feature: ZENKO-1439 Conditional PUT logic

lib/storage/metadata/MetadataWrapper.js

@@ -172,6 +172,37 @@ class MetadataWrapper {
         });
     }
 
+    _handleJobFuncResult(bucket, key, params, res, log, cb) {
+        const { retry, objVal } = res;
+        if (retry) {
+            // Apply exponential timeout.
+            return this.safePutObjectMD(bucket, key, params, log, cb);
+        }
+        if (objVal === undefined) {
+            return cb();
+        }
+        // If the given tag is not matched, then use exponential backoff to retry.
+        return this.putObjectMD(bucket, key, objVal, params, log, cb);
+    }
+
+    safePutObjectMD(bucket, key, params, log, cb) {
+        // Read the MD of the given bucket and key.
+        this.client.getObject(bucket, key, params, log, (err, objMD, tag) => {
+            if (err) {
+                log.debug('error from metadata', { 
+                    implName: this.implName,
+                    error: err,
+                });
+                // TODO: Are there special cases we need to handle?
+                return cb(err);
+            }
+            // TODO: Add validation of the jobFunc.
+            // Perform the jobFunc action on the newly fetched MD.
+            const res = params.jobFunc(bucket, key, tag, objMD, log);
+            return this._handleJobFuncResult(bucket, key, params, res, log, cb);
+        });
+    }
+
     putObjectMD(bucketName, objName, objVal, params, log, cb) {
         log.debug('putting object in metadata');
         const value = typeof objVal.getValue === 'function' ?

lib/storage/metadata/mongoclient/MongoClientInterface.js

@@ -356,7 +356,9 @@ class MongoClientInterface {
                     _id: vObjName,
                 },
                 update: {
-                    _id: vObjName, value: objVal,
+                    _id: vObjName,
+                    tag: MongoUtils.getTag(),
+                    value: objVal,
                 },
                 upsert: true,
             },
@@ -378,7 +380,9 @@ class MongoClientInterface {
                          ],
                 },
                 update: {
-                    _id: objName, value: objVal,
+                    _id: objName,
+                    tag: MongoUtils.getTag(),
+                    value: objVal,
                 },
                 upsert: true,
             },
@@ -419,14 +423,18 @@ class MongoClientInterface {
         const versionId = generateVersionId(this.replicationGroupId);
         // eslint-disable-next-line
         objVal.versionId = versionId;
-        c.update({
-            _id: objName,
-        }, {
+        const query = { _id: objName };
+        const update = {
             _id: objName,
+            tag: MongoUtils.getTag(),
             value: objVal,
-        }, {
-            upsert: true,
-        }, err => {
+        };
+        const options = { upsert: true };
+        if (params.condPut && params.condPut.tag) {
+            query.tag = params.condPut.tag;
+            options.upsert = false;
+        }
+        c.update(query, update, options, err => {
             if (err) {
                 log.error(
                     'putObjectVerCase2: error putting object version',
@@ -451,12 +459,19 @@ class MongoClientInterface {
         // eslint-disable-next-line
         objVal.versionId = params.versionId;
         const vObjName = formatVersionKey(objName, params.versionId);
-        c.findOne({ _id: objName }, (err, checkObj) => {
+        const query = { _id: objName };
+        if (params.condPut && params.condPut.tag) {
+            query.tag = params.condPut.tag;
+        }
+        c.findOne(query, (err, checkObj) => {
             if (err) {
                 log.error('putObjectVerCase3: mongoDB error finding object');
                 return cb(errors.InternalError);
             }
             const objUpsert = !checkObj;
+            if (objUpsert && params.condPut.tag) {
+                return cb();
+            }
             c.bulkWrite([{
                 updateOne: {
                     filter: {
@@ -465,6 +480,7 @@ class MongoClientInterface {
                     update: {
                         $set: {
                             _id: vObjName,
+                            tag: MongoUtils.getTag(),
                             value: objVal,
                         },
                     },
@@ -480,6 +496,7 @@ class MongoClientInterface {
                     update: {
                         $set: {
                             _id: objName,
+                            tag: MongoUtils.getTag(),
                             value: objVal,
                         },
                     },
@@ -512,14 +529,18 @@ class MongoClientInterface {
      * Put object when versioning is not enabled
      */
     putObjectNoVer(c, bucketName, objName, objVal, params, log, cb) {
-        c.update({
-            _id: objName,
-        }, {
+        const query = { _id: objName };
+        const update = {
             _id: objName,
+            tag: MongoUtils.getTag(),
             value: objVal,
-        }, {
-            upsert: true,
-        }, err => {
+        };
+        const options = { upsert: true };
+        if (params.condPut && params.condPut.tag) {
+            query.tag = params.condPut.tag;
+            options.upsert = false;
+        }
+        c.update(query, update, options, err => {
             if (err) {
                 log.error(
                     'putObjectNoVer: error putting obect with no versioning',
@@ -576,7 +597,7 @@ class MongoClientInterface {
                 return undefined;
             }
             MongoUtils.unserialize(doc.value);
-            return cb(null, doc.value);
+            return cb(null, doc.value, doc.tag);
         });
     }
 

lib/storage/metadata/mongoclient/utils.js

@@ -1,3 +1,4 @@
+const uuidv4 = require('uuid/v4');
 
 function escape(obj) {
     return JSON.parse(JSON.stringify(obj).
@@ -27,4 +28,8 @@ function unserialize(objMD) {
     }
 }
 
-module.exports = { escape, unescape, serialize, unserialize };
+function getTag() {
+    return uuidv4();
+}
+
+module.exports = { escape, unescape, serialize, unserialize, getTag };