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Drastically improve generator.so performance for /nocache #6834

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Merged
zwoop merged 1 commit into from
Jun 1, 2020
Merged

Drastically improve generator.so performance for /nocache #6834

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37 changes: 35 additions & 2 deletions plugins/generator/generator.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -594,6 +594,21 @@ GeneratorInterceptHook(TSCont contp, TSEvent event, void *edata)
}
}

// Little helper function, to turn off the cache on requests which aren't cacheable to begin with.
// This helps performance, a lot.
static void
CheckCacheable(TSHttpTxn txnp, TSMLoc url, TSMBuffer bufp)
{
int pathsz = 0;
const char *path = TSUrlPathGet(bufp, url, &pathsz);

if (path && (pathsz >= 8) && (0 == memcmp(path, "nocache/", 8))) {
// It's not cacheable, so, turn off the cache. This avoids major serialization and performance issues.
VDEBUG("turning off the cache, uncacehable");
TSHttpTxnConfigIntSet(txnp, TS_CONFIG_HTTP_CACHE_HTTP, 0);
}
}

// Handle events that occur on the TSHttpTxn.
static int
GeneratorTxnHook(TSCont contp, TSEvent event, void *edata)
Expand All @@ -603,6 +618,19 @@ GeneratorTxnHook(TSCont contp, TSEvent event, void *edata)
VDEBUG("contp=%p, event=%s (%d), edata=%p", contp, TSHttpEventNameLookup(event), event, edata);

switch (event) {
case TS_EVENT_HTTP_READ_REQUEST_HDR: {
TSMBuffer recp;
TSMLoc url_loc;
TSMLoc hdr_loc;

TSReleaseAssert(TSHttpTxnClientReqGet(arg.txn, &recp, &hdr_loc) == TS_SUCCESS);
TSReleaseAssert(TSHttpHdrUrlGet(recp, hdr_loc, &url_loc) == TS_SUCCESS);
CheckCacheable(arg.txn, url_loc, recp);
TSHandleMLocRelease(recp, hdr_loc, url_loc);
TSHandleMLocRelease(recp, TS_NULL_MLOC, hdr_loc);
break;
}

case TS_EVENT_HTTP_CACHE_LOOKUP_COMPLETE: {
int status;

Expand All @@ -612,7 +640,6 @@ GeneratorTxnHook(TSCont contp, TSEvent event, void *edata)
VDEBUG("intercepting origin server request for txn=%p", arg.txn);
TSHttpTxnServerIntercept(TSContCreate(GeneratorInterceptHook, TSMutexCreate()), arg.txn);
}

break;
}

Expand Down Expand Up @@ -656,6 +683,10 @@ TSPluginInit(int /* argc */, const char * /* argv */[])

GeneratorInitialize();

// We want to check early on if the request is cacheable or not, and if it's not cacheable,
// we benefit signifciantly from turning off the cache completely.
TSHttpHookAdd(TS_HTTP_READ_REQUEST_HDR_HOOK, TxnHook);

// Wait until after the cache lookup to decide whether to
// intercept a request. For cache hits we will never intercept.
TSHttpHookAdd(TS_HTTP_CACHE_LOOKUP_COMPLETE_HOOK, TxnHook);
Expand All @@ -669,8 +700,10 @@ TSRemapInit(TSRemapInterface * /* api_info */, char * /* errbuf */, int /* errbu
}

TSRemapStatus
TSRemapDoRemap(void * /* ih */, TSHttpTxn txn, TSRemapRequestInfo * /* rri ATS_UNUSED */)
TSRemapDoRemap(void * /* ih */, TSHttpTxn txn, TSRemapRequestInfo *rri)
{
// Check if we should turn off the cache before doing anything else ...
CheckCacheable(txn, rri->requestUrl, rri->requestBufp);
TSHttpTxnHookAdd(txn, TS_HTTP_CACHE_LOOKUP_COMPLETE_HOOK, TxnHook);
return TSREMAP_NO_REMAP; // This plugin never rewrites anything.
}
Expand Down