Using Elastic Search with Rust actix-web

I am writing this post to document how to use Elastic Search with Rust actix-web.

The problem

As both actix-web uses tokio runtime internally to create async runtime and elastic search crate also uses tokio, we tried believed using actix-web
with elastic-search would be easy — however, hit the following error :

there is no reactor running, must be called from the context of Tokio runtime

The message says no tokio runtime running.

if we use #[tokio::main] annotation with every handler. we get an error that we cannot start a runtime inside another runtime something like below:

Cannot start a runtime from within a runtime. This happens because a function (like `block_on`) attempted to block the current thread while the thread is being used to drive asynchronous tasks.

This is as there is an actix-web runtime already running and we are trying to start another inside it.

The solution

Deep dive research and we found out that the problem being both(actix-web and elasticsearch) were using different versions of tokio

So inorder to make these both crates work together the cargo.toml file’s dependencies should be modified to handle versions as below:

[dependencies]
 actix-web = "^3"
 elasticsearch = "7.10.0-alpha.1"

or if you want to use latest version of elastic-search and are fine with beta version of actix-web

[dependencies]
 actix-web = "4.0.0-beta.9"
 elasticsearch = "7.14.0-alpha.1"

So let's use elastic search with actix-web

The working source code is available on our github repository here.

We will have to add serde_json crate, since elastic search is used with JAQL( json queries language)

[dependencies]
 actix-web = "^3"
 serde_json = "~1"
 elasticsearch = "7.10.0-alpha.1"

Create a small actix-web app in main.rs file. or you can take a look at main.rs file in source code. then create a file elastic.rs in src/elastic.rs. we are only going to work in this file. to include this file as module in main.rs add this line at top or bottom:

//main.rs
mod elastic;

We will need a function to create a elastic client, add this function to elsatic.rs

Handler function for searching with elastic search

for this handler function, request body looks like below

{
	"key": "user",
	"value": "abhinav"
}

we can do a more complex search where the request body looks like below

{
	"include": {
		"key": "category",
		"value": "women's"
	},
	"exclude": {
		"key": "category",
		"value": "men's"
	}
}

by replacing the query variable in the above handler function with

Handler function for inserting index in elastic search

for this handler function, request body looks like below

{
	"user": "abhinav"
}

Handler function to update index

for this handler function request body looks like below

{
	"id": "user_id",
	"change": "user name to update"
}

for more update scripts visit here.

Handle function for deleting index

for this handler function request body looks like below

{
	"id": "user_id"
}

You can see the source code at GitHub.

Hope this helps and thank you for reading !!!