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DiskCache: Don't call exists() before reading file

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This commit is contained in:
Winston Chang
2018-06-25 11:46:16 -05:00
parent ce3755676c
commit d7009fd1c8
2 changed files with 42 additions and 14 deletions
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34
R/render-cached-plot.R
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@@ -201,7 +201,7 @@ renderCachedPlot <- function(expr,
isCacheObject <- function(x) {
# Use tryCatch in case the object does not support `$`.
tryCatch(
is.function(x$exists) && is.function(x$get) && is.function(x$set),
is.function(x$get) && is.function(x$set),
error = function(e) FALSE
)
}
@@ -217,7 +217,7 @@ renderCachedPlot <- function(expr,
cache <<- session$getCache()
} else {
stop('`cache` must either be "app", "session", or a cache object with methods `$exists`, `$get`, and `$set`.')
stop('`cache` must either be "app", "session", or a cache object with methods, `$get`, and `$set`.')
}
}
@@ -286,10 +286,22 @@ renderCachedPlot <- function(expr,
key <- digest::digest(list(outputName, cacheKeyResult, width, height, res, pixelratio), "sha256")
if (cache$exists(key)) {
# Get the key. Instead of using exists() before get(), try to simply
# get() the key and catch the exception if it fails. This is to avoid
# possible race conditions between calls to exists() and get()
get_value_failed <- FALSE
tryCatch(
cached_value <- cache$get(key),
error = function(e) {
get_value_failed <<- TRUE
}
)
if (!get_value_failed) {
cat("drawReactive(): cached\n")
# This will NOT include the displaylist.
cache$get(key)
return(cached_value)
} else {
hybrid_chain(
@@ -358,9 +370,17 @@ renderCachedPlot <- function(expr,
key <- digest::digest(list(outputName, cacheKey(), width, height, res, pixelratio), "sha256")
if (cache$exists(key)) {
cat("renderFunc(): cached\n")
result <- cache$get(key)
get_value_failed <- FALSE
tryCatch(
cached_value <- cache$get(key),
error = function(e) {
get_value_failed <<- TRUE
}
)
if (!get_value_failed) {
cat("drawReactive(): cached\n")
result <- cached_value
} else {
if (is.null(result$recordedPlot)) {