Aws lambda supports mongoose middleware? - mongodb

Question

Does AWS lambda supports mongoose middleware, I'm using .pre() to check data exists on save.
here is my function call for save
res = new cModel();
res.pre('save', function (next) {
cModel.find({name: company.name}, function (err, docs) {
if (!docs.length){
next();
}else{
console.log('company name exists: ',company.name);
next(new Error("Company Name exists!"));
}
});
}) ;
this is my function call to update
company_model.companySchema.pre('update', function (next) {
try {
cModel.find({ name: { $regex: new RegExp(`^${this.getFilter().name}$` , 'i') }}, function (err, docs) {
try {
if (!docs.length) {
next();
} else {
console.log('company name exists: ', this.getFilter().name);
next(new Error("Company Name exists!"));
}
} catch (e) {
console.error('error in cModel.find: ' + e.message);
}
});
} catch (e) {
console.error('error in pre save : ' + e.message)
}
});

Answer 1

eInside a pre('save',... hook, the reference to the current document is found under this. Here I've replaced company with this in your example.
const schema = new mongoose.Schema({})
schema.pre('save', function (next) {
cModel.find({name: this.name}, function (err, docs) {
if (!docs.length){
next();
} else {
console.log('company name exists: ', this.name);
next(new Error("Company Name exists!"));
}
});
});
const cModel = mongoose.model("cmodel", schema)
This error doesn't have anything to do with lambda, except that the execution environment in lambda seems to be swallowing the error in the async method. To see the error being thrown, you can wrap the contents of your callback in a try {...} catch (e) {...} block and log the error in the catch block:
const schema = new mongoose.Schema({})
schema.pre('save', function (next) {
try {
cModel.find({name: this.name}, function (err, docs) {
try {
if (!docs.length){
next();
} else {
console.log('company name exists: ', this.name);
next(new Error("Company Name exists!"));
}
} catch (e) {
console.error('error in cModel.find: ' + e.message)
}
});
} catch (e) {
console.error('error in pre save : ' + e.message)
}
});
const cModel = mongoose.model("cmodel", schema)
Update
Using .pre('update'... will have this referencing the query, not the document, as the document is never loaded. You can access parts of the query using getFilter() and getUpdate().
Here is an example to check if company exists before making an update:
const schema = new mongoose.Schema({})
schema.pre('update', function (next) {
let newName = this.getUpdate().name;
cModel.find({name: newName }, function (err, docs) {
if (!docs.length){
next();
} else {
console.log('company name exists: ', newName);
next(new Error("Company Name exists!"));
}
});
});
const cModel = mongoose.model("cmodel", schema)