Facing heap size issue when querying and processing apex logs in LWC component

Question

We are creating a apex log table and users will select a log and we need to show the log body to them. While implementing this we are facing apex heap size issue. From the UI users will select the log id and we will fetch the corresponding log body from the backend. While querying the apexlog we are facing heap size more than 6MB. Please let me know how to retrieve body of the corresponding log and show it in the UI.

Answer 1

If the data is being fetched via apex, you will always run into heap size limitations.

Instead you can do a rest callout from LWC and fetch the log:

https://developer.salesforce.com/docs/component-library/documentation/en/lwc/lwc.js_api_calls

REST api for logs: /services/data/v49.0/sobjects/ApexLog/{ID}/Body

You can use a combination of Apex and rest calls from LWC.

Just pass Ids and Name of the logs from the apex and display, and when user clicks the name or clicks 'Fetch Log' button, fire a callout from LWC with the ID of the debug log , as indicated in the second link.

For fetching vfdomain session id to fire salesforce apis check this link. Also it might be a good idea to pass the whole page content to client side and then filter the session id from that , as passing session id from serer side to client side is not possible. https://salesforce.stackexchange.com/a/111396/45062

This should overcome your heap size limitations, as its on client side.

Some code snippet for your reference:

From Apex side just add your log ids, I have just included session id and instance URL logic.

@AuraEnabled
public static String fetchSessionID(){
    VFDomainData objDomainData = new VFDomainData();
    objDomainData.instanceURL = Url.getSalesforceBaseUrl().toExternalForm();
    String strPageContent = Page.CloudIOOauthHelperPage.getContent().toString();
    objDomainData.sessionIDContents = strPageContent;
    return JSON.serialize(objDomainData);
}
public class VFDomainData{
    private String instanceURL {set; get;}
    private String sessionIDContents {set; get;}
}

---

VFPAge (VFPageHelper):

<apex:page id="VFPageHelper">
    Start_Of_Session_Id{!$Api.Session_ID}End_Of_Session_Id
</apex:page>

---

LWC: modify the below snippet to call the logic when the user clicks a button. Replace the log id with your log id which can be fetched via the event.

    fetchSessionID().then(result => {
        const objResult = JSON.parse(result);
        this.sessionID = objResult.sessionIDContents.substring(objResult.sessionIDContents.indexOf('Start_Of_Session_Id') +
            'Start_Of_Session_Id'.length, objResult.sessionIDContents.indexOf('End_Of_Session_Id'));
        fetch(objResult.instanceURL+'/services/data/v49.0/sobjects/ApexLog/07L7******b5YGaUAM/Body', // End point URL
            {
                method: "GET",
                headers: {
                    "Content-Type": "text/plain",
                    "Authorization": "Bearer " + this.sessionID,
                    "Access-Control-Allow-Origin": '*'
                }
            })
            .then((response) => {
                console.log('response ->>>>>>>>>>> '+response);
                return response.text(); // returning the response in the form of JSON
            })
            .then((jsonResponse) => {
                console.log('jsonResponse ===> ' + jsonResponse);
            })
            .catch(error => {
                console.log('callout error ===> ' + error);
            })
    }).catch(error => {
});