**Branch/Environment/Version**
- 5.3.1, master, some earlier versions
- Enviro…nment: On-prem
-
**Describe the bug**
if upstream of the reverse proxy is a sse enabled/streaming server, tyk should be providing data back as soon as it receives it, whats happening instead is "tyk not providing any response until either it reaches the timeout or the connections is closed upstream". So basically buffering until it can.
**Reproduction steps**
Given following app
```
{
"name": "Tyk Test API",
"api_id": "3000",
"org_id": "default",
"definition": {
"location": "",
"key": ""
},
"use_keyless": true,
"auth": {
"auth_header_name": ""
},
"version_data": {
"not_versioned": true,
"versions": {
"Default": {
"name": "Default",
"expires": "3000-01-02 15:04",
"use_extended_paths": true,
"extended_paths": {
"ignored": [],
"white_list": [],
"black_list": []
}
}
}
},
"proxy": {
"listen_path": "/sse/",
"target_url": "https://sse.dev/test",
"strip_listen_path": true
},
"do_not_track": true
}
```
and this tyk conf
```json
{
"listen_address": "",
"listen_port": 8080,
"secret": "352d20ee67be67f6340b4c0605b044b7",
"template_path": "./templates",
"use_db_app_configs": false,
"app_path": "./apps",
"middleware_path": "./middleware",
"log_level": "debug",
"track_404_logs": true,
"http_server_options": {
"read_timeout": 0,
"write_timeout": 0,
"use_ssl": false,
"enable_http2": true,
"enable_strict_routes": false,
"ssl_insecure_skip_verify": false,
"enable_websockets": true,
"certificates": null,
"ssl_certificates": null,
"server_name": "",
"min_version": 0,
"max_version": 0,
"skip_client_ca_announcement": false,
"flush_interval": 0,
"skip_url_cleaning": false,
"skip_target_path_escaping": false,
"ssl_ciphers": null,
"max_request_body_size": 0
},
"storage": {
"type": "redis",
"host": "10.19.80.14",
"port": 6379,
"username": "",
"password": "",
"database": 0,
"optimisation_max_idle": 2000,
"optimisation_max_active": 4000
},
"enable_analytics": false,
"analytics_config": {
"type": "",
"ignored_ips": []
},
"dns_cache": {
"enabled": false,
"ttl": 3600,
"check_interval": 60
},
"allow_master_keys": false,
"policies": {
"policy_source": "file"
},
"hash_keys": true,
"hash_key_function": "murmur64",
"suppress_redis_signal_reload": false,
"force_global_session_lifetime": false,
"max_idle_connections_per_host": 500
}
```
any calls to `/sse/` will result in no response being received in realtime.
**Additional context**
Upon the investigation I found the issue (but I do not have enough familiarity with the project to attempt a proper resolution).
when request arrives at this point https://github.com/TykTechnologies/tyk/blob/0d1183c354a1342e6a3408b1c0b4a8ce3935a544/gateway/reverse_proxy.go#L1446-L1465
the flow will enter correctly in the `if flushInterval != 0 {` block (due to being recognised here
https://github.com/TykTechnologies/tyk/blob/0d1183c354a1342e6a3408b1c0b4a8ce3935a544/gateway/reverse_proxy.go#L1428-L1436) but the casting `if wf, ok := dst.(writeFlusher); ok {` will fail, and it won't enter inside.
The reason for this can be traced here:
https://github.com/TykTechnologies/tyk/blob/0d1183c354a1342e6a3408b1c0b4a8ce3935a544/gateway/reverse_proxy.go#L1337-L1341
If the cache is enabled, then the `dst` is going to be a `bytes.Buffer` and won't satisfy the required interface.
As a workaround I've changed
https://github.com/TykTechnologies/tyk/blob/0d1183c354a1342e6a3408b1c0b4a8ce3935a544/gateway/reverse_proxy.go#L517-L521
into
```
switch {
case IsGrpcStreaming(req), req.Header.Get("Enable-Stream") == "true":
resp = p.WrappedServeHTTP(rw, req, false)
default:
resp = p.WrappedServeHTTP(rw, req, true)
}
```
With that piece which disables the caching, the streaming works correctly.
The downside with that solution (besides usage of a specific header), is that if the `TYK_GW_ANALYTICSCONFIG_ENABLEDETAILEDRECORDING` is true, the tyk will panic out on https://github.com/TykTechnologies/tyk/blob/0d1183c354a1342e6a3408b1c0b4a8ce3935a544/gateway/handler_success.go#L227 because the `responseCopy.Body` will be nil (it has been already dumped earlier during the streaming).
