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Echoserver is an HTTP server that returns request details as JSON document and it includes client-side web apps for testing requests and authentication.

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Echoserver

Echoserver is a simple HTTP server that listens on incoming requests and echoes back information about the request. It is inspired by the echoserver from the ingress-controller-conformance project. Additionally, the server can be used to test authentication and authorization features in ingress controllers by providing browser based clients that make requests to the echoserver. See also echoclient project, a programmable HTTP load testing library.

Usage

To run the server locally it can be installed or run directly using following commands:

go install github.com/tsaarni/echoserver@latest # Install the binary.
go run github.com/tsaarni/echoserver@latest     # Run the server without installing.

Echoserver is also available as a container image:

ghcr.io/tsaarni/echoserver:latest

Echoserver can be configured either using command line arguments or environment variables. Command line arguments take precedence over environment variables. Following table lists the available configuration options:

Command line Variable Description Default
-http-addr HTTP_ADDR Address to bind the HTTP server socket. :8080
-https-addr HTTPS_ADDR Address to bind the HTTPS server socket. :8443
-tls-cert-file TLS_CERT_FILE Path to TLS certificate file.
-tls-key-file TLS_KEY_FILE Path to TLS key file.
ENV_* List of environment variables to be included in the env field of the JSON response and accessible in HTML templates.
-live Serve static files directly from the ./apps directory instead of using bundled files in the binary. false
SSLKEYLOGFILE Path to write the TLS master secret log file to. See Wireshark documentation for more information.
-log-level LOG_LEVEL Log level. Possible values are debug, info, warn, and error. debug

The certificate and key files will be loaded from the filesystem every time a request is made to the server, so it is possible to update the certificate and key files without restarting the server.

API

Example commands in the descriptions are given using the HTTPie tool.

/* - Returns request details in JSON format.

Responses
Status Description
200 OK Request details in JSON format.

Following fields is included in the response:

  • content_length: Length of the request body.
  • env: Environment variables provided in the configuration.
  • headers: Request headers.
  • host: Host and port of the server.
  • method: HTTP method of the request.
  • url: Request URL.
  • proto: HTTP protocol version.
  • remote: Remote address of the client.
  • env: Variables from the process environment that match the ENV_* prefix.
  • tls: TLS details if the request was made over HTTPS.
    • alpn_negotiated_protocol: Application Layer Protocol Negotiation protocol.
    • cipher_suite: Cipher suite used in the connection.
    • peer_certificates: Peer certificates in PEM format if the client provided a certificate.
    • peer_certificates_decoded: Decoded peer certificate details if the client provided a certificate.
      • subject: Subject of the certificate.
      • issuer: Issuer of the certificate.
      • serial_number: Serial number of the certificate.
      • not_before: Not before date of the certificate.
      • not_after: Not after date of the certificate.
    • version: TLS version.
  • query: Query parameters of the request if the URL contains a query string.
  • form: Form parameters of the request body, if the content type is application/x-www-form-urlencoded.
  • cookies: Cookies in the request if the request had a Cookie header.
  • body: Request body.
  • jwt: JWT claims if the request had JWT in the Authorization header.
    • header: JWT header.
    • claims: JWT claims.
      • If the claims field contains iat or exp claims, they are converted to human-readable format and added as iat_date and exp_date fields (these fields are added by the server and are not part of the original token).
  • basic_auth: Basic authentication credentials if the request had Authorization header with Basic scheme.
    • username: Username.
    • password: Password.
Example
$ http --cert testdata/certs/client.pem --cert-key testdata/certs/client-key.pem --verify testdata/certs/ca.pem https://localhost:8443/foobar
{
    "content_length": 0,
    "headers": {
        "Accept": [
            "*/*"
        ],
        "Accept-Encoding": [
            "gzip, deflate"
        ],
        "Connection": [
            "keep-alive"
        ],
        "User-Agent": [
            "HTTPie/3.2.4"
        ]
    },
    "host": "localhost:8443",
    "method": "GET",
    "proto": "HTTP/1.1",
    "remote": "[::1]:57961",
    "tls": {
        "alpn_negotiated_protocol": "http/1.1",
        "cipher_suite": "TLS_AES_128_GCM_SHA256",
        "peer_certificates": "-----BEGIN CERTIFICATE-----\nMIIBRTCB7aADAgECAggYXbRNl099CjAKBggqhkjOPQQDAjANMQswCQYDVQQDEwJj\nYTAeFw0yNTA4MjEwNjI3NTVaFw0yNjA4MjEwNjI3NTVaMBExDzANBgNVBAMTBmNs\naWVudDBZMBMGByqGSM49AgEGCCqGSM49AwEHA0IABPhO4qIu71Cm5Ox5U5Pb6Og2\n4EMh/lWU4+OGDBkHIRXtyKTZCXzH5a1vQ0TO1jq6sjShZR8ihDYXRuPfcNVefj6j\nMzAxMA4GA1UdDwEB/wQEAwIFoDAfBgNVHSMEGDAWgBQGgzaN2tRzErVZCEe7Ucju\nTY5XBzAKBggqhkjOPQQDAgNHADBEAiB+Oc4DPody43cZ0e+MY7F63DnIPM5xtgwR\nG6IYdhXiAwIgYxOlBxxupGDvvhXyS7IV8KadGD8LVm8G059OJC9vIG0=\n-----END CERTIFICATE-----\n-----BEGIN CERTIFICATE-----\nMIIBUTCB+KADAgECAggYXbRNlzUisDAKBggqhkjOPQQDAjANMQswCQYDVQQDEwJj\nYTAeFw0yNTA4MjEwNjI3NTVaFw0yNjA4MjEwNjI3NTVaMA0xCzAJBgNVBAMTAmNh\nMFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEFWG+fC3bE4X0oOHIGbH0d1VY1vQc\nDeu/ey1+bCXTsyFLld8rwk5KDjPGI+QGlL5lnEVYWZUQ8QQLYQLhK//uKKNCMEAw\nDgYDVR0PAQH/BAQDAgEGMA8GA1UdEwEB/wQFMAMBAf8wHQYDVR0OBBYEFAaDNo3a\n1HMStVkIR7tRyO5NjlcHMAoGCCqGSM49BAMCA0gAMEUCIAJLtjBdGvDYO18xZ2wI\nJYyzoxN8K4I5VodVwuF/4J5cAiEAmMeY8VbFFKBRLJhnd2wPHaK3pbbMozJ99nSC\nI2xUCvs=\n-----END CERTIFICATE-----\n",
        "peer_certificates_decoded": [
            {
                "issuer": "CN=ca",
                "not_after": "2026-08-21T06:27:55Z",
                "not_before": "2025-08-21T06:27:55Z",
                "serial_number": "1755757675088411914",
                "subject": "CN=client"
            },
            {
                "issuer": "CN=ca",
                "not_after": "2026-08-21T06:27:55Z",
                "not_before": "2025-08-21T06:27:55Z",
                "serial_number": "1755757675086684848",
                "subject": "CN=ca"
            }
        ],
        "version": "TLS 1.3"
    },
    "url": "/foobar"
}

/status - Responds with the provided HTTP status code. Default: 200 OK.

Description

By default, this endpoint returns an HTTP 200 OK status code. You can modify the status code using the set query parameter. The server will persist the updated status code, and subsequent requests to /status will return the new status code until it is changed again.

Parameters
Name Description
set HTTP status code to persist (integer).
Responses
Status Description
code Request details in JSON format.

code is the HTTP status code set by the set query parameter or 200 OK by default. Body contains the request details in JSON format as described in the /* endpoint.

Example
$ http GET http://localhost:8080/status
HTTP/1.1 200 OK
Content-Length: 0
Date: Fri, 29 Nov 2024 06:24:46 GMT

... Request details in JSON format ...
$ http GET http://localhost:8080/status?set=503
HTTP/1.1 503 Service Unavailable
Content-Length: 0
Date: Sun, 19 Oct 2025 18:05:20 GMT

... Request details in JSON format ...

/status/{code}

Returns the specified HTTP status code.

Parameters
Status Description
code Request details in JSON format.

code is the HTTP status code specified in the URL path. Body contains the request details in JSON format as described in the /* endpoint.

Optionally, you can include additional HTTP headers in the response by providing a JSON object in the body or using a query string.

Example
$ http POST http://localhost:8080/status/301 Location=http://localhost/bar

Body of the request

{
  "Location": "http://localhost/bar"
}

Response:

HTTP/1.1 301 Moved Permanently
Content-Length: 0
Date: Fri, 29 Nov 2024 06:10:25 GMT
Location: http://localhost/bar

... Request details in JSON format ...
$ http "http://localhost:8080/status/200?Set-Cookie=foo%3Dbar&Set-Cookie=hello%3Dworld"

Response:

HTTP/1.1 200 OK
Content-Length: 0
Date: Sun, 15 Dec 2024 12:00:06 GMT
Set-Cookie: foo=bar
Set-Cookie: hello=world

... Request details in JSON format ...

/sse - Server-Sent Events (SSE) endpoint that sends a message every second.

Responses
Status Description
200 OK Server is operational.
Example

Server will respond with Content-Type: text/event-stream with the following content:

$ http http://localhost:8080/sse
HTTP/1.1 200 OK
Cache-Control: no-cache
Connection: keep-alive
Content-Type: text/event-stream
Date: Wed, 19 Feb 2025 10:10:15 GMT
Transfer-Encoding: chunked

data: { "counter": "1", "timestamp": "2025-02-19T12:10:15+02:00" }

data: { "counter": "2", "timestamp": "2025-02-19T12:10:16+02:00" }
...

/websocket - WebSocket endpoint that sends a text frame every second.

/upload - File upload.

Description

Accepts POST requests with bodies of any size. Responds with the total number of bytes received, rather than request details.

Parameters
Name Description Default
throttle Throttle the upload speed to bytes/sec (integer with optional suffix "K", "M", "G")
Responses
Status Description
200 OK Uploaded bytes JSON format.

Following fields is included in the response:

  • bytes_uploaded: Length of the request body.
Example
$ dd if=/dev/zero bs=10M count=1 | http POST http://localhost:8080/upload
HTTP/1.1 200 OK
content-length: 26
content-type: application/json
date: Thu, 21 Aug 2025 12:27:06 GMT
server: envoy
x-envoy-upstream-service-time: 0

{
    "bytes_uploaded": 1048576
}

To upload a file, while throttling the upload speed to 1MB/s at the server side:

$ dd if=/dev/zero bs=10M count=1 | http http://localhost:8080/upload?throttle=1M

/download - File download.

Description

Accepts GET requests and responds with a binary stream of bytes. The number of bytes can be specified with the bytes query parameter. The default size for the download is 1MB. The response body consists of a sequence of bytes from 1 to 256.

Parameters
Name Description Default
bytes Number of bytes to download (integer) 1048576
throttle Throttle the download speed to bytes/sec (integer with optional suffix "K", "M", "G")
Responses
Status Description
200 OK File download in progress.
Example

Download the default 1MB file:

$ http --download http://localhost:8080/download --output download.bin

Response headers:

HTTP/1.1 200 OK
content-length: 1048576
content-type: application/octet-stream
date: Thu, 21 Aug 2025 16:37:15 GMT
server: envoy
x-envoy-upstream-service-time: 0

Download a 10-byte file:

$ http --download http://localhost:8080/download?bytes=10 --output download.bin

Download a 10MB file while throttling the upload speed to 1MB/s at the server side:

$ http --download http://localhost:8080/download?bytes=10M\&throttle=1M --output download.bin

/metrics - Metrics for monitoring.

Description

This endpoint provides Prometheus-compatible metrics for monitoring the server.

Responses
Status Description
200 OK Metrics in prometheus exposition format.
Example
$ http GET http://localhost:8080/metrics
# HELP http_requests_total Total number of HTTP requests received.
# TYPE http_requests_total counter
http_requests_total{method="GET",status_code="200"} 5
...

See metrics.go for details about the available metrics.

/apps/ - Returns a list of available applications.

/apps/fetch.html - Interactive HTTP request tool.

Description

A JavaScript application that enables users to make HTTP requests towards the echoserver using different methods and view the responses.

Image

/apps/form.html - HTML form submission.

Description

An HTML form that enables data submission using both POST and GET methods towards the echoserver.

Image

/apps/oauth.html - Interactive OAuth2 client.

Description

OAuth2-aware JavaScript application that implements the Authorization Code flow. It allows users to interactively trigger login/refresh/logout and to make authenticated requests towards the echoserver and view the responses.

Image

/apps/keycloak.html - Interactive client using keycloak-js adapter.

Description

A JavaScript application that uses the Keycloak-js JavaScript adapter to authenticate users.

Image

/apps/streaming.html - Streaming client.

Description

A JavaScript application that makes Server-Sent Events (SSE) or WebSocket connection towards the echoserver and displays the responses.

Image

Development

To build and run the echoserver locally, use the following commands:

make
./echoserver

To serve HTML files from the filesystem instead of using bundled files, use the following command:

./echoserver -live

To build the container image, use the following command:

make container

To lint the code, use the following command:

make lint

To test the OIDC applications, you need to have an OIDC provider. To run Keyclaok as an OIDC provider, use the following command:

make run           # Generate test certificates and run echoserver in one terminal.
docker compose up  # Run Envoy and Keycloak in another terminal.

Then access the echoserver server at https://echoserver.127.0.0.1.nip.io/apps/ and Keycloak admin console at https://keycloak.127.0.0.1.nip.io/. Envoy will validate JWT for endpoints matching with https://echoserver.127.0.0.1.nip.io/protected.

⚠️ NOTE ⚠️

You will get an error for first login, because the certificate is self-signed. To fix this, visit Keycloak admin console once and accept the certificate.

If running on Linux with firewall like UFW, traffic from docker bridge network to host network may be blocked. For UFW use sudo ufw allow from 172.0.0.0/8to allow traffic.

The admin console credentials are admin:admin, and the user credentials in echoserver realm are joe:joe and jane:jane.

Keycloak has been configured with the following clients:

  • echoserver-public
  • echoserver-public-dpop

The latter one is configured to require DPoP.

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Echoserver is an HTTP server that returns request details as JSON document and it includes client-side web apps for testing requests and authentication.

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