# Sync will appear Failed, but cannot reach 100%, what is the general reason?

**URL:** <https://forum.thegraph.com/t/sync-will-appear-failed-but-cannot-reach-100-what-is-the-general-reason/3181>\
**Category:** Questions & Feedback\
**Created:** [March 14, 2022, 8:55am UTC](https://forum.thegraph.com/t/sync-will-appear-failed-but-cannot-reach-100-what-is-the-general-reason/3181 "2022-03-14T08:55:28Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![0xz58](https://avatars.discourse-cdn.com/v4/letter/0/7ba0ec/32.png) [@0xz58](https://forum.thegraph.com/u/0xz58)\
**Post date:** [March 14, 2022, 8:55am UTC](https://forum.thegraph.com/t/sync-will-appear-failed-but-cannot-reach-100-what-is-the-general-reason/3181/1 "2022-03-14T08:55:28Z")

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Sync will appear Failed, but cannot reach 100%, what is the general reason?  
In addition, what is the best way for me to write, deploy, upgrade, and test subgraphs?

Now For Me:

1. graph cli + abi → init a project (Rinkeby)
2. write mapping and schema ,then. codegen and build
3. Token auth and Deploy to upload IPFS and The Graph
4. see on the graph playground

but when I got a error or fail , I need wait sync and then to fix it ?

is there the better way for this ?

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**Author:** ![Ethan](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.thegraph.com/ethan/32/2512_2.png) [@Ethan](https://forum.thegraph.com/u/Ethan)\
**Post date:** [June 30, 2022, 5:33am UTC](https://forum.thegraph.com/t/sync-will-appear-failed-but-cannot-reach-100-what-is-the-general-reason/3181/2 "2022-06-30T05:33:10Z")

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Hi,

I believe you would benefit from the subgraph debug tool developed by Limechain.

> The subgraph debug tool saves developers time during the debug process. Sometimes, when a subgraph is deployed, it fails at specific point in the syncing process. Typically, a developer would need to attempt to fix the problem, redeploy and wait for syncing to complete to see if the problem was fixed.
> 
> The subgraph debug tool allows developers to run their mappings using the store from the failed subgraph. It will run locally on the block the subgraph failed, so that developers can receive feedback on their attempts to fix the problem quickly.
> 
> The tool also allows developers to easily fork and build off existing subgraphs which enables a larger use case for the tool.

You can view the demo of this tool shared at Core R&D Call #10 at 35:48 in this video⬇️

[![](https://us1.discourse-cdn.com/flex020/uploads/thegraph1/original/2X/1/1a59bd9c08718d4afd88a30f5bedd155cc0881c6.jpeg "The Graph - Core Devs Meeting #10") ](https://www.youtube.com/watch?v=eFQohkr328A)

There is also a subgraph testing playlist here⬇️

https://www.youtube.com/embed/videoseries?list=PLTqyKgxaGF3SNakGQwczpSGVjS_xvOv3h&wmode=transparent&rel=0&autohide=1&showinfo=1&enablejsapi=1

Here are some additional resources in The Graph Docs:

- [Quick and Easy Subgraph Debugging Using Forks | Docs | The Graph](https://thegraph.com/docs/en/developer/subgraph-debug-forking/)

- [Unit Testing Framework | Docs | The Graph](https://thegraph.com/docs/en/developer/matchstick/)

If you need more assistance join The Graph’s [Discord](https://discord.gg/vtvv7FP) and direct your question to the subgraph development channel.

Hope this helps,  
Ethan