Glo
Copyright (c) Anders Roos. Licensed under the MIT License.
About
A simple status data format, javascript client and server libraries for live monitoring of server status. It is extremly valueble to be able to get specific measurements or data points from a system, either for debugging or for just understanding the system better.
This is inspired by JMX and MBeans, but read only and much simpler to use. The basic idea is to only specify a JSON message format and leave the rest to each implementation.
Status Data Format
The status data is communicated through JSON, either plain JSON or wrapped in a Javascript callback.
Message Format
The current version is 1.
{
"version": <number, the current version>,
"timestamp": <number, server time since EPOC in milliseconds>,
"data": [
{
"key": "<string, name + : + tag>",
"value": "<string, the value as a string>",
"desc": "<string, a human readable description>",
"lvl": "<number, level of importance where 0 is the highest>
},
...
]
}
To make clients complatible with future versions they should silently ignore unrecognized keys in the top dict and in the data dicts.
Tags
Currently available tags are:
| count | A counter that increases over time. For example a request counter. |
|---|---|
| current | A current value. For example the numer of objects in a cache. |
| last | The last value of something. For example the size of the last request. |
| last-duration-us | The last duration in microseconds. For example the last duration of processing a request. |
| total-duration-us | The total duration in microseconds, a value that will increase over time. For example the total duration of pricessing all requests. |
| max-us | The maximum time of something in microseconds. For example the maximum time to process a request. |
Changes From Version 0
The version number was added. This was added to make the code be able to distinguish between versions.
The data changed from a list of lists to a list of dicts containing the keys "key", "value", "desc", "lvl". This was done to make it easier to extend the data entries without breaking existing implementations. Clients should ignore keys they don't recognize.
Message Example
{
"version": 1,
"timestamp": 1313152128209,
"data": [
{
"key": "/server/request:count",
"value": "45023",
"desc": "Number of successful requests to server.",
"lvl": 1
},
{
"key": "/server/cache/size:current",
"value": "134",
"desc": "The current cache size.",
"lvl": 2
},
{
"key": "/server/cache/miss:count",
"value": "23",
"desc": "Number of cache misses.",
"lvl": 3
},
{
"key": "/server/cache/hit:count",
"value": "224233",
"desc": "Number of cache hits.",
"lvl": 3
},
{
"key": "/server/request:last-duration-us",
"value": "12323090239",
"desc": "The duration of the last request in microseconds.",
"lvl": 2
}
]
}
Previous Versions
List of old versions.
Version 0
Version 0 was never publicly released.
{
timestamp: <timestamp ms>,
data: [
["<key>", "<value>", "<description>"],
...
]
}
Source
The source can be found at GitHub.
