Initial commit for EELF Logger

Issue-ID: DCAEGEN2-633
Change-Id: I108929219d2d6570080d2fe7792cbc5a6530bb59
Signed-off-by: Singla, Rajiv (rs153v) <rs153v@att.com>

8 files changed, 660 insertions, 0 deletions

diff --git a/eelf-logger/eelf-logger-api/src/main/java/org/onap/dcae/utils/eelf/logger/api/log/AuditLog.java b/eelf-logger/eelf-logger-api/src/main/java/org/onap/dcae/utils/eelf/logger/api/log/AuditLog.java
new file mode 100644
index 0000000..952176e
--- /dev/null
+++ b/eelf-logger/eelf-logger-api/src/main/java/org/onap/dcae/utils/eelf/logger/api/log/AuditLog.java
@@ -0,0 +1,130 @@
+/*
+ * ================================================================================
+ * Copyright (c) 2018 AT&T Intellectual Property. All rights reserved.
+ * ================================================================================
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ * ============LICENSE_END=========================================================
+ *
+ */
+
+package org.onap.dcae.utils.eelf.logger.api.log;
+
+
+import org.onap.dcae.utils.eelf.logger.api.info.LogLevelCategory;
+import org.onap.dcae.utils.eelf.logger.api.spec.AuditLogSpec;
+import org.onap.dcae.utils.eelf.logger.api.spec.OptionalLogSpec;
+
+/**
+ * Audit Log captures all log levels supported by audit specifications
+ *
+ * @author Rajiv Singla
+ */
+public interface AuditLog {
+
+    /**
+     * Logs audit message with provided {@link LogLevelCategory}
+     *
+     * @param logLevelCategory log level category
+     * @param message log message
+     * @param auditLogSpec audit log spec
+     * @param optionalLogSpec optional log spec
+     * @param args argument values for log message interpolation
+     */
+    void log(LogLevelCategory logLevelCategory, String message, AuditLogSpec auditLogSpec,
+             OptionalLogSpec optionalLogSpec, String... args);
+
+    /**
+     * Logs audit message with provided {@link LogLevelCategory} and with default {@link OptionalLogSpec}
+     *
+     * @param logLevelCategory log level category
+     * @param message log message
+     * @param auditLogSpec audit log spec
+     * @param args argument values for log message interpolation
+     */
+    void log(LogLevelCategory logLevelCategory, String message, AuditLogSpec auditLogSpec, String... args);
+
+
+    /**
+     * Logs audit message with provided INFO {@link LogLevelCategory}
+     *
+     * @param message log message
+     * @param auditLogSpec audit log spec
+     * @param args argument values for log message interpolation
+     */
+    void info(String message, AuditLogSpec auditLogSpec, OptionalLogSpec optionalLogSpec, String... args);
+
+    /**
+     * Logs audit message with provided INFO {@link LogLevelCategory} and with default {@link OptionalLogSpec}
+     *
+     * @param message log message
+     * @param auditLogSpec audit log spec
+     * @param args argument values for log message interpolation
+     */
+    void info(String message, AuditLogSpec auditLogSpec, String... args);
+
+
+    /**
+     * Logs audit message with provided WARN {@link LogLevelCategory}
+     *
+     * @param message log message
+     * @param auditLogSpec audit log spec
+     * @param args argument values for log message interpolation
+     */
+    void warn(String message, AuditLogSpec auditLogSpec, OptionalLogSpec optionalLogSpec, String... args);
+
+    /**
+     * Logs audit message with provided WARN {@link LogLevelCategory} and with default {@link OptionalLogSpec}
+     *
+     * @param message log message
+     * @param auditLogSpec audit log spec
+     * @param args argument values for log message interpolation
+     */
+    void warn(String message, AuditLogSpec auditLogSpec, String... args);
+
+    /**
+     * Logs audit message with provided ERROR {@link LogLevelCategory}
+     *
+     * @param message log message
+     * @param auditLogSpec audit log spec
+     * @param args argument values for log message interpolation
+     */
+    void error(String message, AuditLogSpec auditLogSpec, OptionalLogSpec optionalLogSpec, String... args);
+
+    /**
+     * Logs audit message with provided ERROR {@link LogLevelCategory} and with default {@link OptionalLogSpec}
+     *
+     * @param message log message
+     * @param auditLogSpec audit log spec
+     * @param args argument values for log message interpolation
+     */
+    void error(String message, AuditLogSpec auditLogSpec, String... args);
+
+    /**
+     * Logs audit message with provided FATAL {@link LogLevelCategory}
+     *
+     * @param message log message
+     * @param auditLogSpec audit log spec
+     * @param args argument values for log message interpolation
+     */
+    void fatal(String message, AuditLogSpec auditLogSpec, OptionalLogSpec optionalLogSpec, String... args);
+
+    /**
+     * Logs audit message with provided FATAL {@link LogLevelCategory} and with default {@link OptionalLogSpec}
+     *
+     * @param message log message
+     * @param auditLogSpec audit log spec
+     * @param args argument values for log message interpolation
+     */
+    void fatal(String message, AuditLogSpec auditLogSpec, String... args);
+
+}
diff --git a/eelf-logger/eelf-logger-api/src/main/java/org/onap/dcae/utils/eelf/logger/api/log/DebugLog.java b/eelf-logger/eelf-logger-api/src/main/java/org/onap/dcae/utils/eelf/logger/api/log/DebugLog.java
new file mode 100644
index 0000000..98a0921
--- /dev/null
+++ b/eelf-logger/eelf-logger-api/src/main/java/org/onap/dcae/utils/eelf/logger/api/log/DebugLog.java
@@ -0,0 +1,76 @@
+/*
+ * ================================================================================
+ * Copyright (c) 2018 AT&T Intellectual Property. All rights reserved.
+ * ================================================================================
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ * ============LICENSE_END=========================================================
+ *
+ */
+
+package org.onap.dcae.utils.eelf.logger.api.log;
+
+import org.onap.dcae.utils.eelf.logger.api.info.LogLevelCategory;
+import org.onap.dcae.utils.eelf.logger.api.spec.DebugLogSpec;
+import org.onap.dcae.utils.eelf.logger.api.spec.OptionalLogSpec;
+
+/**
+ * Debug Log captures all log levels supported by debug specifications.
+ * <p>
+ * <b>NOTE: DEBUG Log is optional as per EELF Specifications</b>
+ *
+ * @author Rajiv Singla
+ */
+public interface DebugLog {
+
+    /**
+     * Logs debug message with provided {@link LogLevelCategory}
+     *
+     * @param logLevelCategory log level category
+     * @param message log message
+     * @param debugLogSpec debug log spec
+     * @param optionalLogSpec optional log spec
+     * @param args argument values for log message interpolation
+     */
+    void log(LogLevelCategory logLevelCategory, String message, DebugLogSpec debugLogSpec,
+             OptionalLogSpec optionalLogSpec, String... args);
+
+    /**
+     * Logs debug message with provided {@link LogLevelCategory} and with default {@link OptionalLogSpec}
+     *
+     * @param logLevelCategory log level category
+     * @param message log message
+     * @param debugLogSpec debug log spec
+     * @param args argument values for log message interpolation
+     */
+    void log(LogLevelCategory logLevelCategory, String message, DebugLogSpec debugLogSpec, String... args);
+
+
+    /**
+     * Logs debug message with provided DEBUG {@link LogLevelCategory}
+     *
+     * @param message log message
+     * @param debugLogSpec debug log spec
+     * @param args argument values for log message interpolation
+     */
+    void debug(String message, DebugLogSpec debugLogSpec, OptionalLogSpec optionalLogSpec, String... args);
+
+    /**
+     * Logs debug message with provided DEBUG {@link LogLevelCategory} and with default {@link OptionalLogSpec}
+     *
+     * @param message log message
+     * @param debugLogSpec debug log spec
+     * @param args argument values for log message interpolation
+     */
+    void debug(String message, DebugLogSpec debugLogSpec, String... args);
+
+}
diff --git a/eelf-logger/eelf-logger-api/src/main/java/org/onap/dcae/utils/eelf/logger/api/log/EELFLogFactory.java b/eelf-logger/eelf-logger-api/src/main/java/org/onap/dcae/utils/eelf/logger/api/log/EELFLogFactory.java
new file mode 100644
index 0000000..2cfb2ec
--- /dev/null
+++ b/eelf-logger/eelf-logger-api/src/main/java/org/onap/dcae/utils/eelf/logger/api/log/EELFLogFactory.java
@@ -0,0 +1,85 @@
+/*
+ * ================================================================================
+ * Copyright (c) 2018 AT&T Intellectual Property. All rights reserved.
+ * ================================================================================
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ * ============LICENSE_END=========================================================
+ *
+ */
+
+package org.onap.dcae.utils.eelf.logger.api.log;
+
+
+import org.onap.dcae.utils.eelf.logger.api.noop.NoOpEELFLogger;
+
+import java.lang.reflect.InvocationTargetException;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Map;
+import java.util.ServiceLoader;
+import java.util.WeakHashMap;
+
+/**
+ * EELF Log Factory uses {@link ServiceLoader} to load implementations of {@link EELFLogger} in application
+ * classpath. If no EELF Logging implementations are found - eelf logging is disabled and {@link NoOpEELFLogger}
+ * is used.
+ *
+ * @author Rajiv Singla
+ */
+public class EELFLogFactory {
+
+    private static final ServiceLoader<EELFLogger> SERVICE_LOADER = ServiceLoader.load(EELFLogger.class);
+    private static final Map<Class<?>, EELFLogger> LOGGER_CACHE = new WeakHashMap<>(64);
+
+    private static List<EELFLogger> loggerImplementations = new LinkedList<>();
+
+    static {
+
+        for (EELFLogger loggerImplementation : SERVICE_LOADER) {
+            loggerImplementations.add(loggerImplementation);
+        }
+
+        if (loggerImplementations.isEmpty()) {
+            System.err.println(
+                    "EELF LOGGING ERROR: Unable to find any EELF Logger Implementations in the classpath.");
+            System.err.println("=============EELF LOGGING IS DISABLED================");
+            loggerImplementations.add(NoOpEELFLogger.getInstance());
+        }
+
+    }
+
+    private EELFLogFactory() {
+        // private constructor
+    }
+
+    public static <T> EELFLogger getLogger(Class<T> clazz) {
+
+        if (LOGGER_CACHE.get(clazz) != null) {
+            return LOGGER_CACHE.get(clazz);
+        }
+
+        EELFLogger EELFLogger = null;
+        try {
+            EELFLogger = loggerImplementations.get(0).getClass().getConstructor(Class.class)
+                    .newInstance(clazz);
+            return EELFLogger;
+
+        } catch (
+                InstantiationException | IllegalAccessException | InvocationTargetException | NoSuchMethodException e) {
+            throw new IllegalStateException("Error while Creating EELF Logger", e);
+        }
+
+    }
+
+
+}
diff --git a/eelf-logger/eelf-logger-api/src/main/java/org/onap/dcae/utils/eelf/logger/api/log/EELFLogger.java b/eelf-logger/eelf-logger-api/src/main/java/org/onap/dcae/utils/eelf/logger/api/log/EELFLogger.java
new file mode 100644
index 0000000..500d814
--- /dev/null
+++ b/eelf-logger/eelf-logger-api/src/main/java/org/onap/dcae/utils/eelf/logger/api/log/EELFLogger.java
@@ -0,0 +1,67 @@
+/*
+ * ================================================================================
+ * Copyright (c) 2018 AT&T Intellectual Property. All rights reserved.
+ * ================================================================================
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ * ============LICENSE_END=========================================================
+ *
+ */
+
+package org.onap.dcae.utils.eelf.logger.api.log;
+
+/**
+ * EELF Logger is main abstraction which applications use to log EELF Compliant log messages
+ *
+ * @author Rajiv Singla
+ */
+public interface EELFLogger {
+
+    /**
+     * Provides Audit Log
+     *
+     * @return Audit log
+     */
+    AuditLog auditLog();
+
+
+    /**
+     * Provides Metric Log
+     *
+     * @return metric log
+     */
+    MetricLog metricLog();
+
+    /**
+     * Provides Error Log
+     *
+     * @return error log
+     */
+    ErrorLog errorLog();
+
+
+    /**
+     * Provides Debug Log
+     *
+     * @return debug log
+     */
+    DebugLog debugLog();
+
+    /**
+     * Provides logging context
+     *
+     * @return logging context
+     */
+    EELFLoggerContext loggingContext();
+
+
+}
diff --git a/eelf-logger/eelf-logger-api/src/main/java/org/onap/dcae/utils/eelf/logger/api/log/EELFLoggerContext.java b/eelf-logger/eelf-logger-api/src/main/java/org/onap/dcae/utils/eelf/logger/api/log/EELFLoggerContext.java
new file mode 100644
index 0000000..5910da5
--- /dev/null
+++ b/eelf-logger/eelf-logger-api/src/main/java/org/onap/dcae/utils/eelf/logger/api/log/EELFLoggerContext.java
@@ -0,0 +1,56 @@
+/*
+ * ================================================================================
+ * Copyright (c) 2018 AT&T Intellectual Property. All rights reserved.
+ * ================================================================================
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ * ============LICENSE_END=========================================================
+ *
+ */
+
+package org.onap.dcae.utils.eelf.logger.api.log;
+
+
+import org.onap.dcae.utils.eelf.logger.api.spec.AppLogSpec;
+
+/**
+ * EELF Logger Context contains fields are set during application creation time and are fixed for the entire
+ * duration of the application lifetime
+ *
+ * @author Rajiv Singla
+ */
+public interface EELFLoggerContext {
+
+    /**
+     * Returns App Log Spec
+     *
+     * @return current app log spec
+     */
+    AppLogSpec getAppLogSpec();
+
+
+    /**
+     * Sets new App Log Spec
+     *
+     * @param appLogSpec new app log spec
+     */
+    void setAppLogSpec(AppLogSpec appLogSpec);
+
+
+    /**
+     * Returns true if logging context is already initialized
+     *
+     * @return true if logger context is already initialized
+     */
+    boolean isInitialized();
+
+}
diff --git a/eelf-logger/eelf-logger-api/src/main/java/org/onap/dcae/utils/eelf/logger/api/log/ErrorLog.java b/eelf-logger/eelf-logger-api/src/main/java/org/onap/dcae/utils/eelf/logger/api/log/ErrorLog.java
new file mode 100644
index 0000000..6b27755
--- /dev/null
+++ b/eelf-logger/eelf-logger-api/src/main/java/org/onap/dcae/utils/eelf/logger/api/log/ErrorLog.java
@@ -0,0 +1,93 @@
+/*
+ * ================================================================================
+ * Copyright (c) 2018 AT&T Intellectual Property. All rights reserved.
+ * ================================================================================
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ * ============LICENSE_END=========================================================
+ *
+ */
+
+package org.onap.dcae.utils.eelf.logger.api.log;
+
+
+import org.onap.dcae.utils.eelf.logger.api.info.LogLevelCategory;
+import org.onap.dcae.utils.eelf.logger.api.spec.ErrorLogSpec;
+import org.onap.dcae.utils.eelf.logger.api.spec.OptionalLogSpec;
+
+/**
+ * @author Rajiv Singla
+ */
+public interface ErrorLog {
+
+    /**
+     * Logs error message with provided {@link LogLevelCategory}
+     *
+     * @param logLevelCategory log level category
+     * @param message log message
+     * @param errorLogSpec error log spec
+     * @param optionalLogSpec optional log spec
+     * @param args argument values for log message interpolation
+     */
+    void log(LogLevelCategory logLevelCategory, String message, ErrorLogSpec errorLogSpec,
+             OptionalLogSpec optionalLogSpec, String... args);
+
+    /**
+     * Logs error message with provided {@link LogLevelCategory} and with default {@link OptionalLogSpec}
+     *
+     * @param logLevelCategory log level category
+     * @param message log message
+     * @param errorLogSpec error log spec
+     * @param args argument values for log message interpolation
+     */
+    void log(LogLevelCategory logLevelCategory, String message, ErrorLogSpec errorLogSpec, String... args);
+
+
+    /**
+     * Logs error message with ERROR {@link LogLevelCategory}
+     *
+     * @param message log message
+     * @param errorLogSpec error log spec
+     * @param args argument values for log message interpolation
+     */
+    void error(String message, ErrorLogSpec errorLogSpec, OptionalLogSpec optionalLogSpec, String... args);
+
+    /**
+     * Logs error message with ERROR {@link LogLevelCategory} and with default {@link OptionalLogSpec}
+     *
+     * @param message log message
+     * @param errorLogSpec error log spec
+     * @param args argument values for log message interpolation
+     */
+    void error(String message, ErrorLogSpec errorLogSpec, String... args);
+
+
+    /**
+     * Logs error message with WARN {@link LogLevelCategory}
+     *
+     * @param message log message
+     * @param errorLogSpec error log spec
+     * @param args argument values for log message interpolation
+     */
+    void warn(String message, ErrorLogSpec errorLogSpec, OptionalLogSpec optionalLogSpec, String... args);
+
+    /**
+     * Logs error message with WARN {@link LogLevelCategory} and with default {@link OptionalLogSpec}
+     *
+     * @param message log message
+     * @param errorLogSpec error log spec
+     * @param args argument values for log message interpolation
+     */
+    void warn(String message, ErrorLogSpec errorLogSpec, String... args);
+
+
+}
diff --git a/eelf-logger/eelf-logger-api/src/main/java/org/onap/dcae/utils/eelf/logger/api/log/MetricLog.java b/eelf-logger/eelf-logger-api/src/main/java/org/onap/dcae/utils/eelf/logger/api/log/MetricLog.java
new file mode 100644
index 0000000..ebc33ca
--- /dev/null
+++ b/eelf-logger/eelf-logger-api/src/main/java/org/onap/dcae/utils/eelf/logger/api/log/MetricLog.java
@@ -0,0 +1,130 @@
+/*
+ * ================================================================================
+ * Copyright (c) 2018 AT&T Intellectual Property. All rights reserved.
+ * ================================================================================
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ * ============LICENSE_END=========================================================
+ *
+ */
+
+package org.onap.dcae.utils.eelf.logger.api.log;
+
+
+import org.onap.dcae.utils.eelf.logger.api.info.LogLevelCategory;
+import org.onap.dcae.utils.eelf.logger.api.spec.MetricLogSpec;
+import org.onap.dcae.utils.eelf.logger.api.spec.OptionalLogSpec;
+
+/**
+ * Metric Log captures all log levels supported by metric specifications
+ *
+ * @author Rajiv Singla
+ */
+public interface MetricLog {
+
+    /**
+     * Logs metric message with provided {@link LogLevelCategory}
+     *
+     * @param logLevelCategory log level category
+     * @param message log message
+     * @param metricLogSpec metric log spec
+     * @param optionalLogSpec optional log spec
+     * @param args argument values for log message interpolation
+     */
+    void log(LogLevelCategory logLevelCategory, String message, MetricLogSpec metricLogSpec,
+             OptionalLogSpec optionalLogSpec, String... args);
+
+    /**
+     * Logs metric message with provided {@link LogLevelCategory} and with default {@link OptionalLogSpec}
+     *
+     * @param logLevelCategory log level category
+     * @param message log message
+     * @param metricLogSpec metric log spec
+     * @param args argument values for log message interpolation
+     */
+    void log(LogLevelCategory logLevelCategory, String message, MetricLogSpec metricLogSpec, String... args);
+
+
+    /**
+     * Logs metric message with provided INFO {@link LogLevelCategory}
+     *
+     * @param message log message
+     * @param metricLogSpec metric log spec
+     * @param args argument values for log message interpolation
+     */
+    void info(String message, MetricLogSpec metricLogSpec, OptionalLogSpec optionalLogSpec, String... args);
+
+    /**
+     * Logs metric message with provided INFO {@link LogLevelCategory} and with default {@link OptionalLogSpec}
+     *
+     * @param message log message
+     * @param metricLogSpec metric log spec
+     * @param args argument values for log message interpolation
+     */
+    void info(String message, MetricLogSpec metricLogSpec, String... args);
+
+
+    /**
+     * Logs metric message with provided WARN {@link LogLevelCategory}
+     *
+     * @param message log message
+     * @param metricLogSpec metric log spec
+     * @param args argument values for log message interpolation
+     */
+    void warn(String message, MetricLogSpec metricLogSpec, OptionalLogSpec optionalLogSpec, String... args);
+
+    /**
+     * Logs metric message with provided WARN {@link LogLevelCategory} and with default {@link OptionalLogSpec}
+     *
+     * @param message log message
+     * @param metricLogSpec metric log spec
+     * @param args argument values for log message interpolation
+     */
+    void warn(String message, MetricLogSpec metricLogSpec, String... args);
+
+    /**
+     * Logs metric message with provided ERROR {@link LogLevelCategory}
+     *
+     * @param message log message
+     * @param metricLogSpec metric log spec
+     * @param args argument values for log message interpolation
+     */
+    void error(String message, MetricLogSpec metricLogSpec, OptionalLogSpec optionalLogSpec, String... args);
+
+    /**
+     * Logs metric message with provided ERROR {@link LogLevelCategory} and with default {@link OptionalLogSpec}
+     *
+     * @param message log message
+     * @param metricLogSpec metric log spec
+     * @param args argument values for log message interpolation
+     */
+    void error(String message, MetricLogSpec metricLogSpec, String... args);
+
+    /**
+     * Logs metric message with provided FATAL {@link LogLevelCategory}
+     *
+     * @param message log message
+     * @param metricLogSpec metric log spec
+     * @param args argument values for log message interpolation
+     */
+    void fatal(String message, MetricLogSpec metricLogSpec, OptionalLogSpec optionalLogSpec, String... args);
+
+    /**
+     * Logs metric message with provided FATAL {@link LogLevelCategory} and with default {@link OptionalLogSpec}
+     *
+     * @param message log message
+     * @param metricLogSpec metric log spec
+     * @param args argument values for log message interpolation
+     */
+    void fatal(String message, MetricLogSpec metricLogSpec, String... args);
+
+}
diff --git a/eelf-logger/eelf-logger-api/src/main/java/org/onap/dcae/utils/eelf/logger/api/log/package-info.java b/eelf-logger/eelf-logger-api/src/main/java/org/onap/dcae/utils/eelf/logger/api/log/package-info.java
new file mode 100644
index 0000000..e24ccc9
--- /dev/null
+++ b/eelf-logger/eelf-logger-api/src/main/java/org/onap/dcae/utils/eelf/logger/api/log/package-info.java
@@ -0,0 +1,23 @@
+/*
+ * ================================================================================
+ * Copyright (c) 2018 AT&T Intellectual Property. All rights reserved.
+ * ================================================================================
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ * ============LICENSE_END=========================================================
+ *
+ */
+
+/**
+ * Contains Logging API contracts for various EELF Logs (e.g. Audit, Metric, Error, Debug etc)
+ */
+package org.onap.dcae.utils.eelf.logger.api.log;