forked from Deuxfleurs/garage
PollRange: return immediately if no seen marker is provided
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09a3dad0f2
commit
ba384e61c0
2 changed files with 46 additions and 18 deletions
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@ -723,6 +723,13 @@ The query body is a JSON object consisting of the following fields:
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The timeout can be set to any number of seconds, with a maximum of 600 seconds (10 minutes).
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If no seen marker is known by the caller, it can do a PollRange call
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without specifying `seenMarker`. In this case, the PollRange call will
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complete immediately, and return the current content of the range (which
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can be empty) and a seen marker to be used in further PollRange calls. This
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is the only case in which PollRange might return an HTTP 200 with an empty
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set of items.
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The response is either:
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- A HTTP 304 NOT MODIFIED response with an empty body, if the timeout expired and no changes occurred
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@ -268,6 +268,8 @@ impl K2VRpcHandler {
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seen_str: Option<String>,
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timeout_msec: u64,
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) -> Result<Option<(BTreeMap<String, K2VItem>, String)>, Error> {
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let has_seen_marker = seen_str.is_some();
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let mut seen = seen_str
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.as_deref()
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.map(RangeSeenMarker::decode)
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@ -318,7 +320,7 @@ impl K2VRpcHandler {
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}
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}
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if new_items.is_empty() {
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if new_items.is_empty() && has_seen_marker {
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Ok(None)
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} else {
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Ok(Some((new_items, seen.encode()?)))
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@ -432,16 +434,44 @@ impl K2VRpcHandler {
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range: &PollRange,
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seen_str: &Option<String>,
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) -> Result<Vec<K2VItem>, Error> {
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let seen = seen_str
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.as_deref()
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.map(RangeSeenMarker::decode)
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.transpose()?
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.unwrap_or_default();
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if let Some(seen_str) = seen_str {
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let seen = RangeSeenMarker::decode(seen_str)?;
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// Subscribe now to all changes on that partition,
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// so that new items that are inserted while we are reading the range
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// will be seen in the loop below
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let mut chan = self.subscriptions.subscribe_partition(&range.partition);
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// Check for the presence of any new items already stored in the item table
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let mut new_items = self.poll_range_read_range(range, &seen)?;
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// If we found no new items, wait for a matching item to arrive
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// on the channel
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while new_items.is_empty() {
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let item = chan.recv().await?;
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if range.matches(&item) && seen.is_new_item(&item) {
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new_items.push(item);
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}
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}
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Ok(new_items)
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} else {
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// If no seen marker was specified, we do not poll for anything.
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// We return immediately with the set of known items (even if
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// it is empty), which will give the client an inital view of
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// the dataset and an initial seen marker for further
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// PollRange calls.
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self.poll_range_read_range(range, &RangeSeenMarker::default())
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}
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}
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fn poll_range_read_range(
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&self,
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range: &PollRange,
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seen: &RangeSeenMarker,
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) -> Result<Vec<K2VItem>, Error> {
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let mut new_items = vec![];
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let mut chan = self.subscriptions.subscribe_partition(&range.partition);
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// Read current state of the specified range to check new items
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let partition_hash = range.partition.hash();
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let first_key = match &range.start {
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None => partition_hash.to_vec(),
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@ -461,15 +491,6 @@ impl K2VRpcHandler {
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}
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}
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// If we found no new items, wait for a matching item to arrive
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// on the channel
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while new_items.is_empty() {
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let item = chan.recv().await?;
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if range.matches(&item) && seen.is_new_item(&item) {
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new_items.push(item);
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}
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}
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Ok(new_items)
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}
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}
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