[DPE-3388] Write logs to files (#384)

## Issue
We need to write mongod logs and audit logs into files instead of
syslog.

## Solution
Write logs to files located on a separate mount point
<img width="1142" alt="Screenshot 2024-04-05 at 10 47 21"
src="https://github.com/canonical/mongodb-operator/assets/132273757/ab47d0a2-a760-4d03-a858-1aaf0dcbc35e">

lib/charms/mongodb/v1/helpers.py

@@ -46,19 +46,37 @@
 
 DATA_DIR = "/var/lib/mongodb"
 LOG_DIR = "/var/log/mongodb"
-LOG_TO_SYSLOG = True
 CONF_DIR = "/etc/mongod"
 MONGODB_LOG_FILENAME = "mongodb.log"
 logger = logging.getLogger(__name__)
 
 
 def _get_logging_options(snap_install: bool) -> str:
-    # TODO sending logs to syslog until we have a separate mount point for logs
-    if LOG_TO_SYSLOG:
-        return ""
-    # in k8s the default logging options that are used for the vm charm are ignored and logs are
-    # the output of the container. To enable logging to a file it must be set explicitly
-    return f"--logpath={LOG_DIR}/{MONGODB_LOG_FILENAME}" if snap_install else ""
+    """Returns config option for log path.
+
+    :param snap_install: indicate that charmed-mongodb was installed from snap (VM charms)
+    :return: a path to log file to be used
+    """
+    log_path = f"{LOG_DIR}/{MONGODB_LOG_FILENAME}"
+    if snap_install:
+        log_path = f"{MONGODB_COMMON_DIR}{log_path}"
+    return f"--logpath={log_path}"
+
+
+def _get_audit_log_settings(snap_install: bool) -> List[str]:
+    """Return config options for audit log.
+
+    :param snap_install: indicate that charmed-mongodb was installed from snap (VM charms)
+    :return: a list of audit log settings for charmed MongoDB
+    """
+    audit_log_path = f"{LOG_DIR}/{Config.AuditLog.FILE_NAME}"
+    if snap_install:
+        audit_log_path = f"{MONGODB_COMMON_DIR}{audit_log_path}"
+    return [
+        f"--auditDestination={Config.AuditLog.DESTINATION}",
+        f"--auditFormat={Config.AuditLog.FORMAT}",
+        f"--auditPath={audit_log_path}",
+    ]
 
 
 # noinspection GrazieInspection
@@ -172,6 +190,7 @@ def get_mongod_args(
     full_data_dir = f"{MONGODB_COMMON_DIR}{DATA_DIR}" if snap_install else DATA_DIR
     full_conf_dir = f"{MONGODB_SNAP_DATA_DIR}{CONF_DIR}" if snap_install else CONF_DIR
     logging_options = _get_logging_options(snap_install)
+    audit_log_settings = _get_audit_log_settings(snap_install)
     cmd = [
         # bind to localhost and external interfaces
         "--bind_ip_all",
@@ -182,10 +201,10 @@ def get_mongod_args(
         # for simplicity we run the mongod daemon on shards, configsvrs, and replicas on the same
         # port
         f"--port={Config.MONGODB_PORT}",
-        "--auditDestination=syslog",  # TODO sending logs to syslog until we have a separate mount point for logs
-        f"--auditFormat={Config.AuditLog.FORMAT}",
+        "--setParameter processUmask=037",  # required for log files perminission (g+r)
         logging_options,
     ]
+    cmd.extend(audit_log_settings)
     if auth:
         cmd.extend(["--auth"])
 

src/config.py

@@ -44,6 +44,7 @@ class AuditLog:
         """Audit log related configuration."""
 
         FORMAT = "JSON"
+        DESTINATION = "file"
         FILE_NAME = "audit.log"
 
     class Backup:

tests/integration/ha_tests/helpers.py

@@ -37,7 +37,7 @@
 MONGODB_LOG_PATH = f"{MONGO_COMMON_DIR}/var/log/mongodb/mongodb.log"
 MONGOD_SERVICE_DEFAULT_PATH = "/etc/systemd/system/snap.charmed-mongodb.mongod.service"
 TMP_SERVICE_PATH = "tests/integration/ha_tests/tmp.service"
-LOGGING_OPTIONS = f"--logpath={MONGO_COMMON_DIR}/var/log/mongodb/mongodb.log --logappend"
+LOGGING_OPTIONS = "--logappend"
 EXPORTER_PROC = "/usr/bin/mongodb_exporter"
 GREP_PROC = "grep"
 

tests/integration/sharding_tests/test_sharding_tls.py

@@ -107,7 +107,6 @@ async def test_tls_then_build_cluster(ops_test: OpsTest) -> None:
 @pytest.mark.group(1)
 @pytest.mark.abort_on_fail
 async def test_tls_inconsistent_rels(ops_test: OpsTest) -> None:
-
     await ops_test.model.deploy(
         CERTS_APP_NAME, application_name=DIFFERENT_CERTS_APP_NAME, channel="stable"
     )

tests/unit/test_mongodb_helpers.py

@@ -14,8 +14,12 @@ def test_get_mongod_args(self):
             "--replSet=my_repl_set",
             "--dbpath=/var/snap/charmed-mongodb/common/var/lib/mongodb",
             "--port=27017",
-            "--auditDestination=syslog",
+            "--setParameter",
+            "processUmask=037",
+            "--logpath=/var/snap/charmed-mongodb/common/var/log/mongodb/mongodb.log",