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authorDaniel Baumann <daniel.baumann@progress-linux.org>2019-07-08 20:14:42 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2019-07-08 20:14:42 +0000
commit4f88e1a9be89a257fd6ed3045703db6e900027ee (patch)
tree518eb3c3aa1dce9ea281d02e0fd3cc01a9e7913f /database/engine/README.md
parentAdding upstream version 1.15.0. (diff)
downloadnetdata-4f88e1a9be89a257fd6ed3045703db6e900027ee.tar.xz
netdata-4f88e1a9be89a257fd6ed3045703db6e900027ee.zip
Adding upstream version 1.16.0.upstream/1.16.0
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'database/engine/README.md')
-rw-r--r--database/engine/README.md40
1 files changed, 38 insertions, 2 deletions
diff --git a/database/engine/README.md b/database/engine/README.md
index 28a2528cb..adc69ffd7 100644
--- a/database/engine/README.md
+++ b/database/engine/README.md
@@ -96,9 +96,9 @@ There are explicit memory requirements **per** DB engine **instance**, meaning *
- `page cache size` must be at least `#dimensions-being-collected x 4096 x 2` bytes.
-- an additional `#pages-on-disk x 4096 x 0.06` bytes of RAM are allocated for metadata.
+- an additional `#pages-on-disk x 4096 x 0.03` bytes of RAM are allocated for metadata.
- - roughly speaking this is 6% of the uncompressed disk space taken by the DB files.
+ - roughly speaking this is 3% of the uncompressed disk space taken by the DB files.
- for very highly compressible data (compression ratio > 90%) this RAM overhead
is comparable to the disk space footprint.
@@ -106,4 +106,40 @@ There are explicit memory requirements **per** DB engine **instance**, meaning *
An important observation is that RAM usage depends on both the `page cache size` and the
`dbengine disk space` options.
+## File descriptor requirements
+
+The Database Engine may keep a **significant** amount of files open per instance (e.g. per streaming
+slave or master server). When configuring your system you should make sure there are at least 50
+file descriptors available per `dbengine` instance.
+
+Netdata allocates 25% of the available file descriptors to its Database Engine instances. This means that only 25%
+of the file descriptors that are available to the Netdata service are accessible by dbengine instances.
+You should take that into account when configuring your service
+or system-wide file descriptor limits. You can roughly estimate that the netdata service needs 2048 file
+descriptors for every 10 streaming slave hosts when streaming is configured to use `memory mode = dbengine`.
+
+If for example one wants to allocate 65536 file descriptors to the netdata service on a systemd system
+one needs to override the netdata service by running `sudo systemctl edit netdata` and creating a
+file with contents:
+
+```
+[Service]
+LimitNOFILE=65536
+```
+
+For other types of services one can add the line:
+```
+ulimit -n 65536
+```
+at the beginning of the service file. Alternatively you can change the system-wide limits of the kernel by changing `/etc/sysctl.conf`. For linux that would be:
+```
+fs.file-max = 65536
+```
+In FreeBSD and OS X you change the lines like this:
+```
+kern.maxfilesperproc=65536
+kern.maxfiles=65536
+```
+You can apply the settings by running `sysctl -p` or by rebooting.
+
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