ZENKO-1124: mongo listing, avoid to loop

lib/algos/list/skip.js

@@ -0,0 +1,65 @@
+const assert = require('assert');
+
+const { FILTER_END, FILTER_SKIP, SKIP_NONE } = require('./tools');
+
+
+const MAX_STREAK_LENGTH = 100;
+
+
+class Skip {
+    constructor(params) {
+        assert(params.extension);
+
+        this.extension = params.extension;
+        this.gteParams = params.gte;
+
+        this.listingEndCb = null;
+        this.skipRangeCb = null;
+        this.streakLength = 0;
+    }
+
+    setListingEndCb(cb) {
+        this.listingEndCb = cb;
+    }
+
+    setSkipRangeCb(cb) {
+        this.skipRangeCb = cb;
+    }
+
+    filter(entry) {
+        const filteringResult = this.extension.filter(entry);
+        const skippingRange = this.extension.skipping();
+
+        if (filteringResult === FILTER_END) {
+            if (this.listingEndCb) {
+                this.listingEndCb();
+            }
+        } else if (filteringResult === FILTER_SKIP
+                   && skippingRange !== SKIP_NONE) {
+            if (++this.streakLength >= MAX_STREAK_LENGTH) {
+                /* Avoid to loop on the same range again and again. */
+                const newRange = this._inc(skippingRange);
+                if (newRange === this.gteParams) {
+                    this.streakLength = 0;
+                } else if (this.skipRangeCb) {
+                    this.skipRangeCb(newRange);
+                }
+            }
+        } else {
+            this.streakLength = 0;
+        }
+    }
+
+    _inc(str) {
+        if (!str) {
+            return str;
+        }
+
+        const lastCharValue = str.charCodeAt(str.length - 1);
+        const lastCharNewValue = String.fromCharCode(lastCharValue + 1);
+        return `${str.slice(0, str.length - 1)}${lastCharNewValue}`;
+    }
+}
+
+
+module.exports = { Skip };

lib/storage/metadata/mongoclient/MongoClientInterface.js

@@ -36,6 +36,7 @@ const {
     DEL_MST,
     DataCounter,
 } = require('./DataCounter');
+const Skip = require('./skip');
 
 const USERSBUCKET = '__usersbucket';
 const METASTORE = '__metastore';
@@ -44,7 +45,6 @@ const __UUID = 'uuid';
 const PENSIEVE = 'PENSIEVE';
 const ASYNC_REPAIR_TIMEOUT = 15000;
 const itemScanRefreshDelay = 1000 * 60 * 60; // 1 hour
-const MAX_STREAK_LENGTH = 100;
 const CONNECT_TIMEOUT_MS = 5000;
 
 const initialInstanceID = process.env.INITIAL_INSTANCE_ID;
@@ -962,47 +962,34 @@ class MongoClientInterface {
 
     internalListObject(bucketName, params, extension, log, cb) {
         const c = this.getCollection(bucketName);
+        const stream = new MongoReadStream(c, params, params.mongifiedSearch);
+        const skip = new Skip({
+            extension,
+            gte: params.gte,
+        });
         let cbDone = false;
-        let streakLength = 0;
-        const stream = new MongoReadStream(c, params,
-                                           params.mongifiedSearch);
+
+        skip.setListingEndCb(() => {
+            stream.emit('end');
+            stream.destroy();
+        });
+        skip.setSkipRangeCb(range => {
+            // stop listing this key range
+            stream.destroy();
+            // update the new listing parameters here
+            // eslint-disable-next-line no-param-reassign
+            params.start = undefined; // 'start' is deprecated
+            // eslint-disable-next-line no-param-reassign
+            params.gt = undefined;
+            // eslint-disable-next-line no-param-reassign
+            params.gte = range;
+            // then continue listing the next key range
+            this.internalListObject(bucketName, params, extension, log, cb);
+        });
+
         stream
             .on('data', e => {
-                // filtering result:
-                // - filteringResult > 0: entry accepted and included in the
-                //                        listing result
-                // - filteringResult = 0: entry accepted but not included in
-                //                        the listing result (skipping)
-                // - filteringResult < 0: entry is rejected, listing finishes
-                const filteringResult = extension.filter(e);
-                // skipping: provides insight into why the extension is
-                // skipping the entry, for example: entry starts with a
-                // commonPrefix or entry is a specific version; in such
-                // case, repd needs to skip this range and go on with the next
-                const skippingRange = extension.skipping();
-                if (filteringResult < 0) {
-                    stream.emit('end');
-                    stream.destroy();
-                } else if (filteringResult === 0 && skippingRange) {
-                    // check if MAX_STREAK_LENGTH consecutive keys have been
-                    // skipped
-                    if (++streakLength === MAX_STREAK_LENGTH) {
-                        // stop listing this key range
-                        stream.destroy();
-                        // update the new listing parameters here
-                        // eslint-disable-next-line no-param-reassign
-                        params.start = undefined; // 'start' is deprecated
-                        // eslint-disable-next-line no-param-reassign
-                        params.gt = undefined;
-                        // eslint-disable-next-line no-param-reassign
-                        params.gte = inc(skippingRange);
-                        // then continue listing the next key range
-                        this.internalListObject(bucketName, params,
-                                                extension, log, cb);
-                    }
-                } else {
-                    streakLength = 1;
-                }
+                skip.filter(e);
             })
             .on('error', err => {
                 if (!cbDone) {