"503 Service Unavailable" hiding other issue

Technical Issue Reporting
#1

I use the REST API to sync up NFT sales data to a local database. Every once in a while when doing the syncing, one of the queries gets stuck in the following issue:

Requesting https://deep-index.moralis.io/api/v2/nft/0x15a2d6c2b4b9903c27f50cb8b32160ab17f186e2/transfers?chain=eth&format=decimal&limit=500&offset=0
Service unavailable - trying again after 5s - https://deep-index.moralis.io/api/v2/nft/0x15a2d6c2b4b9903c27f50cb8b32160ab17f186e2/transfers?chain=eth&format=decimal&limit=500&offset=0
Full body: <html><body><h1>503 Service Unavailable</h1>No server is available to handle this request.</body></html>

(this is from my logs)

The error keeps happening until either:

  • I Ctrl-C the process and start it again; or
  • I let it continue until my code decides to move on to the next project to sync

Before I added code that stops trying after a number of tries, I once let this run for hundreds of attempts overnight and it did not manage to get a useful response.

But as soon as I do either of those things, the service works again immediately. This suggests, to me, thereā€™s some other issue happening thatā€™s not a case of ā€œService Unavailableā€ (which would suggest the server being down or some similar issue), but instead an error happening on your side when the query comes in.

Iā€™ve been asked to post this up by Ivan on the Discord.

Thanks for looking into it :pray:

Daniel

1 Like
#2

Did you try with different intervals of delay between requests?
It always happens on same request with the same parameters?

What tool you use to make those requests?

#3

Iā€™ve tried with 0.1s, 2s, and 5s.

It happens on different requests. If I do enough requests (and when I was syncing up several dozen highly active projects there were a lot of requests), eventually this happens. At first I thought it was when I reached a certain offset - but it turns out itā€™s quite random and sometimes happens on the first request.

Iā€™m using Rubyā€™s standard Net::HTTP to make the requests.

#4

I know that you can get that error randomly, but it should not get stuck on that error at the same request.

#5

Can you try with bigger delays? It should work fine with 1s, but I donā€™t know what is the problem of getting stuck.

#6

Sure, I can try setting it to 10 seconds, but then I wonā€™t keep it looping for too long because I do need to get on with syncing the data!..

My guess is when I do this thereā€™s a pile of errors accumulating in your logs - are those recorded somewhere? Can you link them up to e.g. the request above?

#7

Can you skip on error, do the next request and try later again the request that gave the error?

#8

I could but Iā€™d have to write rather awkward code to do so :laughing:

#9

yes we will fix it! :slight_smile:
we are just clarifying the behavior you see

#10

The way Iā€™ve been solving this is just to run the sync a few times - or, on my server, run it every hour, so if a project gets stuck it should be picked up again later. Though that depends how early it gets stuck, annoyingly. Itā€™d be nice to have this solved properly. I might do a resync on that occasion.

#12