Improve troubleshooting doc/flows

- Use better wording for unknown server error
- Add basic troubleshooting doc

README.md

@@ -74,6 +74,9 @@ Also, check [our FAQ entry](docs/faq.md#what-kind-of-setup-is-mxisd-really-desig
 See the [dedicated document](docs/getting-started.md)
 
 # Support
+## Troubleshooting
+A basic troubleshooting guide is available [here](docs/troubleshooting.md).
+
 ## Community
 Over Matrix: [#mxisd:kamax.io](https://matrix.to/#/#mxisd:kamax.io) ([Preview](https://view.matrix.org/room/!NPRUEisLjcaMtHIzDr:kamax.io/))
 

docs/getting-started.md

@@ -144,7 +144,8 @@ by the relevant hostname which you configured in your reverse proxy.
 **NOTE:** You might not see a suggestion for the e-mail address, which is normal. Still proceed with the invite.
   
 If it worked, it means you are up and running and can enjoy mxisd in its basic mode! Congratulations!  
-If it did not work, [get in touch](../README.md#support) and we'll do our best to get you started.
+If it did not work, read the basic [troubleshooting guide](troubleshooting.md), [get in touch](../README.md#support) and
+we'll do our best to get you started.
 
 ## Next steps
 Once your mxisd server is up and running, there are several ways you can enhance and integrate further with your

docs/troubleshooting.md

@@ -0,0 +1,53 @@
+# Troubleshooting
+- [Purpose](#purpose)
+- [Logs](#logs)
+  - [Locations](#locations)
+  - [Reading Them](#reading-them)
+  - [Common issues](#common-issues)
+- [Submit an issue](#submit-an-issue)
+
+## Purpose
+This document describes basic troubleshooting steps for mxisd.
+
+## Logs
+### Locations
+mxisd logs to `STDOUT` (Standard Output) and `STDERR` (Standard Error) only, which gets redirected
+to log file(s) depending on your system.
+
+If you use the [Debian package](install/debian.md), this goes to `syslog`.  
+If you use the [Docker image](install/docker.md), this goes to the container logs.  
+
+For any other platform, please refer to your package maintainer.
+
+### Reading them
+Before reporting an issue, it is important to produce clean and complete logs so they can be understood.
+
+It is usually useless to try to troubleshoot an issue based on a single log line. Any action or API request
+in mxisd would trigger more than one log lines, and those would be considered necessary context to
+understand what happened.
+
+You may also find things called *stacktraces*. Those are important to pin-point bugs and the likes and should
+always be included in any report. They also tend to be very specific about the issue at hand.
+
+Example of a stacktrace:
+```
+Exception in thread "main" java.lang.NullPointerException
+        at com.example.myproject.Book.getTitle(Book.java:16)
+        at com.example.myproject.Author.getBookTitles(Author.java:25)
+        at com.example.myproject.Bootstrap.main(Bootstrap.java:14)
+```
+
+### Common issues
+#### Internal Server Error
+`Contact your administrator with reference Transaction #123456789`
+
+This is a generic message produced in case of an unknown error. The transaction reference allows to easily find
+the location in the logs to look for an error.
+
+**IMPORTANT:** That line alone does not tell you anything about the error. You'll need the log lines before and after,
+usually including a stacktrace, to know what happened. Please take the time to read the surround output to get
+context about the issue at hand.
+
+## Submit an issue
+In case the logs do not allow you to understand the issue at hand, please submit clean and complete logs
+as explained [here](#reading-them) in a new issue on the repository, or [get in touch](../README.md#contact).

src/main/java/io/kamax/mxisd/http/undertow/handler/BasicHttpHandler.java

@@ -101,6 +101,10 @@ public abstract class BasicHttpHandler implements HttpHandler {
         return GsonUtil.parseObj(getBodyUtf8(exchange));
     }
 
+    protected void putHeader(HttpServerExchange ex, String name, String value) {
+        ex.getResponseHeaders().put(HttpString.tryFromString(name), value);
+    }
+
     protected void respond(HttpServerExchange ex, int statusCode, JsonElement bodyJson) {
         respondJson(ex, statusCode, GsonUtil.get().toJson(bodyJson));
     }

src/main/java/io/kamax/mxisd/http/undertow/handler/SaneHandler.java

@@ -27,8 +27,7 @@ import io.kamax.matrix.json.InvalidJsonException;
 import io.kamax.mxisd.exception.*;
 import io.undertow.server.HttpHandler;
 import io.undertow.server.HttpServerExchange;
-import io.undertow.util.HttpString;
+import org.apache.commons.lang3.StringUtils;
-import org.apache.commons.lang.StringUtils;
 import org.apache.http.HttpStatus;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -37,15 +36,22 @@ import java.time.Instant;
 
 public class SaneHandler extends BasicHttpHandler {
 
+    private static final Logger log = LoggerFactory.getLogger(SaneHandler.class);
+
+    private static final String CorsOriginName = "Access-Control-Allow-Origin";
+    private static final String CorsOriginValue = "*";
+    private static final String CorsMethodsName = "Access-Control-Allow-Methods";
+    private static final String CorsMethodsValue = "GET, POST, PUT, DELETE, OPTIONS";
+    private static final String CorsHeadersName = "Access-Control-Allow-Headers";
+    private static final String CorsHeadersValue = "Origin, X-Requested-With, Content-Type, Accept, Authorization";
+
     public static SaneHandler around(HttpHandler h) {
         return new SaneHandler(h);
     }
 
-    private transient final Logger log = LoggerFactory.getLogger(SaneHandler.class);
+    private final HttpHandler child;
 
-    private HttpHandler child;
+    private SaneHandler(HttpHandler child) {
-
-    public SaneHandler(HttpHandler child) {
         this.child = child;
     }
 
@@ -58,9 +64,9 @@ public class SaneHandler extends BasicHttpHandler {
         } else {
             try {
                 // CORS headers as per spec
-                exchange.getResponseHeaders().put(HttpString.tryFromString("Access-Control-Allow-Origin"), "*");
+                putHeader(exchange, CorsOriginName, CorsOriginValue);
-                exchange.getResponseHeaders().put(HttpString.tryFromString("Access-Control-Allow-Methods"), "GET, POST, PUT, DELETE, OPTIONS");
+                putHeader(exchange, CorsMethodsName, CorsMethodsValue);
-                exchange.getResponseHeaders().put(HttpString.tryFromString("Access-Control-Allow-Headers"), "Origin, X-Requested-With, Content-Type, Accept, Authorization");
+                putHeader(exchange, CorsHeadersName, CorsHeadersValue);
 
                 child.handleRequest(exchange);
             } catch (IllegalArgumentException e) {
@@ -89,9 +95,9 @@ public class SaneHandler extends BasicHttpHandler {
                 handleException(exchange, e);
             } catch (InternalServerError e) {
                 if (StringUtils.isNotBlank(e.getInternalReason())) {
-                    log.error("Reference #{} - {}", e.getReference(), e.getInternalReason());
+                    log.error("Transaction #{} - {}", e.getReference(), e.getInternalReason());
                 } else {
-                    log.error("Reference #{}", e);
+                    log.error("Transaction #{}", e);
                 }
 
                 handleException(exchange, e);
@@ -105,14 +111,11 @@ public class SaneHandler extends BasicHttpHandler {
                 respond(exchange, e.getStatus(), buildErrorBody(exchange, e.getErrorCode(), e.getError()));
             } catch (RuntimeException e) {
                 log.error("Unknown error when handling {}", exchange.getRequestURL(), e);
-                respond(exchange, HttpStatus.SC_INTERNAL_SERVER_ERROR, buildErrorBody(exchange,
+                String message = e.getMessage();
-                        "M_UNKNOWN",
+                if (StringUtils.isBlank(message)) {
-                        StringUtils.defaultIfBlank(
+                    message = "An internal server error occurred. Contact your administrator with reference Transaction #" + Instant.now().toEpochMilli();
-                                e.getMessage(),
+                }
-                                "An internal server error occurred. If this error persists, please contact support with reference #" +
+                respond(exchange, HttpStatus.SC_INTERNAL_SERVER_ERROR, buildErrorBody(exchange, "M_UNKNOWN", message));
-                                        Instant.now().toEpochMilli()
-                        )
-                ));
             } finally {
                 exchange.endExchange();
             }