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Apr 16, 2023
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docs: disclaim write load for agent metadata #7048

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docs: disclaim write load for agent metadata
ammario Apr 7, 2023
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Update docs/templates/agent-metadata.md
ammario Apr 16, 2023
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Update docs/templates/agent-metadata.md
ammario Apr 16, 2023
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docs: disclaim write load for agent metadata
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@ammario
ammario committed Apr 7, 2023
commit d303efb179147751d85981ef372816533f0e214c
27 changes: 24 additions & 3 deletions docs/templates/agent-metadata.md
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Expand Up @@ -70,7 +70,7 @@ resource "coder_agent" "main" {
distributions and provides virtual memory, CPU and IO statistics. Running `top`
produces output that looks like:

```
```text
%Cpu(s): 65.8 us, 4.4 sy, 0.0 ni, 29.3 id, 0.3 wa, 0.0 hi, 0.2 si, 0.0 st
MiB Mem : 16009.0 total, 493.7 free, 4624.8 used, 10890.5 buff/cache
MiB Swap: 0.0 total, 0.0 free, 0.0 used. 11021.3 avail Mem
Expand All @@ -80,7 +80,7 @@ MiB Swap: 0.0 total, 0.0 free, 0.0 used. 11021.3 avail Mem
distributions and provides virtual memory, CPU and IO statistics. Running `vmstat`
produces output that looks like:

```
```text
procs -----------memory---------- ---swap-- -----io---- -system-- ------cpu-----
r b swpd free buff cache si so bi bo in cs us sy id wa st
0 0 19580 4781680 12133692 217646944 0 2 4 32 1 0 1 1 98 0 0
Expand All @@ -91,8 +91,29 @@ than `vmstat` but often not included in base images. It is easily installed by
most package managers under the name `dstat`. The output of running `dstat 1 1` looks
like:

```
```text
--total-cpu-usage-- -dsk/total- -net/total- ---paging-- ---system--
usr sys idl wai stl| read writ| recv send| in out | int csw
1 1 98 0 0|3422k 25M| 0 0 | 153k 904k| 123k 174k
```

## DB Write Load

Agent metadata can generate a significant write load and overwhelm your
database if you're not careful. The approximate writes per second can be
calculated using the formula:

```text
(metadata_count * num_running_agents * 2) / metadata_avg_interval
```

For example, let's say you have

- 10 running agents
- each with 6 metadata snippets
- with an average interval of 4 seconds

You can expect `(10 * 6 * 2) / 4` or 30 writes per second.

One of the writes is is to the `UNLOGGED` `workspace_agent_metadata` table and
the other the `NOTIFY` query that enables live stats streaming in the UI.