Merge pull request #9 from nasa/feature/GUUI-3595-data-rods-default-plot

feature(data-rods): add variable caching to avoid race conditions

Author: joncarlson

src/metadata-catalog/tasks.ts

@@ -2,6 +2,22 @@ import { Task } from '@lit/task'
 import { GiovanniVariableCatalog } from './giovanni-variable-catalog.js'
 import type { HostWithMaybeProperties } from './types.js'
 import { getVariableEntryId } from './utilities.js'
+import type { Variable } from '../components/browse-variables/browse-variables.types.js'
+
+// Global cache for variable data to prevent duplicate requests
+const variableCache = new Map<string, Variable>()
+const pendingRequests = new Map<string, Promise<Variable | null>>()
+
+function setHostPropertiesFromVariable(
+    host: HostWithMaybeProperties,
+    variable: Variable,
+    variableEntryId: string
+) {
+    host.startDate = host.startDate ?? variable.exampleInitialStartDate?.toISOString()
+    host.endDate = host.endDate ?? variable.exampleInitialEndDate?.toISOString()
+    host.catalogVariable = variable
+    host.variableEntryId = variableEntryId
+}
 
 export function getFetchVariableTask(
     host: HostWithMaybeProperties,
@@ -10,31 +26,59 @@ export function getFetchVariableTask(
     const catalog = new GiovanniVariableCatalog() // TODO: replace this with a factory call when we switch to CMR
 
     return new Task(host, {
-        task: async (_args, { signal }) => {
+        task: async _args => {
             const variableEntryId = getVariableEntryId(host)
 
-            console.debug('fetch variable ', variableEntryId)
+            console.debug('Fetch variable ', variableEntryId)
 
             if (!variableEntryId) {
                 return
             }
 
-            const variable = await catalog.getVariable(variableEntryId, {
-                signal,
-            })
+            // Check if we already have this variable cached
+            if (variableCache.has(variableEntryId)) {
+                console.debug('Using cached variable ', variableEntryId)
+                const cachedVariable = variableCache.get(variableEntryId)!
+                setHostPropertiesFromVariable(host, cachedVariable, variableEntryId)
+                return
+            }
 
-            console.debug('found variable ', variable)
+            // Check if there's already a pending request for this variable
+            if (pendingRequests.has(variableEntryId)) {
+                console.debug(
+                    'Waiting for pending request for variable ',
+                    variableEntryId
+                )
+                const variable = await pendingRequests.get(variableEntryId)!
 
-            if (!variable) {
+                if (variable) {
+                    console.debug('Using cached variable ', variableEntryId)
+                    setHostPropertiesFromVariable(host, variable, variableEntryId)
+                }
                 return
             }
 
-            host.startDate =
-                host.startDate ?? variable.exampleInitialStartDate?.toISOString()
-            host.endDate =
-                host.endDate ?? variable.exampleInitialEndDate?.toISOString()
-            host.catalogVariable = variable
-            host.variableEntryId = variableEntryId
+            // Create a new request and cache the promise
+            const requestPromise = catalog.getVariable(variableEntryId)
+            pendingRequests.set(variableEntryId, requestPromise)
+
+            try {
+                const variable = await requestPromise
+
+                console.debug('Found variable ', variable)
+
+                if (!variable) {
+                    return
+                }
+
+                // Cache the variable for future use
+                variableCache.set(variableEntryId, variable)
+
+                setHostPropertiesFromVariable(host, variable, variableEntryId)
+            } finally {
+                // Clean up the pending request
+                pendingRequests.delete(variableEntryId)
+            }
         },
         args: () => [host.variableEntryId, host.collection, host.variable],
         autoRun,