Cache tiles locally within the ServiceWorker. Fix #40.

This commit is contained in:
Lucas Verney 2019-01-04 11:49:24 +01:00
parent 76f54932bf
commit 07ab80542d
2 changed files with 181 additions and 12 deletions

View File

@ -172,8 +172,15 @@ export default {
},
},
mounted() {
if ('serviceWorker' in navigator) {
runtime.register().catch((error) => {
// Service worker is for caching only, so it needs both SW support and
// caching API support.
if ('serviceWorker' in navigator && 'caches' in window) {
runtime.register().then(
// Clean expired tiles from the cache at startup
() => navigator.serviceWorker.controller.postMessage(JSON.stringify({
action: 'PURGE_EXPIRED_TILES',
})),
).catch((error) => {
console.log(`Registration failed with ${error}.`);
});
}

182
src/sw.js
View File

@ -1,4 +1,10 @@
import { VERSION as CACHE_NAME } from '@/constants';
import localforage from 'localforage';
import {
TILE_SERVERS,
VERSION as CACHE_NAME,
} from '@/constants';
import { loadDataFromStorage } from '@/storage';
const DEBUG = (process.env.NODE_ENV !== 'production');
@ -17,11 +23,52 @@ assetsToCache = assetsToCache.filter(
const ALLOW_CACHING_FROM = [
global.location.origin,
];
const TILE_SERVERS_ORIGINS = [];
// Allow alterations of tile servers requests
Object.keys(TILE_SERVERS).forEach((tileServer) => {
const tileServerURL = TILE_SERVERS[tileServer].url;
if (tileServerURL.indexOf('{a-c}') !== -1) {
TILE_SERVERS_ORIGINS.push(
(new URL(tileServerURL.replace('{a-c}', 'a'))).origin,
);
TILE_SERVERS_ORIGINS.push(
(new URL(tileServerURL.replace('{a-c}', 'b'))).origin,
);
TILE_SERVERS_ORIGINS.push(
(new URL(tileServerURL.replace('{a-c}', 'c'))).origin,
);
} else {
TILE_SERVERS_ORIGINS.push((new URL(tileServerURL)).origin);
}
});
// Get duration (in s) before (cache) expiration from headers of a fetch
// request.
function getExpiresFromHeaders(headers) {
// Try to use the Cache-Control header (and max-age)
if (headers.get('cache-control')) {
const maxAge = headers.get('cache-control').match(/max-age=(\d+)/);
return parseInt(maxAge ? maxAge[1] : 0, 10);
}
// Otherwise try to get expiration duration from the Expires header
if (headers.get('expires')) {
return (
parseInt(
(new Date(headers.get('expires'))).getTime() / 1000,
10,
)
- (new Date()).getTime()
);
}
return null;
}
global.self.addEventListener('install', (event) => {
DEBUG && console.log('SW: installing…');
event.waitUntil(
!DEBUG && global.caches.open(CACHE_NAME) // Don't cache during dev
global.caches.open(CACHE_NAME) // Don't cache during dev
.then((cache) => {
DEBUG && console.log('SW: cache opened.');
cache.addAll(assetsToCache).then(
@ -61,14 +108,17 @@ global.self.addEventListener('fetch', (event) => {
// Do not touch requests which are not GET
if (request.method !== 'GET') {
DEBUG && console.log(`SW: ignore non-GET request: ${request.method}`);
DEBUG && console.log(`SW: ignore non-GET request: ${request.method}.`);
return;
}
// Do not touch requests from a different origin
// Only touch requests which we can cache or from tiles servers.
const requestURL = new URL(request.url);
if (ALLOW_CACHING_FROM.indexOf(requestURL.origin) === -1) {
DEBUG && console.log(`SW: ignore different origin ${requestURL.origin}`);
if (
ALLOW_CACHING_FROM.indexOf(requestURL.origin) === -1
&& TILE_SERVERS_ORIGINS.indexOf(requestURL.origin) === -1
) {
DEBUG && console.log(`SW: ignore different origin ${requestURL.origin}.`);
return;
}
@ -76,28 +126,140 @@ global.self.addEventListener('fetch', (event) => {
if (requestURL.pathname.startsWith('/api')) {
// Note that if API is on a different location, it will be ignored by
// the previous rule.
DEBUG && console.log(`SW: ignore API call ${requestURL.pathname}`);
DEBUG && console.log(`SW: ignore API call ${requestURL.pathname}.`);
return;
}
// Serve tiles from cache or download and cache them
if (TILE_SERVERS_ORIGINS.indexOf(requestURL.origin) !== -1) {
event.respondWith(global.caches.open(`${CACHE_NAME}-tiles`).then(
cache => cache.match(request).then(
(response) => {
// If there is a match from the cache
if (response) {
DEBUG && console.log(`SW: serving ${request.url} from cache.`);
const expirationDate = Date.parse(response.headers.get('sw-cache-expires'));
const now = new Date();
// Check it is not already expired and return from the
// cache
if (expirationDate > now) {
return response;
}
}
// Otherwise, let's fetch it from the network
DEBUG && console.log(`SW: no match in cache for ${request.url}, using network.`);
return fetch(request.url).then((liveResponse) => {
// Get tile caching duration from settings
let tileCachingDurationPromise = (
Promise.resolve(0) // no caching by default
);
if (
localforage.driver() === localforage.INDEXEDDB
) {
tileCachingDurationPromise = loadDataFromStorage(
'settings', 'tileCachingDuration',
);
}
return tileCachingDurationPromise.then((tileCachingDuration) => {
// This is caching duration from settings
const cachingDuration = (
tileCachingDuration || 0
);
// This is caching duration specified in HTTP headers
const cachingDurationFromHeaders = getExpiresFromHeaders(
liveResponse.headers,
) || 0;
// If any form of caching is possible, do it
if (tileCachingDuration > 0 || cachingDurationFromHeaders > 0) {
// Compute expires date from caching duration
const expires = new Date();
expires.setSeconds(
expires.getSeconds()
// Caching duration cannot be less than
// specified by HTTP headers.
+ Math.max(cachingDuration, cachingDurationFromHeaders),
);
// Recreate a Response object from scratch to put
// it in the cache, with the extra header for
// managing cache expiration.
const cachedResponseFields = {
status: liveResponse.status,
statusText: liveResponse.statusText,
headers: { 'SW-Cache-Expires': expires.toUTCString() },
};
liveResponse.headers.forEach((v, k) => {
cachedResponseFields.headers[k] = v;
});
// We will consume body of the live response, so
// clone it before to be able to return it
// afterwards.
const returnedResponse = liveResponse.clone();
return liveResponse.blob().then((body) => {
DEBUG && console.log(
`SW: caching tiles ${request.url} until ${expires.toUTCString()}.`,
);
// Put the duplicated Response in the cache
cache.put(request, new Response(body, cachedResponseFields));
// Return the live response from the network
return returnedResponse;
});
}
// Otherwise, just return the live result from the network
return liveResponse;
});
});
},
),
));
return;
}
// For the other requests, try to match it in the cache, otherwise do a
// network call
if (DEBUG) {
// Never match from cache in production
// Never match from cache in development
return;
}
const resource = global.caches.open(CACHE_NAME).then(
cache => cache.match(request).then(
(response) => {
if (response) {
DEBUG && console.log(`SW: serving ${request.url} from cache`);
DEBUG && console.log(`SW: serving ${request.url} from cache.`);
return response;
}
DEBUG && console.log(`SW: no match in cache for ${request.url}, using network`);
DEBUG && console.log(`SW: no match in cache for ${request.url}, using network.`);
return fetch(request);
},
),
);
event.respondWith(resource);
});
global.self.addEventListener('message', (event) => {
console.log(`SW: received message ${event.data}.`);
const eventData = JSON.parse(event.data);
// Clean tiles cache
if (eventData.action === 'PURGE_EXPIRED_TILES') {
DEBUG && console.log('SW: purging expired tiles from cache.');
global.caches.open(`${CACHE_NAME}-tiles`).then(
cache => cache.keys().then(
keys => keys.forEach(
key => cache.match(key).then((cachedResponse) => {
const expirationDate = Date.parse(cachedResponse.headers.get('sw-cache-expires'));
const now = new Date();
// Check it is not already expired
if (expirationDate < now) {
DEBUG && console.log(`SW: purging (expired) tile ${key.url} from cache.`);
cache.delete(key);
}
}),
),
),
);
}
});