fix(pacakging): fix cpu/memory metrics when running inside LXC container as systemd service (#14255)

Fixes https://github.com/netdata/netdata/issues/14238

3 files changed, 43 insertions, 3 deletions

diff --git a/collectors/proc.plugin/plugin_proc.c b/collectors/proc.plugin/plugin_proc.c
index 220f9cb3db..ab974d4977 100644
--- a/collectors/proc.plugin/plugin_proc.c
+++ b/collectors/proc.plugin/plugin_proc.c
@@ -98,6 +98,41 @@ static void proc_main_cleanup(void *ptr)
     worker_unregister();
 }
 
+bool inside_lxc_container = false;
+
+static bool is_lxcfs_proc_mounted() {
+    procfile *ff = NULL;
+
+    if (unlikely(!ff)) {
+        char filename[FILENAME_MAX + 1];
+        snprintfz(filename, FILENAME_MAX, "/proc/self/mounts");
+        ff = procfile_open(filename, " \t", PROCFILE_FLAG_DEFAULT);
+        if (unlikely(!ff))
+            return false;
+    }
+
+    ff = procfile_readall(ff);
+    if (unlikely(!ff))
+        return false;
+
+    unsigned long l, lines = procfile_lines(ff);
+
+    for (l = 0; l < lines; l++) {
+        size_t words = procfile_linewords(ff, l);
+        if (words < 2) {
+            continue;
+        }
+        if (!strcmp(procfile_lineword(ff, l, 0), "lxcfs") && !strncmp(procfile_lineword(ff, l, 1), "/proc", 5)) {
+            procfile_close(ff);
+            return true;   
+        }            
+    }
+
+    procfile_close(ff);
+
+    return false;
+}
+
 void *proc_main(void *ptr)
 {
     worker_register("PROC");
@@ -128,6 +163,8 @@ void *proc_main(void *ptr)
     heartbeat_t hb;
     heartbeat_init(&hb);
 
+    inside_lxc_container = is_lxcfs_proc_mounted();
+
     while (service_running(SERVICE_COLLECTORS)) {
         worker_is_idle();
         usec_t hb_dt = heartbeat_next(&hb, step);
diff --git a/collectors/proc.plugin/plugin_proc.h b/collectors/proc.plugin/plugin_proc.h
index d67ccd6e59..b4fd7b83d4 100644
--- a/collectors/proc.plugin/plugin_proc.h
+++ b/collectors/proc.plugin/plugin_proc.h
@@ -48,6 +48,7 @@ int get_numa_node_count(void);
 
 // metrics that need to be shared among data collectors
 extern unsigned long long zfs_arcstats_shrinkable_cache_size_bytes;
+extern bool inside_lxc_container;
 
 // netdev renames
 void netdev_rename_device_add(
diff --git a/collectors/proc.plugin/proc_meminfo.c b/collectors/proc.plugin/proc_meminfo.c
index 2f390c6535..6988c70e01 100644
--- a/collectors/proc.plugin/proc_meminfo.c
+++ b/collectors/proc.plugin/proc_meminfo.c
@@ -158,9 +158,11 @@ int do_proc_meminfo(int update_every, usec_t dt) {
     unsigned long long MemCached = Cached + SReclaimable - Shmem;
     unsigned long long MemUsed = MemTotal - MemFree - MemCached - Buffers;
     // The Linux kernel doesn't report ZFS ARC usage as cache memory (the ARC is included in the total used system memory)
-    MemCached += (zfs_arcstats_shrinkable_cache_size_bytes / 1024);
-    MemUsed -= (zfs_arcstats_shrinkable_cache_size_bytes / 1024);
-    MemAvailable += (zfs_arcstats_shrinkable_cache_size_bytes / 1024);
+    if (!inside_lxc_container) {
+        MemCached += (zfs_arcstats_shrinkable_cache_size_bytes / 1024);
+        MemUsed -= (zfs_arcstats_shrinkable_cache_size_bytes / 1024);
+        MemAvailable += (zfs_arcstats_shrinkable_cache_size_bytes / 1024);
+    }
 
     if(do_ram) {
         {