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Fixes TypeError: Cannot read property 'pop' of undefined
#530
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nicholasjpaterno
approved these changes
Jan 14, 2020
| @@ -3,6 +3,8 @@ var AbstractLevelDOWN = require("abstract-leveldown").AbstractLevelDOWN; | |||
| var async = require("async"); | |||
| var fs = require("fs"); | |||
| var path = require("path"); | |||
| var tmp = require("tmp"); | |||
| tmp.setGracefulCleanup(); | |||
Comment on lines
+20
to
+39
| const accessQueue = { | ||
| next: (lKey) => { | ||
| const cont = accessQueue.cache[lKey].shift(); | ||
| if (cont) { | ||
| cont(); | ||
| } else { | ||
| delete accessQueue.cache[lKey]; | ||
| } | ||
| }, | ||
| execute: (lKey, callback) => { | ||
| let cache = accessQueue.cache[lKey]; | ||
| if (cache) { | ||
| cache.push(callback); | ||
| } else { | ||
| accessQueue.cache[lKey] = []; | ||
| callback(); | ||
| } | ||
| }, | ||
| cache: {} | ||
| }; |
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👍 on the abstraction. Much cleaner
davidmurdoch
added a commit
that referenced
this pull request
Jan 16, 2020
1 task
This was referenced Jun 6, 2021
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This fixes an issue caused by writing AND reading the same key multiple times simultaneously. Sometimes the read operation would end up reading the value as 0 bytes due to the way writes are performed in node. To fix this, we implemented a queue so only a single read or write operation can occur at a time for each key; basically an in-memory lock.
Additionally, during testing we found that it was possible for a write operation to fail due to program termination. This failure would sometimes cause the key to exist but contain 0 bytes (which is always invalid). To fix this we write to a temp file, and only if it works do we move this temp file to its correct key location. This prevents early termination from writing partial/empty values.
Of course, all this will eventually be for nothing as we are migrating the db to actual an leveldb implementation that doesn't use a separate file for every key Soon(TM).