Verbose InfluxDB Error Logging

On a non 204 response we parse the HTTP response until complete e.g. do the headers
and body, not just the header.  A new interface is added to the response to allow us
to determine the body size so that it may be read out and buffered.  The body is
parsed and any error message printed out.  In the event that the parsing fails the
raw body is dumped out; better than nothing!

fixes #4411

Signed-off-by: Michael Friedrich <michael.friedrich@icinga.com>

lib/perfdata/influxdbwriter.cpp

@@ -34,6 +34,7 @@
 #include "base/convert.hpp"
 #include "base/utility.hpp"
 #include "base/stream.hpp"
+#include "base/json.hpp"
 #include "base/networkstream.hpp"
 #include "base/exception.hpp"
 #include "base/statsfunction.hpp"
@@ -43,6 +44,7 @@
 #include <boost/algorithm/string/split.hpp>
 #include <boost/algorithm/string/replace.hpp>
 #include <boost/regex.hpp>
+#include <boost/scoped_array.hpp>
 
 using namespace icinga;
 
@@ -507,6 +509,36 @@ void InfluxdbWriter::FlushHandler(const String& body)
 	if (resp.StatusCode != 204) {
 		Log(LogWarning, "InfluxdbWriter")
 		    << "Unexpected response code " << resp.StatusCode;
+
+		// Finish parsing the headers and body
+		while (!resp.Complete)
+			resp.Parse(context, true);
+
+		String contentType = resp.Headers->Get("content-type");
+		if (contentType != "application/json") {
+			Log(LogWarning, "InfluxdbWriter")
+			    << "Unexpected Content-Type: " << contentType;
+			return;
+		}
+
+		size_t responseSize = resp.GetBodySize();
+		boost::scoped_array<char> buffer(new char[responseSize + 1]);
+		resp.ReadBody(buffer.get(), responseSize);
+		buffer.get()[responseSize] = '\0';
+
+		Dictionary::Ptr jsonResponse;
+		try {
+			jsonResponse = JsonDecode(buffer.get());
+		} catch (...) {
+			Log(LogWarning, "InfluxdbWriter")
+			    << "Unable to parse JSON response:\n" << buffer.get();
+			return;
+		}
+
+		String error = jsonResponse->Get("error");
+
+		Log(LogCritical, "InfluxdbWriter")
+		    << "InfluxDB error message:\n" << error;
 	}
 }
 

lib/remote/httpresponse.cpp

@@ -241,6 +241,14 @@ size_t HttpResponse::ReadBody(char *data, size_t count)
 		return m_Body->Read(data, count, true);
 }
 
+size_t HttpResponse::GetBodySize(void) const
+{
+	if (!m_Body)
+		return 0;
+	else
+		return m_Body->GetAvailableBytes();
+}
+
 bool HttpResponse::IsPeerConnected(void) const
 {
 	return !m_Stream->IsEof();

lib/remote/httpresponse.hpp

@@ -55,6 +55,7 @@ public:
 
 	bool Parse(StreamReadContext& src, bool may_wait);
 	size_t ReadBody(char *data, size_t count);
+	size_t GetBodySize(void) const;
 
 	void SetStatus(int code, const String& message);
 	void AddHeader(const String& key, const String& value);