throw an exception for "retryable" errors such as downstream request failures. If the error is a permanent error, the handler should use a try-catch block to capture the error and let the handler succeed.

Avoiding event loops #

It's possible to create an "event loop" where your event handler triggers itself and results in an infinite loop that exhausts resources. If you are calling set() or remove() within a handler, make sure it will not result in the same handler being invoked again with a new event.