lib/storage/s3.js

// Copyright (c) 2018, Compiler Explorer Authors
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import assert from 'assert';

import AWS from 'aws-sdk';
import _ from 'underscore';

import { logger } from '../logger';
import { S3Bucket } from '../s3-handler';
import { anonymizeIp } from '../utils';

import { StorageBase } from './base';

/*
 * NEVER CHANGE THIS VALUE
 *
 * This value does not control the length of generated
 * short links. It is purely an implementation detail
 * of the underlying dynamodb table, and changing it
 * will break all existing links in the database.
 */
const PREFIX_LENGTH = 6;

/*
 * This value can be changed freely to control the minimum
 * generated link length.
 *
 * Changing it will have no impact on existing links.
 */
const MIN_STORED_ID_LENGTH = 9;

assert(MIN_STORED_ID_LENGTH >= PREFIX_LENGTH, 'MIN_STORED_ID_LENGTH must be at least PREFIX_LENGTH');

export class StorageS3 extends StorageBase {
    static get key() { return 's3'; }

    constructor(httpRootDir, compilerProps, awsProps) {
        super(httpRootDir, compilerProps);
        const region = awsProps('region');
        const bucket = awsProps('storageBucket');
        this.prefix = awsProps('storagePrefix');
        this.table = awsProps('storageDynamoTable');
        logger.info(`Using s3 storage solution on ${region}, bucket ${bucket}, ` +
            `prefix ${this.prefix}, dynamo table ${this.table}`);
        AWS.config.update({region: region});
        this.s3 = new S3Bucket(bucket, region);
        this.dynamoDb = new AWS.DynamoDB();
    }

    async storeItem(item, req) {
        logger.info(`Storing item ${item.prefix}`);
        const now = new Date();
        let ip = req.get('X-Forwarded-For') || anonymizeIp(req.ip);
        const commaIndex = ip.indexOf(',');
        if (commaIndex > 0) {
            // Anonymize only client IP
            ip = `${anonymizeIp(ip.substring(0, commaIndex))}${ip.substring(commaIndex, ip.length)}`;
        }
        now.setSeconds(0, 0);
        try {
            await Promise.all([
                this.dynamoDb.putItem({
                    TableName: this.table,
                    Item: {
                        prefix: {S: item.prefix},
                        unique_subhash: {S: item.uniqueSubHash},
                        full_hash: {S: item.fullHash},
                        stats: {
                            M: {clicks: {N: '0'}},
                        },
                        creation_ip: {S: ip},
                        creation_date: {S: now.toISOString()},
                    },
                }).promise(),
                this.s3.put(item.fullHash, item.config, this.prefix, {}),
            ]);
            return item;
        } catch (err) {
            logger.error('Unable to store item', {item, err});
            throw err;
        }
    }

    async findUniqueSubhash(hash) {
        const prefix = hash.substring(0, PREFIX_LENGTH);
        const data = await this.dynamoDb.query({
            TableName: this.table,
            ProjectionExpression: 'unique_subhash, full_hash',
            KeyConditionExpression: 'prefix = :prefix',
            ExpressionAttributeValues: {':prefix': {S: prefix}},
        }).promise();
        const subHashes = _.chain(data.Items)
            .pluck('unique_subhash')
            .pluck('S')
            .value();
        const fullHashes = _.chain(data.Items)
            .pluck('full_hash')
            .pluck('S')
            .value();
        for (let i = MIN_STORED_ID_LENGTH; i < hash.length - 1; i++) {
            let subHash = hash.substring(0, i);
            // Check if the current base is present in the subHashes array
            const index = _.indexOf(subHashes, subHash, true);
            if (index === -1) {
                // Current base is not present, we have a new config in our hands
                return {
                    prefix: prefix,
                    uniqueSubHash: subHash,
                    alreadyPresent: false,
                };
            } else {
                const itemHash = fullHashes[index];
                /* If the hashes coincide, it means this config has already been stored.
                 * Else, keep looking
                 */
                if (itemHash === hash) {
                    return {
                        prefix: prefix,
                        uniqueSubHash: subHash,
                        alreadyPresent: true,
                    };
                }
            }
        }
        throw new Error(`Could not find unique subhash for hash "${hash}"`);
    }

    getKeyStruct(id) {
        return {
            prefix: {S: id.substring(0, PREFIX_LENGTH)},
            unique_subhash: {S: id},
        };
    }

    async expandId(id) {
        // By just getting the item and not trying to update it, we save an update when the link does not exist
        // for which we have less resources allocated, but get one extra read (But we do have more reserved for it)
        const item = await this.dynamoDb.getItem({
            TableName: this.table,
            Key: this.getKeyStruct(id),
        }).promise();

        const attributes = item.Item;
        if (!attributes)
            throw new Error(`ID ${id} not present in links table`);
        const result = await this.s3.get(attributes.full_hash.S, this.prefix);
        // If we're here, we are pretty confident there is a match. But never hurts to double check
        if (!result.hit)
            throw new Error(`ID ${id} not present in storage`);
        const metadata = attributes.named_metadata ? attributes.named_metadata.M : null;
        return {
            config: result.data.toString(),
            specialMetadata: metadata,
        };
    }

    async incrementViewCount(id) {
        try {
            await this.dynamoDb.updateItem({
                TableName: this.table,
                Key: this.getKeyStruct(id),
                UpdateExpression: 'SET stats.clicks = stats.clicks + :inc',
                ExpressionAttributeValues: {
                    ':inc': {N: '1'},
                },
                ReturnValues: 'NONE',
            }).promise();
        } catch (err) {
            // Swallow up errors
            logger.error(`Error when incrementing view count for ${id}`, err);
        }
    }
}