You misunderstand me. Create the new file "target.json.new" from scratch.
If you want to merge data from the old target.json then read the old data
in, modify it, and write out to the new file.
You cannot simply append to the end of a JSON file. What you will have is
multiple JSON objects in one file, rather than one JSON object. AFAIK,
Prometheus will not let you do that. However, whatever JSON validator
you're using *might* allow multiple JSON objects.
If you show the contents of the file you've created, then it may become
clear what the problem is.
For example, the following is not a valid JSON file:
{"hello":"world"}
{"foo":"bar"}
You would have to merge the objects, like this:
{"hello":"world", "foo":"bar"}
On Wednesday 13 December 2023 at 04:00:13 UTC akshay sharma wrote:
> If I rename the new file to the existing file, then it would lose the old
> data in the existing file right?
> so what we can do!
> On Tuesday, December 12, 2023 at 6:52:46 PM UTC+5:30 Brian Candler wrote:
>
>> Perhaps you didn't write the file atomically. If you start appending to
>> the file, and Prometheus notices you've changed it, it may read it before
>> you've finished writing.
>>
>> You should:
>> 1. Write out a new file, e.g. target.json.new
>> 2. fsync it (os.File.Sync)
>> 3. rename target.json.new to target.json
>>
>> On Tuesday 12 December 2023 at 13:11:53 UTC akshay sharma wrote:
>>
>>> Hi,
>>>
>>> I have an application running, which is accepting the post request to
>>> add targets in the path /etc/prometheus/config/target.json.
>>>
>>> Currently, I'm posting 2-3 targets using curl to the application which
>>> in turn adds to the Prometheus path, post is happening in a time difference
>>> of 2-3 minutes.
>>>
>>> In Prometheus UI, I could see it is adding only one target or can see
>>> only one target in service discovery, but I have added 3 targets.
>>>
>>> could see some errors in Prometheus:
>>>
>>> ts=2023-12-12T10:27:15.936Z caller=file.go:343 level=error
>>> component="discovery manager scrape" discovery=file config=ne-federation
>>> msg="Error reading file" path=/etc/prometheus/config/targets.json
>>> err="unexpected end of JSON input"
>>> ts=2023-12-12T10:35:50.707Z caller=file.go:343 level=error
>>> component="discovery manager scrape" discovery=file config=ne-federation
>>> msg="Error reading file" path=/etc/prometheus/config/argets.json
>>> err="unexpected end of JSON input"
>>>
>>> I checked the JSON file using JSON validator, it's perfectly valid.
>>>
>>> can you please help with what could be the issue?
>>>
>>
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