Is it possible to query (GET) a document from within a document update handler in CouchDB?
I have written a simple document update handler in CouchDB 2.0 to accept a POST from a third party (CognitoForms). This works fine, and I take the ID from their JSON payload and use that as the doc _id.
You can then specify an 'update' URI in CognitoForms, so I could create a new update handler or use the same one. However, in CognitoForms:
The update does a POST rather than a PUT
There does not appear to be a way to send any query parameters
As the ID for the document which needs to be updated is within the body, I could use this to query the database for the document, get the _rev, and return the payload with the _id and _rev to perform the update. However, I simply don't know if I can do such a query within the update handler. I feel like I am either missing something obvious, or there is a very good reason that I wouldn't be allowed to do that.
Thanks very much
edit: I should add that I understand I could create a small application to parse the request before forwarding on to couchdb, but I was interested to see if I could implement this in couchdb only to understand how far I can get without another layer!
In your particular case, it's quite hard to do this. A document update handler is basically a pure function that gets the data it needs and returns a response, but it has no way to reach out into the database.
If you add a doc id to the url, the update function gets the doc from the database as a parameter. For details see the CouchDB docs for update functions.
The way to a possible solution is to use a rewrite in CouchDB in order to extract the id from the body. In CouchDB 2.0, a new way for rewrites as functions has been introduced.
For pushing the limits, using a rewrite function for this sounds like fun. But for a production use case, it's probably easier and more maintainable to create a small node.js app that parses the body.
Related
Im wondering if its bad idea for me to send DELETE Request on server endpoint
lectures/remove?id=${lecture._id}
I am aware that DELETE Requests shouldn't include req.body.
Does it matter if i pass information via params or query? or is there perhaps better way to sending info as delete request in order to delete some info from db?
Feels like just matter of semantics.
Thanks for answers in advance.
In general, if you have a RESTful API, and you want to refer to a resource you use URL parameters as you want to identify that single resource.
So you would have something like
DELETE /lectures/:lectureId
As it's a single resource of lectures.
However, you may want to delete multiple resources and in that case, it is a common practice to use query parameters
DELETE lectures?id=LECTURE_1&id=LECTURE_2&id=LECTURE_3...
So the "best practice" that you might be missing here is that you should use nouns instead of verbs in endpoints as you are dealing with resources:
Keep URLs verb-free
Avoid actions — think about resources
Unless you design your API in a way that you trigger a deletion task/process by calling this endpoint then you can challenge this recommendations.
See more:
http://opensource.zalando.com/restful-api-guidelines/#delete
RESTful - What should a DELETE response body contain
https://stackoverflow.blog/2020/03/02/best-practices-for-rest-api-design/
https://learn.microsoft.com/en-us/azure/architecture/best-practices/api-design
Is it possible to use cache based on a key in the request payload?
Eg. let's say we got a json or xml request payload where one of the elements is CustomerId.
Would it then be possible to cache based on CustomerId?
Thanks
I hope I understood your query properly and am not too late. I think you want to cache only when 'CustomerId' is present in the input OR it contains a certain value.
You can refer to the samples given in the foll link
https://azure.microsoft.com/en-us/blog/policy-expressions-in-azure-api-management/
It will help you to write policy expressions to check the presence or value of a particular field. Then you can cache or ignore based on that.
On a side note, Custom Caching is also something cool to check
https://learn.microsoft.com/en-us/azure/api-management/api-management-sample-cache-by-key
How can I update the multiple records using PUT in Web Api in one Call?
For updating single record the URL would be
http://localhost:4211/api/AuditChecklist/{id},
but what should I pass in place of {id} for updating multiple records in one call?
Your API would need to support this, and it doesn't look like it does. Your best bet might be to employ a for loop in the client code calling the API. Or you could write your API to accept a JSON body with a variable length hashtable containing the values to update and their new value.
In the TAMA implementation, I came across an issue with Couchdb. (Version 1.2.0) ,
We are using named documents to maintain unique constraint logic in the application. (named documents : whose _id is user defined, and not couch generated.)
We are using the REST API to add the documents to Couchdb, where we found strange behavior :
When we try to recreate the documents using HTTP PUT which have been deleted in the past(because of bug in the code), the documents are not created the first time .
HTTP Put - Returns HTTP 200, but doc is not saved in couchdb.
Again trying the same request,
HTTP Put - Returns HTTP 200 and adds the doc in database.
HTTP PUT request needs to be sent twice to create and save the doc.
I have checked that the above bug is reproducible for deleted docs, i.e the response for GET _id is {"error":"not_found","reason":"deleted"}.
This looks like a bug in CouchDB to me, could you please let us know if you could think of any scenario where above error might occur and any possible workarounds/solutions ?
Couchdb has a builtin mechanism to ensure that you do not overwrite the same document as someone else.
If you PUT any existing document, you'll have to accompany this process with the current doc._rev value, so that couchdb can confirm the document you are updating is based on the most recent version in the database.
I've not come across this case with deletions, but it makes sense to me that couchdb should not allow you to overwrite a deleted document as the assumption should be, you just don't know about the deletion.
Have you tried if you can access the revision of the deleted document and if so, whether by adding it to the new document, you can succeed with the PUT on the first call?
I'm using nano to connect to couchDB through node.js; I have read the basic documentation for couch.db and understand it for the most part, but I didn't see a simple query function anywhere. All I would like to do is (from my server), get the value of a field , from a specific document. How would I do this?
Additionally, while looking for the answer to this, I ran across one site that said an html page can directly send a GET to the DB to get values; I thought the database was secure though, so how is this possible? I guess I'm missing something big here.
The simplest way to get a specific document by id is using the get method. This will return you the document itself:
var Nano = require('nano'),
db = new Nano('http://admin:password#localhost:5984').use(yourDatabase),
db.get(yourDocumentId, function (err, yourDocument, headers) {
return console.log(err || yourDocument);
});
Re your second question about a webpage requesting data straight from CouchDB: this can be done securely as long as you have a login specifically for your end user in CouchDB. Your end user would log in to CouchDB and CouchDB would return a cookie which your browser would send on each subsequent request to CouchDB as a way of authenticating itself.
see http://guide.couchdb.org/editions/1/en/security.html#cookies for more info.
Personally I would not use this approach as it makes it too easy to couple your UI to your data making future changes harder. I would recommend creating a REST api in express and call that from your UI. It will keep your UI code more focused on UI logic and your api implementation focused on dealing with CouchDB document and view operations.