76 lines
2.5 KiB
JavaScript
76 lines
2.5 KiB
JavaScript
// Copyright IBM Corp. 2014,2016. All Rights Reserved.
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// Node module: loopback
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// This file is licensed under the MIT License.
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// License text available at https://opensource.org/licenses/MIT
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/**
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* Module Dependencies.
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*/
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var assert = require('assert');
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/**
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* Checkpoint list entry.
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*
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* @property id {Number} the sequencial identifier of a checkpoint
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* @property time {Number} the time when the checkpoint was created
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* @property sourceId {String} the source identifier
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*
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* @class Checkpoint
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* @inherits {PersistedModel}
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*/
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module.exports = function(Checkpoint) {
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// Workaround for https://github.com/strongloop/loopback/issues/292
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Checkpoint.definition.rawProperties.time.default =
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Checkpoint.definition.properties.time.default = function() {
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return new Date();
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};
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/**
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* Get the current checkpoint id
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* @callback {Function} callback
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* @param {Error} err
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* @param {Number} checkpoint The current checkpoint seq
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*/
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Checkpoint.current = function(cb) {
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var Checkpoint = this;
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Checkpoint._getSingleton(function(err, cp) {
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cb(err, cp.seq);
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});
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};
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Checkpoint._getSingleton = function(cb) {
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var query = { limit: 1 }; // match all instances, return only one
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var initialData = { seq: 1 };
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this.findOrCreate(query, initialData, cb);
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};
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/**
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* Increase the current checkpoint if it already exists otherwise initialize it
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* @callback {Function} callback
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* @param {Error} err
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* @param {Object} checkpoint The current checkpoint
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*/
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Checkpoint.bumpLastSeq = function(cb) {
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var Checkpoint = this;
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Checkpoint._getSingleton(function(err, cp) {
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if (err) return cb(err);
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var originalSeq = cp.seq;
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cp.seq++;
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// Update the checkpoint but only if it was not changed under our hands
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Checkpoint.updateAll({ id: cp.id, seq: originalSeq }, { seq: cp.seq }, function(err, info) {
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if (err) return cb(err);
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// possible outcomes
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// 1) seq was updated to seq+1 - exactly what we wanted!
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// 2) somebody else already updated seq to seq+1 and our call was a no-op.
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// That should be ok, checkpoints are time based, so we reuse the one created just now
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// 3) seq was bumped more than once, so we will be using a value that is behind the latest seq.
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// @bajtos is not entirely sure if this is ok, but since it wasn't handled by the current implementation either,
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// he thinks we can keep it this way.
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cb(null, cp);
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});
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});
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};
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};
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