Merge ~gschiano/squid-reverseproxy-charm:add-systemd-support into squid-reverseproxy-charm:master

[Grégory Schiano]

Support setting Max file descriptor if service is using Systemd

[🤖 Canonical IS Merge Bot (canonical-is-mergebot)]

This merge proposal is being monitored by mergebot. Change the status to Approved to merge.

[Haw Loeung (hloeung)]

LGTM

review: Approve (+1)

[🤖 Canonical IS Merge Bot (canonical-is-mergebot)]

Change successfully merged at revision a50829993d60c0be60618ec3617d834a41d0f103

diff --git a/hooks/hooks.py b/hooks/hooks.py
index 3aad58c..ae2e1b2 100755
--- a/hooks/hooks.py
+++ b/hooks/hooks.py
@@ -51,7 +51,8 @@ metrics_script_path = "/usr/local/bin/squid_metrics.py"
 metrics_config_path = "/usr/local/etc/squid_metrics.ini"
 site_mib_path = "/usr/share/mibs/site"
 Server = collections.namedtuple("Server", "name address port options")
-service_affecting_packages = ['squid']
+service_affecting_packages = ["squid"]
+max_fd = 65536
 
 ###############################################################################
 # Supporting functions
@@ -450,7 +451,6 @@ def write_metrics_cronjob(script_path, config_path, cron_path):
 def service_squid3(action=None, squid3_config=default_squid3_config):
     """Convenience function to start/stop/restart/reload the squid3
     service"""
-    release = int(host.lsb_release()['DISTRIB_RELEASE'][0:2])
     service_name = squid_name
     if action is None or squid3_config is None:
         return
@@ -562,12 +562,93 @@ def install_hook():
     if not os.path.exists(default_squid3_config_cache_dir):
         host.mkdir(default_squid3_config_cache_dir, 'proxy', 'proxy', 0o755)
     if not os.path.exists(default_squid3_cache_dir):
-        host.mkdir(default_squid3_cache_dir, 'proxy', 'proxy', 0o755)
-    shutil.copy2('%s/files/default.squid3' % charm_dir, '/etc/default/squid3')
+        host.mkdir(default_squid3_cache_dir, "proxy", "proxy", 0o755)
     install_packages()
+
+    service_file_path = f"/lib/systemd/system/{squid_name}.service"
+    new_service_file_path = f"/etc/systemd/system/{squid_name}.service"
+    if host.init_is_systemd(squid_name) and os.path.exists(service_file_path):
+        edit_systemd_file_descriptors_limit(
+            service_file_path, new_service_file_path, max_fd
+        )
+        systemd_daemon_reload()
+    else:
+        shutil.copy2(
+            "%s/files/default.squid3" % charm_dir, f"/etc/default/{squid_name}"
+        )
     return True
 
 
+def edit_systemd_file_descriptors_limit(
+    service_file_path: str, new_service_file_path: str, file_descriptor_limit: int
+):
+    """
+    Edits a systemd service unit file to set the file descriptor limit.
+
+    Args:
+        service_file_path: The path to the systemd service file.
+        file_descriptor_limit: The new file descriptor limit.
+
+    """
+    updated = False
+    in_service_block = False
+
+    directive = f"LimitNOFILE={file_descriptor_limit}\n"
+
+    with open(service_file_path, "r") as service:
+        with open(new_service_file_path, "w") as new_service:
+            for line in service:
+                if line.strip() == "[Service]":
+                    in_service_block = True
+                elif line.startswith("[") and in_service_block:
+                    # Exiting the [Service] block without finding the directive
+                    if not updated:
+                        new_service.write(directive)
+                        updated = True
+                    in_service_block = False
+
+                if in_service_block and line.startswith("LimitNOFILE"):
+                    new_service.write(directive)
+                    updated = True
+                    continue
+
+                new_service.write(line)
+
+            if not updated and in_service_block:
+                # If still in the [Service] block and haven't updated, append the directive
+                new_service.write(directive)
+
+
+def systemd_daemon_reload(check: bool = False) -> int:
+    """Reload systemd service files.
+
+    Args:
+        check: Check the output of the systemctl command. Default: False.
+
+    Returns:
+        Returncode of systemctl command execution.
+
+    Raises:
+        SystemdError: Raised if calling systemctl returns a non-zero returncode and check is True.
+    """
+    cmd = ["systemctl", "daemon-reload"]
+    log(f"Executing command: {cmd}", "debug")
+    proc = subprocess.run(
+        cmd,
+        stdout=subprocess.PIPE,
+        stderr=subprocess.STDOUT,
+        text=True,
+        bufsize=1,
+        encoding="utf-8",
+        check=check,
+    )
+    log(
+        f"Command {cmd} exit code: {proc.returncode}. systemctl output:\n{proc.stdout}",
+        "debug",
+    )
+    return proc.returncode
+
+
 def service_can_start():
     # If wait_for_auth_helper is set, wait until squid has started and the
     # squid-auth-helper relation has been joined.