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refactor: Extract listResources utility function for handling pagination
This also fixes an issue where EventGroupsServiceTest was waiting for a real 30s deadline to pass.
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92 changes: 92 additions & 0 deletions
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src/main/kotlin/org/wfanet/measurement/common/api/grpc/ListResources.kt
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/* | ||
* Copyright 2024 The Cross-Media Measurement Authors | ||
* | ||
* Licensed under the Apache License, Version 2.0 (the "License"); | ||
* you may not use this file except in compliance with the License. | ||
* You may obtain a copy of the License at | ||
* | ||
* http://www.apache.org/licenses/LICENSE-2.0 | ||
* | ||
* Unless required by applicable law or agreed to in writing, software | ||
* distributed under the License is distributed on an "AS IS" BASIS, | ||
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
* See the License for the specific language governing permissions and | ||
* limitations under the License. | ||
*/ | ||
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package org.wfanet.measurement.common.api.grpc | ||
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import com.google.protobuf.Message | ||
import io.grpc.kotlin.AbstractCoroutineStub | ||
import kotlin.coroutines.coroutineContext | ||
import kotlinx.coroutines.ExperimentalCoroutinesApi | ||
import kotlinx.coroutines.ensureActive | ||
import kotlinx.coroutines.flow.Flow | ||
import kotlinx.coroutines.flow.asFlow | ||
import kotlinx.coroutines.flow.flattenConcat | ||
import kotlinx.coroutines.flow.flow | ||
import kotlinx.coroutines.flow.map | ||
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/** A [List] of resources from a paginated List method. */ | ||
data class ResourceList<T : Message>( | ||
val resources: List<T>, | ||
/** | ||
* A token that can be sent on subsequent requests to retrieve the next page. If non-empty, there | ||
* are no subsequent pages. | ||
*/ | ||
val nextPageToken: String, | ||
) : List<T> by resources | ||
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/** | ||
* Lists resources from a paginated List method on this stub. | ||
* | ||
* @param pageToken page token for initial request | ||
* @param list function which calls the appropriate List method on the stub | ||
*/ | ||
fun <T : Message, S : AbstractCoroutineStub<S>> S.listResources( | ||
pageToken: String = "", | ||
list: suspend S.(pageToken: String) -> ResourceList<T>, | ||
): Flow<ResourceList<T>> = | ||
listResources(Int.MAX_VALUE, pageToken) { nextPageToken, _ -> list(nextPageToken) } | ||
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/** | ||
* Lists resources from a paginated List method on this stub. | ||
* | ||
* @param limit maximum number of resources to emit | ||
* @param pageToken page token for initial request | ||
* @param list function which calls the appropriate List method on the stub, returning no more than | ||
* the specified remaining number of resources | ||
*/ | ||
fun <T : Message, S : AbstractCoroutineStub<S>> S.listResources( | ||
limit: Int, | ||
pageToken: String = "", | ||
list: suspend S.(pageToken: String, remaining: Int) -> ResourceList<T>, | ||
): Flow<ResourceList<T>> { | ||
require(limit > 0) { "limit must be positive" } | ||
return flow { | ||
var remaining: Int = limit | ||
var nextPageToken = pageToken | ||
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while (true) { | ||
coroutineContext.ensureActive() | ||
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val resourceList: ResourceList<T> = list(nextPageToken, remaining) | ||
require(resourceList.size <= remaining) { | ||
"List call must ensure that limit is not exceeded. " + | ||
"Returned ${resourceList.size} items when only $remaining were remaining" | ||
} | ||
emit(resourceList) | ||
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remaining -= resourceList.size | ||
nextPageToken = resourceList.nextPageToken | ||
if (nextPageToken.isEmpty() || remaining == 0) { | ||
break | ||
} | ||
} | ||
} | ||
} | ||
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/** @see [flattenConcat] */ | ||
@ExperimentalCoroutinesApi // Overloads experimental `flattenConcat` function. | ||
fun <T : Message> Flow<ResourceList<T>>.flattenConcat(): Flow<T> = | ||
map { it.asFlow() }.flattenConcat() |
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