[Salesforce]Failed to load data Log from Salesforce.com: Salesforce automatically deletes system logs 24 hours after they’re generated. If the log you had open was less than 24 hours old, someone deleted it. To save logs, select File > Download Log.

「Failed to load data Log from Salesforce.com: Salesforce automatically deletes system logs 24 hours after they’re generated. If the log you had open was less than 24 hours old, someone deleted it. To save logs, select File > Download Log.」エラー対応方法例を紹介します。

エラー

解決法の一つの例

DeveloperConsoleFix.page作成

<apex:page docType="html-5.0" id="thepage">
  <script src="//cdnjs.cloudflare.com/ajax/libs/jsforce/1.7.0/jsforce.min.js"></script>
  
  <p>
Yes, "Delete my IDEWorkspace" sounds a little scary. But that's actually what this script will do.
The developer console state is maintained in a record in table IDEWorkspace. 
When that record is deleted, there is no state. If the dev
console decides to save something, it notices that and creates a new record.
  </p>
  
  <p>
This is not really documented anywhere. You can learn a little bit by reading
the Salesforce help article <a href="https://help.salesforce.com/articleView?id=000205964&language=en_US&type=1">Developer Console menus not working</a>
The API we are using is the 
<a href="https://developer.salesforce.com/docs/atlas.en-us.api_tooling.meta/api_tooling/">Tooling API</a>. 
The documentation merely notes that "The following
Tooling API objects are used internally by the Developer Console."

  </p>
  
  <apex:form id="theform">
  <apex:pageblock id="thepageblock">
  <apex:pageblockButtons location="top" id="buttons">
    <apex:commandButton value="Delete my IDEWorkpace" 
        onclick="deleteIDEWorkspace()"
        disabled="True"
        id="deletebutton"
     />
  </apex:pageblockButtons>  
  <apex:pageBlockSection id="section">
    <apex:pageblocksectionitem id="item1">
        <apex:outputlabel value="IDEWorkspace ID:" styleclass="bold"/>
        <apex:outputtext value="not found" id="IdDisplay" />
    </apex:pageblocksectionitem>

  </apex:pageBlockSection>
  </apex:pageblock>
  </apex:form>
  
  <apex:outputPanel id="emptypanel">
  </apex:outputPanel>

  <script>
      var conn = new jsforce.Connection({ accessToken: '{!$Api.Session_Id}' });
      var workspaceId;
      var deleted = false;
      var button = document.getElementById('{!$Component.thepage.theform.thepageblock.buttons.deletebutton}');
      var notFoundMessage = 'No IDEWorkspace found for your user';
      
      var idDisplay = document.getElementById('{!$Component.thepage.theform.thepageblock.section.item1.IdDisplay}');

      conn.tooling.query("select id, name, createdbyid from ideworkspace where createdbyid = '{!$User.Id}'", 
          function(err, result) {
              if (err) { alert(err); }
              else if (result.totalSize > 1) {
                  alert('Query returned multiple IDEWorkspaces ' + JSON.stringify(result));
              }
              else if (result.totalSize < 1) {
                  idDisplay.innerHTML =  notFoundMessage;
              }
              else {
                  // exactly one IDEWorkspace found for this user
                  
                  workspaceId = result.records[0].Id;
                  console.log(workspaceId);
                  button.className = "btn";
                  button.disabled = false;
                  document.getElementById('{!$Component.thepage.theform.thepageblock.section.item1.IdDisplay}').innerHTML =  workspaceId;
              }
      });

      
      function deleteIDEWorkspace() {
      
        conn.tooling.query("select id, name, createdbyid from ideworkspace where createdbyid = '{!$User.Id}'", 
            function(err, result) {
              if (err) { alert(err); }
              else if (result.totalSize > 1) {alert('Query returned multiple IDEWorkspaces ' + JSON.stringify(result));}
              else if (result.totalSize < 1) {alert('Could not determine Id of your IDEWorkspace');}
              else {
                  console.log(workspaceId);
                  console.log("deleting...");
                  conn.tooling.sobject('IDEWorkspace').delete(workspaceId, function(err, ret) {
                      if (err || !ret.success) { return console.error(err, ret); }
                      alert('Deleted IDEWorkspace Successfully : ' + ret.id);
                      button.className = "btnDisabled";
                      button.disabled = false;
                  });
              }
        });
      }


  </script>

</apex:page>

参考URL：https://github.com/bolaurent/salesforce-developer-console-fix/blob/master/DeveloperConsoleFix.page

上記のVisualforceページ表示する。

https://{インスタンス}/apex/DeveloperConsoleFix

「Delete my IDEWorkspace」ボタン押下する。

ボタン押下後いかのように表示されます。

もちろん、開発者コンソール押下したら、今回のエラーは出ないはずです。