improve(API): Make gasFeeTotal more accurate in /limits and increase cache hit frequency #1369

nicholaspai · 2025-01-10T22:34:42Z

This PR contains several optimizations that ultimately make the gasFeeTotal as accurate as possible while ensuring that the /limits endpoint is retrieving gas fee components from the cache as often as possible, keeping the endpoint latency down.

`stale-while-revalidate`

We can reduce the /limits endpoint cache time to 1s while the revalidate period is 59s so that after the cached value is >1s old we can immediately start recomputing the limits value. This means in the best case we'll have as fresh gas cost data as possible--essentially, as quickly as we can re-compute the gas fee totals.

Gas price caching:

We should ideally use less stale gas price data. This PR reduces the gas price caching time to 10s from 5s.

Gas cost caching:

We currently cache the entire tokenGasCost value but this means we are negating some of the optimizations we have made to use as accurate gas fee estimation as possible. This is because tokenGasCost is dependent on the gasPrice so if we cache the tokenGasCost longer than the gas price gets updated, then we're ultimately returning stale gas price data.

This PR breaks down the tokenGasCost computation into nativeGasCost and l1DataFee values and caches them individually. This allows us to use a longer TTL for these values which are expected to change less frequently than the gasPrice estimation which we can reset the cached value very frequently.

Cron job

This PR adds nativeGasCost and l1DataFee cache resets to the cron job to keep these values fresh in the cache as often as possible. The ultimate effect is that the /limits endpoint should always hit the cache for nativeGasCost, gasPrice and l1DataFee and that these cached values are as fresh as possible.

This PR depends on across-protocol/sdk#826

## `stale-while-revalidate` We can reduce this cache time to 1s so that after the cached value is >1s old we can immediately start recomputing the limits value. This means in the best case we'll have as fresh gas cost data as possible. ## Gas price caching: We should ideally use less stale gas price data. However, we don't want to increase the /limits response time. We currently use the gas price to compute the gas cost so it makes sense to make the gas price cache time slightly longer or equal to the gas cost. This way if the gas cost cache is set, then we'll use the cached gas cost value. If its stale, then we'll fetch the gas price and hopefully hit the cache sometimes. This is why it doesn't make sense to set the gas price cache less than the gas cost cache time otherwise we'll very rarely hit the gas price cache.

vercel · 2025-01-10T22:34:47Z

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…kenGasCost calculation Willl allow us to use more customized caching times for different gas cost components that are expected to change on different time periods

nicholaspai · 2025-01-11T05:13:17Z

api/limits.ts

+      _tokenPriceUsd,
+      latestBlock,
+      gasPrice,
+      nativeGasCost,


Added nativeGasCost to this promise.all since now its no longer dependent on gasPrice.

nicholaspai · 2025-01-11T05:13:43Z

api/limits.ts

+      getCachedLatestBlock(HUB_POOL_CHAIN_ID),
+      // We only want to derive an unsigned fill txn from the deposit args if the destination chain is Linea
+      // because only Linea's priority fee depends on the destination chain call data.
+      latestGasPriceCache(


latestGasPriceCache gets called now for every single chain, as opposed to skipping for Linea, but for Linea, the depositArgs are defined

dohaki

This looks great 👍 I left one comment on the TTL. I think we could achieve a higher cache hit rate if we keep the gas price cache TTL slightly longer than the updateInterval of the cron job in cron-cache-gas-prices.ts.

dohaki · 2025-01-11T11:24:02Z

api/_utils.ts

  const ttlPerChain = {
-    default: 30,
-    [CHAIN_IDs.ARBITRUM]: 15,
+    default: 5,


When we consider the cron job cron-cache-gas-prices, this TTL doesn't matter much. The more correct value to tweak would be this one

frontend/api/cron-cache-gas-prices.ts

Lines 15 to 18 in 9e18813

const updateIntervalsSecPerChain = {

default: 10,

1: 12,

};

Good call, updated this again. I've also updated the cron-cache-gas-prices file to also cache native gas cost and L1 data fees in the cron job. This should be a one-stop cron job we can use to keep all caches pretty warm

Can you check the TTL's in _utils and the cron-cache-gas-price secondsToUpdate to make sure the values make sense?

nicholaspai · 2025-01-11T20:52:20Z

api/_utils.ts

  const ttlPerChain = {
-    default: 10,
-    [CHAIN_IDs.ARBITRUM]: 10,
+    default: 60,


We should ideally update this once per cron job if it runs every 60 seconds

nicholaspai · 2025-01-11T20:52:36Z

api/_utils.ts

+  // We set this higher than the secondsPerUpdate value in the cron cache gas prices job which will update this
+  // more frequently.
+  const ttlPerChain = {
+    default: 60,


We should update this ideally every 12s--every ethereum block

api/_utils.ts

nicholaspai · 2025-01-11T20:53:57Z

api/cron-cache-gas-prices.ts

+        if (diff >= maxDurationSec * 1000) {
+          break;
+        }
+        const gasCost = await gasCostCache.get();


So if this loop runs every 10s and we're updating the OpStackL1DataFee every 10s, we also should update the native gas cost once per 60s assuming one of these loops the gasCostCache.get() call forces the cache to reset its data

nicholaspai · 2025-01-11T20:55:05Z

api/limits.ts

@@ -221,15 +237,21 @@ const handler = async (
        )
      ),
    ]);
-    // This call should not make any additional RPC queries if gasCosts is defined--for any deposit
-    // with an empty message.
+    const tokenGasCost =


We no longer cache the tokenGasCost as its dependent on the gasPrice, the nativeGasCost and the opStackL1GasCost, each of which should be cached at different intervals and using those values we can trivially derive the tokenGasCost

Keep cache warm

dohaki

Looking good 👍

dohaki · 2025-01-12T10:52:35Z

api/limits.ts

+      nativeGasCost,
+      tokenGasCost


NIT: Should we also return those values as part of the response? I think it could be useful.

dohaki

Looking gooood

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Separate native gas cost and op stack l1 gas cost calculation from to…

0e94791

…kenGasCost calculation Willl allow us to use more customized caching times for different gas cost components that are expected to change on different time periods

nicholaspai changed the title ~~improve(API): Reduce stale-while-revalidate and gas price cache times~~ improve(API): Make gasFeeTotal more accurate in /limits by reducing cache time Jan 11, 2025

Use gas price cache for Linea as well

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fix: only cron cache gas prices for non Linea chains

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nicholaspai added 3 commits January 10, 2025 20:45

Update limits.ts

5e4fd39

Only pass in depositArgs for Linea

296056f

add extra part to cache key

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Use sdk for helper methods

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nicholaspai commented Jan 11, 2025

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Update limits.ts

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Fix gas-prices

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Use utils in gas-prices.ts to read data from cache

9e18813

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dohaki reviewed Jan 11, 2025

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update cache times

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nicholaspai requested a review from dohaki January 11, 2025 20:50

Update _utils.ts

ce45f12

nicholaspai commented Jan 11, 2025

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nicholaspai commented Jan 11, 2025

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Update cron-cache-gas-prices.ts

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Add native gas cost caching

7449e8c

Keep cache warm

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nicholaspai marked this pull request as ready for review January 11, 2025 22:11

nicholaspai requested review from mrice32, james-a-morris and pxrl as code owners January 11, 2025 22:11

dohaki previously approved these changes Jan 12, 2025

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Increase ttl of native gas cost, add gasFeeDetails to response

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nicholaspai dismissed dohaki’s stale review via 5441dc6 January 12, 2025 15:17

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nicholaspai changed the title ~~improve(API): Make gasFeeTotal more accurate in /limits by reducing cache time~~ improve(API): Make gasFeeTotal more accurate in /limits and increase cache hit frequency Jan 12, 2025

sdk

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nicholaspai merged commit 09d3771 into master Jan 13, 2025
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improve(API): Make gasFeeTotal more accurate in /limits and increase cache hit frequency #1369

improve(API): Make gasFeeTotal more accurate in /limits and increase cache hit frequency #1369

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improve(API): Make gasFeeTotal more accurate in /limits and increase cache hit frequency #1369

improve(API): Make gasFeeTotal more accurate in /limits and increase cache hit frequency #1369

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nicholaspai commented Jan 10, 2025 • edited Loading

stale-while-revalidate

Gas price caching:

Gas cost caching:

Cron job

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nicholaspai commented Jan 10, 2025 •

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`stale-while-revalidate`

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