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try if trust-dns-resolver works or not #190

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try if trust-dns-resolver works or not #190

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3 changes: 3 additions & 0 deletions examples/http_headers/Cargo.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -13,6 +13,9 @@ crate-type = ["cdylib"]
[dependencies]
log = "0.4"
proxy-wasm = { path = "../../" }
trust-dns-resolver = "0.22.0"
tokio = "1.26.0"
hostname = "^0.3"

[profile.release]
lto = true
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46 changes: 46 additions & 0 deletions examples/http_headers/src/lib.rs
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Expand Up @@ -12,6 +12,37 @@
// See the License for the specific language governing permissions and
// limitations under the License.

use std::net::*;
use trust_dns_resolver::Resolver;
use trust_dns_resolver::config::*;

use std::{
net::*,
str::FromStr,
sync::{Arc, Mutex as StdMutex},
};

use tokio::runtime::Runtime;

use trust_dns_proto::{
op::{NoopMessageFinalizer, Query},
rr::{DNSClass, Name, RData, Record, RecordType},
xfer::{DnsExchange, DnsMultiplexer, DnsResponse},
TokioTime,
};
use trust_dns_resolver::{
caching_client::CachingClient,
config::LookupIpStrategy,
error::ResolveError,
lookup::{Lookup, LookupFuture},
lookup_ip::LookupIpFuture,
Hosts,
};
use trust_dns_server::{
authority::{Authority, Catalog},
store::in_memory::InMemoryAuthority,
};

use log::info;
use proxy_wasm::traits::*;
use proxy_wasm::types::*;
Expand Down Expand Up @@ -43,10 +74,25 @@ impl Context for HttpHeaders {}

impl HttpContext for HttpHeaders {
fn on_http_request_headers(&mut self, _: usize, _: bool) -> Action {

let lookup = LookupFuture::lookup(
vec![Name::from_str("www.example.com.").unwrap()],
RecordType::A,
Default::default(),
CachingClient::new(0, client, false),
);

let io_loop = Runtime::new().unwrap();
let lookup = io_loop.block_on(lookup).unwrap();
Comment on lines +85 to +86
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This seems like a bad idea, since each worker thread (in case of Envoy) is going to be blocked on this, and DNS resolution can potentially take hundreds of milliseconds... not to mention the overhead of starting Tokio runtime per each request.

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Can we have a meeting about this? Can we mitigate the overhead per request by cache layer?

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You could store the runtime in a global variable and share it across the callbacks, but I suspect that Tokio runtime couldn't make any progress without deep integration with Proxy-Wasm's callbacks.

Also, if you try to compile your example, you can see that Tokio async doesn't work in Wasm (yet):

compile_error!("Only features sync,macros,io-util,rt,time are supported on wasm.");

What are you trying to achieve? What's your end goal?

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@Cindia-blue Cindia-blue Mar 10, 2023 •
edited
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yup... I can not compile through for that reason. I am trying to get cname chain in WASM. Could you recommend some feasible way? I saw there are some other lib besides Tokio, like RustDNS maybe others but not sure if they have similar issue. It will be nice if you can suggest

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@PiotrSikora PiotrSikora Mar 14, 2023 •
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Are you interested only in the final answer or the whole CNAME chain? If the former, and you're using Envoy, then there are envoy_resolve_dns / envoy_on_resolve_dns extensions that you could call and use Envoy's built-in DNS resolver... Note that they are not exposed in the Rust SDK yet.


self.set_http_request_header("wasm-request-header-xh", lookup);

for (name, value) in &self.get_http_request_headers() {
info!("#{} -> {}: {}", self.context_id, name, value);
}



match self.get_http_request_header(":path") {
Some(path) if path == "/hello" => {
self.send_http_response(
Expand Down