14
February
2022
Engineering

How 40 Lines of Code Improved Our React App’s Performance by 70%

On Appsmith, developers can quickly build any custom business software with pre-built UI widgets that connect to any data source. These widgets can be controlled with JavaScript. We created this framework to help developers save on valuable time building complex applications for internal uses within their organizations. For this to work for everyone, we believe that the core parts of Appsmith need to run smoothly and should be continuously improved.  Appsmith’s UI is built using React, Redux, Web Workers, Immer among other things. 


In this blog, Sathish Gandham, a frontend engineer focusing on UI performance at Appsmith, will talk about how we improved the editing experience on Appsmith.

What is the Editing Experience on Appsmith? 

The editing experience on Appsmith involves writing bits of code to customize the functionality of the widgets and writing special commands and actions into the application. It is a crucial function in the Appsmith framework. 

Lag and Delay 

Building an application on Appsmith involves dragging and dropping widgets onto the canvas and writing custom code on the editor; however, we noticed that while editing text/code in the canvas, the editor would often freeze, resulting in a less than optimal user experience. When building an application, there should be no delay or lag. This was a huge issue that needed our immediate attention from an engineering perspective. For a natural typing experience, users want the keypress latency to be under 100ms, though 50ms would be ideal. 

To solve this problem, we needed to understand what happens when a user types. For this, we used: 

React profiler: This measures how often components in the application render and the “cost” of rendering. The profiler helps in identifying parts of an application that are slow. In our case, this allowed us to understand what components were rendered as we typed. 

Chrome Performance tools: This helped us quantify the problem, measure our progress, find the code taking longer to execute, and find unnecessary repaints. 

Please note that the React profiler is part of the React Developer tools browser add-on which is available for Chrome and Firefox.

From the React profiler, we see three pairs of long commits; each of these corresponds to the following property pane, and UI widget renders. Ideally, the property pane should render much faster than the canvas since there is nothing changing in the property pane except the input we are editing. Even the canvas should be rendering the widgets currently in use and not the rest. We realized that this was not the case and needed to be fixed. 

We profiled the property pane issue in isolation to identify what it takes to render it. For this, we used the performance tab in Chrome DevTools to see what happens when the property pane opens. This gives us some helpful information. 

  • ComponentDidMount of code editor is taking a lot of time 
  • Styles are also taking a long time to render
If you see the property pane commit in the screenshot above, you will notice that evaluatedValuePopup also takes significant time.


Here’s how we listed the tasks that lay ahead of us: 

  1. Identify as to why all the widgets were rendering when they don’t have to and fix it
  2. Optimize the code editor [Not apparent from the React profiles]
  3. Identify why all the controls in the property pane are rendering and fix it
  4. Optimize the global styles
  5. Optimize the evaluatedvalue pop-up

In this blog, I will talk about how we went about the first task. Before I get to that, here are a few tips for profiling: 

  • Try to split your problem into smaller pieces and profile them. With this, you won’t crowd your profile, and you can find the performance issues with ease. 

Example 1: To improve the editing experience, we just profiled a single keypress. 

Example 2: To profile a drag and drop action, we can split that into drag start, move, and drop.

  • Leave the application idle for 5 seconds after starting the profile and before stopping it. It will make it very easy to identify the work that has been done. [See A & C From profile above]
  • To measure the overall performance improvements, instead of measuring each optimization individually, it’s better to consider focussing on the overall scripting and time taken to render during an action. You can get this number from the chrome performance tab. [B & D from profile above]
  • In the React profiler, don’t just focus on the large commits. Go through each commit at least once, and see what’s getting rendered in that commit. The chances are that one or two small components are accounting for all those renders.

Here’s a short guide on reading the React profile: 

  • A: List of commits during our profile
  • B: The commit we are looking at
  • C: Details about the selected component (WidgetsEditor). Our widgets editor rendered three times during the profile at 6.1s, 8.6s, and 14.1s. 102ms, 328ms,83.1ms is the duration each commit took; it is not the total time the selected component took to render.
  • D: Zoomed in view on the component we selected and its children.

Here are the notes on the profile based on which we worked on improving the editing experience. You can download the attached profile and import it in your React profiler to follow along or just refer to the image above.

Please note that the React profiler is available only when you open a react app in dev mode in Chrome/Firefox, if you don’t have a local React development set up, you can use the standalone React developer tools to read the profile. 

Here are instructions on how to install it and start it: 

Install

# Yarn

yarn global add react-devtools

# NPM

npm install -g react-devtools

Run

react-devtools

Follow this link to read the detailed notes from the profile we did to improve the editing experience on Appsmith. 

I’ve put some notes here for your reference: 

1. Evaluated value opening. Not related to editing.

2. Widgets editor, not sure why.

3. Editor focused. We should be able to avoid the rest of the property pane from rendering.

4. Small changes to property pane, its header, lightning menu, and action creator. Nothing changes for them, so they should not be re-rendering. Memoization can help here.

5. Same as above. 

6. We get the evaluated value back. Entire widgets editor is re-rendered (Deduced this from one of the two updates to table), we can optimise this

- If each widget subscribes to its data independently, we should be able to avoid the unnecessary renders of the widgets by

- Doing a deep check at the widget level

- update the store with only values that changed. 

7. PropertyPane is rendered with the updated value. EvaluatedValue taking most of the time.

8. From 8 to 17, these are commits like 4 & 5 above. 

9. 18 & 19 are widgets editor and property pane. I don’t see why these are required. I will look into it. 



Widgets Render When Not Needed


One of the most loved features of Appsmith is reactive updates. With reactive updates, you can see the widget change and show data. With traditional programming, you would have to reload the page in order to see the update in the widget. This is achieved by updating the data tree as and when you change something on the canvas and using the updated data tree to re-render the app. Due to the amount of data we have and the number of calculations we need to do, it took a long time and blocked the main thread.

To solve this problem, we moved the evaluations to a web worker freeing the main thread. A brilliant move to solve the problem at hand, but this created a new issue. The problem here was due to object reference changing. Since the data tree is coming from the worker, we would always get a new reference for every item in the tree even though only some of them changed. This reference change was making all the widgets re-render unnecessarily.


A few approaches we tried to solve this problem were:

  1. Get what keys changed from the worker (worker has this information) and update only those values in the reducer. This did not work because the list of keys was not complete. 
  2. Compute the diffs between the current data tree and the one received from the worker and update only what changed. Though this prevented the renders, we did not improve the overall scripting time we measured earlier. The reason is, computing the diffs itself took a lot of time, which would happen twice for each change.


Web Worker to the Rescue 


We moved the task of computing the diffs to the worker and used the deep-diff library to compute the diffs and let immer take care of immutability.

This helped us in two ways:

  1. Offloaded the expensive task of computing the diffs on the main thread.
  2. Reduced the size of the data we transfer between worker and the main thread (this was never a bottleneck for us, though).


This change alone brought down the keypress latency by half.


Instead of replacing the entire data tree from the worker, we get the only changes (updates) and apply them to the current state. applyChanges is a utility method from deep-diff. Immer takes care of the immutability.


If there’s anything to be said about performance improvement, it’s this, don’t take performance for granted and profile your code on a regular basis. Even a few lines of change or configuration can lead to a great performance gain. 



I hope you found this blog helpful. If you’d like to get in touch with Satish, ping him on Discord or visit his website.

How 40 Lines of Code Improved Our React App’s Performance by 70%

Share this

On Appsmith, developers can quickly build any custom business software with pre-built UI widgets that connect to any data source. These widgets can be controlled with JavaScript. We created this framework to help developers save on valuable time building complex applications for internal uses within their organizations. For this to work for everyone, we believe that the core parts of Appsmith need to run smoothly and should be continuously improved.  Appsmith’s UI is built using React, Redux, Web Workers, Immer among other things. 


In this blog, Sathish Gandham, a frontend engineer focusing on UI performance at Appsmith, will talk about how we improved the editing experience on Appsmith.

What is the Editing Experience on Appsmith? 

The editing experience on Appsmith involves writing bits of code to customize the functionality of the widgets and writing special commands and actions into the application. It is a crucial function in the Appsmith framework. 

Lag and Delay 

Building an application on Appsmith involves dragging and dropping widgets onto the canvas and writing custom code on the editor; however, we noticed that while editing text/code in the canvas, the editor would often freeze, resulting in a less than optimal user experience. When building an application, there should be no delay or lag. This was a huge issue that needed our immediate attention from an engineering perspective. For a natural typing experience, users want the keypress latency to be under 100ms, though 50ms would be ideal. 

To solve this problem, we needed to understand what happens when a user types. For this, we used: 

React profiler: This measures how often components in the application render and the “cost” of rendering. The profiler helps in identifying parts of an application that are slow. In our case, this allowed us to understand what components were rendered as we typed. 

Chrome Performance tools: This helped us quantify the problem, measure our progress, find the code taking longer to execute, and find unnecessary repaints. 

Please note that the React profiler is part of the React Developer tools browser add-on which is available for Chrome and Firefox.

From the React profiler, we see three pairs of long commits; each of these corresponds to the following property pane, and UI widget renders. Ideally, the property pane should render much faster than the canvas since there is nothing changing in the property pane except the input we are editing. Even the canvas should be rendering the widgets currently in use and not the rest. We realized that this was not the case and needed to be fixed. 

We profiled the property pane issue in isolation to identify what it takes to render it. For this, we used the performance tab in Chrome DevTools to see what happens when the property pane opens. This gives us some helpful information. 

  • ComponentDidMount of code editor is taking a lot of time 
  • Styles are also taking a long time to render
If you see the property pane commit in the screenshot above, you will notice that evaluatedValuePopup also takes significant time.


Here’s how we listed the tasks that lay ahead of us: 

  1. Identify as to why all the widgets were rendering when they don’t have to and fix it
  2. Optimize the code editor [Not apparent from the React profiles]
  3. Identify why all the controls in the property pane are rendering and fix it
  4. Optimize the global styles
  5. Optimize the evaluatedvalue pop-up

In this blog, I will talk about how we went about the first task. Before I get to that, here are a few tips for profiling: 

  • Try to split your problem into smaller pieces and profile them. With this, you won’t crowd your profile, and you can find the performance issues with ease. 

Example 1: To improve the editing experience, we just profiled a single keypress. 

Example 2: To profile a drag and drop action, we can split that into drag start, move, and drop.

  • Leave the application idle for 5 seconds after starting the profile and before stopping it. It will make it very easy to identify the work that has been done. [See A & C From profile above]
  • To measure the overall performance improvements, instead of measuring each optimization individually, it’s better to consider focussing on the overall scripting and time taken to render during an action. You can get this number from the chrome performance tab. [B & D from profile above]
  • In the React profiler, don’t just focus on the large commits. Go through each commit at least once, and see what’s getting rendered in that commit. The chances are that one or two small components are accounting for all those renders.

Here’s a short guide on reading the React profile: 

  • A: List of commits during our profile
  • B: The commit we are looking at
  • C: Details about the selected component (WidgetsEditor). Our widgets editor rendered three times during the profile at 6.1s, 8.6s, and 14.1s. 102ms, 328ms,83.1ms is the duration each commit took; it is not the total time the selected component took to render.
  • D: Zoomed in view on the component we selected and its children.

Here are the notes on the profile based on which we worked on improving the editing experience. You can download the attached profile and import it in your React profiler to follow along or just refer to the image above.

Please note that the React profiler is available only when you open a react app in dev mode in Chrome/Firefox, if you don’t have a local React development set up, you can use the standalone React developer tools to read the profile. 

Here are instructions on how to install it and start it: 

Install

# Yarn

yarn global add react-devtools

# NPM

npm install -g react-devtools

Run

react-devtools

Follow this link to read the detailed notes from the profile we did to improve the editing experience on Appsmith. 

I’ve put some notes here for your reference: 

1. Evaluated value opening. Not related to editing.

2. Widgets editor, not sure why.

3. Editor focused. We should be able to avoid the rest of the property pane from rendering.

4. Small changes to property pane, its header, lightning menu, and action creator. Nothing changes for them, so they should not be re-rendering. Memoization can help here.

5. Same as above. 

6. We get the evaluated value back. Entire widgets editor is re-rendered (Deduced this from one of the two updates to table), we can optimise this

- If each widget subscribes to its data independently, we should be able to avoid the unnecessary renders of the widgets by

- Doing a deep check at the widget level

- update the store with only values that changed. 

7. PropertyPane is rendered with the updated value. EvaluatedValue taking most of the time.

8. From 8 to 17, these are commits like 4 & 5 above. 

9. 18 & 19 are widgets editor and property pane. I don’t see why these are required. I will look into it. 



Widgets Render When Not Needed


One of the most loved features of Appsmith is reactive updates. With reactive updates, you can see the widget change and show data. With traditional programming, you would have to reload the page in order to see the update in the widget. This is achieved by updating the data tree as and when you change something on the canvas and using the updated data tree to re-render the app. Due to the amount of data we have and the number of calculations we need to do, it took a long time and blocked the main thread.

To solve this problem, we moved the evaluations to a web worker freeing the main thread. A brilliant move to solve the problem at hand, but this created a new issue. The problem here was due to object reference changing. Since the data tree is coming from the worker, we would always get a new reference for every item in the tree even though only some of them changed. This reference change was making all the widgets re-render unnecessarily.


A few approaches we tried to solve this problem were:

  1. Get what keys changed from the worker (worker has this information) and update only those values in the reducer. This did not work because the list of keys was not complete. 
  2. Compute the diffs between the current data tree and the one received from the worker and update only what changed. Though this prevented the renders, we did not improve the overall scripting time we measured earlier. The reason is, computing the diffs itself took a lot of time, which would happen twice for each change.


Web Worker to the Rescue 


We moved the task of computing the diffs to the worker and used the deep-diff library to compute the diffs and let immer take care of immutability.

This helped us in two ways:

  1. Offloaded the expensive task of computing the diffs on the main thread.
  2. Reduced the size of the data we transfer between worker and the main thread (this was never a bottleneck for us, though).


This change alone brought down the keypress latency by half.


Instead of replacing the entire data tree from the worker, we get the only changes (updates) and apply them to the current state. applyChanges is a utility method from deep-diff. Immer takes care of the immutability.


If there’s anything to be said about performance improvement, it’s this, don’t take performance for granted and profile your code on a regular basis. Even a few lines of change or configuration can lead to a great performance gain. 



I hope you found this blog helpful. If you’d like to get in touch with Satish, ping him on Discord or visit his website.

What’s a Rich Text element?

The rich text element allows you to create and format headings, paragraphs, blockquotes, images, and video all in one place instead of having to add and format them individually. Just double-click and easily create content.

  • xvcmbmvkmnkmbknmbkmlnj
  • A rich text element can be used with static or dynamic content. For static content, just drop it

A rich text element can be used with static or dynamic content. For static content, just drop it into any page and begin editing. For dynamic content, add a rich text field to any collection and then connect a rich text element to that field in the settings panel. Voila!

  1. A rich text element can be used with static or dynamic content. For static content, just drop it into any page and begin editing. For dynamic content, add a rich text field to any collection and then connect a rich text element to that field in the settings panel. Voila!

How to customize formatting for each rich text

Headings, paragraphs, blockquotes, figures, images, and figure captions can all be styled after a class is added to the rich text element using the "When inside of" nested selector system.

ksnopirirfnb [aorewmb[oiewsn b[opebr
  1. then connect a rich text

dfbstjsrykmsry

Square
Try Appsmith
Debugging your apps in Appsmith with the Appsmith Debugger, part 2
27
September
2022
Product

Debugging your apps in Appsmith with the Appsmith Debugger, part 2

Debugging your apps in Appsmith with the Appsmith Debugger, part 2
Ayush Pahwa
0
 minutes ↗
#
product
#
errors
#
troubleshooting
#
debugger
Product
Meet the sidekicks, Logs and Inspect Entity

The first part of this teardown helped you see how the Error pane can save you hours in debugging and build better internal apps. In this one, let’s meet two seemingly innocuous features that can give you debugging super-powers when used right.

Logs

The Logs pane shows you everything logged by Appsmith and, like Errors, in lockstep with the sequence of code execution in your build. Borrowing from the experience of showing logs in general—in the browser console, from a shell, or on your favorite IDE—the Logs pane has four views for specific debugging use cases.

Post_5.jpg (1920×1080)

All Logs

This view shows you all logs timestamped by when we saw them in your Appsmith session. Updated a widget’s property? Wrote a new action to your GraphQL datasource? Ran a JS Object to concat two queries? It all gets logged, including the errors you see in the Errors pane, in a separate view called Error Logs. You will see how that can be useful in a GIF, pun intended.

The All Logs view can be a little overwhelming, though, and a bit of work when you have been at your build for a while. For easier tracking of relevant logs, use one of the three options below.

Post_6.gif (1440×810)

Errors Logs

Everything you learned about the Errors pane applies to this view, too, but there’s more to this view. Here's a likely scenario to show that.

State #1

You have a button to reload a table, presumably to refresh the data from your datasource.

Condition #1

You use the Button property, onClick, which runs the query to fetch the latest data into the table.

Scenario #1

Your query fails.

- On just the Error pane

  • You see just the error for the failing query. Although helpful, it doesn’t offer context for the before and after of the error.

- On the Error Logs pane under Logs

  1. You see logs for the Button click and the executed onClick event .
  2. Because the onClick property is binded to queries and JS Objects, you see the ones that are successfully executed and those that fail.
Error_Logs__Appsmith.gif (1440×810)

The triaging in our example above is especially useful when you have nested queries, several dependent bindings, and a more complex workflow overall.

Console Logs

console.log_in_the_Editor__Appsmith.jpg (1920×1080)

Just introduced in the Debugger, console methods in Appsmith help you see statements for just JS Objects and JavaScript bindings so much better than in the browser sub-window.

Set points in your code that you want to log statements at, view tabular data, or see groups for repeated errors.

System Logs

Post_7.jpg (1920×1080)

Automatically tracking all your interactions with Appsmith during build, System Logs show a helpful trail of activity by descending order of timestamp, especially useful when you want to go back in time or pivot from a point of failure to everything that led to it.

They show up for different situations and interactions for the type of entity you are working with.

With widgets, you see a log when you

  • Drag-and-drop a new widget on the canvas.
  • Update the widget’s properties
    Updating a property also updates all its dependent properties which then show up in System Logs.
Dependent_properties_updates_in_system_logs__Appsmith.gif (1280×720)
For example, when you update the tableData property, you also see its dependent properties like selectedRowIndex, filters, triggeredRowIndex, and so on.
  • Trigger events with an end-user action.
Trigger_events_with_an_end-user_action__Appsmith.gif (1280×720)
For example, when you are using an end-user action to store a value with storeValue or when you want a click-action to trigger an operation like an update or delete and are using onClick, you see them show up in System Logs.
  • Delete a widget from the canvas

With actions, you see them when you

  • Create a new datasource or a query
  • Update query properties like queryName, queryBody, queryConfiguration, and queryProperties.
  • Execute a query
Execute_a_query.gif (1440×810)
This can be either from query pane, running a plain REST API query, a JS Object, or via a widget’s bindings.
  • Delete a query

With JS Objects, you’ll see system logs when you

  • Create and update code inside JS Objects
  • Execute JS Objects
Execute_JS_Objects.gif (1440×810)

Just like errors, system logs are native to entities and have four parts to them.

Parts_of_a_system_log_line__Appsmith.jpg (1920×1080)

The timestamp

Logged as your entities are created, updated and deleted, these little breadcrumbs help you track back from when the error occurred to when it was last A-Okay.

Timestamped_logs_in_System_Logs.gif (1440×810)

The message

Useful during build, the message of the log answers two questions— what were you doing with an entity—creating it, updating it, deleting it—and what happened with your action—success or failure.

  • With widgets, outside of CRUD information, you also see event-specific info like onClick and showAlert linked to those widgets.
  • Queries and JS Objects are straightforward with start and end points that indicate if they were updated, ran, and failed.

The source

Like errors, a system log has two parts to its source—the entity’s name.the type of entity, e.g., SELECT1.TABLE1.WIDGET.

Redirect_from_an_Inspect_Entity_sub-window.gif (1440×810)
👌🏽 Appsmith Experience plug

Clicking the source from the logs takes you to the associated entity anywhere in Appsmith, be it a widget, a query, or a JS Object. Noice!

The response

This doesn’t always show, but when it does, it can be useful confirmation of a binding working, a query running successfully, or a JS Object executing completely.

  • For widgets, you see which properties are updated when you are configuring them and how.
    Say you’re updating the text widget’s background property and you don’t see it change on the canvas. Track the log to the response for a quick confirmation of that and troubleshoot the canvas next.
  • For queries, you’ll see two different logs—the start of a query run and the status of its execution.
    The first type of log will show you configuration details of the query—helpful to verify if the config matches the request.        

{
    "timeoutInMillisecond":10000
    "paginationType":"NONE"
    "encodeParamsToggle":true
    "body":"SELECT * FROM public."users" LIMIT 10;"
    "pluginSpecifiedTemplates":[
        0:{
            "value":true
        }
    ]
}

  • The second type will throw an error if the run fails. When the query runs successfully, it shows all the parameters that the query ran with and the time taken for the response.

{
	"response" : [...],
	"request" : {
		"actionId" "6321c1193668£71e£7caala2"
		"requestedAt" : 1663912830.640344
		"requestParams": {...}
}

  • With JS Objects, you see the response from the function as a JSON after an object is successfully run. This shows you how Appsmith handles the function while evaluating and running it and can be useful for spotting conflicts, undefined references, or troublesome variables.

Inspect Entity

Borrowing from a modern browser’s Inspect Element feature, Inspect Entity lets you see incoming and outgoing entities for any widget. These entities can be queries, JS Objects, or even other widgets.

Group_8480.png (1920×1080)
  • Incoming entities are those that fetch data from the datasource into the widget.
    For example, if the data on a table is populated by a Postgres query, you’ll see the query name under the Incoming entities column.
  • Outgoing entities are those that can specify the data that’s to be sent to the datasource in a typical CUD operation and then send it to your datasource.
    Say, a text widget is binded to a table's selectedRow property, you will see the text widget’s name under the Outgoing entities column.

The Inspect Entity pane lets you see dependencies for all your widgets on the canvas, especially useful if you have a medium-complex app with several widgets working off of each other. For example, when you have a parent widget or query that controls bindings on other dependent widgets---call them children widgets---, Inspect Entity can show you all those children when you click the parent and quickly take you to any one of them directly.

In combination with Errors, Logs and Inspect Entity round out the Debugger for several scenarios during build and save you hours in building an app end-users love. Try out the Debugger and let us know how you like it, what it's missing, and what we can improve. Our Discord is the best place for that feedback.

The Appsmith Debugger now supports Console methods
23
September
2022
Announcement

The Appsmith Debugger now supports Console methods

The Appsmith Debugger now supports Console methods
Rishabh Rathod
0
 minutes ↗
#
debugger
#
troubleshooting
#
console-methods
Announcement

For a while now, you have used and loved the Appsmith Debugger, nearly complete with a Error pane, system and error logs, and an entity inspector. We say nearly complete because it was missing one of the most popular debugging tools in a dev’s toolkit—console methods.

We are happy to announce the availability of console methods for both cloud users and self-hosters on v1.8.0.

“But, what is the Appsmith Debugger?”

Image_1.png (1920×1080)

Think of the Appsmith Debugger as a set of Chrome DevTools—like for Appsmith. It lives on the familiar 🐞 everywhere in Appsmith and

  • shows helpful error messages for bindings, queries, and variables
  • lets you inspect entity relationships
  • filters system and user logs

All of this is helpful when debugging unexpected API responses or app viewer experiences. Should you care to learn more, this post breaks down the debugger by each one of its features.

“Okay, and console methods are…”

Just one of the most popular ways of print debugging in modern browsers, console methods, exposed by the console API, are a set of functions that help you log the values of variables at set points in your code, messages, or even tabular data so you can investigate them in your browser’s debugging console.

Before today, you could use all supported browser console methods, but only in the browser’s dev tools sub-window. To any developer with their hands dirty with front-end code, the browser debugging subwindow is a necessary evil—a thousand lines of errors, messages, values, and steps that you would have to sift through. We are not going to say, “Looking for the literal needle in the haystack”, but you know you are thinking it.

“And the Appsmith Debugger has a console now?”

Yes! 🥳

So, instead of something like,

you now see,

Image_3.png (1920×1080)

Sweet? This gets sweeter.

Supported methods

  • log

Almost synonymous with console, the .log() method is one of the most popular ways to log a message or the values of variables defined in your Javascript.

It can also be used to show helpful messages or comments, say, the entry and exit points of functions.

Example


getUUID: () => {
		console.log("entry - getUUID function");
		let prefix;
		
		let d = new Date().getTime();
		console.log("new date created -", d);
		d += (parseInt(Math.random() * 100)).toString();
		console.log(d, "random number generated by getUUID")
		if (undefined === prefix) {
			prefix = 'uid-';
		}
		d = prefix + d;
		console.log("UUID created -", d);
		console.log("exit - getUUID function")
		return d;
	}

Result

Image_4.png (1920×1080)
  • error

the .error() method logs an error message to the Appsmith console, be it a a string like, “This is an error message” or the value of a function.

Say you've written a function and you suspect it’s returning an error., but you don’t know what kind. For unknown unknowns like this, `error` comes handy.

Example


checkTextWidget: () => {
		const element = Text1.text;
		if (element == "") {
			console.error("There is an error. The Text property is empty ");
		}
		return element;
	}

Result

Image_5.png (1920×1080)
  • warn

Jus as .error() aids error investigations, .warn() shows, well, warnings for known knowns. Some situations this can come in handy are,- When the evaluated value of binded data on a widget is not using the same datatype as the expected value- When widgets continue to use deprecated queries or functions- When the timezone used in a datetime functions doesn't match the browser’s

Example


selectDefaultValue: () => {
	 const defaultValue = Select1.selectedOptionValue;
		if (defaultValue == ""){
			console.warn("No values selected on Select1 widget ")
		}
		return defaultValue;
}

Result

Image_6.png (1920×1080)
  • table

table (.) just does what it says—logs a Table widget’s data in key-value pairs for rows as objects. While we support this in Appsmith, we are still working on a browser console-like table, especially as we make the Table feature-richer.

Example


table1DataFunc: () =>{
		const data = Table1.tableData;
		console.table(data)
}

Result

Image_7.png (1920×1080)

That’s it! You now have the power of the console right within in Appsmith. There are other useful views available under Logs and we'll talk about them in a follow-up to the Debugger teardown soon. Bookmark this page. Thank us later.

Debugging your app in Appsmith with the Appsmith Debugger, Part 1
20
September
2022
Product

Debugging your app in Appsmith with the Appsmith Debugger, Part 1

Debugging your app in Appsmith with the Appsmith Debugger, Part 1
Ayush Pahwa
0
 minutes ↗
#
product
#
errors
#
troubleshooting
#
debugger
Product

That title is a tongue twister, innit? Almost.

Here’s a meme that isn’t. It’s just the painful truth.

Debugging_is_like_being_lost_in_a_deser.jpg (749×500)

There is no perfect code, so you know debugging is inevitable, but it’s still a chore and is as crushing often times as the meme claims it is.

But, while debugging is inevitable, making it painful is optional, especially when you have the Appsmith Debugger. We have claimed we champion developer experience as many times as we could before without being brazen about it. We think. So, we thought some more and said, “Let’s prove the claim, too.”

“Wait, wait. What is the Appsmith Debugger?”

In 2021, we shipped the Appsmith Debugger, a set of Chrome DevelTools-like features that have helped you investigate and resolve errors in Appsmith.

We recorded a video for it in a series about the Debugger, talked about it in our docs, and referenced it enough times to make you groan about our obsession with errors. If this is the first you are hearing of it, get on our Discord so we can tell you some more about it.

Why we did this

Browser dev tools are as helpful as a magnet when looking for iron fillings in a pristine haystack. To the untrained eye, they can be downright criminal, too.

Browser_debugger.jpeg (960×506)
Source: Reddit

Sure, sure, they nest groups of errors and there are separate tabs for the console and the debugger, but meh! There’s a sea of error messages, system logs, console logs, and then there’s you swimming in it.

Before we shipped the debugger, you saw,

  • errors inside a widget's Property pane that floated on your canvas which probably already had several widgets
  • the Editor’s Response pane, which clubbed legit responses with errors

The Debugger solved several of those problems.

Post_8.jpg (1920×1080)

What’s the Debugger have

Available on app.appsmith.com and our self-hosted release images, it can be called by toggling the debug icon—the one that looks like a bug—on the bottom-right corner of your Appsmith screen or with CTRL/CMD +D.

Inside the Debugger, live three panes, Errors, Logs, and Inspect Entity, each with their own uses. In the first part of this two part post, we will break the Error pane down for you and see how it can save you hours over browser dev tools in debugging.

If you would much rather just learn about Logs and Inspect Entity, bookmark this post. We will link to Part 2 in five days. :-)

Errors

Borrowing from a browser’s dev tools sub-window but improving on it radically, the Error pane lists all errors that we see when you are building inside Appsmith. Familiar examples include syntax errors from JavaScript bindings, reference errors from queries, and datatype mismatch errors.

Errors in the pane are specific to an Appsmith entity. Translated from Appsmithlish, it means you see helpful error messages about a faulting widget, a rogue query, or a stubborn JS Object.

Untitled.gif (1440×810)
Example of a faulting widget and the error beaconing it
Untitled.gif (1440×810)
A JS Object error

  • These errors get logged to the pane in lockstep with the sequence of code execution in Appsmith.
  • The Error pane is the default view when working with widgets—most noticeable if you have the Debugger sub-window resized as in the pictures in purple—so you know what’s going wrong and where in real-time.
  • The Editor's Error Pane is smarter. It doesn’t automatically switch to the Error pane—Response is the default on this screen—when an error occurs. Instead, the Debug icon lights up in red with a numeric notification that’s like a running ticker for the number of errors the Debugger sees with your queries or JS Objects. Click it to open the Error pane.
  • Every error you see in the pane follows a template with a few helpful pieces of info to help you debug.
image_high.jpeg (1920×1080)
Numbers on this image correspond to bullets below. Images in sub-bullets below show what the sub-bullet talks about.

The timestamp

Logged as your code executes or a value evaluates with your widgets, these little breadcrumbs help you track back from when the error occurred to when last it was A-Okay.

The issue

Depending on the error type, you will see a couple different kinds of issues.

  1. With widgets, you’ll see the faulting widget property’s name. An example of this is the commonplace The value at tableData is invalid, occurring when the property tableData expects an Array<Object> datatype but you have an Array<List> instead.
  2. With queries, you see more specific errors, often specific to the datasource you are running your queries to, often indicated by status codes returned by your failing requests.
  3. With JS Objects, we straight-up level with you about the parseability of your functions. Parseability probably isn’t a word, but you know what we mean.

The source

This has two parts to it—the entity’s name.the type of entity the troublesome one is, e.g., SELECT1.WIDGET. As is obvious and has been to you, SELECT1 is the entity’s name and WIDGET is the entity type.

👌🏾 Appsmith Experience plug: Clicking the source takes you to the faulting entity anywhere in Appsmith, be it a widget, a query, or a JS Object. Noice!

The message

This is the most helpful part of the message, beginning with Error and ending with a helpful bit of text or a number.

  1. Because widgets bind to queries or JS Objects using JavaScript, quite a few errors you see are the same as familiar JavaScript errors like SyntaxError or TypeError. Some other errors show is not defined. This is when a variable, a query, or a JS Object isn’t defined, but you have specified it in the Property pane.
  2. In the Editor, these messages go a step further and call out the line number in the editor that has the faulting code. For example, Line 2: Unrecognized token '$'. This type of message has three parts to it.
Post_9.jpg (1920×1080)

1. The type: Error

2. The string: relation “public.user” does not exit

3. The line number: Position 15

😻 Appsmith Experience plug: Clicking the message will open our in-app docs finder and run a helpful search to show you top docs matching the error.

Response from queries or bindings

This doesn’t always show, but when it does, it can show you helpful responses with query params or evaluated values of data bindings.

Post_10.jpg (1920×1080)
  1. With widgets, you’ll see the evaluated value from the bindings.
  2. With queries, you’ll see the payload from the API you are querying.

“How does all of this help?”

Consider two situations we have painfully drawn for you.

State #1

You have several queries and widgets on your way to a complete build.

Condition #1

You have nested queries inside JS Objects. Meaning, these queries are binded to multiple widgets via JavaScript transformations and have dependent parameters with each other.

Scenario #1

A query fails and returns an error.

Without the Appsmith Debugger

You decide to sift through the browser dev tools sub-window, trying to locate the faulty query in something that looks like ↓.

The_browser_console.png (1920×1080)

When you find the first problem query, you’re hoping against hope this is your patient zero.

  1. If so, congratulations aren’t quite in order yet. You’re still going to have to surgery the query to see what went wrong where.
  2. With browser tools, may you be lucky and find a fix in the first hour.

Most times, though, Murphy’s Law applies.

  1. Meaning, you will need to find the last problem query.
  2. Repeat steps #1 and #2 with all the sub-steps in between

If you have a friend who’s on Appsmith, you hear them say, “Good morning. Do you have a ready app? No? Try the Debugger. 🙄”

With the Appsmith Debugger

You see all the errors from all the failed queries In the Error pane and nothing else to crowd your investigation.

  1. You quickly scan by the type of errors.
  2. Errors are listed in the sequence of query execution.
Post_11.jpg (1920×1080)
So you can simply scroll to the first failed query, and investigate further.

  1. The error message tells you what failed with the params in which line, neatly indented neatly for you.

Don’t remember the query’s name? Pfft! We got it. Click the error message, and go right to the error source.

Trouble troubleshooting? Click the error message and find super-relevant docs in Appsmith’s doc finder.

At the end of it, you save a whole night’s hair-pulls, wake up bright and fresh, sip your coffee, and wonder why some people still use browser dev tools. 🤔 Maybe you should refer them to us.

State #2

You have the data from a REST API and the table for your dashboard, but you have left the chart for the very end. You are sensible like that. Charts are tricky things in general.

Condition #2

You have to bind the chart widget from Fusion Charts or one of our defaults with a query that should output the format Array<{ x: string, y: number Required }> as input to the widget. This will need JavaScript transformations.

Scenario #2

You get a datatype mismatch error.

Without the Appsmith Debugger

You toggle around the floating EXPECTED STRUCTURE, EXPECTED STRUCTURE - EXAMPLE, and EVALUATED VALUE panes to understand the chart widget’s configuration.

You have a JS Object for the transformation, so you now switch back and forth between the canvas and the JS Editor for each possible fix in the JS code.

  1. By now, you have console.loged your way to the browser tools sub-window. Magnet, meet Iron Fillings In A Haystack.
  2. Forgot the change you made to the JS Object five tries ago? Yeah, well, no System Logs, so what can you do, right? Maybe note each change on Sublime or VS Code from this point on.

With the Appsmith Debugger

Post_12.jpg (1920×1080)

Right after you run the transformation, you see the floating-pane-that-we-don’t have-a-name-for-yet show you some red and the Error pane light up with all your errors, timestamped and sequenced by the order of code execution.

  1. You see the type of error and the evaluated value for the faulting entity. Stick to this without worrying about the unnamed floating pane.
  2. Your query has trouble getting a response from your datasource, so you see that error, but hey, you also see the binding failure of that same query with the widget.
  3. No hunting for the query or the widget you want to troubleshoot. One click from the Debugger and you are transported to the associated entity.
Debugger_with_click-actions__JS_Editor.jpg (1920×1080)

You see all the errors from the transformation in one pane with click-actions for each one of them.

Docs_finder_from_Response__Appsmith.gif (1440×810)

Error messages not enough? Click the error and choose, Browse code snippets, and voila! You now now search for the chart + the query right there and see some of our helpful docs.

Made it to here? Your life inside Appsmith is going to change.

Also, this is just part one of this two-part breakdown. What’s next?

https://media.giphy.com/media/3kIGmlW0lvpnmF3bGy/giphy.gif

Better than post-credits. A whole other movie featuring Logs and Inspect Entity. Meanwhile, here’s a few things you can do.

Until the next Debugger post, Appsmiths.

P.S.: We love you.