cache log sessionid (#297)

* implemented structured cache logging to be used as audit trail to help analyse potential cache pollution/corruption
* added common header to all known log targets
* made Oid::operator bool explicit to avoid logging/text format mishaps
* HttpClient::operator bool -> explicit
* changed cache logs to not rotate on start in order to retain more history
* added CacheRequestContext
* properly initialize request context
* log session id and request id on zencacehstore get/put
* changelog

1 files changed, 28 insertions, 0 deletions

diff --git a/src/zenutil/include/zenutil/cache/cache.h b/src/zenutil/include/zenutil/cache/cache.h
index 1a1dd9386..5e12c488c 100644
--- a/src/zenutil/include/zenutil/cache/cache.h
+++ b/src/zenutil/include/zenutil/cache/cache.h
@@ -4,3 +4,31 @@
 
 #include <zenutil/cache/cachekey.h>
 #include <zenutil/cache/cachepolicy.h>
+
+ZEN_THIRD_PARTY_INCLUDES_START
+#include <fmt/format.h>
+ZEN_THIRD_PARTY_INCLUDES_END
+
+namespace zen {
+
+struct CacheRequestContext
+{
+	Oid		 SessionId{Oid::Zero};
+	uint32_t RequestId{0};
+};
+
+}  // namespace zen
+
+template<>
+struct fmt::formatter<zen::CacheRequestContext> : formatter<string_view>
+{
+	template<typename FormatContext>
+	auto format(const zen::CacheRequestContext& Context, FormatContext& ctx)
+	{
+		zen::ExtendableStringBuilder<64> String;
+		Context.SessionId.ToString(String);
+		String << ".";
+		String << Context.RequestId;
+		return formatter<string_view>::format(String.ToView(), ctx);
+	}
+};